Defending the indefensible

A couple of weeks back there was a fresh round of bashing on poor little Pantydraco. Bashing the name, not the dinosaur that is. It is a matter of some embarassment to me that I should be tied to what is widely regarded as the worst dinosaur name ever. I take pride in the names I craft, and I don't think I'm too bad at it (Dracovenator, Antetonitrus, Nanalania are some faves) even if I do say so myself.
So here is some of the backstory behind the name. Firstly: it was not my invention! That particular dubious honour goes to Peter Galton. When I first named the species caducus I found some characters that linked it with what I was calling (and still call) Thecodontosaurus antiquus, so thought that the wisest course of action was to name a new species in that genus. However as I found out more about Thecodontosaurus antiquus (and I regard all of the English cave fill sauropodomorphs as one taxon) more and more differences with the Welsh ‘Thecodontosaurus ‘ caducus started to show up. For instance the ischial shafts of T. antiquus are an unusal flattened ovoid cross-sectional shape whereas those of ‘T.’ caducus have the classic triangular cross section seen in most other basal sauropodomorphs. Significantly support for a monophyletic Thecodontosaurus had diminished to the point that it was no longer recovered in all of the most parsimonious trees of my improved cladistic analyses (as more characters were added and more scorings were based on first hand observations) . So I had come to the conclusion that it was time to erect a new genus for ‘T.’ caducus. I even had a tentative name thought up – Cambrambulus – the Welsh wanderer. However I was not quick enough and at the 2005 SVP Peter Galton told me that he was close to submitting an MS giving caducus that infamous generic name.
Naturally I felt rather attached to the first dinosaur species that I named and wanted to remain associated with the generic name (which after all is the most frequently cited name in dinosaur circles). So I told Peter about my plans and we agreed to write the paper together, even though our reasons for naming the new genus were different. Peter felt that Thecodontosaurus was a dubious name because he thought that the type specimen of T. antiquus (the type species of the genus) was indeterminate. I agree that it isn’t the best and that it has no single derived character that cannot be seen in other sauropodomorph taxa. However I am still unconvinced that there are two morphs in the original Durdham Downs quarry, or that Asylosaurus is all that distinct. Taken collectively the Thecodontosaurus antiquus sample is unique and diagnosable. The utility of bone bed taxa is itself the subject for another post but to put it simply I’m all for using them in the right circumstances. In this case the surviving scanty sample from Durdham Downs is backed up by a large sample from Tytherington . This is another set of sauropodomorph bones from a fissure fill in the English south-west. Here there is absolutely no sign of two morphs and all of the recovered bones are virtually identical with those from Durdham Downs.
So there we are, the Pantydraco paper is very much a compromise - melding two different viewpoints but agreeing that little caducus needed a new generic title. Perhaps I should have pushed Peter to change the name, but being my meek and mild self, didn't do so. In anycase I didn't think it was quite that bad at the time,although yes, I was quite aware of the conotations (I guess thats a little bit of my juvenile sense of humor showing though).
Lastly for all those who absolutely hate the name - remember it is correctly pronounced 'Pant - uh - dray - co' which is not quite so bad as 'panty'.

From the galleries of the BPI: The Cape Giant Zebra

This specimen is a partial set of jaws of Equus capensis, the so called cape giant zebra, from Makapansgat, the most northerly australopithecine site in South Africa. Actually, although robust these equids are not so giant, being about the size of a big modern horse. Fossils of this robust equuid are widespread throughout South Africa, with the type coming from close to Cape Town, way down in the southwest.
It is often said that Africa escaped the megafaunal extinctions of the late Pleistocene but there is a definite set of large African mammal species that clearly did not make it through to the present. These include the giant buffalo Pelorovis, other bovids like Megalotragus, and supposedly Equus capensis. But if Charles Churcher is right reports of E. capensis' demise are greatly exaggerated. It s apparently alive and well in the form of.... Grevy's Zebra.


Image from wikimedia commons

Apparently the teeth (which are what most extinct Equus taxonomy is based on)of E. capensis do not differ in significant ways from those of E. grevyi and a bunch of east and northern african fossil equiids (e.g. E. oldowayensis).
Grevy's zebra is now restricted to East Africa and cannot be found anywhere near Suth Africa. So if it doesn't represent an actual extinction it does represent a drammatic range contraction.

reference

Churcher CS (2006)Distribution and history of the Cape zebra (Equus capensis) in the Quaternary of Africa. Transactions of the Royal Society of South Africa 61:89-95

What was it?

That ugly mystery bone is out now. What a disaster! when lifting it from its jacket, an undetected puddle of glue had soaked through the sepparator and firmly welded the underside to the jacket (lesson for the future - make sure there are several layers of sepparator between the bone and the jacket). The remarkable thing about the bones from this quarry is that although the compact outer bone is well-preserved the interior is like compressed flour. Once a break is started the whole bone tends to crumble to powder, much like the unravelling of a woollen jumper once the stiching comes undone in one place. Consequently the finished product is not one of our lab's proudest moments and I won't be showcasing it here. Nonetheless two things are apparent 1) it is a busted ischial peduncle from an ilium - exposed in medial view in the photo. 2) this part alone is about the same size as a middling Massospondylus, so although Rutger was halfway right he doesn't get full marks. The diagram below indicates which part of the ilium the bone is, and should give the astute clues to where I think its relationships lie (incidentally it is from the same site as the sauropod caudal I described in the South African Journal of Science (2004, vol. 100. 504-506)

