The Masked Man Reviews the Jurrasic Park Trilogy

[The Lone Ranger]

Some Thoughts on the Jurassic Park
Trilogy

As you will no-doubt guess, I’ve always liked dinosaurs. I think they’re utterly fascinating. When the original Jurassic Park came out, somebody asked me if I’d have gone to the island if it existed, even knowing there would be a serious risk of injury or death. Let’s see now: chance of a grisly death vs. certainty of seeing real live dinosaurs — what are we waiting for? Let’s go!

So I really enjoyed the Jurassic Park movies, especially the first one. Frankly, I’d have been delighted if each movie had been nothing more than 2 hours or so of photorealistic dinosaurs running around and interacting with each other.

The movies were really impressive — that’s for sure. They did a lot of things really well, though inevitably, some things were done a little less well. Before we can discuss how well the movies did or did not work, I thought it might be a good idea to talk about the movies’ stars — dinosaurs. What do we know about them, and what guesses can we make about how they lived?


Systematics and Taxonomy: How and Why do we Classify Organisms?:

Systematics is the study of the diversity of life, and how organisms are related to each other. A branch of systematics is taxonomy, which is concerned with the classification of living organisms.

We classify organisms into groups called taxa (singular = taxon) based upon shared characteristics — characteristics that the members of the taxon in question presumably share because they’re all descended from the same common ancestor. So, ideally, how an organism is classified tells you something about its evolutionary history (its “phylogeny”).

The most inclusive taxon in general usage is the “kingdom.” For instance, the Kingdom Animalia includes organisms that all share the characteristics of being multicellular heterotrophs without cell walls. (A “single-celled animal” is a contradiction in terms; an amoeba, for example, is not an animal, by definition. “Heterotrophs” are organisms that cannot produce their own food, as plants and other “autotrophs” do, and so must eat other organisms for food. The cells of plants, fungi and most bacteria are surrounded by rigid “cell walls”, unlike those of animals.)

Within a kingdom, the next most inclusive taxon in general usage is the “phylum.” (Botanists and mycologists insist on calling a phylum a “division.") For example, all animals sharing the characteristics of a hollow dorsal nerve cord (at least during the embryonic stage), pharyngeal gill slits (again, at least as an embryo), a stiffening rod called a “notochord” that lies beneath and supports the dorsal nerve cord (at least as an embryo), and a postanal tail belong to the Phylum Chordata.

The next most inclusive taxon is the “class.” Within the chordates, those animals sharing the characteristics of body hair, endothermy (“warm-bloodedness”), and milk-producing females belong to the Class Mammalia.

The next most inclusive taxon is the “order.” Among mammals, those with grasping hands (and feet, usually), flat nails instead of claws, forward-facing eyes giving binocular vision, and well-developed cerebral cortices belong to the Order Primates.

The next most inclusive taxon is the “family.” Among the primates, humans and their immediate ancestors, chimpanzees, and gorillas belong to the Family Hominidae.

The next most inclusive taxon is the “genus.” The genus to which we humans belong is Homo. The genus name, you’ll notice, is always capitalized and is always underlined or written in italics.

Finally, there is the “species.” Modern humans, for example, belong to the species Homo sapiens. The species name consists of the genus name plus a “specific epithet” that’s always written in lowercase. The species name is usually a description of the species in Latin or Greek — for instance, “Homo sapiens” can be roughly translated as “man the wise.” (One could argue about how appropriate that name is, of course.)

When it’s convenient, we can use subtaxa to further distinguish between groups of organisms. For example, consider the Phylum Chordata. All chordates have a hollow dorsal nerve cord by definition, but in some of them — but by no means all of them — the nerve cord is surrounded by bony or cartilaginous structures called vertebrae. These chordates are classified as belonging to the subphylum Vertebrata. Chordates that aren’t vertebrates include the Urochordata and the Cephalochordata.

A “species” is generally defined as a group of organisms that can interbreed freely, and that does so in the wild. For instance, wolves (Canis lupus) and coyotes (Canis latrans) are perfectly capable of interbreeding and producing fertile offspring, but they don’t normally do so in the wild, so we consider them separate species. As you can see though, it’s by no means always easy to decide whether or not two organisms belong to separate species. That’s precisely what you would expect though, given how species evolve.

Most speciation is thought to occur when one population of organisms is split into at least two more or less isolated populations that then begin to evolve independently. Given enough time, the two populations will inevitably become so different that they can no longer interbreed, and so will be different species by definition. There’s going to be a period of time where the two populations are clearly different but nonetheless still capable of interbreeding, though. In that case, whether or not they’re different species is a difficult question to answer.

In theory, a genus is a group of closely-related species, all descended from the same common ancestor. Similarly, a family is theoretically a group of closely-related genera, and so on. In practice, though, taxa are not always so neatly defined. For instance, the Class Reptilia is one that most zoologists (myself included) don’t like very much, because it’s not very helpful to say that something is a reptile. Calling something a “reptile” doesn’t tell you what it is; it tells you what it isn’t. (“Reptiles” are amniotes that aren’t birds or mammals.) Despite superficial outward similarities, lizards are not particularly closely related to crocodilians, and turtles are no more closely related to snakes and lizards than they are to you and me. Strictly speaking, snakes and lizards are “lepidosaurs,” turtles are “anapsids,” and crocodilians (along with dinosaurs and birds) are “archosaurs.” If you want to know how critters are related to each other, don’t ask whether or not they’re reptiles; ask if they’re archosaurs, lepidosaurs, or whatever.

As you can imagine, paleontologists have a real problem when trying to classify extinct organisms. How do you determine if two extinct organisms could have interbred? Taxonomists themselves are often (*snicker*) classified into two groups, “lumpers” and “splitters.” Lumpers tend to classify all organisms that seem similar into the same taxon, while “splitters” tend to separate organisms into different taxa based upon fairly small differences. That’s one reason why estimates of the number of dinosaur species can vary widely, depending on which expert you happen to consult.

Whoever discovers a new species gets to name it, so there might be a bit of a tendency for paleontologists to lean toward the “splitter” extreme. For instance, there was a case in which paleontologists discovered the fossilized remains of a herd of animals in the genus Triceratops and classified them into 16 different species, based on some very small differences between the animals. The ecologist in me says, “no way!” One of the most important principles of ecology is the “Competitive Exclusion Principle,” which states that “competing species cannot coexist.”

If two species happen to be competing for the same resources, one of them will surely be more efficient at acquiring those resources than will the other. So, the more efficient species will monopolize those resources, forcing the other to evolve to do something else or go extinct. So, it’s extremely unlikely that any herd of Triceratops ever existed that contained 16 different species all living in the same area and presumably eating the same food. Surely, that herd consisted of a single, variable species.


[B]Classification of the Dinosaurs and Related Beasts:

The first vertebrates to live on land were the amphibians. There was a time in Earth’s history (about 370 million years ago) when amphibians were the largest animals living on land. These early amphibians still had very fish-like skeletons, and since most modern amphibians are highly dependent on water, these critters surely were too. (By the way, the scenario most people imagine is saltwater fishes crawling out of the sea and becoming amphibians, but amphibians appear to have evolved from freshwater fish. Probably, they evolved from fishes living in ancient swamps.) What these early amphibians clearly had were four legs adapted to supporting their weight on land. So, these animals and all their descendants are known as the tetrapods.

Amphibians have thin, water-permeable skins, and the eggs they lay are not waterproof either. In addition, the young of most amphibians are very fish-like, living in water and breathing with gills rather than lungs. These facts make them highly dependent on water, because they will quickly die of dehydration in a dry environment, and their eggs must be deposited in wet environments.

Somewhat over 300 million years ago, a series of rather important evolutionary innovations occurred. From the amphibians arose a group of animals with skeletons that were better adapted to supporting their weight out of water. They also evolved skin that was more or less waterproof and was covered with protective scales. Perhaps most importantly, they laid eggs that had waterproof outer shells and internal protective membranes including the amnion that kept the developing embryo wet. These are known as amniotic eggs and these animals and all their descendents are therefore known as the amniotes. Because amniotes have waterproof skins and because they can lay their eggs on land (or in many species, retain them within the mother’s body as the embryos develop), they are far more independent of water than are amphibians.

The earliest amniotes, with their dry, scaly skins and their egg-laying ways would be called (*sigh*) “reptiles.” From these early reptiles evolved four distinct lineages, which are classified according to their skull anatomies. These were the anapsids, synapsids, euryapsids, and diapsids. The drawing below should help to clarify things. (In the drawing, the “orbit” is the eye socket, “Sq” indicates the squamosal bone, one of the bones that makes up the skull, and “Po” indicates the postorbital bone.)

http://www.freethought-forum.com/images/jurassic/skullstypes.jpg

In the anapsids, the skull is solid in the temporal region — that is, the region behind and above the eye socket. Early anapsids included the pareiasaurs, which were up to about the size of a modern hippopotamus, but the only surviving anapsids are the turtles.

In the synapsids, there is a single opening in the temporal region of the skull. Early synapsids included an interesting group of animals known as the pelycosaurs, with distinctive dorsal sails. These included the well-known Dimetrodon, a predator that lived about 250 million years ago and reached 10 feet (3 meters) or so in length.

http://www.freethought-forum.com/images/jurassic/dimetrodon.jpg

What the heck was the function of that sail? Well, pelycosaurs were clearly reptiles — notice how the legs were splayed out to the side like a lizard’s, for instance. It seems likely that they had slow, reptile-style metabolisms and were not warm-blooded. There are real advantages to being warm, however, because the warmer your body (up to a point), the faster are the chemical reactions that drive your metabolism. So, warmer animals have more energy available and can be more active; they also tend to have faster reflexes.

The spines on a pelycosaur’s back were quite thin, and it’s likely that a thin layer of skin covered those spines to form a sail. If a pelycosaur were to orient itself perpendicular to the sun, the sail would make an effective absorber of solar energy. Blood pumped into the sail would be warmed and would in turn warm the body. So, pelycosaurs likely used those sails to absorb solar energy. This would give them a great advantage over animals that lacked such sails, because pelycosaurs could quickly and efficiently warm their blood on sunny days and so maintain a more active and energetic lifestyle — very handy for a predator that had to chase down prey.

If the sail could be used to absorb solar energy, it could also be used as a radiator to prevent overheating by shedding excess heat. In hot weather, a pelycosaur could move into shade or orient itself so that the sail was parallel to incoming sunlight, and blood pumped into the sail would radiate away excess heat. In short, it’s likely that the pelycosaurs’ sails allowed them to regulate their body temperatures much more effectively than could animals that lacked them.

Pelycosaurs and their relatives dominated the land for millions of years, but let me point out that they were not dinosaurs. They lived millions of years before the dinosaurs arose. For whatever reason, the synapsids became much less prominent when the dinosaurs arose, but they did indeed survive. They gave rise to the mammals. So, when you see a drawing of a Dimetrodon, keep in mind that this was not a dinosaur at all — it was a distant relative (though not a direct ancestor) of you and me.

In the euryapsids, there was only a single temporal opening in the skull, but it was positioned higher than the opening in the skull of a synapsid. The euryapsids appeared a little later and seem to have been descended from diapsids, so they’re often classified simply as diapsids. The euryapsids included marine reptiles that dominated the world’s oceans at the same the dinosaurs dominated the land. These marine reptiles were the plesiosaurs, in which the four limbs were modified into flippers, and the fishlike ichthyosaurs, which were the Mesozoic equivalent of whales and dolphins.

Finally, there were the diapsids, with two temporal openings in the skull. This was and is a very diverse taxon that is generally subdivided into two subtaxa, the Lepidosauria and the Archosauria. The lepidosaurs include the familiar snakes and lizards, as well as the extinct mosasaurs. Mosasaurs were essentially large sea-going lizards that shared the Mesozoic seas with ichthyosaurs and plesiosaurs. (Mosasaurs were quite distinct from plesiosaurs, but like the plesiosaurs, their limbs were modified into swimming paddles.)

Archosaurs include the crocodilians (crocodiles, alligators, and their kin), avians (birds), pterosaurs (“flying reptiles”) and dinosaurs. The dinosaurs were distinguished from mere “reptiles” by the fact that their legs were not splayed out to the side like those of a reptile, but oriented directly under the body.

http://www.freethought-forum.com/images/jurassic/posture.jpg

In the top of the drawing, you can see how a typical reptile, such as a lizard, has its legs splayed out to the sides. By contrast, the bottom of the drawing shows how a dinosaur’s legs (like those of modern mammals) were oriented directly under the body. This positioning of the limbs was much more efficient at supporting body weight, which allowed dinosaurs to grow to much larger sizes than had any of their predecessors. The upright limb posture also allowed for much more efficient locomotion and so a more active lifestyle.

