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Re: Dinosaur Tracks (long)



Hi Brandon, Allan, et al,

    Determining that a track or track-way  records an original,
first-generation imprint of a foot or hand pushed into a substrate is a very
difficult call, except in extremely rare circumstances wherein
high-resolution dermal impressions remain.

    There is a question of how one defines the term "original", "primary",
or "first-generation".  For example, is a pes (foot) or manus (hand) print
visible in what is the originally imprinted substrate still a "primary" if
it has lost a little bit of silt, sand, mud, or whatever to erosion or other
factors  As in sports (when there is no recourse to video playback), we are
at the mercy of whomever is making the call, unless we have learned to do it
ourselves.

    I strongly recommend that one evaluate the relevance of dinosaur
paleo-ichnology  not by the negative pronouncements of those who seem to
think that bones are the only Rosetta stones to understanding the specifics
of the dinosauria, but by an open-minded examination of what experienced
dinosaur icnologists  have to offer dinosaur science.

    Let us note carefully that while bones have essential value in that they
provide primarily information about DEAD dinosaurs, the study of dinosaur
tracks can wonderfully reveal direct evidence of dinosaur dynamics (LIFE
ACTIVITY), foot and hand morphology, and other many other significant
things.  If one doubts this, it would be well to read Martin G. Lockley's
"The vertebrate track record" under the "progress" heading in NATURE, Vol.
396, 3 December, 1998, pages 429 through 432.  Nature's web site:
www.nature.com .

    But, as to the question of whether tracks are primary, under-prints, or
over-prints, I'm not sure we should believe world-class ichnologist Adolph
Seilacher as he declared during a Dinofest '98's dinosaur track session, "I
think there is no such thing as an 'original' dinosaur print.  What we see
are always either under-prints or overprints."  (This makes me feel that his
real expertise must lie in ichnites other than vertebrate tracks.)

    I vigorously challenged this assertion by asking Seilacher to specify
what factor or factors so BIAS the geological record as to preserve millions
of underprints and overprints, yet NO "ORIGINAL" prints!  He did not answer
this question, maybe because he either could not, or else did not want to
(for whatever reason).

    To Seilacher's credit, however, see the feature article about a major
acheivement of his in SCIENCE NEWS, December 19 and 26, 1998 (combined)
volume 154, nos. 25 & 26, front cover and pages 398 through 400, concerning
his wonderful "Fossil Art" touring exhibit, currently at Yale's Peabody
Museum of Natural History.

    Now, back to our topic of discussion:   A track recorded in wet,
large-grained sand, for example, may still be "primary" (if taphonomy has
favored it) although it would ordinarily record few, if any, of the finer
details of an animal's foot or hand, unless there were the right kind of
silt between the sand grains.  By contrast, some "primary" tracks made in
more favorable-to-detail substrates can record so much graphic detail about
the animal's fleshed-out foot or hand that upon close examination one can
almost imagine the animal was there only moments before and, having
back-tracked, is breathing down one's collar!

    Much about a track's appearance (whether "primary" or secondary) is also
influenced by the STATE OF MOTION of the track maker, in addition to what is
being stepped in -- not to mention the animal's weight and the effect of
other things on substrate conditions.

    Thirdly, one must evaluate the taphonomy of a track or track-way.   What
seems to have happened when a track(way) was made, and in the moments,
minutes, days, months, years, and in all time since it was formed?  Very
careful observation, geological knowledge, and years of studying such things
are prerequisites to insightful taphonomic analysis.   In all of this, as in
all of science (whether one likes it or not), there is always INTERPRETATION
of the raw data, that comes into play in making conclusions and in reporting
them.

    One can deduce a great deal from track-ways even if the individual
tracks are not first-class, primary impressions.  Now, a quote of the last
three sentences of the afore-mentioned NATURE article by Martin Lockley:

    "This empirically derived data base helps us define and measure spacial
and temporal incompleteness in the skeletal record of terrestrial
vertebrates.  Thus, we can focus on which parts of the fossil record must be
described ichnologically, osteologically or by both methods. This holistic
view shows that many questions about foot morphology, posture, locomotion,
behavior, terrestrial vertebrate palaeoecology, stratigraphy
and information biases cannot be fully understood without consideration of
the data encoded in the track record."

    So, let's not throw the baby out with the bath, when one does not have
primary tracks to work with.  And, as to learning to discern the "primary"
tracks from others, there is no substitute for experience.  That is why I
invite intelligently interested, seemingly trustworthy persons I meet to
come 'experience'  the tracks discovered from the Early Cretaceous of
Maryland.

    One might go on for pages contrasting the morphology of "primary" tracks
with secondary tracks, but, honestly, experience via observation and study
are the best way to learn, while DETAIL remains the best indicator of a
"pristine" track.

    Also, study the few good, available books on dinosaur tracks, and --via
the many good dinosaur books -- carefully study the skeletal morphology of
dinosaur feet and hands.  There is much to lean in becoming a student of
dinosaur tracks.  And, indeed, there are more tracks than just those of the
easier-to-recognize 'three-toed' dinos around.  To recognized them, one best
stay informed, patient, and alert.

    In fear that I've said a lot without clarifying much, best wishes, and
thanks for the interest in paleo-ichnology.

    Ray Stanford