Known in South Africa for years as the "caped dragon," Nielson provided the first description of Eowyvern dorsetti in 1929. Given that so few wyverns were known at the time (only Fugaxotitan and Gracilopterus predate it in the literature), Nielson was at first unsure of how to categorize the creature. At a mere six feet long, Eowyvern is slightly larger than Gracilopterus but much heavier, and completely flightless. Its build it far more dinosaurian than wyvernian given its functionally tridactyl pes, reduced hallux, facultatively bipedal (and horizontal) posture. Nielson even considered a connection with Aves, suggesting that Eowyvern was, perhaps, an ancestral relic of birds, surviving to the present. Perhaps not surprisingly, this possibility was briefly revived and endorsed by Feduccia in 1996. However, Nielson eventually placed Eowyvern at the base of the Wyvernia, a location it has not moved from since. Although some workers believe that Eowyvern represents a more modern wyvern which has become secondarily flightless, the current concensus is that it represents an incredibly basal lineage.
The most obviously basal feature of the animal are its wings. More like a pterosaur than a wyvern, Eowyvern's patagium is attached to a single extended digit IV, and the patagium extends down to the end of the ribcage on the body. The wing is incredibly small and has no flight capabilities. Digits II and III are long and move more or less as a single unit. Digit I is opposable. The arms themselves are not particularly long, and a propagagium extends from the wrist to the shoulder, strengthened by a thick tendon. Eowyvern is surprisingly broad-chested, unlike the deep-chested flighted wyverns, and long-bodied. The legs are powerful and tridactyl, making Eowyvern the most cursorial of all wyverns (or dragons). The skull is fairly small given the animal's overall size, and is equipped with numerous dagger-like teeth. The snout is blunt and subrectangular, more like dragons than wyverns. The eyes posess a fair degree of binocular vision. Eowyvern has a stout, powerfully-muscled neck.
The creature is undeniably predatory, often chasing down medium-sized mammalian herbivores such as boars and young or sick antelope. Eowyvern has been known to share territory with Tauropesa ungulatus, although Brimely (1953) noted that, given the latter's larger size and more aggressive attitude, Eowyvern always backs down from a direct confrontation. Eowyvern attacks prey with its hands extended, grabbing prey and tearing away a chunk of meat with its teeth before letting go. The target often dies of shock and bloodloss within a short time. The wyvern is not above scavenging carcasses, either.
Switek (1978) was lucky enough to observe several instances of wing use in Eowyvern. These observations are very powerful, in that they may allow draconologists to study how the wing structure evolved in more derived wyverns. In one instance, a large male Eowyvern had extended its wings, which had become brightly colored, to a female who he was courting. The male stood fully upright, or at least as upright as it could get, and "shivered" its wings in an attempt to show off the bright breeding stripes which had lit up the patagium's underside. The normal-colored female seemed unimpressed, and eventually ran away. In another instance, Switek watched as a female shaded her brood with her wings. The hatchling wyverns were small but looked much like their mother aside from larger relative eyes and proportionately longer hind limbs. However, at no time did Switek observe a wyvern flapping its wings or making use of the wings in any way that would suggest a precursor for flight. Switek reasoned that perhaps over the millenia, Eowyvern, in finding no use for flight-related activities, had lost such behaviors entirely, and that its own uses for its wings had developed apart arboreal needs. Switek's paper is interesting in that he only discusses Eowyvern for about two-thirds of the paper, and spends the last third complaining about the his institution (wink!).
Eowyvern continues to be a point of fascination today. In an upcoming publication on wyvern genetics, Milnar & Fries hope to accurately pinpoint the "first wyvern" on an extent family tree.
References:
Nielson, L. (1929). Comments on the "cape dragon" of South Africa. Brevia (February): 45-52.
Feduccia, A. (1996). Eowyvern dorsetti: evidence for the ancestry of birds. Bulletin of Zoological Curiosities 47: 468-473.
Brimley, W. (1953). Co-occurance of Eowyvern and Tauropesa. Brevia (June): 34-37.
Switek, B. (1978). Observations on wing use in Eowyvern. European Journal of Draconology 68(4): 533-539.