The dinosaurs are generally divided into two major groups, ornithischians and saurischians, according to the arrangement of bones in their hips. Three partially fused bones made up the hip of a dinosaur, the ilium (which I’ve colored red in the drawing), the ischium (blue), and the pubis (yellow). (In this drawing, the animals’ heads would be to the left, and the tails to the right. A typical ornithischian’s pelvis is shown on the left, and a typical saurischian’s on the right.)

http://www.freethought-forum.com/images/jurassic/hips.jpg

In ornithischians, the pubis was turned back toward the tail and often partially fused with the ischium. The name “ornithischian” means “bird-hipped” and refers to the superficial similarity between the hips of ornithischian dinosaurs and modern birds. Birds are not descended from ornithischian dinosaurs, however. Interestingly, there are no ornithischians that appear to have been carnivores. All known species had the sorts of teeth you’d expect to find in herbivores.

The ornithischians included the “armored dinosaurs” that had bony structures embedded in their skins which might have provided some protection against predators. Perhaps the best-known of these were Stegosaurus and its kin. These were the four-legged dinosaurs with distinctive plates on their backs and spikes on their tails that were presumably used to defend against predators.

Another group of armored ornithischians were the ankylosaurs, which were built like Mesozoic tanks. They had heavy bony armor covering their backs and long spikes extending out from their flanks. Many species had bony “clubs” at the end of their tails which would have made dangerous defensive weapons. Ankylosaurs included such genera as Ankylosaurus, Nodosaurus, and Edmontonia.

Ceratopians or “horned dinosaurs” were up to about the size of modern rhinos. They had parrot-like beaks which they presumably used for cropping plants, but they’re best known for the large frills that extended from their skulls and covered their necks and for having horns extending from their faces. They probably used these horns like modern antelopes use theirs; that is, the males probably interlocked their horns and wrestled each other for access to females. In emergencies, the horns would also have made good defensive weapons. Well-known ceratopians included Triceratops, Torosaurus and Styracosaurus.

Ceratopians were quite common during the latter portion of the Mesozoic, but perhaps the most common ornithischians were the hadrosaurs or “duck-billed dinosaurs.” They had broad, duck-like beaks and teeth that were very well adapted for grinding plant matter. Most of them seem to have been bipedal and well-adapted for fast running, but they could probably go on all fours as well. Hadrosaurs didn’t have armored bodies, nor clubs or spikes on their tails, nor dangerous horns, so they apparently depended on raw speed to escape predators. Many of them had elaborate “helmets” on their heads into which the nasal cavities extended. These helmets appear to have served as resonating chambers, and the different species would have had very distinctive-sounding calls, depending on the shapes of their helmets. Well-known hadrosaurs included Corythosaurus, Lambeosaurus and Parasaurolophus.

A rather interesting group of ornithischians were the pachycephalosaurs or “thick-headed dinosaurs.” Like the hadrosaurs, they were apparently bipedal, but their heads were covered by quite thick growths of bone. It seems likely that male pachycephalosaurs got into “head-butting” contests in much the same way that modern Bighorn Sheep do. Well-known pachycephalosaurs included Pachycephalosaurus and Stygimoloch.

In saurischians, the pubis and ischium were distinctly separate, and the pubis usually pointed forward, toward the animal’s head. The saurischians were divided into two major groups, the sauropods and the theropods.

Sauropods were quadrupedal plant-eaters that often grew to enormous sizes. Unlike most ornithischian plant-eaters, most sauropods did not have teeth that were well-adapted for grinding up plant matter. Instead, most of them appear to have swallowed small stones (called gastroliths or “gizzard stones”). If these dinosaurs had muscular gizzards like many modern birds, gastroliths would have been quite effective at grinding up plant matter.

Sauropods included the brachiosaurs, such as Brachiosaurus and Ultrasaurus, which were heavily-built animals that grew to enormous sizes. Some may have weighed 100 tons or more, making them as heavy as the largest whales. Brachiosaurs had longer forelimbs than hindlimbs and appeared to hold their necks upright. They were apparently the Mesozoic equivalents of giraffes. The head of a Brachiosaurus towered something like 50 feet above the ground, which would have made it well-suited for grazing on trees. Other sauropods included the diplodocids or brontosaurs, with their very long necks that were apparently held more horizontally and their long, whip-like tails. Well-known brontosaurs included Apatosaurus, Barosaurus, Diplodocus, and Seismosaurus. Seismosaurus, at perhaps 120 feet (36 meters) or more in length, may have been the longest animal that ever lived.

Theropods were bipeds, and virtually all of them were clearly adapted for eating meat. It’s generally believed that birds evolved from small theropods, and many of the theropods were indeed strikingly bird-like in their anatomy. (Strictly speaking, according to many paleontologists, birds are theropod dinosaurs.) Early theropods included the allosaurs, which had teeth that appeared to be suited toward delivering slashing wounds. Allosaurs were probably pack hunters that went after large sauropods, much the same way that modern wolves go after moose and other such large prey. Later theropods included the dromaeosaurs, which were clearly adapted for running and jumping, and had large sickle-shaped “killing claws” on their hindlimbs. They probably used those killing claws to disembowel prey. Dromaeosaurs included such famous critters as Deinonychus and Velociraptor. Perhaps the most famous theropods were the tyrannosaurs, including Daspletosaurus and Tyrannosaurus rex. Tyrannosaurs were perhaps the largest theropods and had powerful jaws with teeth that would have been well-suited to delivering deep, gouging bites.


[B]When Did Dinosaurs Live?:

Dinosaurs completely dominated the planet’s land areas for well over 100 million years, during the Mesozoic Era. The Mesozoic was divided into three periods. The first of these periods, the Triassic, was from about 248 million years ago until about 213 mya. This was when the first dinosaurs and mammals evolved. Next came the Jurassic (213 - 144 mya). This was the time of the great sauropod dinosaurs like Apatosaurus and Brachiosaurus, as well as such predators as Allosaurus. It’s also when the first birds evolved. Finally, there was the Cretaceous (144 - 65 mya). The Cretaceous saw the “duck-billed” dinosaurs such as Parasaurolophus, the horned dinosaurs such as Triceratops, and predators such as Velociraptor and Tyrannosaurus.

It seems to me that it would have been better to call the movie series "Mesozoic Park," since most of the dinosaurs we saw in the movies were from the Cretaceous, not the Jurassic. But maybe that’s just me.


[B]Were Dinosaurs “Warm-Blooded”?:

When the first dinosaur fossils were discovered in the 1820s and 1830s, paleontologists immediately recognized that they had a number of bird-like characteristics. At the time, though, it was generally believed that taxa were distinctly separate and that organisms didn’t evolve over time (Darwin’s Origin of Species was published in 1859). So, it was assumed that these strange creatures must belong to some already-established group. Since they had teeth, which no modern bird does (this was before the discovery of fossils of Archaeopteryx, Hesperornis, or other early toothed birds), it was decided that they must be reptiles.

Since “everyone knows” reptiles are cold-blooded animals with low metabolic rates, it was assumed for some time that dinosaurs had been “cold-blooded,” slow-moving animals that were essentially great big lizards. The discovery of Deinonychus in 1964 by John Ostrom forced people to begin reevaluating their preconceptions. Deinonychus, as Ostrom showed, had a remarkably bird-like anatomy. It was clearly adapted for running and jumping, and must have been a very active animal. How, then, could it have been just a big lizard?

Perhaps we should define our terms before we go any further. When people talk about animals being “cold-blooded,” they generally mean that the animals in question are heterothermic and poikilothermic. “Warm-blooded” animals are endothermic and homeothermic.

A heterothermic animal is one that cannot produce enough body heat on its own to heat its body above the temperature of its surroundings, so its body temperature is determined by the temperature of its environment. A poikilothermic animal is one whose body temperature is not constant, but fluctuates according to external conditions. For practical purposes, “heterothermy” and “poikilothermy” are synonymous terms .

An endothermic animal is one that produces significant amounts of body heat through metabolic processes, and so such an animal can have a body temperature that’s considerably warmer than its surroundings. An endotherm does not necessarily have the capacity to maintain a more or less constant body temperature, however — an animal which can do that is a homeotherm.

There’s some overlap. For example, though we generally think of fishes and reptiles as “cold-blooded,” some fish in the tuna family have specialized heat-generating tissues that can be used to raise the temperatures of their central nervous systems to well above that of the surrounding water. Large Great White Sharks and Loggerhead Turtles can have body temperatures that are several degrees warmer than the surrounding water. Even some insects can raise their body temperatures to well above that of their surroundings. Even so, while these animals are endothermic to some degree, they’re not homeothermic.

“Warm-blooded” animals (modern birds and mammals) generate body heat internally and maintain near-constant body temperatures of about 100º F (38º C). So what? Well, metabolic processes are typically most effective at about this temperature, so warm-blooded animals can be active over a much broader range of environmental temperatures than can “cold-blooded” animals. Keeping in mind that mammals have been around for as long as have dinosaurs, it seems surprising that dinosaurs so completely dominated the planet for over 100 million years if they were simply big, cold-blooded lizards.


Well then, what evidence do we have to support the conclusion that dinosaurs were, in fact, warm-blooded? If they had fast, mammalian-style metabolic rates, there should be some clues. What might some of them be?

One clue comes from predator/prey ratios. Warm-blooded animals pay a heavy price for this adaptation — they require much more food to fuel their fast metabolisms than do cold-blooded animals of the same size. Because warm-blooded predators require so much food, there must be many more prey animals relative to predators in a warm-blooded ecosystem than in a cold-blooded ecosystem. Otherwise, the predators would soon gobble up all the prey and then starve. Some have argued that if fossils from the time when early synapsids like Dimetrodon are considered, predators were apparently almost as common as prey animals. This suggests that the early synapsids were cold-blooded. By contrast, if you look at modern ecosystems dominated by mammals, predators are much less common than are prey animals. So, what’s the case for dinosaurs? Well, it depends on whom you ask. Some argue that the predator/prey ratios more closely resemble “cold-blooded” ecosystems, and some argue that they more closely resemble “warm-blooded” ecosystems. That issue is most-definitely not settled.

Warm-blooded animals tend to grow much faster than do cold-blooded animals. Because fast-growing tissue needs a good blood supply, bone from fast-growing animals is riddled with microscopic openings for blood vessels. The bones of most modern reptiles lack these openings, as did the bones of early synapsids. By contrast, the bones of most modern mammals are riddled with these blood channels, and it seems that the bones of many dinosaurs were too.

It’s difficult to see how an animal weighing several tons would have been able to hibernate during the winter. Where would it find a suitably large cave? So if dinosaurs inhabited cold climates, this would indeed be convincing evidence that they were warm-blooded. As it happens, dinosaur remains have been found in northern Alaska, where winters would surely have been cold enough that cold-blooded animals would have to either migrate to warmer climates or hibernate. Even more convincing is the fact that dinosaur remains have been found in Antarctica. Antarctica wasn’t so close to the South Pole then, and the Earth’s climate was generally warmer during the Mesozoic, but even so, dinosaurs living in Antarctica would certainly have experienced long, cold winters. Since migration to warmer climates wasn’t an option, this is very strong evidence that some dinosaurs, at least, were endotherms.

One thing that’s necessary to keep in mind is that an animal’s size matters quite a lot. Body heat is gained and lost across the skin surface, but body heat is generated by the interior tissues. If you double an animal’s size, other factors being equal, its surface area increases by 22 or 4 times. But its volume increases by 23 or 8 times. This means that as animals get larger, their surface area (across which they lose body heat) increases much more slowly than does their volume (which generates body heat).

The practical result of this is that a small animal has lots of surface area relative to its volume, and so loses body heat quickly. Small endotherms, therefore, must be well-insulated, because otherwise they’ll lose body heat faster than they can generate it. Larger animals need less insulation, because their own bulk acts as insulation to slow down heat loss. There’s no particular reason for small poikilotherms to be insulated, because such insulation would only impair their ability to absorb solar energy and so warm themselves.

Were small dinosaurs insulated? Well, feathers don’t fossilize very well, but some particularly well-preserved fossils have been found recently in China that show pretty clearly that at least some small dinosaurs were covered with feathers. So, this is more evidence that dinosaurs were warm-blooded.

But was it this simple? Were dinosaurs creatures with fast, mammalian-style metabolisms and very active lifestyles? For the big ones, this would be a real problem. Keep in mind the importance of body size. Muscle contractions generate heat. Think of how much body heat you can generate by going for a run; even in cold weather, you’ll soon be shedding excess clothing to keep from overheating. Because large animals lose body heat much more slowly than do small animals, the biggest mammals do not — and cannot — have metabolic rates that are as fast as those of small mammals. A mammal the size of a mouse must spend practically every waking moment hunting for food and eating in order to fuel its ferociously high metabolic rate, and if you could make a mouse the size of an elephant but give it the same metabolic rate, it would quickly overheat and die. An elephant, by contrast, has relatively lower food demands, and doesn’t need furry insulation to maintain its body temperature. If you could reduce an elephant to the size of a mouse but keep its metabolic rate unchanged, even if you gave the poor mini-elephant insulating fur, it wouldn’t be able to keep itself warm.

