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Re: CRETACEOUS AMPHIBIAN...HELP!



    Special thanks to list members Christian, Ken, Steve, and Tom for your
generous help.  I have been in Pennsylvania, or this note would have been
sent earlier.

    Getting information on Cretaceous amphibians is, as you say, quite
frustrating, because of its scarcity.

    Found: Some photos of fossil frogs, wherein the manus is shaped very
much like the fan-shaped, tetradactyl track I am trying to analyze. (I
didn't know this earlier.)  Yet, fossil trackways of frogs and trackways of
modern frogs that I have seen do not present a manus impression of this
type. There seems to be a consensus among those of you who so kindly
responded, that salamander attribution may be the safest guess as to its
origin, however.  It would be nice to see some more images of the manus of
salamanders (preferably Cretaceous).

    In absence of a photo of the track we are talking about, this brief
description in included in case it may give anyone on the list insight as to
the probable track maker: Again, track length is 52 mm.  The angle of
divarication (on-ground digits I - IV) in the track is 63 - 66 degrees.
Imprecision of angular measurement is because it is a little difficult to
determine the exact location of the vertex of the track in question.  The
digits are very smoothly tapered (almost straight-line edges with very
little signs of the joints) to the small, sharp claw tips, widening toward
the proximal at an angle of about 30 degrees. [Cautionary note:  This angle
might have become somewhat widened by erosion since the original imprint was
made.  I suggest some erosion because the joints are not clear.]  There may
be a slight sign of webbing between two of the toes.  If anyone gets any
insight from this description, please share it.

    Based on my extensive experience with dinosaur tracks, I can confidently
say it is not of dinosaurian origin, and I am almost as certain it could not
have been made by a mammal.

Ray Stanford

"You know my method.  It is founded upon the observance of trifles." --
Sherlock Holmes in The Boscombe Valley Mystery

----- Original Message -----
From: "Steve Brusatte" <dinoland@lycos.com>
To: <dinosaur@usc.edu>
Sent: Friday, August 17, 2001 9:41 PM
Subject: Re: CRETACEOUS AMPHIBIAN...HELP!


On Fri, 17 Aug 2001 18:46:04
 christian farrell kammerer wrote:
><<   Other than salamanders or frogs, the only other possibility I think
>of is that it was one of the last of the temnospondyls which apparently
just
>barely survived into the Early Cretaceous (none in North America that I
>know of).  So that doesn't seem very likely.>>
>
>Not likely for a temnospondyl, but what about an albanerpetonid? Although
>come to think of it, I'm not sure how easy it would be to tell an
>albanerpetonid and a salamander track apart.

Yeah, a temnospondyl would be pushing it.  I have serious doubts that they
even still existed at the time, especially in North America (as Ken said).

Hmmm...and albanerpetonid.  Maybe.  There are two references that may be of
help (that I know of).  Keep in mind that they are Middle and Late
Cretaceous, though, do do address areas other than North America:

Gardner, J.D. & A.O. Averianov., 1998, Albanerpetonid Amphibians from the
Upper Cretaceous of Middle Asia. Acta Palaeontologica Polonica
43(3):453-467.

McGowan, G. & Evans, S. E., 1995, Albanerpetonid amphibians from the
Cretaceous of Spain. Nature: Vol. 373, 12 January, pp. 143-145.

And, this ref may be of even more help.  Keep in mind, again, that it is
specifically about Late Cretaceous forms, but it does address fossils found
along the East Coast:

Denton, Jr. R.K. & O'Neill R.C., 1995, Amphibians from the Late Cretaceous
(Campanian) of Eastern N.America, including a new genus of
batrchosauroidid salamander. J.Vert.Paleont. 15(3, Suppl.): 26A.

This one may be able to help you narrow it down, especially if your track is
actually that of a salamander.  Another possibility is that your track isn't
amphibian in origin at all.  Perhaps it is a small reptile...or mammal.  I
really don't know, as I haven't seen it.  Maybe it is even some sort of
juvenile dinosaur.  But, Ray, if you say you think it is amphibian I trust
your judgment!  I hope that the above references have some nice diagrams,
especially of the feet.  I haven't actually read any of them, though...

It is VERY frustrating working on amphibians!

Steve

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