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Upright bipedalism in dinos



To all and sundry:

First, thanks to all who responded to my arachnid question.  The critter was 
variously identified as an amblypygid, a "wind scorpion," a "sun spider," a 
"whip scorpion" or "false scorpion," and a solpugid (or solifugid), with this 
last being the odds-on favorite.  I wish I had been able to retain the 
specimen over the 20-odd years and thousands of miles since I collected it in 
the Ethiopian rift valley.  I hope one day to return there, so I may be able 
to find more.  

Now for something completely different!  :)  A combination of several 
threads that have been passing through the list recently, as well as my own 
fertile imagination, have caused me to ponder the following question, which I 
now submit for discussion:

One of the features observed in the earliest dinos, and retained not only by 
a large majority of dinos known in the fossil record, but also by all of 
their modern feathered descendants (to a greater or lesser extent), is a 
bipedal posture which includes upright, parallel hind legs, a body whose 
spine is parallel to the ground (and so roughly at right angles to the legs), 
and a flexible neck which projects forward from the spine and carrys the head 
at an angle in front of and above the rest of the body.

Furthermore, it has been pointed out that while many extinct species of 
dinosaurs developed a quadrupedal posture, all birds (both flying and 
flightless) maintain the ancient bipedal stance.

There is one group of birds which is somewhat exceptional in both regards: 
the penguins.  Their stance has changed to a far more vertical, erect 
posture, more like that of hominids than that of any other dinos or birds 
that I can think of.  However, although they are capable of erect walking, 
they also propel themselves on their bellies in a modified quadrupedal manner 
on ice (or is this better described as non-pedal locomotion?), and of course 
swim horizontally in a manner which to my way of thinking could be called 
quadrupedal (although swimming is clearly a special case of locomotion).

My question:  are there any known fossil dinos which may have had an erect 
posture similar to that of the penguins?  The secondary question would be: 
are there any other birds (ancient or modern, other than those leading to the 
penguin line) which show similar adaptations (primarily erect posture, but 
also horizontal/quadrupedal locomotion)?


Skip Dahlgren
Applications Programmer, Office of Educational Development
University of Arkansas for Medical Sciences
Phone: 501/296-1087; FAX: 501/686-7053
e-mail: sdahlgren@liblan.uams.edu; bcsskip@aol.com
-ex-archaeologist; lifelong afficionado of dinosaurs and their latter-day kin 
"If men had wings and bore black feathers, few of them would be clever enough 
to be crows" - Henry Ward Beecher
"You're wasting your time if you try to outsmart a crow!"  :)