In other words, if a very large dinosaur weighing 30 tons or more were to have a fast, mammalian-style metabolism, it would surely overheat. An animal that size would be able to generate all the body heat it needed just by walking around. This phenomenon, whereby large animals can generate and retain body heat much more effectively than can smaller ones is known as gigantothermy. Indeed, overheating was probably the biggest problem facing the larger sauropods. Many paleontologists have suggested that their very long necks and tails were adaptations to increase their surface areas and so help them more effectively shed excess body heat.


So, I would like to propose that dinosaurs were neither “cold-blooded” like overgrown lizards nor strictly “warm-blooded” in that they all had fast, mammalian-style metabolisms. Small dinosaurs and the young of larger species were probably insulated with feathers and had fast, mammal-like metabolic rates which allowed them to maintain high body temperatures. As they grew larger, their metabolic rates would have dropped and the need for insulation would have decreased. By the time big dinosaurs reached adult size, their metabolic rates would be much lower than they had been when the animals were young, because they would have been able to generate enough body heat to keep themselves warm just by moving around.


[B]How Can We Infer the Behavior of Extinct Animals?:

In the last years of the 18th century, Georges Cuvier founded the field of comparative anatomy when he pointed out that “form follows function” in the way animals are “built.” He pointed out that an animal which eats meat, for example, will need certain characteristics that would be useless to a plant-eater, while a plant-eater will need characteristics that would be useless to a meat-eater. An animal that’s specialized for running fast will necessarily have legs that are built entirely differently from those of a digger. And so forth.

Cuvier’s point was that if we apply basic physical and mechanical principles to the skeletons of living animals, we can correlate their skeletal structures to their lifestyles. Certainly, the same should be true for extinct animals.

Consider a meat-eating animal. Naturally, it needs sharp and pointed teeth for piercing and cutting a relatively pliant material like meat. Ideally, the teeth should be serrated on the cutting edge, just as were those of most meat-eating dinosaurs. Having pointed teeth means that when the carnivore bites into its victim’s flesh, the force generated by the carnivore’s bite is concentrated onto a very small area at the tip of each tooth, making it easy for the tooth to pierce. A flat-tipped tooth would spread the bite force over a much larger area by contrast, and so would be useless to a carnivore, since it wouldn’t penetrate pliant meat. Having blade-shaped teeth with relatively thin cutting edges serves the same purpose of concentrating force onto a small area, making it much easier for the tooth to cut through meat. In most carnivores, the teeth come together and slide past each other like the blades of scissors, greatly increasing their cutting efficiency. If the teeth are serrated on the cutting surfaces, this makes them even more effective at cutting meat — think of how much more effective a serrated blade is for cutting steak than is an unserrated blade.

So, a meat-eater needs teeth that are sharply-pointed to pierce flesh, and ideally, they should be blade-shaped and serrated as well, to cut flesh into chunks that can be swallowed. These teeth should be strong and deeply-rooted, ideally, because the prey will doubtless resist. If you’re going to pursue a carnivorous lifestyle, it just won’t do to have all your teeth broken or ripped out the first time you bite into a victim. (Sharks don’t have particularly deeply-rooted teeth, and so they’re constantly losing them. But since they constantly replace their teeth anyway, it’s not really a problem. Besides, the prey that sharks typically deal with generally can’t put up the kind of resistance that a large land animal can.)

To provide anchorage for those deeply-rooted teeth, a predator needs a deep jaw. A shallow jaw wouldn’t be able to hold deeply-rooted teeth, obviously. Besides, the deeper the jaw is, the more room there is for the attachment of powerful jaw-operating muscles, and so the more powerful can be the predator’s bite. (Some carnivorous dinosaurs, such as Dilophosaurus had relatively shallow jaws that would not have been capable of delivering a very powerful bite. This leads paleontologists to speculate that they were adapted for hunting smaller, weaker prey and/or that they tended to scavenge, rather than to go after live prey.)

At the back of the skull is a ridge called the nuchal ridge (or nuchal crest) where many of the neck muscles attach. The larger this ridge, the larger and more powerful can be the neck muscles which attach there. So, the size of the nuchal ridge gives us some idea of how powerful the animal was, and especially how much power it could generate to hold onto struggling prey and to shake it in order to stun or kill it. Lions, for instance, have great big nuchal ridges, whereas they’re all but absent on humans. Tyrannosaurs, like lions, had very large nuchal ridges, which suggests they had exceptionally powerful neck muscles. They probably grabbed victims with those powerful jaws and then used the powerful neck muscles to either shake and disorient the victim or to simply rip out huge chunks of flesh.

At the base of the skull is the foramen magnum, where the spinal cord enters into the skull. The position of the foramen magnum tells us how the animal’s spine was oriented relative to its head. If it walked more or less upright, like a human does, the foramen magnum would be on the underside of the skull, whereas if its spine and neck were aligned, the foramen magnum would be at the back of the skull. Based on this, we can infer that many plant-eating dinosaurs walked with their heads and necks held more or less parallel to the ground, whereas most meat-eaters seemed to hold their heads more erect. (Not to the same extent that a human does, of course.)

Now, as we mentioned earlier, if you’re a meat-eater, lunch will tend to protest. So carnivores typically need claws on their feet, with which to grab their victims. These claws may be merely pointed and curved backwards, so as to pierce the victim’s flesh and hold it in position long-enough for a killing strike to be delivered, such as the claws on the forelimbs of animals such as tigers or Velociraptors. (The fact that they’re curved backwards means that as the victim tries to move forward to escape, the claws simply dig in deeper.) The claws can be blade-like and used as cutting tools to dispatch prey as well, like the large sickle-shaped claws on the hindlimbs of Velociraptor.

When it spots you coming, lunch will probably try to run away. So carnivores typically need legs built for speed, at least for a short distance. Other factors being equal, the longer are your legs, the greater is your stride length and so the faster you can run. Ideally, you want to make the legs as light as possible if you’re to run fast — especially toward the distal ends, where they’re moving fastest. (The proximal end of an appendage is the end that’s closer to the body; the distal end is the one that’s further from the body.) Legs work like pendulums, and the distal ends must move much faster than the proximal ends. As a result, the more mass in the distal portion of the limb, the more energy the animal must exert to run. That’s why running animals tend to have the muscles that operate the legs as high up on the legs as possible and the portion of the leg below the knee tends to be longer than the portion above it. In animals that are specialized for walking, swimming, climbing, or burrowing, the distribution of leg muscles and the relative lengths of the leg sections are notably different.

Plant-eaters need entirely different adaptations than do meat-eaters, of course, though there are obviously some overlaps. For instance, sharp and pointy teeth are of no particular use to a plant-eater. Herbivores typically have flat teeth with ridges on them so that they can grind their food. That herbivores must be able to grind their food is absolutely essential because plant tissues tend to be tough and fibrous, and because all plant cells are surrounded by cell walls made of cellulose. There is no known species of animal that can digest cellulose, and if none live today, there’s no particular reason to expect that others did in the past. So, how do herbivores manage to extract nutrients from plant matter?

Typically, they grind it thoroughly, which breaks open cell walls and allows extraction of nutrients from the plant tissue. Also, herbivores have bacteria living in their guts that can digest cellulose. Herbivores must typically spend much more time eating and digesting their food than do same-sized carnivores. Meat is easy to digest and contains lots of nutrients and calories. Most plant matter, by contrast, is difficult and time-consuming to digest, and is relatively poor in nutrients and calories. That’s why carnivores don’t need to eat as much as do herbivores of the same size, and why carnivores can digest their meals much more quickly. Herbivores need much longer guts to contain the bulky plant matter while their onboard bacteria digest the cellulose-containing cell walls, so that the nutrients contained within the plant cells can be absorbed. (You’ve probably noticed that herbivorous animals tend to have prominent guts, whereas carnivores typically don’t. This isn’t because the herbivores necessarily have much body fat, but because they have to cram much longer intestines into their abdominal cavities.)

Herbivores can cope with the low digestibility of plant matter in various ways. Browsers like horses tend to be quite picky about what they eat. They tend to choose the most tender and nutritious plant parts to eat. Their digestive systems tend to be relatively inefficient, so they must eat relatively high-quality food and a lot of it. Grazers like cows tend to be much less picky eaters. They can eat pretty-much whatever plant matter is available, because they have much more efficient digestive systems. Again, you may have noticed that horses tend to be rather slimmer than cows of the same size. Horses have less voluminous digestive systems and pay for it in that they require lots of relatively high-quality food; cows have much more voluminous digestive systems, including 4-chambered stomachs where food can be stored for some time while bacteria work on it.

Some smaller herbivores simply can’t pack enough gut tissue into their bodies to be very efficient at digesting plant matter, so they deal with their food in a different way. Lagomorphs (hares and rabbits) have a kind of “sorting mechanism” in their guts so that they produce two different kinds of feces. Indigestible matter is compressed into normal feces and expelled, while softer and more digestible matter is expelled as what are called “night feces,” which the animal eats again. If you eat your food two or three times, you can get a lot of nutrients out of it even if you do have a short gut.

Anyway, the general point is that what an animal eats will shape its entire body to some extent, especially the teeth. An animal with sharp, cutting teeth generally eats meat, whereas an animal with flat, grinding teeth eats plant matter. Animals that specialize in eating fish or other slippery prey tend to have numerous sharply-pointed and backwards-facing teeth. The pointed teeth are good for grabbing slippery prey because they pierce the body tissues, and because the teeth point backwards, prey that tries to pull free only succeeds in causing the predator’s teeth to dig in deeper.

On a broader scale, an animal’s lifestyle will dictate the construction of its skeleton. This is necessarily so, because an adaptation that works well under one set of circumstances won’t work well under other circumstances — tradeoffs are inevitable. For instance, biomechanical principles dictate that a limb shape which is well-suited for burrowing is wholly unsuited for running, because it’s physically impossible for the same joint to generate both high power and high speed. So, application of biomechanical principles to animals’ skeletons can tell us a lot about how they lived.

If a skull is well-preserved, an endocast can be made by injecting liquid rubber or some other such material into the skull. When it hardens, it re-creates the structure of the animal’s brain. In this way, we can learn not just how large the animal’s brain was, but the shapes and relative sizes of the various regions of the brain. That’s how we know that Tyrannosaurus rex had large, well-developed olfactory lobes in its brain for instance, and so surely had an excellent sense of smell. Nowadays, CT scans can be used to examine the brains of extinct creatures as well.

Predators and tree-dwelling animals (and their recent descendants, such as ourselves) tend to have forward-facing eyes with overlapping fields of view. This gives them binocular vision and the ability to judge distance accurately. These are obviously advantageous traits for a predator that needs to be able to judge distance accurately when attempting to pounce on a victim, or for a tree-dwelling animal whose life depends on its ability to accurately judge distance before leaping for a branch. The penalty one pays for binocular vision is that there’s little vision to the sides and none to the back. Prey animals tend to have their eyes on the sides of their heads, which gives them a much wider field of vision for spotting potential predators, but means that they can’t judge distances so well.

Preserved skeletal remains aren’t the only kinds of fossils we find. Fossilized footprints and fossilized feces (coprolites) provide information about extinct animals. For instance, if you know how long an animal’s legs were and how far apart its footsteps were, you can calculate how fast it was moving when it made the tracks. Fossilized dinosaur footprints have been found which show pretty convincingly that some large theropods could run at 25 miles per hour (40 kph). Similarly, we can be reasonably certain that some dinosaurs swam, because of trace fossils. One fossil trackway has been found that was probably produced by a Dilophosaurus as it crossed a lake. The animal’s tracks were widely-spaced and only the claw tips pressed into the mud; this strongly suggests the animal was swimming and only occasionally touched the bottom as it crossed the lake.

So, a careful study of an animal’s skeleton will give us a very good idea of what it ate, how fast it could run, and how powerful it was. Other kinds of fossils can give us even more information about the animal. Certainly, there’s a lot that we’ll never know about dinosaurs. Things like coloration will surely always be conjectural at best, for instance. Even so, careful study of fossil remains can provide a surprising amount of information about extinct animals.


[B]Speaking of Colors ... :

Big dinosaurs are usually depicted as gray in color. This is doubtless because we think of them as being like elephants or rhinoceros. But most mammals have little capacity for color vision. It’s not surprising that most mammals are dully-colored, therefore. Just about the only mammals with good color vision are primates. (It’s often suggested that color vision evolved in primates because they needed to be able to quickly distinguish ripe from unripe fruit.) It’s probably not coincidental that primates are among the few mammals that have bright colors. Think of the brightly-colored faces of male mandrills or the way that many female primates’ buttocks turn bright red when they’re sexually receptive.

