[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Do not misunderestimate the king was Re: Evolution of tyrannosauroid
----- Original Message -----
From: "Dann Pigdon" <firstname.lastname@example.org>
Sent: Wednesday, January 02, 2008 1:51 AM
I'm skeptical that *adult* tyrannosaur forelimbs were used to capture or
manipulate prey at all. It wouldn't matter how strong the arm muscles
themselves were if the shoulder joints weren't up to withstanding the
generated by struggling multi-tonne prey.
What is not stable about the shoulder joints? And doesn't the tendon
avulsion illustrated by Carpenter & Smith (2001) look rather fresh?
If I were an adult tyrannosaur,
I'd rather use my massive jaw and neck muscles to subdue prey - or use a
'bite and retreat' method and not attempt to hold onto prey at all.
The latter is what all other theropods of this size seem to have used. They
had weak jaw muscles and normal archosauriform teeth (recurved, compressed
from side to side). Unlike tyrannosaurs. The other method could benefit from
arms holding the prey between two bites if the first bite (that catches the
prey) doesn't suffice to stop it from fighting or running away.
Perhaps the main use adult tyrannosaurs had for their forelimbs was to
help them rise from a crouching position? [...]
You are describing exactly Newman's (1970) scenario. As I explained
yesterday, it is impossible, because *T. rex*, too, was incapable of
pronating its forearms. Put the edges of your hands on the table; this is
the position *T. rex* was capable of. You'll see that digging the claws into
the ground was not an option. (Plus, its wrists were almost immobile.) Also,
how should this produce an avulsion of the tendon of the M. triceps, which
is a forearm extensor?
On the problem of how the poor beast did stand up, it has long been
suggested that it was no problem to extend the legs in such a way that the
animal stood up vertically. Ratites do it that way, and while *T. rex* had a
much heavier head and neck, it also had a fairly reasonable tail...