What do dinosaur bones indicate to paleontologists about the health of these animals?

Dinosaurs, in general, seem to have been relatively healthy animals, if the evidence from and the interpretation of the fossil records are to be believed. A few fossilized bones have shown evidence of abnormalities, such as asymmetrical bone growth, healed traumatic and repetitive stress fractures, arthritis, ossification (the development of bony-like material) of spinal ligaments, and the fusion of the animals spinal bones (or vertebrae).

What caused asymmetrical bone growth in dinosaurs?

Asymmetrical bone growth could have occurred, for example, when a tendon was ripped off the bone. This probably happened during some form of exertion, such as running after prey for carnivores, or trying to escape a predator for herbivores. If bone growth continued in this area after the tendon was torn, it would often grow back in an abnormal shape.

What caused traumatic and repetitive stress fractures in dinosaur bones?

Another feature that has been seen in some dinosaur bones, such as Tyrannosaurus and Iguanodon, are healed traumatic fractures. Such fractures may have occurred during struggles with other dinosaurs or even mating activity.

Another type of fracture, called a stress fracture, apparently occurred in dinosaurs as a result of repetitive stresses to the bone. Stress fractures found in ceratopsians, such as the Triceratops, have often been blamed on foot stamping, sudden accelerations in response to predators, or even fractures brought about during long migrations.

What do traumatic fractures in the bones of large theropods (carnivores) tell us about the behavior of these animals?

Some bones from carnivorous dinosaurs do show signs of traumatic fractures. One example was recently found by scientists using X-rays of the rib bones from an Allosaurus. Scientists believe the fractures could have been caused by a belly flop onto the hard ground while running. This suggests that these large theropods were not sluggish creatures, but were active hunters, running after prey fast enough to crack ribs if they fell during the pursuit.

Scientists used to believe that no DNA could have survived the millions ot years since the dinosaurs became extinct, but in 2007 they discovered collagen proteins trom within a T rex bone. This is an amazing discovery that could prove, among other things, how closely dinosaurs are related to birds (iStock).

Have any dinosaur DNA or proteins survived 65 million years?

It is thought that most dinosaur bones that are at least 65 million years old have all turned to stone, and so there is no hope of DNA or proteins surviving. But a study in 2007 showed that scientists may have been too hasty when proteins were successfully extracted from a Tyrannosaurus rex bone. Using special extraction methods, the scientists found what seems to be collagen, which is one of the major proteins found in our own bones. Why is this exciting to paleontologists? By comparing the dinosaur collagen to contemporary chicken collagen, scientists might be able to answer a question that has plagued them for years: how closely are birds and dinosaurs related?

Do dinosaur bones show evidence of arthritis, a common affliction in humans?

Yes, some dinosaur bones show signs of certain types of arthritis, especially osteoarthritis and inflammatory arthritis. In humans, osteoarthritis, or degenerative arthritis, is common in the elderly. It is the increased deterioration of cartilage around the bone due to age. Inflammatory arthritis, or gout, in humans usually occurs when crystals of uric acid are deposited in a joint. The excess amounts of uric acid are usually unexplainable, but it has often been tied to dietary excesses.

In the vast majority of cases, dinosaur bones show almost no sign of osteoarthritis, leading some paleontologists to theorize these creatures had highly constrained joints, or bone joints with little rotational movement. Two specimens of Iguanodon, however, were found to have evidence of osteoarthritis in the ankle bones, or weightbearing parts of the body. Because scientists dont know the life spans of dinosaurs, they also dont know whether the arthritis was caused by old age. In addition, two tyrannosaurid dinosaur remains showed evidence of inflammatory arthritis in the hand and toe bones possibly the result of a rich, red meat diet.

What bone phenomena do both humans and dinosaurs share?

Humans and dinosaurs share a process called diffuse idiopathic skeletal hyperostosis (DISH), or when the ossification (when something becomes bonylike) of the spinal ligaments stiffens the spinal area. Although it sounds bad, it is a normal process and not recognized as a disease in either humans or dinosaurs.

Creatures such as ceratopsians, hadrosaurs, iguanodonts, pachycephalosaurs, and some sauropods all show DISH a stiffening of the dinosaurs tail area that made it easier to hold the tail off the ground. Dinosaurs that used their tails as weapons, such as the stegosaurs, needed them to be flexible like whips, so they do not show evidence of this spinal ligament fusion. The discovery of DISH in dinosaurs dovetails nicely with a newer theory that many dinosaurs did not drag their tails, but rather held them off the ground as a form of counter-balance.

Another bone-related phenomena humans and certain dinosaurs share is vertebral fusion, where the bones of the spine (the vertebrae) actually become joined and ossified together (as opposed to the spinal ligaments in the DISH process). In the adult ceratopsians, such as the Triceratops, this fusion was limited to the first three neck (cervical) vertebrae, leading to speculation that this was not a disease, but a developmental adaptation. Stiffening in this area may have evolved to better support the animals massive skull. Current fossils reveal that smaller, perhaps younger ceratopsians had incomplete fusion in this area; whereas the fusion was complete in larger, presumably older animals.

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