“But what about tigers?” you may wonder. Keep in mind that most of the animals tigers hunt are essentially color-blind. To them, orange stripes would be just as effective for camouflage in a wooded environment as would be green stripes.

Dinosaurs’ closest living relatives, birds, have excellent color vision as a rule. So it’s not unlikely that dinosaurs saw color well too. As such, it’s likely that many dinosaurs were brightly colored. Of course, it’s not likely that we’ll ever know for sure.


[B]Sexual Dimorphism:

Sexual dimorphism occurs when males and females of a given species are distinctly different in appearance in some way. For instance, in many species males are considerably larger than are females, or males may be more brightly colored, or males may have distinctive features (like antlers in deer) that are much less prominent or completely absent in females. Why are these features almost always much more prominent in males?

I heard recently that some people have been praising the movie March of the Penguins because it proves monogamy is “natural,” and therefore a good thing, presumably. Aside from the fact that this is poor logic, what these people are apparently unaware of is that monogamy is almost unknown in the animal kingdom, and that’s precisely why it’s so noteworthy in Emperor
Penguins.

In most animal species, what determines how many offspring a male can produce are the number of females he mates with. Males, therefore, tend to seek as many mating opportunities with as many different females as possible. (This is only a generalization; there are conditions under which monogamy is absolutely essential for successful rearing of children.)

In most animal species, a healthy male can produce hundreds of millions or even billions of sperm cells in a single ejaculation, which is generally far more than is necessary to fertilize the female’s eggs. For most species then, any healthy male can easily fertilize all of a female’s eggs. So there’s no particular reason for a female to mate with multiple males. What typically determines a female’s ability to produce offspring is not the number of mates she has, but the quality of her mate(s).

So, the general rule is that males tend to seek to mate with as many females as possible, while females tend to try to mate with the best male(s) available. So, males tend to compete for mating opportunities, either directly or indirectly, and it’s to the best interest of males to show off any traits that advertise their suitability as mates.

So, sexual dimorphism occurs. Any trait that makes a male more successful at getting mates will tend to be preserved and passed on.

If males compete with each other for access to females, males are generally larger and stronger than are females. This is true simply because the larger and stronger males tend to win contests and thus the opportunity to mate with females and pass on their genes. (Given that humans are sexually dimorphic in size and strength, any alien zoologist would conclude that modern Homo sapiens is descended from ancestors in which males competed for access to females in some way. Indeed, according to anthropologists, approximately 80% of human societies have permitted men to take more than one wife.)

Adaptations which allow males to more effectively compete with each other for access to females will also be favored. This is why males are far more likely to have horns, antlers, or other features with which they can compete with each other.

In many species, males are much more brightly-colored than are females. (This is especially true in fishes and birds.) Studies have shown that females consistently prefer to mate with the most brightly-colored males available in these species. The most widely-accepted hypothesis to explain this has to do with the cost to males of producing these bright colors. Males that are underfed or parasitized won’t be able to produce such bright colors, so the more brightly-colored the male, the healthier he is, and so the more suitable he is as a mate. (In humans, people of both sexes generally rate “clear skin” as a very desirable trait in a potential mate. Clear skin in humans is generally a good indication that a person is healthy and not suffering from skin parasites.)

Some traits are apparently attractive to the opposite sex precisely because they are debilitating. This seemingly counterintuitive notion is known as the “handicap principle,” and is used to explain such features as the large tail of the male peacock. The basic idea is this: a male peacock’s tail is so large that it’s actually a handicap, because it impairs a male’s ability to fly. If a male is able to feed himself and avoid predators and somehow survive to adulthood despite this handicap, this is proof that he’s strong, alert, and healthy — and therefore a good mate. Sure enough, when researchers artificially lengthened the tails of widowbirds (a species in which robin-sized males have tails several feet long), females greatly preferred these “well-endowed” males, even when their tails were lengthened to such a degree that the males could barely fly. Similarly, when researchers trimmed the tails of males that had been very successful at attracting females, females subsequently refused these “emasculated” males’ advances.

Males may compete with each other in more subtle ways. It has been shown that female bullfrogs, for instance can very accurately judge the size of a male simply by listening to his calls. Female mockingbirds prefer males with larger song repertoires — the more different songs he can sing, the more attractive he is to females.

Body symmetry is often an important feature in mate choice. And so males often have exaggerated features which display how symmetrical their bodies are — think of the long, forked tails of swallows, for instance. Unhealthy animals tend to have less symmetrical features than healthier animals, and animals are often astonishingly good at detecting even very small deviations from perfect body symmetry. (In humans, it has been demonstrated that people of both sexes consistently find people with more symmetrical faces to be more attractive than those with less-symmetrical features.)

Reverse sexual dimorphism occurs in some species. Usually, this occurs when males somehow contribute more to the raising of offspring than females do, and so females compete for access to males. In many species of horsefishes, for instance, females compete for males and are typically larger.

Reverse sexual dimorphism may also occur as a way to reduce competition between males and females for food. For instance, in most birds of prey, males are smaller than females and tend to go after smaller prey. A female’s size influences how many eggs she can produce — larger females can generally produce more offspring — but larger males, while usually stronger, don’t necessarily produce more sperm. Even if they do, it doesn’t matter, since any healthy male can produce all the sperm he needs and then some. In other words, a general rule is that in species where males don’t engage in physical contests for access to females, sexual dimorphism in size is either not present at all or the females are larger than males.

Several dinosaurs appear to have been sexually dimorphic. Many hadrosaurs, for instance, were apparently sexually dimorphic; some individuals (presumably the males) had larger and more elaborate head crests than others (presumably the females). The nasal cavities extended into the crests, and so males probably used the head crests to amplify their calls, perhaps to attract mates and/or intimidate rivals.

http://www.freethought-forum.com/images/jurassic/duckheads.gif

Tyrannosaurus rex, interestingly, may have shown reverse sexual dimorphism. In reptiles, blood vessels entering into the tail travel through what’s known as the hemal arch on the underside of the tail (caudal) vertebrae; because females must pass eggs or live young through their pelvic openings, the first one or two hemal arches tend to be turned somewhat backward in females. So, if a dinosaur’s hips and the first few caudal vertebrae are well-preserved, we can make a good guess at its sex. Interestingly, the largest-known Tyrannosaurus rex specimens appear to be females.

[break=Could We Clone Dinosaurs?]
[B]Could We Clone Dinosaurs as in Jurassic Park?:

The short answer is, “no.”

According to Jurassic Park, they got dinosaur DNA by extracting it from mosquitoes. Now it’s true that mosquitoes lived during the Mesozoic, and presumably they sucked blood from dinosaurs. Female mosquitoes suck blood because they need it to produce eggs, and this was doubtless true during the Mesozoic, as it is now. Occasionally, a mosquito will get trapped in tree sap that eventually fossilizes and becomes amber, thus preserving the unfortunate insect. But to my knowledge, only one mosquito has so far been found in amber that dates back to the Mesozoic Era.

Just because the mosquito died when it got trapped wouldn’t cause the digestive enzymes in its gut to stop working. So, even if a mosquito took a drink of dinosaur blood then immediately got itself trapped in sap that ultimately turned into amber, the DNA in the mosquito’s gut would be seriously degraded by the mosquito’s digestive enzymes.

On top of that, DNA isn’t all that stable, and tends to break down over time even under the best of circumstances. There have been some very controversial reports of scientists extracting fragments of DNA from insects preserved in amber, but no one claims to have been able to recover anything even remotely resembling a complete DNA strand in this way. It would be astonishing to recover even one percent of a 100-million-year-old DNA strand from a mosquito’s gut (assuming anyone even found a preserved mosquito that old), much less the 99 percent or so that the movie implies they were able to recover. Suffice it to say that for practical purposes, it is — and almost certainly forever will be — impossible to recover anything remotely approaching a complete DNA sequence from 100-million-year-old samples.

Even if you somehow did manage to get 99% of a dinosaur’s DNA, that missing 1% is important! After all, there are something like 3 billion base codes in a typical vertebrate’s genome. That’s 30 million substitutions you would need to make in order to complete the animal’s genome — in 430000000 possible combinations! Keep in mind that the vast majority of combinations you’d come up with would surely result not in a dinosaur with some interesting behavioral quirks, but something that’s dead. Any one of those substitutions could cause a lethal mutation, and you’re making 30,000,000 substitutions! The odds of you winding up with a living animal are remote, to say the least.

And getting the DNA would actually be the easy part! Despite what most people seem to think, DNA is not a “blueprint” for a living thing. A much more accurate analogy would be to say that DNA is a “recipe” for a living organism. It specifies the broad outlines of an organism’s development, but not every little detail. DNA doesn’t contain nearly enough information to exactly specify the layout of an animal’s nervous or circulatory systems, for instance. It’s more like a set of instructions along the lines of “put some nerves in this general area” and so forth. That’s why even identical twins don’t have the same fingerprints or circulatory layouts, even though they have identical DNA.

By itself, the DNA would be quite useless. DNA works because enzymes present in the cells activate specific sections of DNA at the proper times and in the proper sequences. In other words, even if you somehow got a complete DNA sequence from a dinosaur, it would be utterly useless unless you also had a dinosaur egg to put it into, complete with all the proper enzymes. Good luck finding one!

It’s highly unlikely that a single piece of amber exists anywhere on the planet with a mosquito preserved inside so perfectly that it would be possible to extract a dinosaur’s complete DNA makeup from the blood in said mosquito’s gut. Even if there is, you’d still need an intact egg from that species of dinosaur to put it into. So, I think it’s safe to say that no one will ever clone a dinosaur.

Having said that, there’s no particular reason to expect that we won’t eventually know enough about genetics and developmental biology that we’ll be able to recreate dinosaurs. But those re-created “dinosaurs” would only represent our best guesses about how real dinosaurs looked and behaved. Who knows how accurate those guesses would be?


[B]The Dinosaurs of Jurassic Park:

Ankylosaurus:
We saw some ankylosaurs in Jurassic Park III. These heavily-armored dinosaurs lived during the Cretaceous. We saw one strolling unconcernedly through the forest soon after the raptors killed Udesky, which struck me as about right, because heavily-armored ankylosaurs armed with lethal clubs on their tails probably had little to worry about as far as being attacked by predators.

Ankylosaurs had sharp-edged beaks that would have been good for cropping vegetation, but their teeth were surprisingly small, and so wouldn’t have been able to grind food very thoroughly. On the other hand, their bodies were exceptionally wide. It’s generally thought that this meant they had very long and complex digestive systems, allowing plenty of storage space for vegetable matter as it was digested.

Apatosaurus(?):
In The Lost World we saw what appeared to be several Apatosaurus in the herd of dinosaurs that was being chased by the hunters in trucks and on motorcycles. One guy on a motorcycle dashed through the legs of what appeared to be an Apatosaurus. (The movie never said what those dinosaurs were, but they looked like Apatosaurus to me.) Apatosaurs were sauropods that lived during the Jurassic, but they weren’t nearly so heavily-built as were brachiosaurs. Apatosaurs had extremely long necks with relatively tiny heads, and long, flexible, whip-like tails. They may have used the long tails to swat at attacking predators.

Apatosaurs were clearly plant-eaters, but instead of flat, grinding teeth, they had pencil-shaped teeth that would have been wholly unsuited for grinding plant matter. Instead, they probably used those teeth to crop vegetation and then gulp it down whole. Apatosaur skeletons often have small rocks in their ribcages, and it’s likely that the animals had muscular gizzards where swallowed rocks were used to grind their food in much the same way that modern ostriches swallow rocks with which they grind food in their gizzards.

Apatosaurs seem to have had tendons running from the vertebrae of their backs to their necks that would have helped to hold the heads above the ground in much the same way that the cables of a suspension bridge hold up the span of the bridge. Paleontologists speculate that apatosaurs could have reared up on their hind legs for brief spans of time to crop leaves from the treetops.

Brachiosaurus:
We saw brachiosaurs in all three Jurassic Park movies. In fact, a Brachiosaurus was the very first dinosaur we got a good look at in Jurassic Park. These animals were enormous sauropods that lived during the Jurassic. They had much shorter and thicker tails than apatosaurs and unlike apatosaurs, brachiosaurs seemed to hold their necks upright. Brachiosaurs and their close relatives were probably the heaviest animals that ever lived on land.

Like apatosaurs, brachiosaurs had teeth that weren’t suited for chewing food, and they probably had gizzards for grinding their food.

Ceratosaurus:
We briefly saw a Ceratosaurus in Jurassic Park III. This was the dinosaur that approached Alan and the Kirbys as they were searching through the Spinosaurus dung for their missing satellite telephone, but retreated after taking a good sniff. Ceratosaurus was a theropod that lived during the Jurassic and was apparently related to the more famous Allosaurus, though more lightly built.

