Biological issues in Jurassic Park

Jurassic Park, a book by Michael Crichton, with a film version directed by Steven Spielberg, revolves around the resurrection of dinosaurs via genetic engineering. Scientists and enthusiasts have brought up a number of issues with facts and feasibility. Some of the speculative or inaccurate features attributed to the dinosaurs of Jurassic Park have become embedded in popular culture, most popular among them being the idea of Tyrannosaurus only seeing motion; giant, featherless, intelligent Velociraptors, and dwarf, frilled, poison-spitting Dilophosaurus. In general, the novel is more accurate than the film, with Spielberg adding some features to the dinosaurs (like the frill on the dilophosaurs). However, it is stated on the tour in the first film that the gaps in the dinosaurs' DNA sequence were filled with amphibian DNA, so it could be argued that most of the following inaccuracies are genetic mutations resulting from the DNA tampering.

Extinct genera

See also: List of extinct genera in Jurassic Park

Velociraptor

The actual size of Velociraptor mongoliensis, compared to a human.

The Velociraptor in the novel, and consequently the film, were larger than the actual animal. The misconception arose because Crichton used "Predatory Dinosaurs of the World" by Gregory S. Paul as a reference when writing his novel, and that work interpreted Deinonychus antirrhopus as a species of Velociraptor; it is closely related to Velociraptor mongoliensis, but is larger. In the novel, Deinonychus is mentioned, but the character Alan Grant then says that scientists have reclassified it as a species of Velociraptor.

The film makers had the size of the film's Velociraptor increased for dramatic reasons, and changed the shape of the snout. However, at the same time the film was being shot, paleontologists came across a larger dromaeosaurid species named Utahraptor and the larger raptors remained, even though Utahraptor was substantially larger (21 feet long) than the film's raptors. At the start of the film, a Velociraptor skeleton is uncovered in Montana; no examples of the dinosaur have been uncovered in the United States (although both Deinonychus and Utahraptor are American dinosaurs). The fossil skeleton is similarly inaccurately large. In the novel the character Alan Grant identifies the Montana fossil specimen as "antirrhopus" as opposed to the park's "mongoliensis"(as identified by Henry Wu) - meaning that the fossil specimen Grant's team found is actually Deinonychus.

Velociraptor mongoliensis restored with large wing feathers, as evidenced by fossil quill knobs.

The high intelligence of the film's Velociraptors is considered unlikely by scientists, given the relative size of their brains and comparisons with modern animals.

It is now known that Velociraptor had feathers. Neither the film nor the novel dinosaurs had feathers; however, both were created before the discovery of feathered dinosaurs closely related to Velociraptor (e.g. Microraptor). In Jurassic Park III, the raptors were remodelled and small feather-like quills were added to the males' heads, while still looking similar to the original design.

As with other bipedal dinosaurs in the films, the hands of Velociraptor are depicted with the palms able to rotate, but this would have been anatomically impossible for the real animals, as their forearm bones (ulna and radius) could not rotate in this way. Their palms should have been relatively fixed facing each other, like a person about to clap.

Dilophosaurus

Size comparison of Dilophosaurus and a human

The film's Dilophosaurus stands about 1.2 meters (4 ft) tall, while its real-life counterparts measured on the order of 6 meters (20 ft) long and 1.4 meters (4.5 ft) tall at the hips. According to a "Making-of" book, this was a deliberate deviation from accuracy for stylistic purposes, and to differentiate it from the velociraptors. Thus likely it could have been a juvenile, as none other is seen whether in this film or another, and by Dennis Nedry adding: "I thought you were one of your big brothers" when encountering it. It also has a frill like the Australian frill-necked lizard, which is not considered accurate by paleontologists. The novel's version is full-sized and lacks the frill. Both depictions of the dinosaur eject a potent, blinding venom in both their bite and their spit, like a spitting cobra, and use it to hunt; the novel acknowledges the fact that this is not suggested by fossil evidence.

Tyrannosaurus

The film theorizes that the Tyrannosaurus would be unable to see someone if he stayed still; however, evidence has shown T. rex to have had high visual acuity and binocular vision. Some argue that it would still be able to smell them regardless. In the novel, it is mentioned that the reason the dinosaurs cannot see someone standing still may be due to the frog DNA in their genome, and it is shown that other dinosaurs, such as the island's Maiasaura, have this problem as well. This is not mentioned in the film; instead it is shown as if the inability to see without movement was an actual trait of Tyrannosaurus (Dr. Grant poses this as a paleontological fact even before knowing about Jurassic Park and its use of genetic engineering). In the sequel novel, The Lost World, it is suggested that the Tyrannosaurus can in fact see inanimate objects, and was actually not hungry, but merely "playing" or attempting to threaten in the first encounter. A character who specifically attempted this technique dies when the T. rex sees him there and kills him; the character Ian Malcolm mentions that he was listening to "the wrong scientists."

