The Awful Tooth
How can one reconstruct a whole animal based on isolated fossil teeth? With great care. Consider the cautionary tale of 'Nebraska Man'.
Based on a single tooth found in a farmer's field, Henry Fairfield Osborne of the American Museum of Natural History deduced that it was of Pleistocene age and represented the earliest known hominid in the Americas. What a scientific boon for the young nation! Osborne - a flamboyant defender of evolution in the fundamentalist climate of the Scopes Trial - promptly named the new species Hesperopithecus haroldcookii (after paleontologist Harold Cook, who originally discovered the tooth in 1922). Further study by subsequent scholars eventually revealed that the tooth was not from a hominid at all, but an ice-age suid: it was a not a man but a pig.
Religious fundamentalists were delighted at Osborne's blunder, regarding it as further evidence that the evolutionists did not know what they were talking about. (It should be borne in mind, however, that just because Osborne was human enough to be influenced by his desires and made a mistake, that fact does not - of itself - invalidate the whole concept of evolution. The evidence from astronomy, geology, paleontology, nuclear physics, biochemistry, morphology, physiology, genetics, and embryology attests to the fact that evolution has occurred. Nor should we judge Osborne too harshly: both humans and pigs are omnivores with rather generalized mammalian dentitions. Isolated teeth from either omnivore can be very difficult to distinguish, even by experts.)
Small wonder that shark paleontologists - who usually have only fossilized teeth with which to work - so often disagree about how long-gone species like Megalodon was related to other sharks, how large it grew, and how it looked in life.