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


> I read somewhere that lizards make a poor model for a mammal but that
> mammals make equally lousy lizards. 

> Cheers, Paul
> pwillis@ozemail.com.au

This paraphrased quote is from the introductory chapter on mammals in Broadhead,
T. 1984. Mammals - notes for a short course organized by P.D. Gingerich and
..?? (Uni of Arizona Press, Tucson). Whoever wrote that introductory chapter
said that, while it is true that a reptile would make a poor mammal, a mammal
would make an equally poor reptile. Those trivia freaks among you might remember
that I actually quoted this some months ago, which is why I've remembered it.

(The ref. is from memory, hence the forgotten bits..)

ON THE PRESSURE EXERTED ONTO FORELIMBS when a rearing sauropod moved back to its
quadrupedal state, I feel it unlikely that much exertion of the forelimbs would
have been needed. To rear into a bi/tripodal stance, a big dinosaur would
probably not need to 'push off the ground' with its forelimbs. Simply leaning
back would tilt the sacrum, the counterbalancing of the tail immediately lifting
the thorax and neck. Lizards that rear in threat displays 'push up' with the
arms, but their tails aren't far enough off the ground to provide a levering
effect for the upper body. 

On coming down, a sauropod certainly must have lowered itself slowly - crashing
down and producing ground tremors a la JP would probably be a little too hard
on the joints - maybe they 'walked' down tree trunks, as stretching cats and
bears do (I've seen it). Upchurch and someone else recently suggested that
sauropods used ungual 1 to steady their forelimbs on tree trunks without
slipping. This perhaps applied when de-rearing.

Speculative? Ha! I've been to the Mesozoic, oohhh yes...

"I'd just as soon kiss a wookie!"  "I can arrange that. You could use a good