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compie



>Nick Longrich <nrlongri@midway.uchicago.edu>
>
>writes (snipped)
>>
>> We're on similar wavelengths- the triangular obturator looks
>>coelurosaurian. I think the lack of skid-like chevrons makes the thing
>>outside tyrannosauridae+maniraptoriformes. But the evidence is really
>>pretty meager for Compie.
>
>What's meager about Compsognathus? I've had a good look at the thing and its
>a stunning fossil - ok the skull is a bit mashed, but the limb bones are
>fabulous - good 3D, and more detail than the G.d. I had for Sunday lunch.
>Hasn't anybody looked, or is it just all primitive/uninformative?



        Yeah, I misspoke- it would be more accurate to say "uninformative"
(at least to me) than to say "meager". There's a lot of bone there, it just
seems hard to place a lot of it in phylogenetic context as information. For
example, the feet are gorgeous. But then, it's hard to think of much
synapomorphic about them- they aren't deinonychosaurian, and they aren't
arctometatarsalian, and this lack of synapomorphy can tell you something-
but "it's not this, it's not that" only goes so far. What *is* the darn
thing?
        The other thing is that a lot of the really useful parts of the
skeleton are missing. Hands can be quite informative but we don't have one
from either skeleton. I think tails are useful, but again, no complete tail
from either. No ilia from the type. Plenty of ribs, but there isn't much
diagnostic about those as far as I know. We can get some limb ratios but
those I get the feeling are pretty homoplastic. It doesn't help that the
second specimen has never been given a thorough published description.
        Also, you lose a great deal of information when you go from 3-D to
2-D, and while Compsognathus isn't 2-D it's pressed into the mud so it's
pretty close. There are a lot of really cool characters out there that
never get discovered because the only way to see them is pick up the fossil
and spin it around and visualize it in 3-d. Lateral view only goes so far.
        So what we are left in my mind with is a generalized small
theropod. I find Ornitholestes and Scipionyx and Sinosauropteryrx pretty
frustrating too. Sometimes you can find a single bone and you know what it
is. For example, the second pedal phalange of a dromaeosaur or the distal
caudal of a troodont is pretty instantly recognizeable as such. I think I
have a way to recognize maniraptorans from single claws. But sometimes you
can have huge amounts of the skeleton that won't answer your questions-
I've been told by a ceratopsian worker that you could have the whole
postcrania of an animal and basically not know what it was or what it was
related to.

        -N