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

Re: choana



Thomas R. Holtz, Jr. <th81@umail.umd.edu> writes:
 
> The internal nares (internal nostrils) of _Velociraptor_ and of
spinosaurids
> were shown at SVP (and the recent spinosaur paper by Taquet & Russell) to
be
> much further back in the snout than previously thought.

So, as Gregory S. Paul has pointed out, we must take the anteriorly
directed "monitor lizard" placement of the internal nares in the
_Dromaeosaurus_ skull illustration from the Ruben et al. paper in _The
Complete Dinosaur_ (p. 515, figure 35.9) to be very far off the mark.  In
retrospect, it is difficult to see why such a short nasal path was ever
proposed for this genus, considering that the depicted nasal passages of
_Ornithomimus_, _Nanotyrannus_, birds, and crocodilians all are a good deal
longer!  On the other hand, GSP has explained that the erroneous
_Dromaeosaurus_ illustration was based on fragmentary remains.

Regarding the metabolic status of non-avian dinosaurs, each of us will sift
through and decide for ourselves what the bona fide evidence suggests (if
we even choose to broach the issue).  It seems to me that criticism can be
leveled at most lines of evidence in the debate, but one must look at the
balance of all the pertinent information available and consider whether
this suggests an animal which is, metabolically speaking, more like an
extant reptile, or a bird, or a mammal, recognizing, of course, that the
dinosaurs were under no obligation to neatly compare with any of these
groups.  And, needless to say, the non-avian dinosaurs were a very diverse
group, so there was likely to have been much metabolic variation therein
(especially when you take ontogeny into account).

-- Ralph Miller III     gbabcock@best.com