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How do we identify incomplete fossils?

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Most animal fossils are found as isolated bones and teeth, rather than complete skeletons. The missing bones might have been destroyed by predators or scavengers as they fed on the animal, swept away by floods, fractured under heavy sediments after burial, or broken while eroding out of the ground.

However, scientists familiar with skeletal anatomy can still identify isolated or fragmentary fossils. For example, look at the crocodile tooth and dromaeosaur dinosaur tooth above, both found at Dinosaur Park. Both are long and pointed, showing they belong to meat-eating animals, but there are plenty of differences, too. The crocodile tooth is shaped like a cone, and is round in cross section. By comparison, the dromaeosaur tooth is flat and blade-like. And while both teeth have serrated edges, the serrations on the dromaeosaur tooth are much larger than those on the crocodile tooth. Paleontologists recognize the distinctive characteristics of these teeth and conclude that both dromaeosaurs and crocodiles lived in Cretaceous Maryland.

Furthermore, isolated bones and teeth can be understood in the context of better-known fossils found elsewhere. Closely related species tend to be similar, so scientists can apply what is known from relatives to create a reasonable approximation of an incompletely known animal. For example, largely complete skeletons of the dromaeosaur Deinonychus have been found in Montana, Wyoming and Oklahoma, in rocks that are the same age as Dinosaur Park. Scientists recognize that the dinosaur teeth found at Dinosaur Park are virtually identical to those of Deinonychus, and therefore must have come from a very similar animal.