Perhaps the most notable features of ceratosaurs were the horn-like projections on the snout and above the eyes. It’s thought the males used them in head-butting contests, much as modern sheep and goats butt each other with their horns.

Corythosaurus:
We saw some Corythosaurus in Jurassic Park when Alan, Billy, Udesky and the Kirbys ran into a herd of grazing dinosaurs in an effect to escape pursuing raptors. Corythosaurs were hadrosaurs that lived during the Cretaceous. Like other “duck-billed” dinosaurs, they had teeth that were very well adapted for grinding plant matter.

Corythosaurus could be distinguished from other hadrosaurs because the head crest (at least in males) was helmet-shaped. The crest was apparently a sexually-selected feature, as it seems to have been much less prominent in young and female corythosaurs. As such, it’s very likely that the crest (at least in males) was brightly colored.

Dilophosaurus:
We saw Dilophosaurus in the original Jurassic Park. It was the dinosaur that killed Nedry. Dilophosaurs were lightly-built theropods that lived during the early Jurassic. Perhaps their most distinctive feature was the pair of thin crests on the tops of their heads. These crests may have been sexually-selected features, and if so, were probably brightly colored in the males. They were quite thin, and were probably too fragile for use in head-butting. Instead, it’s likely that the crests were brightly-colored and used by males to demonstrate their good health and so their suitability as mating partners.

Because they were so lightly built, many have suggested that dilophosaurs were specialized for hunting smaller prey. Their teeth were well adapted for slicing up meat, however, so they probably weren’t fish-eaters. Because of their light builds and relatively weak jaws, Jurassic Park proposed the intriguing idea that dilophosaurs were venomous and so didn’t have to use their teeth and claws to subdue prey. That’s an interesting idea, but if they were venomous, they’d surely have possessed specialized fangs for delivering that venom, which they did not.

There’s not the slightest hint that dilophosaurs possessed the neck frills we saw in the movie.

Gallimimus:
We saw Gallimimus in the original Jurassic Park and in The Lost World. These were the ostrich-like dinosaurs we saw running together in a flock in the original Jurassic Park as they fled from the Tyrannosaurus rex. Unlike virtually all other theropods, Gallimimus was apparently not a predator.

Gallimimus lived during the Cretaceous. It had a toothless beak, very large eyes, and legs and hips that would have made it a very fast runner. They probably ate plants and perhaps small animals when they could catch them. Obviously, they couldn’t grind vegetation with their teeth, so they probably had gizzards, like modern ostriches.

Pachycephalosaurus:
We saw Pachycephalosaurus in The Lost World. These were the dome-headed dinosaurs that Roland called “Friar Tuck.” Pachycephalosaurs lived during the Cretaceous, and males probably used their thickly-reinforced skulls for head-butting contests.

Like ankylosaurs, they were clearly plant-eaters, but had relatively small and weak teeth that would have been poorly suited for grinding plant matter. Also like ankylosaurs, pachycephalosaurs had quite wide bodies, and it’s thought this was an adaptation for housing long and complex guts for digesting their food.

Parasaurolophus:
We saw Parasaurolophus in all three movies. These were the dinosaurs that Roland called “Elvis” in The Lost World, because of their long, tubular head crests. (As in Corythosaurus, the males’ head crests were probably brightly-colored.) Like Corythosaurus, Parasaurolophus was a Cretaceous Period hadrosaur with teeth that were very well-suited for grinding plant matter.

Procompsognathus:
We saw Procompsognathus in The Lost World and in Jurassic Park III. These were the very small theropods that attacked the little girl in the opening of The Lost World. Procompsognathus was one of the earliest dinosaurs, and lived during the Triassic Period. It’s generally thought that Procompsognathus hunted insects, lizards, and small mammals.

Pteranodon:
Strictly speaking, pterosaurs were not dinosaurs, but close relatives. We saw Pteranodon in The Lost World and Jurassic Park III. While many pterosaurs were only the size of a modern sparrow, Pteranodon was one of the largest creatures that ever flew, with a wingspan of more than 23 feet (7 meters). Pterosaurs were clearly built for flight, with their enormous wings and their extremely light builds. Even the largest pterosaurs, with wingspans in excess of 30 feet (10 meters) would have weighed less than 50 pounds (23 kilograms). Big pterosaurs like Pteranodon had paper-thin, hollow bones that greatly reduced their weight, but would also have made them incapable of dealing with large, struggling prey. For this reason it’s generally believed that most were fish-eaters or scavengers.

Pteranodon lived during the Cretaceous and was probably a scavenger. Its straight, toothless beak would have been unsuitable for killing or dismembering prey, and it’s highly unlikely that an animal of that size was capable of active, flapping flight. Instead, it was almost certainly specialized for gliding, though it probably could have flapped with enough force to keep itself airborne once it actually got into the air. Pteranodon probably got airborne the same way that modern albatrosses do, by facing into a strong headwind or by jumping from cliffs. Tests with life-sized models have shown that Pteranodon would have been an excellent glider indeed — it would only have to spread its wings and face into a moderate headwind and it would have been lifted right off the ground. This tremendous gliding capacity means that Pteranodon would have been very well suited to cruising the Cretaceous skies in search of carrion. It could have taken advantage of updrafts as modern vulture do in order to travel tremendous distances with almost no expenditure of energy.

Spinosaurus:
Spinosaurus was a very large theropod that lived during the Cretaceous. It was the large, sail-backed predator that menaced our heroes throughout Jurassic Park III. No complete skeleton of a Spinosaurus is known, so there’s an awful lot of speculation involved in exactly how large they got to be, but there are a few things that can be said with reasonable certainty. A full-grown adult was probably 50 feet (15 meters) or even longer, making it somewhat longer even than a Tyrannosaurus rex. On the other hand, spinosaurs appear to have been quite lightly built, so an adult Spinosaurus probably only about 4 tons or so in weight, making it much lighter than a T. Rex.

As best as can be inferred from its fragmentary remains, Spinosaurus was closely related to Baryonyx and Suchomimus, for which we have much more complete fossils. So this allows us to make some reasonable guesses about how Spinosaurus was built and how it lived. Baryonyx and Suchomimus were both quite lightly-built theropods that seem to have been specialized for eating fish. (One specimen of Baryonyx was discovered with partially-digested fish scales where its stomach had been.) Both Baryonyx and Suchomimus had very crocodile-like skulls and teeth (in fact, “Suchomimus” means “crocodile mimic”), as did Spinosaurus.

The long but shallow jaws of Spinosaurus would have been good for delivering quick bites, but they would not have been very powerful bites. The best guess is that Spinosaurus and its relatives hunted fish somewhat like modern grizzly bears do, by wading into shallow water and snatching fish in their jaws or with their long, clawed forelimbs. Certainly, there’s no reason to think that spinosaurs didn’t hunt on land too, but they almost certainly went after much smaller prey than did tyrannosaurs and other large theropods.

Surely the most distinctive feature of Spinosaurus was the sail on its back. This was 6 feet (2 meters) or so high. Suchomimus also had a dorsal sail, but it was much less pronounced — only about 2 feet high.

What was the function of this sail? Possibly, it was used in thermoregulation, much as the dorsal sail of Dimetrodon had been. Some have objected to this hypothesis because if dinosaurs were warm-blooded, they wouldn’t need to use sunlight to warm their bodies. This doesn’t strike me as a very good objection, however, because plenty of modern warm-blooded birds and mammals bask in sunlight to gain solar energy — why waste metabolic energy generating body heat when you can get it for free from the sun?

Another possibility is that the sail was a signaling device of some sort. It may have been used to attract mates, for instance. If the skin covering the sail was thin enough, when blood was flushed into the sail, it would turn bright red. In this way, a spinosaur could signal its sexual receptivity to a potential mate. In many primate species, females’ buttocks flush bright red when they’re sexually receptive — a spinosaur’s sail may have served a similar function.

There’s some indication that the spines which supported the sail were movable. If that was the case, this suggests the spine was a signaling device of another sort. Maybe the spine could be erected to make the spinosaur look bigger, and so it could be used to intimidate potential rivals, or even potential predators. (Spinosaurus lived millions of years before Tyrannosaurus rex and on another continent, but there were several species of large allosaurs which lived at the same time and might possibly have attacked lightly-built spinosaurs from time to time.) So, the sail of a Spinosaurus may have worked in much the same way as a cat or a dog erecting the fur on its back (and a cat arching its back) when threatened, thus making itself look bigger and more formidable.

All of this assumes that the long extensions on Spinosaurus’ back supported a sail, as depicted in Jurassic Park III, but that’s by no means certain. The dorsal spines on the early synapsid Dimetrodon were quite thin, and so almost certainly supported a thin sail, but the dorsal spines of a Spinosaurus were much thicker, so perhaps they didn’t support a sail at all. Modern bison have similar thick spines on some of their vertebrae that provide attachment points for the large “hump” over their shoulders where muscles that help support the large head attach. Perhaps spinosaurs didn’t have sails at all, but instead had humps to which attached muscles to help support the head. This actually makes a lot of sense, because spinosaurs had fairly long but surprisingly thin necks.

Stegosaurus:
Stegosaurus was an armored dinosaur that lived during the Jurassic. We saw stegosaurs in The Lost World and in Jurassic Park III. Probably their most distinctive characteristics were the large plates on their backs and the long spines near the ends of their tails.

What, exactly, were the functions of those dorsal plates is still an unsettled question. When stegosaurs were first discovered, it was generally assumed that the plates were protective in nature, but they were too thin to resist the bite of large allosaurs, and they would have provided no protection to a stegosaur’s most vulnerable region, its flanks.

Other researchers speculated that the plates were for thermoregulation. This seems like a reasonable hypothesis, because the plates had lots of channels in them that might have supported blood vessels. Examination of the interiors of stegosaur plates showed that most of those channels have blind ending though, and so would not have returned blood pumped into them back to the body. This makes it highly unlikely that the plates had any kind of thermoregulatory function.

There’s no evidence that stegosaurs were sexually dimorphic, so the plates were probably not used for sexual displays of any sort.

The most likely explanation for the dorsal plates of stegosaurs is that they were species-recognition signals. There were numerous stegosaur species, and they differed in the shapes and arrangements of their dorsal plates and spines. This suggests that the plates and spines functioned like the variously-shaped horns of modern antelopes — as a means of allowing animals in mixed-species herds to quickly and easily locate members of their own species.

Triceratops:
Triceratops was a horned dinosaur that lived during the Cretaceous. We saw Triceratops in Jurassic Park and in The Lost World. Triceratops, like other ceratopians, had parrot-like beaks that were apparently for cropping vegetable matter, and teeth that were very well suited for grinding it up. The large head shield of a Triceratops was not thick-enough to resist the bite of a large predator like Tyrannosaurus rex, and so was probably not protective in nature, but rather for sexual display. Similarly, while the long horns would have been effective defensive weapons, their primary purpose was probably to allow males to compete with each other for access to females.


Tyrannosaurus rex:
This very large Cretaceous theropod is arguably the most famous dinosaur that ever lived. T. Rex appeared in all three Jurassic Park movies.

One of the principle advisors for the Jurassic Park movies was Jack Horner, who is probably best-known for his work with hadrosaurs such as Maiasaura. He’s also known for his insistence that tyrannosaurs weren’t active predators, but instead were basically “big walking vultures.”

Of course, portraying Tyrannosaurus rex as a scavenger rather than an active predator would have made Jurassic Park rather less exciting, and that’s not how the movie-makers did it. Even so, it’s an issue that’s worth considering. Was T. rex primarily a scavenger as Horner thinks, or an active predator, as the movie portrays? Let’s look at Horner’ s evidence and argument.

When you look at the skeleton of Tyrannosaurus rex, especially the skull, one thing that’s very clear is that this was an exceptionally powerfully-built animal. Where muscles attach to bones they leave scars, and where bones must deal with great amounts of stress they’re thicker. The size of the muscle-attachment scars on bones tells you how strong were the muscles that attached to those bones, and the thickness of those bones tells you how much stress they could withstand. T. rex’s bones indicate that it was an exceptionally powerful and robust animal, even considering its great size — one with powerful muscles and bones adapted for dealing with great amounts of stress. Horner argues that the great size and power were adaptations to allow it to chase other carnivores away from carcasses, rather than to overpower struggling prey.

