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Thomas R.
Holtz, Jr. wrote-
Quite. Incidentally, even if there were a
mid-sized tyrannosaurid in the Hell Creek, it doesn't make a difference to the
big pattern we were describing: namely, the extreme taxonomic diversity and even
size distribution in the Morrison versus the more restricted taxonomic diversity
and very uneven size distribution (all big carnivores being tyrannosaurids) in
the Hell Creek, Judith River, and the like.
Do
you think that the Morrison could simply be much better sampled than
virtually any other formation? I know I have the most theropod taxa listed
from it than any other place in my stratigraphy file. Most Late Cretaceous
North American small theropods are known from partial remains so that all
troodontids are grouped as Troodon formosus and all "velociraptorine" remains
into Saurornitholestes. Bambiraptor and a few other unnamed taxa are
showing us that diversity of the latter is higher than previously thought, which
may hold true for other families as well. It is odd how pretty much all
Late Cretaceous large theropods are tyrannosauroids or abelisaurids
though.
Actually, the Two
Medicince Form (which comes out as the sister to Daspletosaurus
torosus) is not a particularly long-snouted form. This is the form
considered by Horner et al. (1992) to be transitional between
Daspletosaurus and T. rex.
Oops. Which is the "long-snouted"
daspletosaur specimen then?
David Marjanovic wrote-
>> Pleurocoels are absent from all dorsals
[...].
> Sounds like a juvenile character. Is
it that size-related?
I'm pretty certain these were adults.
The absence of pleurocoels from most of the dorsals in ornithomimosaurs seems to
eliminate the possibility of size-relatedness. Plus the small taxa with
lots of dorsal pleurocoels, like Saurornitholestes and basal
pygostylians...
>> Oddly, all metacarpals are
subequal in length, with digit I having an especially large ungual.
> Are you sure the hand is not from
something else?
Well, they are attached to Microraptor
specimens with Microraptor autapomorphies (accessory trochantor, very long
proximal caudals, etc.). So basically, yes, quite sure.
>> The specimen that was to be named
"Huaxiasaurus" (NGMC 98-5-003) from the Lower
>> Yixian Formation at Sihuten,
Liaoning Province.
> Why "was to be named"?
> It isn't the Czerkas aye-aye dino, is it?
Because they're unsure how much is from one
specimen, as well as the identity of various elements placed
incorrectly.
No, it's not the aye-aye
theropod.
>> Another Sinornithosaurus specimen
(BI 3-13) is also described. It is almost complete,
>> preserved in side view.
There are long feathers with rachis on the forelimbs and hindlimbs, >> as
well as a 250 millimeter long tail frond.
> So it has wings and a
Caudipteryx-like tail???
Wings, yes. I don't know the details
of the tail, other than the feathers project that far beyond the tip.
Whether there were also feathers lining the side up to the base, I can't
say.
Mickey
Mortimer |