Tyrannosaurus is also shown as being able to keep (sprinting) pace with a jeep traveling at considerable speed; however, it is debated within the paleontological community whether a T. rex could even achieve this speed in real life, much less maintain it for as long a period of time as the film depicts. Anatomically, its short forelimbs would have been unable to cushion an impact if it were to fall, meaning that accidents at such speeds could have been fatal. Also, biomechanical studies by Dr. John Hutchinson of the Royal Veterinary College have shown that in order to run at this speed in a crouched position, Tyrannosaurus would have needed over 43% of its muscle mass in each leg. That would mean 86% of its muscle mass would be in its legs, leaving little room for anything else in its body: a physical impossibility. Dr. Hutchinson’s work also suggests that an upper speed limit for Tyrannosaurus would, actually, only fall in the 10–25 mph range. Animators at Industrial Light & Magic were forced to use optical illusions in order to make the computer-generated Tyrannosaurus appear to convincingly keep pace with the vehicle.

Brachiosaurus

The Brachiosaurus in the film is shown to be chewing its food with a side to side motion of its lower jaw. In reality, it could not feed like this. Brachiosaurid skulls and jaws were limited to up and down motions, and their teeth were specialized for shearing and cropping plant material. Other sauropods, such as diplodocoids, could move their jaws backward and forward, but were probably using this motion to strip branches, not to chew plants . Instead of processing food in the mouth, sauropods probably relied on taking in as much food as possible and processing it farther down the digestive tract, either through gastroliths (rocks swallowed and used for grinding in a gizzard-like organ; note however that this hypothesis, while common in the popular literature, is now considered unlikely in sauropods), or simply by digestion through fermentation by microorganisms.

One of the most well known scenes of the movie shows a brachiosaur rearing into a bipedal stance. However, a biomechanical analysis of sauropod rearing abilities shows that Brachiosaurus is probably the sauropod least able to rear. It has a center of mass placed further forward than any other sauropod, which means that a bipedal or tripodal pose would be highly unstable. The legs and feet of the brachiosaurs were also portrayed as too bulky, whereas they would have been slender in reality.

Pteranodon

Variation in the crest of Pteranodon (right), which is not reflected in the movies

Like the Cearadactylus in the novel, the Pteranodon in Jurassic Park III is interpreted as aggressive and able to pick a teenager up with its feet (a similar scene was planned for the climax of The Lost World: Jurassic Park, but scrapped when Steven Spielberg decided to instead use the Tyrannosaurus rampage in San Diego as a better finale). Both pterosaur genera were thought to have eaten fish, and were incapable of grasping with their feet^{[citation needed]}. A Pteranodon could possibly have used its pointed beak as an alternative weapon, but in a hypothetical scenario would be unlikely to use it on a human being unless provoked. However, in the novelization it states that they were able to carry things with their feet due to them being genetically engineered. Also, although the name Pteranodon means 'winged without teeth' or 'toothless wing', the Pteranodon in Jurassic Park III have small, sharp teeth in their bills. Their beaks are also straight, whereas they should have an upwards bend. There was great variation in individual Pteranodon crests, with large ones being interpreted as those of males, and short ones being female or juvenile. In the films, all adults have identical crests, and the crests of the juveniles are too large.

Procompsognathus and Compsognathus

The Procompsognathus are given several attributes in the novels that cannot be determined from the fossil evidence to date. They are presented as living and hunting in large groups; as scavengers and coprophagists (eaters of feces), useful in keeping the park clean of sauropod excrement; and as secreting a venom described as similar to that of a cobra, although more primitive. In the films, they are dropped in favour of Compsognathus, as well as their venomous bite.

Procompsognathus is known from a single partial skeleton from the Late Triassic of Germany, with a partial skull that may belong to it or, more likely, an early relative of modern crocodilians. Because only one individual is known, there is no direct evidence that it lived in groups; however, related animals such as Coelophysis and Megapnosaurus have been found in groups of numerous individuals, such as at Ghost Ranch. As there are no uncontroversial remains of the head of Procomposognathus, its diet cannot be inferred from the form of its teeth and jaws; other coelophysoids are seen as carnivores with skull adaptations that may have been advantageous when handling small prey.

There is no evidence that the bite of Procompsognathus was venomous. A venomous bite has been proposed for a possible theropod from the Late Cretaceous of Baja California, known from a single tooth with grooving similar to that found on the teeth of venomous snakes and lizards. A venomous bite has also been proposed for the Lower Cretaceous Chinese dromaeosaurid Sinornithosaurus, based on its long grooved teeth similar to those of rear-fanged snakes, as well as a possible venom-gland cavity in the bone of the upper jaw.

Further reading

• Lindley, David; DeSalle, Rob (1997). The science of Jurassic Park and the Lost World, or, How to build a Dinosaur. New York: BasicBooks. ISBN 0-465-07379-4. 
• Cano RJ, Poinar HN, Pieniazek NJ, Acra A, Poinar GO (June 1993). "Amplification and sequencing of DNA from a 120–135-million-year-old weevil". Nature 363 (6429): 536–8. doi:10.1038/363536a0. PMID 8505978. 
• Weaver, Robert J. (2002). Molecular Biology. New York: McGraw-Hill. p. 76. ISBN 0-07-234517-9. 
• Noonan JP, Hofreiter M, Smith D, et al. (July 2005). "Genomic sequencing of Pleistocene cave bears". Science 309 (5734): 597–9. doi:10.1126/science.1113485. PMID 15933159. http://www.sciencemag.org/cgi/pmidlookup?view=long&pmid=15933159.