According to Horner, Tyrannosaurus rex was adapted to walk great distances in search of carcasses for scavenging, not to chase down prey. Robert Bakker has conjured fantasies of tyrannosaurs running at 45 miles per hour or even faster, but they’re just that — fantasies. Biomechanical studies have shown pretty conclusively that an adult tyrannosaur couldn’t possibly have run that fast. First of all, its legs were built more like those of a walker than a runner, according to Horner. If it had been specialized for running, you’d expect the legs to be longer and more slender, according to Horner. Besides, if a 6-ton, 12-foot-tall tyrannosaur running at 40 m.p.h. were to trip and fall, it would certainly be killed or at least crippled by the fall. (As an interesting aside, some fossils of juvenile tyrannosaurs have been found, and they appear to have been very definitely built for running. A juvenile Tyrannosaurus rex was probably one of the fastest dinosaurs that ever lived! As they got older, though, they apparently got slower.)

According to Horner, the eyes of Tyrannosaurus rex were too small for it to have seen well. In addition, though it’s true that tyrannosaurs had forward-facing eyes which gave it binocular vision (allowing it to judge distance accurately) and that this trait is an important one for a predator but not for a scavenger, Horner argues that binocular vision in tyrannosaurs was simply an “evolutionary holdover” — a trait that it inherited from its predatory ancestors.

The small forelimbs of a Tyrannosaurus rex, according to Horner, would have been useless for grasping prey, and they therefore provide evidence that tyrannosaurs were scavengers, not active predators.

Scans of the interiors of tyrannosaur skulls show that their brains had very large olfactory lobes. This suggests they had excellent senses of smell. Horner argues that this adaptation was so that they could locate rotting carcasses by smell. Below is a drawing of a Tyrannosaurus rex’s brain, made from a CT scan of a T. rex skull. The two very large projections at the top are the olfactory lobes. More than half of a T. rex’s brain seems to have been devoted to processing olfactory information. This is certainly good evidence that the animals had keen senses of smell.

http://www.freethought-forum.com/images/jurassic/brain.jpg

Finally, Horner argues that there’s no direct evidence tyrannosaurs ever attacked live animals.

So, how well do Horner’s arguments hold up? Well, though he does have some legitimate points there are some serious problems, I think.

Great size and power in Tyrannosaurus rex could certainly have been adaptations for chasing other carnivores away from their kills, but it seems just as plausible that the obvious interpretation is true — that they were adaptations for overpowering and subduing prey. Still, tyrannosaurs had to deal with large and dangerous animals like Triceratops; if tyrannosaurs chased down animals like Triceratops and tried to wrestle them into submission, they’d be very likely to receive serious — even fatal — wounds in the process. So, the romantic image of tyrannosaurs chasing down animals like Triceratops and subduing them by brute force is probably a fantasy.

Horner’s second point is a good one. Tyrannosaurs were almost certainly incapable of speeds much in excess of 20 mph, especially for prolonged periods. On the other hand, they only needed to be as fast as their prey. Biomechanical analyses of ceratopians and hadrosaurs that lived at the same time as Tyrannosaurus rex indicate that they probably weren’t any faster than was T. rex. In fact, T. rex’s legs were proportionately longer and more slender than those of most hadrosaurs. So tyrannosaurs were evidently as fast as they needed to be in order to catch prey. Still, tyrannosaurs surely weren’t capable of running at high speeds for great distances.

[There's a joke that's popular among biologists which illustrates this general point — predators only need to be slightly faster than their prey; there's no reason for them to be any faster. Two guys were walking through the woods when suddenly they saw a grizzly bear about 100 yards away coming toward them. The first guy started to run in his heavy hiking boots. The second guy paused to pull off his boots, pull a pair of running shoes out of his backpack, and put them on. The first guy yelled to him, "What are you doing? Those shoes won't give you the speed to outrun a grizzly!" "I don't have to outrun the grizzly," his companion replied.]

Eyes only have to be so big. Generally speaking, the larger an animal’s eye is, the more light the eye can gather, allowing for more acute vision (especially at night). Past a certain point, though, there’s little to be gained by making the eyes any larger. So, while T. rex did have small eyes relative to its size, it did not have smaller eyes than other animals of the same great size. (Elephants and whales, too, have relatively small eyes, but this doesn’t mean they have poor eyesight.) So, T. rex’s relatively small eyes don’t imply that it had poor vision.

The binocular vision of tyrannosaurs wasn’t just some “evolutionary leftover.” The eye sockets of tyrannosaurs were rotated forward and the animals’ snouts were narrowed in just such a way as to ensure that the snouts didn’t block forward vision. In other words, tyrannosaurs had specific traits which were apparently adaptations to improve their binocular vision. Tyrannosaurs, in fact, may have had the best binocular vision of any meat-eating dinosaurs, so it hardly seems like an inconsequential evolutionary holdover.

It’s true that tyrannosaurs’ forelimbs were quite small, and probably useless for dealing with prey under most circumstances. This doesn’t imply that tyrannosaurs were incapable of subduing resisting prey, however. After all, they had exceptionally powerful jaws and neck muscles with which they could have subdued prey. Sharks, wolves, snakes, and plenty of other active predators manage to subdue resisting prey without using their forelimbs (if any), so lack of large forelimbs is hardly convincing evidence that the animal in question wasn’t an active predator.

While tyrannosaurs evidently had excellent senses of smell, the fact that they did doesn’t imply they were scavengers. If having an excellent sense of smell implies that you aren’t an active predator, then wolves aren’t active predators. Predators can and do use their senses of smell to track prey.

Finally, there’s the issue of tyrannosaur attacks on living animals. In fact, there is direct evidence that tyrannosaurs attacked live prey. Hadrosaur fossils have been found with partially-healed injuries on the bones of their tails — injuries that could only have been inflicted by one known species, Tyrannosaurus rex. Apparently, these hadrosaurs were chased and attacked by tyrannosaurs, but managed to escape. Similarly, at least one Triceratops skull has been found with healed injuries that could only have been inflicted by a T. rex. So, at least occasionally, tyrannosaurs must have attacked even large and dangerous animals like Triceratops.

Numerous fossils of herbivorous dinosaurs have been found that bear tooth marks that appear to have been inflicted by tyrannosaurs. If tyrannosaurs were scavengers, it wouldn’t matter how dangerous its prey was while alive, but if tyrannosaurs were active predators, you’d expect them to concentrate their efforts primarily on the least-dangerous prey. This is precisely what we see. Hadrosaurs had no obvious defenses, and hadrosaur bones often bear tooth-marks apparently made by feeding tyrannosaurs. Ceratopians were larger and had dangerous horns; their fossils show tyrannosaur tooth marks much less often than do hadrosaur fossils. Ankylosaurs were large, heavily armored, and frequently armed with dangerous spikes and bony clubs on their tails that could have broken a tyrannosaur’s legs with a single blow. To date, no anklyosaur fossils have been found with tyrannosaur-inflicted tooth marks on them.

So, I’d say the evidence clearly indicates that tyrannosaurs did indeed attack living prey. Of course, few predators will pass up a chance to scavenge — why on earth would they pass up a free meal? So, tyrannosaurs surely scavenged when the opportunity arose.

But I’ve already said that tyrannosaurs were probably incapable of prolonged chases, and trying to overpower dangerous opponents like big ceratopians would have been a very bad hunting strategy. So, how did tyrannosaurs hunt?

If you look at the teeth of most predatory dinosaurs, like Velociraptor or Allosaurus, you’ll note that they had blade-like teeth that appear to have been well-adapted to deliver shallow, slashing bites. Tyrannosaurs, on the other hand, had exceptionally robust “cookie-cutter” teeth that appear to have been adapted for delivering deep, gouging bites and that were capable of crunching right through bone. An adult Tyrannosaurus rex, with its unique tooth arrangement and its exceptionally powerful jaws, could have removed somewhere between 350 and 500 pounds of flesh from a victim in a single bite. This would probably have been a mortal wound even to a 3-ton Triceratops.

William Abler tested the teeth of Tyrannosaurus rex by using actual tyrannosaur teeth to cut meat, and discovered that the teeth have serrations on them that would have trapped bits of tendon and flesh as the tyrannosaur bit into its prey. So, when feeding, a T. rex would have gotten flesh trapped on and between its teeth. Try to imagine a tyrannosaur coming at you: ragged strips of rotting flesh would be hanging from its teeth, and if you didn’t die right away of a heart attack, its stinking breath alone might have been sufficient to do you in.

So what? Well, modern-day komodo dragons have a similar arrangement. Bits of rotting flesh get trapped between the teeth of komodo dragons, which means their mouths are simply full of septic bacteria. Consequently, few animals can survive even one bite from a komodo dragon, because even if the victim escapes, it will almost certainly die of infection within a day or two. In other words, it seems that tyrannosaurs were effectively venomous!

I would like to propose that tyrannosaurs hunted much like modern-day rattlesnakes do. A rattlesnake strikes its victim from ambush, delivering a lethal amount of venom in one bite, and then immediately retreats. In this way, it doesn’t have to risk injury from its prey fighting back. The snake then tracks its mortally-wounded prey from a safe distance until it dies.

I suspect tyrannosaurs attempted to get close to potential victims in order to launch surprise attacks, rather than running down victims like overgrown wolves. Perhaps they used their great strength to overpower small and unthreatening prey like hadrosaurs when they could catch them. For larger and better-armed prey like ceratopians, I suspect that tyrannosaurs tried to approach closely then dash in and take a single, large bite at the victim’s flank. Then the tyrannosaur would quickly retreat to avoid counterattack — and wait. This is where the good sense of smell comes in: with its excellent sense of smell, the tyrannosaur could easily track the wounded animal from a safe distance while waiting for it to collapse from blood loss or infection.

One fossil site in Montana contains the remains of several Tyrannosaurus rex individuals, providing intriguing evidence that they may have traveled in packs. If tyrannosaurs were pack hunters, then it’s easy to see how they could have gone after dangerous animals like Triceratops; one or two tyrannosaurs could get in front of the victim to distract it, while others attempted to attack from the sides. Once a mortal wound had been delivered, the tyrannosaurs could then simply retreat and wait for the victim to succumb.

[BREAK=Velociraptor]
Velociraptor:
Velociraptor was a small theropod that lived during the Cretaceous. Like all dromaeosaurs, Velociraptor was clearly built for an active hunting lifestyle, and was well adapted for running and jumping. In addition, Velociraptor and other “sickle claws” were almost certainly pack hunters that used the enlarged, retractable claws on their hindlimbs to slash at and disembowel prey. For dinosaurs, dromaeosaurs had rather large brains (but nowhere near as large as the movie implies), and so were probably pretty smart, comparatively speaking.

The dromaeosaurs that menaced our heroes in all three Jurassic Park movies were constantly referred to as “Velociraptors.” That’s not quite accurate, though. Those critters were much larger than real Velociraptors, and were from the wrong part of the world. Remember how we were discussing “lumpers” and “splitters” earlier? Calling those critters “Velociraptors” is a pretty blatant (and excessive, in my opinion) example of lumping.

Only one species is currently known from the genus Velociraptor, namely V. mongoliensis. As its name implies, it lived in what’s today China and Mongolia, not North America. So the raptor fossils Alan and Ellie were excavating near the beginning of Jurassic Park were certainly not fossils of Velociraptor mongoliensis. Besides, V. mongoliensis was rather small — only about 6 feet (2 meters) long from snout to tip of tail and perhaps 40 pounds (18 kilograms) or so in weight. The closest match to the “Velociraptors” of Jurassic Park would be Deinonychus antirrhopus, which was about the size of the movie “raptors” and did indeed live in what’s today Montana. So, I’d say that the raptors of Jurassic Park weren’t Velociraptor at all, but Deinonychus.

Another reason to think that those were Deinonychus instead of Velociraptor is the shape of the animals’ skulls. Velociraptor had a relatively long and narrow snout, as can be seen from this model.

http://www.freethought-forum.com/images/jurassic/velociraptor.jpg

Deinonychus had a relatively shorter, more rounded, and much more heavily-built skull than Velociraptor, as you can see from this model. This skull shape much more closely resembles the skulls of the “Velociraptors” we saw in the Jurassic Park movies than does the skull shape of Velociraptor mongoliensis.

http://www.freethought-forum.com/images/jurassic/deinonychus.jpg

So why do they keep calling those raptors “Velociraptors”? In the novel version of Jurassic Park, Michael Crichton claimed that paleontologists now know that Deinonychus “properly” belongs to the same genus as Velociraptor, and so Deinonychus antirrhopus is “properly” known as Velociraptor antirrhopus. If I recall correctly, one character even uses this “fact” to demonstrate his superior knowledge of dinosaur taxonomy.

Rubbish.

To my knowledge, only one prominent paleontologist, Gregory Paul, has suggested that Velociraptor and Deinonychus were sufficiently closely-related that they should be reclassified into the same genus. (Since the genus Velociraptor was named before the genus Deinonychus, if they were to be combined, the older name — Velociraptor — would be the one used.) The overwhelming consensus of the paleontology community is that Paul is wrong. Velociraptor and Deinonychus were quite closely-related, to be sure, but the numerous morphological differences between them are sufficient to convince the general paleontology community that they should be considered separate genera.

