Re: Hypsilophodontid toes & tracks

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

    Dann Pigdon asked of Hypsilophodontid feet:

"Did the first toes actually reach the ground, and if so, would they have
borne enough weight to leave impressions in trackways?
Skeletal reconstructions of Hypsilophodon and kin seem to show sizable
first toes with decent sized claws, yet it would seem to me that an
animal that probably relied on speed to escape predators would have
reduced the first toe more than this, if not lost it all together. Could
it have played a role in improving traction? If so, I'd expect to see
impressions in trackways. Are there any four-toed small ornithopod
tracks known (I'm not aware of any)?"

    Unequivocally, yes.   Digit I (first toe) of a type of hypsilophodontid
that lived in
Maryland during Early Cretaceous of Maryland, U.S.A., touched the ground
firmly, leaving much more of an impression than just an ungual.

    Seven seemingly adult size pes (back foot) prints have been found, and
also a three-footprint trackway made by a very young hypsilophodontid (which
also shows the digit one impression).  Two of the adult-size pes imprints
are each accompanied by a diagnostic manus impression, showing all five
manual digits.  One of the manus/pes sets is particularly spectacular.
Comparison of the manus and pes imprints show unmistakable correlation with
skeletal reconstructions of the Hypsilophodon manus and pes.  The imprints
to which I refer occur in diverse substrates, yet all are of the very same
remarkable morphology.

    The pedal digit impressions of the Maryland Hypsilophodontid show a very
distinctive morphology unlike those in any other ornithopod tracks with
which I am familiar, and unlike those of any theropod, as well.  The
Hypsilophodon manus is likewise unique.

    There are those on this list who declare (having done so in the past)
until they are red in the face that no footprints can point to a specific
dinosaur unless the dead trackmaker is found at the end of the trackway, but
they have not seen the Early Cretaceous Hypsilophodontid tracks of Maryland.

    Unlike the nay sayers, list member Jim Farlow (a dinosaur track
researcher of many years experience) HAS seen  four or five of the examples
I have mentioned (including the diagnostic manus/pes imprint sets) and it
would be wise of those who might want to take aim at me for saying that the
tracks are diagnostic to see them, as did Jim, before making a fool of
oneself (or forever hold your peace).  In fact, so far as I can recall,
every professional paleontologist and paleoichnologist who has ever seen the
diagnostic tracks and manus/pes sets has agreed with my attribution, when
shown the excellent Hypsilophodon pes and manus skeletal reconstructions
shown on page 107 of David Norman's book, The Illustrated Encyclopedia of
Dinosaurs, for comparison.

    It is the unique pes and manus of hypsilophodontids that make their
imprints unmistakable, once you have seen them.  So far as I know,
Hypsilophodontids are the only type of dinosaur that could produce such
diagnostic tracks, even considering dromeosaurid tracks (which are also in
the Maryland collection).  No dead Hypsilophodontid at the end of a trackway
is needed to demonstrate the origin of the tracks of such an animal,
provided those tracks are of good quality, as are those to which I refer.

    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!

    Ray Stanford
    Mesozoic Track Project
    College Park, Maryland, USA

"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: Saturday, August 03, 2002 1:46 AM
Subject: Hypsilophodontid toes & tracks


Here's a quick question about hypsilophodontid feet: ...