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Re: Airbagged(was Dive!Dive!Dive!)



At 03:37 PM 11/5/96 -0500, Jeff Martz wrote:

Okay, the discussion previous on this topic was good enough, so I didn't
feel the need to join in.  However...

>     All in all, I just think that given:
>1) T.rex lived in a forested environment with quite a few potential 
>obstacles, and which might make it difficult to pick up speed compared to 
>a flat, open area.

T. rex lived in many environments.  As Farlow (1993) and others have pointed
out, predators today and in the past tend to be more widely distibuted over
space and environments than contemporary herbivores (compare the historic
range of pumas and wolves on the one hand with those of pronghorns or
caribou on the other).  Furthermore, T. rex fossils have been found in
(nearly?) all the Lancian terrestrial seds of western North America for
which fossils are known, which included upland, coastal, and other environments.

>2) Some anatomical evidence (femur strength and the relative shortness of 
>the metatarsals) seems to indicate that T.rex wasn't incredibly speedy.

Relative shortness of the metatarsals?  Relative to WHAT?  Giraffes? Giant
camels?  Other than those two, there are no other multi-ton animals known
which had longer metatarsi than tyrannosaurids.  I really hope you are not
looking at the AMNH specimen (with an improperly shortened foot) or
listening to Jack Horner on this subject...

T. rex's metatarsi are proportionately as long as those of Dryosaurus and
Deinonychus, in an animal 100x or more their mass.

In fact, if you go by metatarsal proportion, it strongly suggests that
tyrannosaurids were probably swifter than any other animal *in their size
class* (note that it says nothing about comparisons with smaller animals).

{In case you are looking for the appropriate ref, it is Holtz, 1995, JVP
14:480-519.)

>3) The significant likelyhood and risks of T.rex falling increasing with 
>speed, and

Yes.  Agreed.

>4) The fact that they larger animals of T.rex's environment might have 
>the same problems in the dealing with environmental obstacles as T.rex, 
>and also generally had shorter legs anyway,

Yes.  A predator doesn't have to be faster than animals which came much
later (horses, etc.): it just has to be faster than its potential prey.

>    I tend to lean toward the idea that T.rex was not a high speed runner 
>or sprinter.  What is so sluggish about 12-15 mph anyway?

Yes.  I might go up to 10 m/s (22 km/hr), [Oops!  You mean 22 mph,
Tom! -- MR ] which IS a high speed runner for large animals!

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661

"There are some who call me...  Tim."
-- Tim the Enchanter, "Monty Python and the Holy Grail"
---------- subtitle --[Monty Python ik den Holy Grailen]

"Tim?!?  They called me TIM?!?!"
-- Tom the Paleontologist, on seeing "The Ultimate Guide to T. rex" :-)