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What do dinosaur bones tell us about a dinosaurs stance?
All dinosaur skeletons show that these creatures had a fully improved stance. In other words, dinosaur legs were held straight under their bodies at all times. This enabled dinosaurs to grow bigger, cover longer distances, and move faster, compared to their reptile relatives that had their legs spread out on either side of their body. The dinosaur stance also enabled some of the animals to become bipedal (walk on two legs). It also helped all dinosaurs with something called locomotor stamina, which is the ability to run and breathe at the same time.
What can paleontologists tell about the lifestyle of a large herbivore (sauropod) from its fossil bones?
The bones of giant dinosaurs like the Diplodocus tell us a great deal about this herbivore. Its legs were thick and widely spaced, acting as pillars to hold up the cross beams of its shoulder bones and hip girdle. The vertebrae across the hip were fused for strength, allowing it to support an almost 11-ton (10-metric-ton) body weight. The legs ended in short, broad feet (similar to an elephants) with claws on the back foot used as an anti-slip device. The bone structure limited the dinosaur to a normal walking pace of approximately 4 miles (6.4 kilometers) per hour, although they could have moved modestly faster for short periods of time. Thus, they were thought to be large, slow moving, four-legged walkers. In addition, the large adult sauropods were probably relatively immune from predators because of their large size.
What were unique skeletal features of large sauropods?
There were a number of unique skeletal features of large sauropods that evolved mostly to support their massive size and weight. These dinosaurs were similar in construction to a suspension bridge: the front and rear legs acted as underlying supports for the backbone; in turn, the backbone was supported from above by ligaments and muscles of the back. The vertebrae of the backbone were joined together so the neck, back, and tail were bent slightly upwards at the ends, spreading the massive weight toward the ends.
The top leg bone was shaped to swing underneath the body. The knee was constructed so the leg could move back and forth, similar to the knee of humans. The ankle had very limited movement, with no possible sideways motion. These and other skeletal features helped the large sauropods to support and move their tremendous bulk.
What can paleontologists tell about the lifestyle of a small herbivore from its fossil bones?
One good example of small herbivores is the Hypsilophodon, an ornithischian with a skeleton very different from its larger sauropod cousins. The small dinosaurs entire structure seemed shrunk down, giving it strength with minimum weight. Its bones were hollow and thin-walled for lightness, and the thigh bone was very short for rapid stride movements. The small dinosaurs feet were long and thin, with long, upper-foot bones (metatarsals), and it had short, sharp claws for gripping the ground. The long tail bone was stiffened by bony rods, and probably swung from side to side, helping it to quickly change directions. All of these structures paint a picture of a small, two-legged herbivore using its bony features to swiftly run and maneuver as a defense against predators.
What can paleontologists tell about the lifestyle of a large carnivore (theropod) from its fossil bones?
The Tyrannosaurus is currently the most recognizable of the large carnivorous dinosaurs. Its skeleton had heavy, large bones, with massive vertebrae, hip girdle, and thigh bones. The upper foot bones (metatarsals) were locked together for strength, while the toes were powerful and short. The knees show evidence of thick cartilage, similar to modern birds.
There are two scenarios concerning the speed and mobility of the Tyrannosaurus based on the animals skeletal structure, and both sides point to the same evidence to bolster their claims. One group thinks that the skeletal structure of a Tyrannosaurus caused the animal to move at a slow pace, which limited its main hunting abilities to either scavenging or ambush techniques. The other group suggests that the dinosaurs bone structure, along with the animals massive musculature, enabled the Tyrannosaurus to run and sprint, making it an active, dangerous hunter.
Until more direct evidence is gathered, the most agreed upon theory is based on a major deduction: the Tyrannosaurus would need more meat than was available from scavenging, so it would have to hunt. To do so, it would have to at least match the speed of its prey. In other words, it would have to keep up with such dinosaur prey as the herbivores Triceratops and Edmontosaurus (ornithischians), both of which are thought to have reached 9 to 12 miles (14 to 19 kilometers) per hour for short bursts.