End of year blues

Hi guys,

This blog has become far more quiescent than I ever intended it to be. I am currently feeling exhausted and swamped by marking at the end of the year, including honours projects, exam papers and essays - urgh. Of all my duties I hate marking the most. Time is of the essence but I want to be scrupulously fair to all, a desire that used to compell me to read and re-read each essay two or three times before finally settling on a mark. When not marking I am tidying up various other bits of end of year business - and occasionally writing up some of my research for publication. I wish I could tell you guys about it (it is one of the most enjoyable aspects of my job) but sadly this work has to go through the long drawn out process of peer-review and publication first. Maybe I'll be able to say something in 2010!
Anyway I've dragged up a picture of an old field trip from my vaults. You can see that the weather was kind of .... damp. This happened a lot on my field trips (and not always in rainy season either) so much so that one of the dinosaurs we happened to find in between rainstorms received the nickname 'Rainmaker'.
Anyway the load on shoulders should be lifting soon. I'll have a visit from my mum soon and we'll be doing a few trips round Gauteng. Then I'll be off on a short field trip to retrieve a dinosaur we left behind earlier in the year. So by December my batteries will be recharged and blogging will begin with renewed vigour (I hope!)

What is it?

...... The answer is - I don't know. This is one of those weird 'head scratchers' or GOKs (God only knows) that we get from time to time. Celeste is prepping it up right now. Its been sitting down in the lab for over two years and various volunteer preparators have had a go at it and quickly left it for easier more exciting projects. It comes from the upper Elliot Formation in a quarry that has produced more than one type of sauropodomorph as well as a protosuchian crocodile and some honkin' big theropod teeth. Any suggestions?

Good News Everyone!

After spending the whole week in hospital (it wasn't just tonsilitis after all) Matthew will probably be coming home tomorrow ..... and one of palaeontology's holy grails - a basal stem turtle has been found and published.

I imagine most of my readers know that pinning down the closest relatives of turtles and the origins of their bizarre morphology has been one of the most recalcitrant problems in tetrapod evolution.
While the lack of holes in the cheek region of the skull suggests that they are an offshoot of the anapsid reptiles, with procolophonoids or pareiasaurs being the main contenders, more than one large scale morphological cladistic analysis has found that turtles are members of the Diapsida (derived reptiles with two pairs of holes in the temporal region of the skull). Molecular work also supports a diapsid origin for turtles but tends to place them close to, or within, the Archosauria (crocodilians, dinosaurs, birds and their kin)whereas the morphological work tends to align them with the Lepidosauromorpha (lizards, snakes and kin).

Sadly the new turtle described by Walter Joyce and colleagues in Proceedings of the Royal Society is too fragmentary to really speak to this vexatious issue. But it does tell us quite a bit about how their most distinctive feature - their shells - evolved and lets us know that the answers are out there (given the recent spate of excellent discoveries in the Chinle and its equivalents I'm sure a more complete proto-turtle won't be be a long time coming).

But first a little of the who, what where and when. The new fossil is called Chinlechelys tenertesta (the thin shelled turtle from the Chinle)and the known remains consist of fragments of shell with attached underlying parts of the vertebrae and ribs and isolated osteoderms found in the Bull Canyon Formation of New Mexico. The name is taken from the Chinle Formation, which is a little odd since most stratigraphers and palaeontologists would not to place the Bull Canyon Formation in the Chinle Formation (or Group according to some), prefering instead to place it in the Dockum Group. The age of this part of the Dockum is probably mid-late Norian of the Late Triassic, somewhere between 210 and 219 million years old.
There are other equally old turtles in Europe, Greenland and South America but none so primitive in shell design as Chinlechelys. For starters its shell is unusually thin but more importantly it still has rather individualised ribs, that although joined to the inside of the shell, are not fully subsumed into it.
The telltale fragment - a piece of shell with an individualised rib beneath it.Modified from Joyce et al. 2008

This is important because it helps falsify the model that the shell is a modified ribcage alone and supports the hypothesis that the shell is a composite structure formed from the agglomeration of trunk vertebrae, ribs and several rows of osteoderms (bony armour in the skin). Intriguingly modern developmental studies have suggested the former hypothesis because it appears that the shell grows as part of the endoskeleton (that is it is made of replacement bones that are preformed in cartilage and derived from scleritomic mesodermal cells. Developmental studies can yeild powerfull evolutionary data but I think the takehome message here is that developmental pathways can and do evolve. Palaeontology definately still has a place at the high table of evolutionary studies!
Hypothetical steps in the evolution of the turtle shell following the osteoderm hypothesis. From Joyce et al. 2008

Bonus musing: If the molecular data are correct it is perhaps no co-incidence that some pseudosuchian, or crurotarsan - whatever you preference, archosaurs have rather turtle-like carapaces. Aetosaurs even have a plastron of plate-like osteoderms.
Paratypothorax, an aetosaur. Compare to hypothetical stage II above. Image from www.dinotime.de

WG Joyce, SG Lucas, TM Scheyer, AB Heckert, AP Hunt (2008). A thin-shelled reptile from the Late Triassic of North America and the origin of the turtle shell Proceedings of the Royal Society B DOI: 10.1098/rspb.2008.1196

Tonsilitis again!

My little guy, Matthew, who is one month shy of his second birthday, has come down with serious tonsilitis for the second time in as many months. It would appear to be a law of nature that kids always fall sick on a weekend, usually a Sunday evening when medical services tend to be a little thin on the ground (especially for those not wishing to sit in a casualty waiting room for hours). At the moment this is my main blog-writing time. So sadly I'm empty handed - once again. I don't feel to bad about this however because I managed to get hours of research writing in, before Matthew got sick.
In lieu of my own work I would like to point folks to Matt Wedel's thorough dissection of the recent Aerosteon paper.

Matthew in better health doing some computer work of his own.