[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: New theropod (or is it?) from Poland

To forestall the departure of David Marjanovic... :)

To anticipate my return from triassotherapy (Â Jan BrejÅa)?

Yes, on Thursday we* all went to Lisowice OOPS Lipie ÅlÄnski**, where the museum was opened for the public***, and we saw the humongous dicynodont and the supposed theropod. The site is thought to be Rhaetian or perhaps late Norian, thus much younger than the Carnian KrasiejÃw, and the sediment is different -- in KrasiejÃw it's red and green marl (mostly red = iron-III, but green = iron-II in some layers and around most fossils), while in Lipie ÅlÄnski it's uniformly gray and contains lots and lots of gagate, a kind of coal. The excavations are ongoing, and new finds are being made constantly.

* Participants in the excavation in KrasiejÃw, the site where *Silesaurus* comes from.
** After the opening ceremony, several people got very angry at Tomasz Sulej because the National Geographic Polska article says "Lisowice", which is the community that Lipie ÅlÄnski belongs to, rather than just saying "Lipie ÅlÄnski". It was, in any case, not his fault...
*** Pompous ceremony with a press conference, three mayors, a priest (hey, it's Poland), cutting of ribbons, and the like. Nice to see paleontology is taken seriously :o)

David thinks (like some others) the "Dragon" may in fact be a hybrid of theropod and "rauisuchian" material.

The "others" are Daniel Madzia and VladimÃr Socha, who alerted me to the possibility. The femur has an inturned head, which means it's not rauisuchian and is probably dinosaurian; the braincase is said to be unambiguously dinosaurian, which is something I can't tell and am willing to believe at face value; but all the rest could be rauisuchian, and the maxilla and the jugal clearly are rauisuchian. The antorbital fenestra was very small, far away from the ventral margin of the maxilla, and had a sharply tipped rostral end instead of a round edge; the lateral temporal fenestra was placed far more ventrally. Both features occur throughout rauisuchians and never in theropods. The condition looks identical to that of *Postosuchus* and *Teratosaurus*. The dentary also looks like that of *Postosuchus* (at least). Even the humeri could be rauisuchian; I recommend a comparison with the paper on *Postosuchus* in the latest JVP (June 2008).

Importantly, the parts of the skull between the premaxilla, maxilla and jugal on the one hand and the braincase on the other hand are so far unknown. Also, I don't know which teeth the enamel was examined of; there are many isolated teeth in the site.

- the workers took this as one of the possibilities from the beginning;

In that case I'd really like to see an explanation for at least the antorbital fenestra.

- the mixture of primitive ("rauisuchian"-grade), through coelophysoid, up
to advance tetanuran features is expected in a big Late Triassic theropod;

Erm... no, it isn't. Especially the presence of _derived_ rauisuchian features like those mentioned above is totally unexpected, and I also don't see why "advanced tetanuran features" should be there.

- foot tracks (and some of the bones, like femur) undoubtly point to a big theropod, most parsimonously would be to assume that's the same animal.

A completely unknown amount of Triassic "theropod" tracks was made by rauisuchians like the dreaded *Effigia* and *Poposaurus*. (Well, not completely unknown -- those with hand prints are obviously not from theropods.)

To sum up:

- The dicynodont is genuine. Very big, and very late. I'm not really surprised, because the Triassic-Jurassic boundary mass extinction came later.
- It's an end-Triassic site, so I'd be surprised if theropods were completely absent, and indeed some material -- the Dragon's femur, the braincase, the material called coelophysoid -- may well belong to them, as may some or all of the footprints (but not necessarily all of them). In other words, the claims of "the first Polish dinosaur" may well be justified.
- However, most of the Dragon could be rauisuchian, and some of it almost certainly is. I'd be surprised if it were specifically *Teratosaurus silesiacus*, though, because it's around 20 million years younger than the type material of that "species".