Dinosaurs of Jurassic Park: Velociraptor

Velociraptor was a mid-sized dromaeosaurid, with adults measuring up to 2.07 m (6.8 ft) long, 0.5 m (1.6 ft) high at the hip, and weighing up to 15 kg (33 lb).[3] The skull, which grew up to 25 cm (9.8 in) long, was uniquely up-curved, concave on the upper surface and convex on the lower. The jaws were lined with 26–28 widely spaced teeth on each side, each more strongly serrated on the back edge than the front—possibly an adaptation that improved its ability to catch and hold fast-moving prey.

Velociraptor, like other dromaeosaurids, had a large manus ('hand') with three strongly curved claws, which were similar in construction and flexibility to the wing bones of modern birds. The second digit was the longest of the three digits present, while the first was shortest. The structure of the carpal (wrist) bones prevented pronation of the wrist and forced the 'hands' to be held with the palmar surface facing inwards (medially), not downwards.The first digit of the foot, as in other theropods, was a small dewclaw. However, whereas most theropods had feet with three digits contacting the ground, dromaeosaurids like Velociraptor walked on only their third and fourth digits. The second digit, for which Velociraptor is most famous, was highly modified and held retracted off of the ground. It bore a relatively large, sickle-shaped claw, typical of dromaeosaurid and troodontid dinosaurs. This enlarged claw, which could be over 6.5 cm (2.6 in) long around its outer edge, was most likely a predatory device used to tear into prey, possibly delivering a fatal blow.

Long bony projections (prezygapophyses) on the upper surfaces of the vertebrae, as well as ossified tendons underneath, stiffened the tail of Velociraptor. The prezygapophyses began on the tenth tail (caudal) vertebra and extended forward to brace four to ten additional vertebrae, depending on position in the tail. The stiffening forced the entire tail to act as a single rod-like unit, preventing vertical motion between vertebrae. However, at least one specimen preserves a series of intact tail vertebrae curved sideways into an S-shape, suggesting that there was considerably more horizontal flexibility. These adaptations of the tail probably provided balance and stability while turning, especially at high speeds.

Dinosaurs of Jurassic Park: Spinosaurous Aegypticus

Although Spinosaurus is well-known to dinosaur enthusiasts due to its sail and elongated skull, it is mostly known from remains that have been destroyed, aside from a few more recently discovered teeth and skull elements. Additionally, so far only the skull and backbone have been described in detail, and limb bones have not yet been recovered. Some speculation occurs in arguments among scientists and paleontologists that the Spinosaurus aegyptiacus may have walked on all four limbs, but most are not convinced.

Jaw and skull material published in 2005 show that it had one of the longest skulls of any carnivorous dinosaur, said to be 1.75 meters (5.75 ft) long. The skull had a narrow snout filled with straight conical teeth that lacked serrations. There were six or seven teeth on each side of the very front of the upper jaw, in the premaxilla bones, and another twelve in both maxillae behind them. The second and third teeth on each side were noticeably larger than the rest of the teeth in the premaxilla, creating a space between them and the large teeth in the anterior maxilla; large teeth in the lower jaw faced this space. The very tip of the snout holding those few large anterior teeth was expanded, and a small crest was present in front of the eyes.

The sail of Spinosaurus was formed of very tall neural spines growing on the back vertebrae. These spines were seven to eleven times the height of the vertebrae from which they grew. The spines were slightly longer front to back at the base than higher up, and were unlike the thin rods seen in the pelycosaur finbacks Edaphosaurus and Dimetrodon, the two sailed reptiles from the Permian period.