I must like this "reading" thing, because I just bought another book online. The Big Cats and Their Fossil Relatives looks to be a sister tome to the dog book I bought a few weeks ago (which is awesome, by the way). Cat evolution is something I've always wondered about, moreso than dogs. I mean, dogs are great, but cats can drag carcasses up trees! And there were never any saber-toothed dogs. Also, after reading this book, I'm sure I'll be able to give Catsby a hard time for being a very, very lazy cat, and thus, an embarrassment to her wild ancestors.
At least two of my readers (Sheryl and Glendon) currently think or have thought (respectively) that the dragons and wyverns and lindworms I write about are sculptures, sculptures that I have made. Nothing could be further from the truth. Anybody can buy these creatures at toy stores or comic shops. Or online.
What I do is make up scientific descriptions for these dragons and wyverns as if they were living animals. The McFarlane dragons have their own epic fantasy storyline, something about a hydra destroying the dragon kingdom and then humans gaining control of some magical stone and learning how to talk and...it's wierd. I'd prefer to think of these dragons as real animals, and I'm interested in how they might be related to each other. Incidentally, there are several McFarlane dragons I have not included (or bought) based on my preference for what dragons and wyverns are supposed to be. So I'm not sculpting these dragons, although whoever did is a great sculptor. I just try to give them life!
Last night, while loading some firewood into our shed, something hopped around the grass at my feet. I immediately suspected a moth, or perhaps injured dragonfly, but I was surprised to find a wood frog, Alaska's only ectothermic tetrapod. I grabbed the little amphibian and ran into the house. I put a bunch of my gecko's unused rock's in the cricket tank (there were no crickets), then filled the tank partially with water. Then in went the frog! It sat, barely moving, on one of the larger rocks before realizing that water was near. The frog scuried into the water and proceeded to float. Catsby realized that something was up and started meowing incesently.
I wanted to keep the frog, because during the winter, there's a good chance these frogs could die. They freeze themselves for two weeks at a time, but I felt sorry for the little guy. Gina reminded me that he'd probably rather be outside with his froggy friends, a point I conceded, so I let him go in our flower garden. I made Gina promise that if we found a frog in late September, she'd have to let me keep it. I'd like to help at least one frog get through the freezing winters!
Here's a question for you: See the picture on the left? That's the famous marine ground-sloth, Thalassocnus. As you can see, the genus is split into five distinct species, T. antiquus, T. natans, T. littoralis, T. carolomartini, and T. yaucensis. If they were dinosaurs, most of these species would probably be given distinct generic names. In paleomammology, it seems that authors are far more reluctant to separate animals at the genus level, even when the various species within that genus are irritatingly disparate. This may be because of another hallmark of mammalian paleontology that I find infuriating: In one of the three or four papers I have on aquatic sloths, the author(s) toy with the idea of separating some of the sloths at the generic level, but decide against it, concluding that the five creatures form a linear progression from semi-aquatic sloth to more fully-aquatic sloth. As in one population simply replaces another.
That thinking is carried over dog evolution, too. I'm reading a great book right now called Dogs: Their Fossils Relatives and Evolutionary History. My only knock against it is that the author continually posits that a known form of ancient dog (like Hesperocyon) simply "gave rise" to another dog, which in turn evolved into yet another form. In the discussion on borophagines in particular, the idea of succession is hammered into the reader's head. Paleoanthropologists used to have this idea about hominid evolution. Remember when there were only two hominid genera, Australopithecus and Homo? Now things have gotten a little better, with Paranthropus, and Ardipithecus added to the mix. Each distinct genus, however, is packed with several species. Homo consists of at least five, Australopithecus includes four or five, and even Ardipithecus, which is known from scrappy remains, consists of two species.
In mammal taxonomy, it seems like generic distinctions are tied either to chronology or some debatable "breakthrough" feature within a particular lineage. For example, very little differentiates H. habilus from the later australopithecines except for circumstantial evidence of tool usage. And even tool usage is shakey ground for a new genus name--chimps, gorillas, and orangs all use tools to some degree, and I'm sure australopithecines did, too. I read back in college about an anthropologist who wanted humans to share the same genus as chimps. We'd just be called Pan sapiens. Seriously? There are enormous morphological differences, both skeletal and otherwise, between me and Cheetah. Luckily, this thinking has not flown with the scientific community.