I suspect that by claiming Deinonychus should “properly” be referred to as “Velociraptor,” Crichton was trying to show that his was “cutting edge” knowledge of dinosaur taxonomy. Unfortunately, he didn’t do his homework properly in this case, methinks. (Or maybe it’s that “Oh God, it’s a pack of raptors!” sounds more frightening than “Look out, it’s a pack of Deinonychus!”)

Anyway, now that we know a bit about the dinosaurs, let’s look at the Jurassic Park movies themselves, shall we? How much sense do they make?

[BREAK=Jurassic Park]
[B]Jurassic Park

In the opening scene, we saw that a “Velociraptor” was being held in a large crate for transport to her new living quarters. An adult “Velociraptor” would have weighed less than 200 pounds (91 kilograms). It took 6 men to move the crate into place, and then Muldoon claimed that it was locked into position. So how is it that as soon as the gate was opened, that one raptor was able to push the crate away from the gate and grab an unfortunate worker? Somehow, that doesn’t seem likely.

The next scene was set in the Dominican Republic, where they were mining amber, presumably so that they could get dinosaur DNA from mosquitoes trapped therein. The problem with this is that the Dominican Republic amber deposits are only about 20 million years old — more than 40 million years too young to yield any dinosaur DNA.

We next traveled to Montana, to Alan Grant and Ellie Sattler’s dig site. Some guys were using a nifty device to create sound waves with which to locate fossils underground. There has actually been some experimentation with such devices, but I don’t think they can provide anywhere near the resolution seen in the movie. Also, it kinda bugged me that the operator called his technique “radar.” It was actually a form of sonar.

Alan was going on about how raptors “turned into birds.” Huh? Even if he was speaking metaphorically, that statement doesn’t really make much sense. Raptors lived tens of millions of years after the first birds evolved, so birds most-certainly did not evolve from raptors! While it is true that dromaeosaurs are widely thought to be closely related to the dinosaurs from which birds evolved, they were not ancestral to birds, as Alan was suggesting.

While trying to scare an annoying kid, Alan claimed that Tyrannosaurus rex’s vision was “movement-based.” How could he possibly have known that? It’s not very likely in any event, and even if it were true, it’s not like vertebrate eyes fossilize. So how did Grant know that tyrannosaurs couldn’t see anything that wasn’t moving? In the book, Crichton claimed that the dinosaurs’ movement-based vision was a side effect of the fact that Jurassic Park technicians used frog DNA to fill the gaps in recovered dinosaur DNA. That at least makes some sense, since frogs do have movement-based vision. Their vision is highly specialized to detect moving objects, and studies have shown that if there is nothing moving within a frog’s field of vision, there is little or no activity in the visual centers of the frog’s brain. (There are cells in a frog’s retina that seem to be specialized for the particular task of noting the presence of small moving objects within the frog’s visual field. They’re sometimes called “bug detectors.”)

Hammond lured Alan and Ellie to his island by offering to fund their work for three years. I liked that scene. Paleontology is a notoriously under-funded field, so I can easily imagine that a couple of paleontologists would practically sell their souls for three years of guaranteed funding.

The character of Ian Malcolm bugged me. He went on and on (and on and on and on . . .) about how he was a “chaotician” and about the unpredictability of complex systems, but his claims didn’t ring true. He kept claiming that Jurassic Park was “destined” to fail — well, if he believed it was destined to fail, then he was a determinist, not a believer in the inherent unpredictability of such a system. He should make up his mind. (Of course, chaotic systems are not completely unpredictable; he could have said that all possible outcomes would ultimately end in the park’s failure, but that they couldn’t predict how or when it would fail. That would be untrue, but at least it’d be consistent with his repeatedly-stated beliefs.)

Once they reached the island, Ellie snatched a leaf from a plant and claimed that “This species of Veriforman’s been extinct since the Cretaceous.” Oddly, I can’t find the taxon “Veriforman” or any variant of it in my plant systematics texts, but perhaps I missed it. Anyway. Since the Jurassic Park technicians cloned dinosaurs from blood taken from fossilized mosquitoes, are we expected to believe they cloned some plants in a similar manner? It’s actually not an outrageous idea. Female mosquitoes suck blood, but in most mosquito species, males suck plant juices. So, if Jurassic Park technicians could get dinosaur DNA from female mosquitoes, it’s not at all impossible that they could get plant DNA from male mosquitoes.

When Ellie and Alan first saw a Brachiosaurus, Alan asked how long its neck was. This was a good question. To see why, let’s consider vertebrate hearts.

Fishes have hearts with only two chambers; blood enters the heart into a single atrium and is pumped out through a single ventricle. Blood exiting the heart is pumped first to the gills, where it picks up oxygen, then to the body tissues, where it releases the oxygen. By the time the blood has reached the body tissues, however, the pressure is quite low, and so oxygen is not delivered to body tissues very quickly or efficiently. This is one reason why fishes cannot sustain the high metabolic rates that mammals and birds can.

In amphibians and most reptiles, the heart has three chambers, two atria and a single ventricle. These animals have much more efficient delivery of oxygen to body tissues than do fishes. Nonetheless, there is partial mixing of oxygenated blood from the lungs with deoxygenated blood from the body in the ventricle.

Crocodilians, birds and mammals have four-chambered hearts with two atria and two ventricles. This allows them to generate high blood pressures and to keep oxygenated blood and deoxygenated blood completely separate.

Animals with four-chambered hearts have double circulations — that is, they effectively have two separate circulatory systems. In mammals, the right side of the heart pumps blood to and from the lungs under fairly low pressure. This is the pulmonary circulation. (If the pressure in the pulmonary circulation were very high, the delicate vessels inside the lungs would rupture.) Oxygenated blood returning from the lungs enters the left side of the heart and is pumped to the rest of the body under high pressure by the systemic circulation. Because the pulmonary and systemic circulations are kept completely separate, there is no mixing of oxygenated and deoxygenated blood. This means that oxygen can be efficiently delivered to body tissues, allowing high metabolic rates. Because the two circulations are completely separate, the systemic circulation can generate high pressure to efficiently deliver oxygen to body tissues while the pulmonary circulation has much lower pressure to avoid damaging the lungs.

Animals with three-chambered hearts cannot generate high blood pressure for fast and efficient delivery of oxygen to body tissues, because they have only one ventricle pumping blood out of the heart. Even if we ignore the mixing of oxygenated and deoxygenated blood in the single ventricle, if the pressure was high-enough for fast delivery of oxygen to body tissues, it would be high-enough to essentially destroy the lungs.

So Alan’s question about the Brachiosaurus’ neck was a good one because the animal was clearly holding its head upward. An animal that large might have been able to pump blood to its head with a three-chambered heart if it kept its neck parallel to the ground at all times, but only a four-chambered heart could possibly generate enough pressure to pump blood 30 feet upward without destroying the animal’s lungs in the process. So, the fact that the brachiosaur was holding its head 30 feet above its body was proof that it had a four-chambered heart. If dinosaurs had four-chambered hearts, they would potentially be capable of delivering oxygen to body tissues with sufficient speed and efficiency to support fast mammalian-style metabolisms.

So, I quite liked Alan’s question. On the other hand, I wish they hadn’t then shown the brachiosaur rearing up on its hindlimbs. An adult Brachiosaurus would have weighed well over 50 tons, and maybe more than 80 tons. It’s doubtful such an animal could have reared up onto its hind legs at all, and even less likely that it could have then dropped to all fours as it did in the movie without the bones of its forelimbs shattering as it hit. (Smaller and more lightly-built sauropods like Apatosaurus might have been capable of rearing up onto their hindlimbs, but probably not adult Brachiosaurus.)


Hammond claimed they clocked their T. rex at 32 miles per hour. Not likely.

When Ellie and Alan looked out over the landscape at the pond, there were several brachiosaurs in the water, and a number of Parasaurolophus at the water’s edge. Since the crests of hadrosaurs like Parasaurolophus appear to have been a sexually dimorphic trait, you’d expect those crests to have been much more developed in males than in females. Since it was claimed that all the park’s animals were females, it seems odd that those Parasaurolophus had such well-developed crests, therefore.

Doctor Wu claimed that a population composed entirely of female animals couldn’t breed. Not only is it true that in many vertebrate species (particularly fishes), individuals can change from females to males under the appropriate circumstances (or vice versa), but there are species in which females can and do reproduce parthenogenically. For instance, there are several species of lizards in the genus Cnemidophorus whose populations apparently consist entirely of females. Granted, it would be unlikely that any particular species of dinosaur could switch sexes or reproduce through parthenogenesis, even if you gave it some frog DNA, but it’s hardly an impossibility. It’s surprising that Dr. Wu didn’t know this. Dr. Grant certainly did know this, so it’s surprising that he didn’t point it out sooner.

They made a big point about how the baby raptor that hatched out while they were in the lab was homeothermic. If that were the case, it should have had feathers or some other form of insulative covering. Except in a very warm environment, an endotherm that small couldn’t have maintained a high body temperature without some form of insulation.

Muldoon claimed that raptors were capable of “cheetah speed.” That hardly seems likely. True, dromaeosaurs were clearly built for speed, but among the reasons cheetahs are so fast is because of their unusually flexible spines allowing them to achieve very long strides with their four limbs. Two-legged raptors couldn’t possibly achieve high speed in the same way. Cheetahs have paid a high price for their speed; they’re much weaker and more fragile than are other predators of the same size, because they’ve sacrificed every bit of “excess” weight for more flexibility and speed. That’s why they go after much smaller prey than do other big cats. Dromaeosaurs weren’t so fragile and weak, by any means. So, while “raptors” were probably pretty fast for an animal their size, it’s hardly likely that they were capable of anything approaching “cheetah speed.”

Malcolm claimed that “Nature selected them [dinosaurs] for extinction.” What an utterly silly thing for him to say. “Nature” isn’t some conscious entity deciding which species live and which species die!

Shortly after Malcolm said this silly thing, Grant said something almost as strange when he claimed that dinosaurs and man have just been “thrown back into the mix together.” Huh? Dinosaurs and humans had never before coexisted, so how could they be thrown back into the mix together?

When Alan, Ellie, Ian, Gennaro and the kids started the park tour, the first exhibit they passed was the Dilophosaurus paddock. The narrator claimed that dilophosaurs were “poisonous.” No. Dilophosaurs may have been venomous, but they surely weren’t poisonous! A “venomous” animal is one that can inject toxic chemicals into a victim through fangs, stingers, or other means. A “poisonous” animal is one whose body tissues contain toxic substances that will sicken or kill another animal that tries to eat it.

The neck frills the movie dilophosaurs sported were clearly modeled after the neck frills of Australian frilled lizards. Frilled lizards erect those neck frills to startle and (hopefully) frighten off potential predators. It makes no sense at all that the dilophosaurs in the movie erected their neck frills just before attacking their victims — why on earth would they try to frighten away potential prey?

Real dilophosaurs were rather larger than the animals shown in the movie. Maybe the ones we saw were supposed to be juveniles?

When Ellie, Alan and company stopped to take a look at the sick Triceratops, there was a very large pile of dung present. Unless Triceratops had the unusual habit of always defecating in the same place, this was much more than that animal could possibly have been responsible for!

An adult Tyrannosaurus rex probably would have weighed somewhere between 5 and 8 tons. This is approximately the weight of a large African elephant. I’ve seen elephants on numerous occasions, but I’ve never seen one that could cause the ground to shake noticeably just by walking! Yet the T. rex in the movie made the ground shake every time it took a step, and from at least 100 yards away, no less! Maybe it was actually leaping up and down like a giant kangaroo just off-screen? (If it were it'd have broken its legs in the process. Six-ton animals do not jump — not more than once, anyway.)

Shortly after the power failed, we saw the T. rex resting its forearm on the fence. How likely was this? If the rex had touched the fence before and been shocked, it wouldn’t be likely to try again, since it had no way to know the power was out. If it hadn’t touched the fence before, how likely is it that this would be the first time it’d choose to do so?

Why wasn’t the Tyrannosaur Paddock surrounded by a moat? Modern zoos have deep and steeply-angled concrete moats surrounding the enclosures for the dangerous animals. This ensures that, even if the fences should fail, the animals won’t be able to escape. You’d certainly think that such moats would be present around the tyrannosaur, dilophosaur, and raptor enclosures!

I don’t care how smart the raptors are supposed to be, let’s see them climb a 50-foot wall that slopes inward and is glazed to be as smooth and hard as glass — and that has 10 feet of water at its base so that the raptors can’t get any leverage to jump. Of course, I’d put an electrified fence on the top of the wall, just to be safe, but if your enclosure were properly designed, it shouldn’t be necessary. If the raptors turned out to be so smart that they started felling trees and trying to use them to scale the wall, I think I’d just shoot them and be done with it.

