Peter K. Dearden.
If you haven’t read Stephen Jay Gould’s collected essays then you have missed out on a treat. Stephen was remarkable for his ability to get across an evolutionary or biological point in an easy to understand, and often fun, way. Even his fixation on baseball statistics is forgivable in the face of his clarity of writing. One of Stephen’s more famous essays is entitled ‘Bully for Brontosaurus’ where he explains that, while Brontosaurus is a brilliant name (means ‘thunder lizard’) for a huge dinosaur, it is, unfortunately wrong, and the name shouldn’t be used.
The problem is that the fossil that was named Brontosaurus turned out to be the same as an earlier named fossil, Apatosaurus (meaning not-so-aptly-named lizard). Brontosaurus is Apatosaurus, and because Apatosaurus came first, it wins. First to be named claims priority. Brontosaurus never was.
But these are dinosaurs right? They have been extinct for some time, and all we have left is a scattering of fragmentary remains. We do not have a skull of the original Brontosaurus specimen, only what is known by people stating the bleeding obvious as the post-cranial skeleton. The skull that was perched jauntily on top of the Brontosaurus in the Yale Museum for a long time was from a different sauropod, a Camarasaurus.
If all we have are bits and pieces, how do we know which is what species? Could we tell a kea from a kaka from just their bones if we had no record of them? Alongside this, is a small version of your dinosaur a young one? A different species? The other sex? The story of our Moa come to mind in which smaller versions, first named as different species, turn out, by DNA evidence (here and here), to be the males of the species (raising the important question of the source of step ladders in pre-human New Zealand). BTW, if you haven’t read the brilliant Moa book by Quinn Berentson, you should read that BEFORE Stephen Jay Gould.
Biologists have problems identifying species even in living animals. We have a bunch of concepts of what a species might be, but they are all inaccurate when applied to the living world (look up Ring-species for example). Species clearly exist in nature, but defining them exactly is pretty hard. It must be a hell of a lot harder to do that with the fragmentary remains of fossils (that’s one good reason, much better than Jurassic Park, that we need dinosaur DNA).
Now, however, entering stage left, a group of dinosaur palaeontologists have reanalysed old specimens of Apatosaurus and Brontosaurus, as well as some new fossil finds, and claim to have found a difference between then, sufficient to say that Brontosaurus and Apatosaurus are not the same animal. Brontosaurus is back (and he’s angry). Actually he is not back, ‘cos he never was here in the first place, but you get what I mean.
Other palaeontologists are skeptical, probably for all the reasons I discussed above, but they all agree that what is really needed are more examples of Apato- and Bronto-sauri, especially their heads.
Should we care? I think so. These arguments are symptoms of biologists trying to understand the distant past, which is, to put it mildly, very hard. The arguments may seem a little pedantic, but actually they are about the complexities of biology and evolution. The past is hard to understand, but we cannot understand where we are today without doing so.