Re: Sauropods in wet versus dry environments... a tip of the hatto some past artists (Was Re. Lost Worlds)

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

    Tracy wrote,"Come on Ray ease up here, I hope your not having a bad
day."

    Thanks, Tracy, but no.  I'm having a good day. The exercise that such
discussion provides is good for the mind and invigorating, at least to me.
You see, I'm an identical twin, and we grew up arguing and enjoying it.

    Ford also asked, "Ok, educate us. How could a terrestrial, dry track be
fossilized without it being covered up by sediment from an aquatic force?
(Had to think how to write that one :) )."

    Because I am a Biblical typist -- "Seek and ye shall find." -- :), I
will not try that at any depth (pun intended) tonight.  Golly gee, it's
after mid-night over here in the east!  Suffice it to say, however, that if
you really want the answer, there is plenty of it in the paleoichnological
literature.  Tracks made in desert sands are well know, and if it were not
so late I'd give you a reference. Nature is pretty amazing at preserving
things that we might not expect to be preserved.  Although of a different
category, witness Scipionyx (may be spelled wrongly at this hour) with that
marvelously preserved intestine.  One can easily detect 'frozen' peristaltic
waves within it.  Before that find, I don't know of any paleontologist who
would have believed the preservation possible.

    A geologist friend of mine has a marvelous Permian multi-trackway where
some reptiles were crawling up a sand dune.  One can pretty well calculate
the angle of the dune being climbed, from the push-up by the back parts of
the pedes. Manus impressions were clearly there, too, but with not so much
push-back, informing one of the difference in the way the manus and pes were
utilized in climbing the dune.  There is nothing whatsoever in that trackway
to suggest that the dune was damp at all.  Had it been, one should have seen
some surface breakage in the areas of push-back, but they are perfectly
smooth.  Don't ask me to explain exactly how such examples are preserved,
but there are many such examples, which we must accept even if we cannot
understand them, so that some day maybe we can understand.

    I have also seen dinosaur trackways made in very dry environments.

    But, let me proffer a hypothetical but realistic case that will exercise
one's taphonomic grasp to the extreme:  A big sauropod plods along on a
hard, dry surface, but is ever so slightly more damp beneath the surface --
a common situation.  With each step, the animal is compressing the hard
substrate at the grain level, driving the grains closer together for some
respectable depth, although the depression atop the ground where the foot
has been is very shallow.  What happens is not a text-book pretty footprint,
but a column beneath where the foot was, that is more compressed and, thus,
more resistant to erosion that adjacent areas. In time, waters come, eroding
the hard dirt to the sides of the foot's compression area, but being in
great part resisted by the compressed area. In time, what results is a
'stand up and be counted' trackway.  :-)  In turn, this whole amazing thing
is covered by either wind or water-driven deposits.  Ultimately, millions of
years later, however, the covering deposit erodes away.  It was less
endurated than the 'stand up and be counted' trackway.  One looks across an
eroded surface and there is a recognizable sauropod trackway, incredibly
standing higher that the rest of the rock!

    Yes, there trackways of such a remarkable nature.  Compressional
preservation (in its various manifestations) is well known.  I simply
describe this one bizarre and rare type with hopes that there are simpler
scenarios for creating and preserving tracks in dry sand or dirt that you
(or anyone who cares to try) might imagine.  For me, analysis of taphonomy
is one of the greatest joys of track study.

    Now, let no one say I don't try to accommodate honest questions, even
after midnight. =)

    Thanks for your neat question, Tracy.  Now I shall make tracks to bed, I
hope.

    Ray Stanford

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