When the T. rex broke out of its enclosure, Lex broke out a flashlight and started waving it around aimlessly for some strange reason. Naturally, this attracted the tyrannosaur’s attention. What on earth would have possessed Lex to do such an incredibly stupid thing? With a large and dangerous predator just a few feet away, wouldn’t any sane person have remained quiet and still in the car, waiting for it to go away?

When the tyrannosaur grabbed Gennaro, it shook him violently. I thought that was a nice touch. When predators grab a victim, they typically shake it viciously, which disorients the victim and makes it harder for it to escape or fight back.

After it gobbled up Gennaro, the tyrannosaur walked up to the car where Alan was trying to free Lex and Timmy. Alan and Lex had been moving around right up until the tyrannosaur was literally only one or two steps away, so how come it couldn’t locate them? Even if it (somehow) couldn’t see them, it could surely have heard and smelled them!

When the tyrannosaur started pushing the car around, Alan and Lex were moving around right in front of it — how come the T. rex it didn’t try to grab one or both of them? Heck, at one point Alan climbed up on top of the car while the tyrannosaur was maybe 10 or 15 feet away. You can’t possibly tell me that it didn’t see him!

After the tyrannosaur attack, Tim was stuck in the car and about 20 feet up in a tree. When Alan climbed up and got Tim out of the car, the car began to shift, leading them to fear that it would fall down and crush them. Granted, they were a bit flustered at the time, but wouldn’t any sane person have moved to the side, so as to get out from under the car, rather than climbing straight down?

It doesn’t seem likely that the car would have gone straight down like that anyway, since the front was supported by branches and the rear was not. It seems much more likely that it would have flipped end-over-end instead of going straight down.

When Alan and the kids climbed into another tree to spend the night, they got up close and personal with a Brachiosaurus. That movie brachiosaur had a much bigger head than a real one did!

The Brachiosaurus was clearly depicted as chewing its food in the movie, but brachiosaurs, with their peg-like teeth, were surely incapable of chewing.

When Mister Arnold left the control center to go to the maintenance shed in order to reset the system, Hammond suggested that the rest of them should move to the emergency shelters until he got back. This indicates that he clearly knew they were in danger of attack. Surely, Mr. Arnold was in rather greater danger of attack, since he was going outside, no? So, shouldn’t Muldoon have gotten his gun and accompanied Arnold to the maintenance shed? Or was it that they didn’t like Mr. Arnold and were hoping he’d get killed (preferably after he got the power back on)?

When Alan and the kids were trudging across the plain and they saw a flock of Gallimimus approaching, Alan actually commented that it looked like they were running from a predator. So, wouldn’t it have been a really good idea to immediately seek shelter, before the T. rex appeared?

After the tyrannosaur caught one of the Gallimimus, the rest of the flock stopped running. I thought that was a very nice touch on the movie-makers’ parts. If you’ve ever seen a herd of antelope when they’re being chased by a lion or other such predator, once the predator makes its kill, the rest of the herd generally stops running. After all, the predator has no reason to keep chasing them once it has made its kill, so there’s no need for the prey animals to keep running. Whoever animated that sequence displayed a fairly good knowledge of predator/prey behavior.

[BREAK]
When Mr. Arnold failed to return from the maintenance shed, Ellie volunteered to go get the power back on. Apparently, it finally occurred to Muldoon that it was dangerous out there, and so he volunteered to go along as protection. But you have to wonder what on earth Muldoon was thinking once they got outside!

Soon after they got outside, Muldoon claimed that he and Ellie were being hunted by the raptors. Okay. But he knew raptors were pack hunters and very smart. So how come he stupidly let himself be distracted by the one raptor he could see and completely ignored the fact that there were two other raptors out there? I expected better from him!

So anyway, he had one raptor in his sights when a second raptor appeared right beside him. Now, this would certainly be enough to fluster most people, but Muldoon remained admirably calm. Under the circumstances, he surely knew he couldn’t turn fast-enough to shoot the second raptor before she could get him, so it seems to me that the rational thing to do would have been to go ahead and shoot the first raptor. At the very least, this would have made it more likely that Ellie could accomplish her mission of getting the power back on, so his death would have some meaning. Besides, the noise of the gunshot and the shock of seeing her pack-mate killed might well have disoriented the second raptor long-enough for Muldoon to get a good shot at her. In any event, I wouldn’t expect Muldoon to have behaved as stupidly as he did. Wasn’t this guy supposed to be an expert in such matters?

Alan actually grabbed the electric fence to test it. That was just plain stupid! This was a fence that was supposed to carry enough power to stop animals weighing several tons. Had it been operating, he’d probably have been killed almost instantly. Didn’t Alan know that a powerful electric current will cause spontaneous muscle contraction? If the fence had been powered, chances are good that he wouldn’t have been able to let go after grabbing the wires. Even if the shock hadn’t been instantly fatal, it wouldn’t have taken long for the current to kill him if he’d been unable to let go of the fence! It would have been a lot more sensible for him to touch the fence with the back of his hand in order to test it.

Maybe Alan was too big to get through the gaps in the fence, but it looked to me like those gaps were plenty big-enough for the kids to squeeze through. So why did the kids bother to climb the fence at all, especially since Tim (the one who would have found squeezing through the fence easiest) was so frightened by the prospect of climbing it?

By the way, the purpose of CPR is to keep a person alive long-enough for medical help to arrive with equipment that can re-start the heart. It’s rare that someone’s breathing and heartbeat will spontaneously resume under CPR, so it’s hardly likely that Alan could have gotten Timmy’s heart and lungs re-started after Timmy was electrocuted. After such a shock, Tim’s heart would likely have gone into ventricular fibrillation, and CPR almost certainly would not have gotten his heart back into a normal rhythm. Of course, you’d expect Alan to try to revive Timmy, but it’s highly unlikely that he’d have actually succeeded.

Once they reached the Visitor Center, why did Alan leave the kids? They had trudged halfway across the park with him by this time, so why not let them accompany him for the last 100 feet or so? Besides, they knew there were dangerous animals like raptors running around, so would the kids be inclined to let him leave them unattended? It doesn’t seem likely!

After the raptor attack, Alan, Ellie and the kids retreated to the Control Room. As soon as they got there, a raptor tried to force the door open. Alan and Ellie tried to hold the door closed while Lex tried to reboot the computers. Even if we allow for the fact that they were just a mite distracted, wouldn’t you expect either Alan or Ellie to think of asking Timmy to hand them the gun so that they could deal with the raptor?

Near the very end, Alan, Ellie and the kids were trapped in the Entrance Hall by two raptors. As the raptors approached to finish them off, you could clearly see them curling their tails. Nope. Dromaeosaurs had bony rods in their tails that would have made their tails quite stiff and capable of little if any flexion. (Because of the stiffening rods, a dromaeosaur’s tail would move as a single unit. It’s thought that the purpose of those rods was so that dromaeosaurs could suddenly shift their tails from one side to the other. This would allow the tail to serve as an effective counterweight to the body, thus making it possible for raptors to turn quickly while running. Cheetahs do this while pursuing evading prey, though cheetahs’ tails aren’t so stiff as dromaeosaurs’ were. If a cheetah wants to make a quick right turn while running, for instance, it throws its tail to the left, which tends to push its body to the right, allowing for a quicker and tighter turn.)

Just as one of the raptors jumped at our heroes, the T. rex grabbed it and thus inadvertently saved Alan, Ellie and the kids. Our heroes were clearly surprised by this turn of events, but how could they (or the raptors) possibly have failed to notice the tyrannosaur standing not 20 feet away? Alan and Ellie would have been looking right at the tyrannosaur, as would have one of the raptors, so it’s not like they could have failed to notice it!

Also, why is it that the tyrannosaur had literally caused the ground to shake with every step earlier in the movie, but when it was convenient for our heroes, it was suddenly a master of stealth? (Not only was it quiet as a mouse, but invisible too!)

How did the tyrannosaur get into the Visitor Center? It certainly didn’t appear to have any doors through which a T. rex could have entered!

A final thought on the movie has to do with how much animals of this size would be expected to eat. Since the movie clearly expects us to believe that these dinosaurs had fast, mammalian-style metabolisms, we’ll use this as our starting point.

To calculate the active metabolic rate of an endothermic animal, you use the following formula: M = 140(W)0.75. “M” is the number of kilocalories the animal must burn per day in order to maintain its normal activity levels and “W” is the animal’s weight in kilograms. Because the exponent is less than 1, this tells you that larger animals are more energy-efficient than are smaller animals, which is why they don’t have to eat as often. (Really small endotherms like shrews have to spend almost literally every waking moment searching for and consuming food, while really big endotherms like whales can go for weeks or even months after a large meal without eating.)

Plug in some numbers, and you’ll find that a large, 8-ton Tyrannosaurus rex would burn about 120,000 kilocalories per day, while a 70-kilogram human-sized or raptor-sized animal would be expected to burn about 3,300 kilocalories per day.

Now that we know how much energy they expend in a day’s time, we can easily calculate how much a carnivore must eat in order to keep up with its energy demands. Meat is calorie-rich and easily digested, so a predator can typically absorb about 90% of the energy in meat. The equation for calculating food consumption in endothermic predators is therefore: F = 0.11(W)0.75. “F” is the kilograms of wet meat needed each day. Again, you’ll notice that larger animals are more energy-efficient, and so require proportionately less food.

So, a tyrannosaur-sized animal should require about 90 kilograms of meat per day. Movie monsters tend to eat a lot more than real animals would, in my experience, but the eating habits of the Tyrannosaurus rex don’t seem too extreme. Granted, it may have scarfed down a few victims off-camera, but it didn’t seem to be eating too much more than you’d expect for an animal of that size. A raptor-sized animal, on the other hand, would need less than 4 kilograms of wet meat per day. It seems to me that the raptors were eating a lot more than they should have during the course of this movie.


[BREAK=Jurassic Park: The Lost World]
[B]Jurassic Park: The Lost World

Right at the beginning, we were informed that whereas the “amusement park” (Jurassic Park) had been located on the island of Isla Nublar, “Site B” was located on Isla Sorna, some 87 miles to the southwest. We later learned that Site B had been evacuated after a hurricane hit, and the animals escaped to set up an ecosystem of their own on the island.

Doesn’t it seem odd that the InGen Corporation never put up any warning signs or otherwise attempted to keep people off of Isla Sorna? It was made clear in the movie that occasional fishermen had landed on the island and never returned, and it was surely only a matter of time before a serious incident occurred. An incident like, say, a wealthy family on a yachting trip stumbling on the island and raising a big stink when their little girl was injured in a dinosaur attack. Even if Hammond was determined to leave the island undisturbed as a sort of nature preserve, you’d think InGen would be highly motivated to keep people away from the island, not just to avoid lawsuits, but also to prevent competitors from stealing their “products.”

Hammond claimed that animals were bred on Isla Sorna, then transferred to Isla Nublar for display. They were transported some 90 miles across the ocean from the breeding facility to the display facility? This seems rather inefficient somehow. Besides, we saw that Isla Nublar had breeding facilities in the original Jurassic Park, and a big deal was made about how the animals were bred there, on Isla Nublar. Apparently, the breeding facility on Isla Nublar was only a small-scale operation. We saw in Jurassic Park III that the breeding facility on Isla Sorna was much more extensive, so Hammond wasn’t being very truthful when he claimed all the animals were bred there on Isla Nublar. Hmm ... one wonders what else he was being dishonest about.

Once Ian, Nick and Eddie reached Isla Sorna, they encountered a group of Stegosaurus while searching for Sarah. Nick was standing maybe 20 feet or so behind Sarah at one point, and looking almost directly at her. So how come he failed to see her? Granted, he was distracted by seeing some live stegosaurs, but it doesn’t seem at all plausible that he didn’t notice Sarah’s presence. And how is it that though Ian, Nick and Eddie had been yelling her name at the tops of their lungs just moments before, she apparently didn’t hear them?

Sarah spoke of how the stegosaurs’ nests contained crushed eggshells, indicating parental care of the young. I thought that was a nice touch. Jack Horner discovered nests of dinosaurs of the genus Maiasaura containing thoroughly crushed egg shells. What Horner pointed out was that if the young maiasaurs had left the nests right after they hatched, their egg shells would not have been crushed; the fact that they had been thoroughly trampled and crushed implied that the young maiasaurs had remained in the nests for some time after they hatched. This could only have been true if the parents were feeding and caring for their young, so we can infer that some dinosaurs, at least, were attentive parents.

It seemed strange to me that the young stegosaur tolerated Sarah’s presence, let her touch it, and made no protest at the sounds of her camera clicking and the motor advancing the film — but then freaked out at the sound of the camera motor rewinding the film.


Ian claimed that the Heisenberg Uncertainty Principle makes it impossible to observe a system without changing it, and that Sarah’s goal of observi