Monday, October 30, 2017

A quiet tribute to dinosaurs of yore

I'm not going to pick a single Extinct Animal of the Week this week, and I'm not going to (yet) do the second half of MEET THE MEGALOSAURS either.  Rather, I'm going to do a nostalgic trip through the kinds of dinosaur stuff that I used to read as a kid.  The whole "gigantic lizards, living in the swamps and lakes" business, with names that I saw in practically every dinosaur book that nobody ever uses anymore.  Scientifically, we find that most of these names were assigned to dubious, scrappy, incomplete, or non-diagnostic remains, and then the name was used normally to describe remains that should have been assigned other names.  Today, of course, we 1) use different names to describe the animals that used to have the names listed below, mostly, and 2) know that most of what we thought we knew about them was wrong anyway.  Given 2, then maybe it doesn't mean that 1 didn't get renamed; it means that they simply never existed at all.  The whole aquatic Trachodon, for instance—one could say that they were renamed Anatosaurus, then Anatotitan, then Edmontosaurus.  But although the remains of Edmontosaurus are those that used to have the name Trachodon, the two animals are really quite different.  Edmontosaurus is a terrestrial, pine-needle eating Late Cretaceous buffalo, if you will, while Trachodon was a lake-dwelling, two-legged, tall, buck-billed herbivorous crocodile.  So, without further ado...

Trachodon—well, I was just talking about it, so let's start there.  In every old dinosaur book I ever read as a kid, Trachodon was the "boring" duck-bill, and he'd be sitting there on the lakeshore along with Lambeosaurus, Corythosaurus and Parasaurolophus.  They always hung out together on the beach.  And whenever Tyrannosaurus rex came along, they'd make a scramble for the water, which T. rex was so afraid of that he wouldn't even let his feet get a tiny bit wet in a few inches of water, it seems.

This is of course nonsense, as only Edmontosaurus lived at the same as as T. rex; the other three were all part of Judithian or Edmontonian faunas.  None of them lived at the same time as each other either.  And while it's true that these hadrosaurs all seem to have favored wetlands as habitat, they weren't lake-dwellers, and T. rex hunted those same terrains without worrying too much about it.  There is also a theory that the transition from the Judithian to the Lancian fauna came as sea levels decreased and generalists from the more arid uplands flourished, while wetlands specialists declined.  This is more marked in the south, with the Alamosaurus-Quetzalcoatlus guys.  Migration from Asia and possibly South America as sea levels fell is another theory.  In any case, nothing about the environment or habits of Trachodon turns out to be true, so maybe it's not such a bad idea that the name is closely associated with the debunked paradigm of dinosaurs anyway.

Fabrosaurus—This one, on the other hand, is just unfortunate.  Fabrosaurs were long listed as these really primitive, early Ornithischian from the Early Jurassic of South Africa.  They were presumed to have had wide-spread, probably even global distribution.  (This in spite of the fact that almost all of what we've found for them is in South Africa, and maybe some very recent findings now from China.)  No doubt, there were some interesting, early Ornithischians that were more or less similar to what we long thought Fabrosaurus looked like—Pisanosaurus from South America is even earlier and isn't all that different than what we would expect from Fabrosaurus.  But fabrosaurs themselves are no longer believed to be a group; they're just a bunch of stuff "on it's way" to becoming another, more advanced ornithopod group, or something like that.  And the specific animal on which most restorations of Fabrosaurus were based is now called Lesothosaurus instead.

Monoclonius—While some still say that this might be a valid animal, most think that Monoclonius was actually a fragmentary juvenile Centrosaurus these days.  As with the duckbills, horned dinosaurs in old books were often thrown together regardless of whether they were from Judithian, Edmontonian or Lancian faunas—although at least they were more or less geographically close (much of the fossils of the southern province of Laramidia hadn't been found yet, with names like Bravoceratops, Eotriceratops, Arrhinoceratops, etc.)  In those old books, a hungry T. rex almost always found the duckbills—who ran into the lakes, thus frustrating him, then he stumbled across an Ankylosaurus, which he couldn't do anything with because of its armor, and then he went looking for the horned dinosaurs, which oddly enough were always believed to be out on the plains like scaly buffalo.  Monoclonius and Styracosaurus were usually pictured together, but for whatever reason, T. rex didn't try to eat them, always looking instead for the Triceratops.  Often these other two were pictured forming musk-ox like circles around the young.  Triceratops, on the other hand, were always the big bad loners.

Complete with Triceratops in the distance
Brontosaurus—This is a real crime, in my opinion.  Brontosaurus was the most famous dinosaur ever, and a bunch of nerdy, nebbish paleontologists made a gamma male play to be self-righteous and self-important and tell everyone in the whole world that no, we need to call it Apatosaurus.  At around the same time that the name was disappearing from popular literature, we also found out that it had been given the wrong skull, and the boxy, squared-nose skull associated with Brontosaurus should have been replaced with one more like Diplodocus, making the newly christened (at least in popular literature) Apatosaurus a very different animal than Brontosaurus that was.  At about the same time, the whole snorkeling lake-dwelling sauropods was replaced; we now believe that there's actually a strong correlation between sauropods and drier climates, if anything.  Granted; what we've learned about sauropods is much more interesting than what we used to think.  Most old dinosaur books associated the sauropods very distinctly with the Jurassic, and we were often only shown three of them; Diplodocus (the longest), Brachiosaurus (the biggest) and Brontosaurus (the most famous) while the much more common (yet fairly boring) Camarasaurus and the rare Haplocanthosaurus plus the European (yet poorly known) Cetiosaurus.  Maybe if you were really lucky, you heard of Barosaurus somewhere.  But those three were all we talked about.

Curiously, Brontosaurus has made a return; some specialists now believe that Apatosaurus deserves to be split into two genera, and Brontosaurus was the obvious choice.  There are now two to three species of both Apatosaurus and Brontosaurus specifically (probably separated in time, so that there was only one of each in the Morrison at a time, most of the time.)

Classic square-headed Brontosaurus trying to escape by going to the lake.

Very interesting.  Listening to the stuff about halfway through (a few minutes after one hour) they talk about sauropods being really big all of the time; that clearly isn't true, though.  He does talk about island dwarfs briefly, but the fact is, there really are a number of modest sized sauropods, and much of the latest Cretaceous sauropods are modestly sized.

He also talks about the polyphyly of Sauropoda.  This is not something that he really believes (in fact, he specifically says that) but it's still an interesting idea.


Konsumterra said...

those carnivores look so happy

Desdichado said...

I do like the lizardy smile on Allosaurus, as he stands almost as upright as I do and waves his tiny arms around.

Sigh. I admit to a lot of nostalgia about old dinosaur art. In spite of the lack of scientific rigor, even for the time (I dare you to try and fit the skeletons inside those bodies) they were often very good pieces of ART.