[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Bipedal apatosaurs and stegosaurs?



This notion is going to get me into trouble. 

Emily Giffin has published data showing that the neural controls of the
forelimbs (indicated by the cross-sectional area of the neural canal in the
shoulder region) of Stegosaurus and Apatosaurus were less well developed than
in other quadrupedal dinos and mammals. A similar condition appears to be
true of dicraeosaur sauropods. Reptiles have a similar condition, and EG
suggested that this meant that stegosaur and apatosaur forelimbs were more
sprawling than in mammals. The problem with this is that the articulations of
stego and apato forelimbs preclude a reptilian posture. 

An alternative starts with the observation that flightless birds also
have poorly developed neural control of their arms, because they do
not use them much. It is interesting and pertinent that Stegosaurus,
Apatosaurus, Dicraeosaurus and Amargasaurus share the following
characteristics. The neck is not extremely long, the trunk is short,
the trunk vertebrae decrease rapidly in height approaching the hips,
the sacrum and hips are massive, the tail is heavy, the arms are much
shorter and weaker than the hindlimb (humerus circ. is 1/3 less than
femur circ.) to the point that most of the animals weight is borne on
the hindlimbs, and the hindlimb is as strong as in bipeds. Indeed, all
of these are adaptations are normally observed in bipeds.

I therefore speculate that Stegosaurus, Apatosaurus and dicraeosaurs often
walked on just two legs. The failure to use the arms more often explains
their poor neural controls. Body posture when walking on just two legs would
have been horizontal, because the hips were not modified for a more erect
posture (as in therizinosaurs). This idea is very difficult to confirm or
deny. Even if hindprint only stego or apato trackways are found, it remains
possible that the animals were merely stepping onto their foreprints with the
hindfeet. 

Speculatively yours, 

GSPaul