Things get even more bizarre when you think about modern mammals. The Indian and African elephants are generically separate (Elephas and Loxodonta, respectively). In a few million years, when future paleontologists are digging up their bones, will they be considered similar enough to warrant unification under one genus? Better yet, rather than dividing up the numerous populations of Indian and African elephants into distinct species, they are merely given subspecies variations. The savanna African elephant is L. africana africana while the forest elephant is E. africana cyclotis. Even better? One of the closest extinct relatives of the modern elephant, the mammoth, comprises of one genus and up to eleven species, based mainly on where they lived.
None of this would be tolerated in dinosaur taxonomy. Virtually every bone that comes out of the ground is given, at the very least, a new species designation. More often, you get a new genus, but this is often based on how complete the material is. While mammal taxonomy might be a case of under-splitting, dinosaur taxonomy seems over-split. Arguments about as to whether the European species of Allosaurus is a new species or an old species. If Allosaurus was a mammal, it would probably be considered a different subspecies. The mind boggles. I was blown away when Microraptor gui, Microraptor zhaoianus, and Cryptovolans pauli were theorized as being synonymous (Senter, et al. 2004), an idea that has continued to hold sway. "Dave," a juvenile sinornithosaurine dromaeosaur from China, has not yet been officially given a taxonomic name, even though it's pretty clear that the little bugger is a juvenile Sinornithosaurus. But what species is it? Liu, et al., in 2004, named a new species (S. haoiana) based on differences in the skull and pelvis. YARG!
How would mammalian taxonomy deal with a group like tyrannosaurs, where each animal seems to represent its own distinct place in the family? There isn't really a lot of "progression" with tyrannosaurs. You've got the basal forms, like Dilong and Guanlong, sure, but after that things tend to go to hell. Asian alectrosaurs are wholly different than, say, Alioramus or Appalachiosaurus. And those basal forms are, themselves, quite distinct from the albertosaurines and tyrannosaurines. And where does Eotyrannus fit in? Heck, what about Tarbosaurus, which could either be a sister taxa to Tyrannosaurus or the ultimate Asian tyrannosaurine that evolved in parallel to the North American tyrannosaurini from some Alioramus-like ancestor?
Is the mammalian fossil record that much more complete that we can point to Hesperocyon and say, "Okay, this was the direct ancestor of Osbornodon?" That just seems ridiculous! And even within Osbornodon, there are different species, including O. fricki, O. iamonensis, and O. sesnoni. And the ones in the middle are considered transitional between the earliest and the latest, as though a smooth progression from one end of Osbornodon to the other occurred! It's maddenning!
As Scott Elyard has reminded me on many occasions, fossil ancestry can never actually be known. The best we can hope for is to find a sister-group relationship between any two animals. You cannot point to Daspletosaurus and call it the ancestor of Tyrannosaurus. Instead, the two are sister groups, both born from some unknown common ancestor.
And that brings me back to Thalassocnus, the marine ground sloth. Maybe those different species occur in a fairly linear progression through time, one seemingly replacing the other, but that can never be known. Look, let's pretend that Dromaeosaurus, Velociraptor, Deinonychus, and Utahraptor are all called Velociraptor. For fun. V. albertensis, V. mongolensis, V. antirrhoppus, and V. ostrommaysi. Much as we'd like to, we can't say that one just evolved into the next, which evolved into the next, which evolved into the "pinnacle" of Velociraptor.
The best we can do is create a long tree, like this (I don't have a scanner at my side):
V. albertensis + (V. mongolensis + (V. antirrhoppus + V. ostrommaysi)
And each new step would require its own specific name. The most inclusive group might be Velociraptoria, the next step up might be Velociraptoridae, and the most inclusive group, comprising of V. antirrhoppus and V. ostrommaysi, might be the Velociraptorinae. But it's not a "line of descent," it's a branching bush with unknown common ancestors.
So that's what I don't understand about mammal taxonomy. And that's my rant for the day. :-)
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