Re: Hypsilophodontid toes & tracks

["dinotracker" <dinotracker@earthlink.net>]

    Dann Pigdon wondered of those three-toed ornithopod footprints found
around Australia, "Could perhaps Australian
hypsies (if they were the track makers) have reduced their first toes,
unlike their relatives from other parts of the world? Now there's a
radical thought - that something unusual happened to Australian faunae!"

    Considering Australian faunae, it might not be surprising, even though
it would be surprising!  :)

    But if Dan would provide me a link to some images of the tracks
involved, it would be appreciated.  Meantime, I shall presume that he refers
to the ichnogenus Wintonopus (Cenomanian) , as seen abundantly at the Lark
Quarry site (Wintonopus, and said by John A. Long in DINOSAURS OF AUSTRALIA
AND NEW ZEALAND, vary between 3 and 27 cm in length ("...but usually 7 - 8
cm long...").

    If the 27 cm type are identical to the smaller ones, them I think we can
eliminate hypsilophodontids as the trackmakers  because IMO a 27 cm
footprint is just too large to be attributed to a hypsilophodontid, except
something like Thescelosaurus, which may or may not be a hypsilophodontid,
and which existed substantially later than the animals that left the tracks
found in the Lark Quarry.

    Now as to the smaller ornithopod tracks which predominate at the Lark
quarry, one might speculate that if the trackmakers were indeed
hypsilophodontids and were running 'all out', then digit I (the first toe)
might not have been reaching the substrate, so digitigrade was the running.
However, since Long says that the trackways at the Lark Quarry were made in
clay, either it was a quite hard clay, or a digit I should have depressed
the substrate, if the foot was built like the skeletal reconstruction
mentioned in my earlier post on this subject, or like the Maryland hypsie
pes impressions.

    Long, wisely, does not try to attribute Wintonopus to a specific type of
Ornithopod, and quite frankly, I suspect that the tracks there could have
been made by some other type ornithopod, perhaps by a group of sub-adults.
The diagnostic hypsilophodontid manus/pes sets and pes prints found in the
Early Cretaceous of Maryland show a pes that at longest is about 10 cm long
(the shortest being about 6 cm long).

    Quite aside from size, judging from the large Wintonopus example (17 cm
wide!) shown by photo on page 131 of Long's book, unless that is an
extremely digitigrade track, the digits are just too 'fat' looking and close
together to compare favorably with the Maryland hypsie tracks.

    It might be of interest to point out (for purpose of comparison), that
the Maryland hypsie pedal digits are, invariably, widest about 75% out from
the back end of each digit impression, from which they taper quite sharply
to the tip, making for a very distinctive footprint, with the toes showing
separation excepting very close to the back of the footprint, unlike the
example of Wintonopus shown by Long.

    At this point, I would vote for the idea that the Lark Quarry ornithopod
tracks are not those of hypsilophodontids, although the idea is appealing,
considering how abundant hypsies were in Australia.

Hypsies Forever!  (Er, well, they were very successful and did exist in
various forms for quite a long period.)
Ray Stanford

"You know my method.  It is founded upon the observance of trifles." --
Sherlock Holmes in The Boscombe Valley Mystery
----- Original Message -----
From: "Dann Pigdon" <dannj@alphalink.com.au>
To: "DML" <dinosaur@usc.edu>
Sent: Monday, August 05, 2002 5:03 PM
Subject: Re: Hypsilophodontid toes & tracks


dinotracker wrote:

>
>     Yes, Dann, (at least some) 'Hypsies' had 'four on the floor'.  And
when
> they came to a stop, they had five 'on the floor', up front.  They were
> remarkable and very successful little animals!
>

Thanks. It just raises one question though: What animals made all of
those three-toed ornithopod footprints found around Australia? I don't
recall seeing any with a fourth toe impression. Could perhaps Australian
hypsies (if they were the track makers) have reduced their first toes,
unlike their relatives from other parts of the world? Now there's a
radical thought - that something unusual happened to Australian faunae!

Or could most of the Oz tracks be running impressions? Would the first
toe be in full contact with the ground in a fast run? The Lark Quarry
tracks seem to show only the tips of the toes, and judging by the depth
of the "heel" marks they seem to have been propelling themselves
forward. Or are most of the tracks actually undertracks, with shallower
first-toe impressions now gone?

The only articulated hypsie foot I know of from Oz is the partial
articulated skeleton from Dinosaur Cove (with the osteomyelitic leg). I
can't tell from photos exactly how the foot looked (although it looks
well preserved). Anyone with first-hand experience with the beastie in
question?

--
________________________________________________________________

Dann Pigdon                   Australian Dinosaurs:
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://www.alphalink.com.au/~dannj/
________________________________________________________________