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Re: Morrison Formation turtle tracks question
Jurassic West is a great book; if you haven't read it you should.
John is also a great speaker. He did a wonderful presentation for the
Friends of Dinosaur Ridge last year.
Rather than speculate, I took the liberty of e-mailing him myself.
Here is John's response:
"What happened with the turtle tracks is...well, let's start at the beginning.
In 1999 Martin and I did a paper about the first turtle track site in the
Morrison (down by Lake Powell). We didn't assign those to an ichnogenus at
that time. We later thought they might be Chelonichnium. The second
Morrison turtle track site at Colorado National Monument was found in 2005
and in the process of doing a paper on these (Lockley and Foster, 2006) we
decided the Morrison turtle tracks from both sites were better assigned to
Chelonipus. Jurassic West was already pretty far along by this point,
however, and I'd already written the tracks up as Chelonichnium, so late
in 2006 (in page proofs) I switched the text (p. 235) to Chelonipus.
Unfortunately, it was too late to switch the figure by then. You'll notice
I tried to tie the text and figure together a little in the Figure 6.52
caption on p. 236, where I changed the caption text to read
"Chelonichnium-Chelonipus". With the figure already locked in at that
point in the process, those two changes were the best I could do to
coordinate text and figure.
The neat thing is those are still the only two Morrison turtle track sites
that I'm aware of. There have to be more out there."
Here is the full citation he provided:
Lockley, M .G., and Foster, J. R. 2006. Dinosaur and turtle tracks from
the Morrison Formation (Upper Jurassic) of Colorado National Monument,
with observations on the taxonomy of vertebrate swim tracks. New Mexico
Museum of Natural History and Science Bulletin 36:193-198.
So, if anyone knows of any other Morrison turtle tracks now would be
the time to chime in.
On Wed, Mar 24, 2010 at 10:45 AM, Saint Abyssal <firstname.lastname@example.org> wrote:
> I've been reading John Foster's "Jurassic West" about the Morrison, and in
> the chapter on trace fossils Foster talks about the formation's few turtle
> trackways being classified in the ichnogenus Chelonipus, yet on the next page
> the diagram of the tracks refers them to Chelonichnium. Does anyone know
> which it is? Or both?
> The text sort of obliquely implies that the tracks may have actually been
> REclassified into Chelonipus from an unnamed ichnogenus. Presumably they
> could have been reclassified from Chelonichnium, but I'm loathe to try to
> guess at what the author wanted to say, since I lack any expertise.
> Does anyone have any knowledge or good references discussing Morrison turtle
> trace fossils?
> ~ Abyssal