Re: Paper on drepanosaurids

[Tim Williams <twilliams_alpha@hotmail.com>]

Silvio Renesto wrote:

> Simiosauria sounds appropriate, in fact if they are really so basal, they 
> mimic very well lots of characters of more advanced diapsids, pterosaurs 
> included.

And birds too!  But all of these bird-like ("avimorph") characters appear to 
be superficial, such as the triangular bird-like head.  Wouldn't it be funny 
if _Protoavis_ (or part of _Protoavis_) ended up in the Avicephala?

> More seriously, an applause to Phil Senter for stating  that no 
> drepanosaurid is aquatic, something I stated since 1994, but few believed 
> (guess why?).

I can't begin to guess.

> Perhaps some more people will now consider it as feasible.

Colbert and Olsen (2001) were so convinced that their new drepanosaurid from 
New Jersey was aquatic that they named it _Hypuronector limnaios_ ("deep 
tailed swimmer from the lake").  However, the authors did support the idea 
that other drepanosaurids may have been arboreal:

"_Hypuronector_ has a very deep tail, superficially comparable in shape to 
that of gymnotid or gymarchid fishes (figs. 6, 15 ). No other tetrapod has 
such elongate chevrons, or a tail with a strongly similar structure. The 
similarity at least superficially to the deepened tails in aquatic tetrapods 
such as newts and crocodilians, however, strongly suggests that the tail of 
_Hypuronector_ was adapted for sculling in water. [snip] There is no 
evidence that _Hypuronector_ could lift its tail so that it was at an acute 
angle to the dorsal series; all of the articulated specimens found thus far 
have the caudal series in line with the dorsal vertebrae. Thus, it appears 
unlikely that it could have been a balancing organ for arboreal life, as 
might be suggested by its relationship with _Megalancosaurus_ and 
_Drepanosaurus_. Evidently, _Hypuronector_ had a beak anteriorly, as judged 
from the pointed but toothless anterior mandible, the functional 
significance of which is obscure."

Reference:

Colbert, E.H. and Olsen, P.E. (2001).  A new and unusual aquatic reptile 
from the Lockatong Formation of New Jersey (Late Triassic, Newark 
Supergroup).  Am. Mus. Novit. 3334: 1?24.

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