dinosaur footprints again

Joel Duff (crinoid@midwest.net)
Wed, 28 Apr 1999 09:34:01 -0500

About six months ago there was a protracted discussion about the origin of
various fossilized footprints (the Coccino sandstone footprints). The
issue was whether they could be made underwater or not if I remember right.
In the most recent issue of Geology Today I see that there has been a
discovery of what appears to be a single layer of rock from a quarry in
Brazil that contains some 15,000 individual prints from it is claimed some
170 species of dinosaurs. These footprints include many different sizes
and one set that appears to be of one dinosaur coming together with a
smaller one at which time the smaller set of prints disappears.

Even disregarding the later, I will tell you what I logically conclude from
this. I have been asking myself if these footprints could have been
produced underwater and I have concluded probably not. The reason is that
there are footprints from many different dinosaurs of different sizes. It
seems to me that the water depth has to be just right for a dinosaur to be
swimming along and leave a trail of prints and that same water depth will
not allow for smaller or larger dinosaurs to efficiently leave prints. I
would have to propose wildly changing depths of water over time in order to
account for the variety of prints. Is my logic way off, the only thing I
can come up with otherwise is that all the prints were made by the same
animal but at different times at different depths of water (thus the weight
placed on the sediment varied giving what appears to be different prints).
Anyway, I thought this particular discovery might be worth keeping an
eye on for future developments.

Joel Duff