|Table Header||Table Header|
|Everyday Name||Eoraptor: Was it Really a Dinosaur?|
|Pronunciation||Ee - Oh - Rahp - Tor|
Well, right now, if you do a search, Eoraptor is called a dinosaur on all the sites that come up. On the other hand, they all consider it a very early dinosaur. It is definitely a lizard, and it ate other animals. Also, it was bipedal (it ran on two legs). But as I read more, I began to question whether it really is a dinosaur. Does it really belong to this group? After all, there are a number of features that dinosaurs have, and if an animal does not have them, it is not part of the group. So I looked a little deeper.
Well, there are a number of features that make it seem a little different from the classic image of a dinosaur. Not totally different, but that's the point. Is it different enough to be thrown out of the group, or not? Let's take a look at some of the things that are a bit different:
How many fingers do dinosaurs have? Well, if you look at the skeletons of the big predators, they all have three fingers, or even two (like T. rex). Eoraptor has five. Well, that's certainly a lot more than two or three. That's quite a big difference. Of course, Coelophysis has four fingers, so that is a step closer but still different from five.
Eoraptor has two kinds of teeth: hervbivore teeth and carnivore teeth. Many dinosaurs have a distinct set of teeth; either one or the other. They fall into two simple groups: the meat eaters, and the plant eaters. Easy. But this guy, Eoraptor doesn't fit in so easily. He has both. What's going on here? Is he a dinosaur or not?
Then another difference popped up. The jaw of most predators has a sliding joint, which makes it easier to hold prey in the mouth. Eoraptor does not have this ability. Of course, Eoraptor sure looks like a hunter. They are sleek and light, for running, with enough sharp teeth to be convincing. But most of the carnivorous dinosaurs have the sliding joint in their jaw. Why not Eoraptor?
After all, it has been classified as a theropod. This classification came out in a recent paper by Nesbitt, S.J. in 2009. The theropods are classified in the group of saurischian dinosaurs, which are definitely dinosaurs. And just because it is not completely the same as later dinosaurs in the regular dinosaur features does not take it out of the group altogether. It is so early that it simply did not have all the features of the later dinosaurs.
Eoraptor was a step in the evolution of dinosaurs. Stages in the evolution after Eoraptor show the number of fingers decreasing. The jaw also took a bit of time to develop fully into the sliding jaw type which makes it easier to hold prey. And as for the teeth, well there are other dinosaurs that had booth kinds of teeth, so that is not a big problem either.
The conclusion is that Eoraptor was a dinosaur. It was an early dinosaur so it did not have all the full features of the classic dinosaurs of our imagination. But if you met it, you would not hesitate to call it a dinosaur, I am sure. Eoraptor, was small, so if you did meet one, you might not be too scared by it. That's just part of being early in the evolutionary chain.