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Bird vs. theropod dinosaur tracks/trackways

 We recently had a guest speaker at Tyrrell and he had both Middle
Cretaceous shorebird footprints/trackways and theropod (large and small)
tracks/trackways. How to tell them apart? It was shown that birds show a
greater angle apart between the outside toes; walk pigeon-toed (with the
toes turned in towards the midline) and a straight line can be drawn inside
(in between the tracks) a straight bird trackway and not touch any of the
footprints. For theropods? Trackways are in a nice straight line and the
toes pointed more or less forward.

 Birds and theropods are widely accepted as being very closely related yet,
by the middle Cretaceous, birds were already walking like birds today, and
unlike their theropod relatives. Which raised some questions at the talk and
subsequently, for which I could not get clear answers. So, I thought I'd
raise them here for discussion.

 1). Why do birds "waddle" (and thus turn their toes inwards) and theropods
apparently did not (as manifested by the trackway evidence)? Someone thought
theropods did "waddle", but due to their greater height the direct effect of
this was somehow "lost" by the time the foot touched the ground (whatever
that meant!).
 2). What skeletal or other morphological feature(s) cause a bird to walk
pigeon-toed and theropods not?
 3). Could the difference be related to behavior? A suggestion was that
"waddling" bird tracks were of feeding birds while those of theropods were
simply walking from point A to B.
 4). Theropods are able to put one foot directly in front of the other,
birds apparently not. True? If so why? I'm not a bird footprint expert, but
if memory serves, I think I have seen some rather straight trackways with
the middle toe pointing more or less forward.

 Given the close relationships between both groups (one group?!), I find the
difference in their walking capabilities/strategies quite striking. Ideas


FAEVUS QUAESITOR SCIENTIA                                  FODERE AUT CADERE

DARREN TANKE, Technician I, Dinosaur Research Program, ROYAL TYRRELL MUSEUM
OF PALAEONTOLOGY, Box 7500, Drumheller, Alberta, CANADA  T0J 0Y0 and:

Senior editor of: Annotated Bibliography of Paleopathology, Dento-Osteopathy
and Related Topics. 12,702 citations as of January 28, 1999.
For details, visit the bibliography homepage at: http://dns.magtech.ab.ca/dtanke