David Marjanovic <david.marjanovic@gmx.at> wrote:
----- Original Message -----
From: "Thomas R. Holtz, Jr."
Sent: Monday, February 14, 2005 4:39 PM
In any case, the terrestrial Tr/J extinction event is a weird one. It
seems as if many (if not all) the big non-dinosaurian
archosaurs and non-mammaliaform therapsids were actually extinct by the
Norian-Rhaetian boundary, and didn't make it to the Tr/J
itself. (NOTE: this remains a subject of some debate). So the Tr/J on
land
may not be as catastrophic as the P/Tr or the K/T.
How easy, actually, is it to _find_ the Norian-Rhaetian boundary outside
of
western/central European marine strata...?
Regardless, the existence of Triassic sauropods does suggest (as you
note)
that large metabolically active creatures did survive the event.
_If_ we assume that the hatchlings were not cared for, which means they
didn't need their parents to survive, there could be an easy way around
this. However, this is hard to imagine -- an animal the length of a
computer
keyboard plus mouse pad that cannot run caring for itself!
Joe Cantrell adds these to David Marjanovic's response:
Imagine an energy depleted environment where herbivore populations
are beginning to wane and predators are very hungry. The survival of baby
sauropods would be problematic in the absence of parental protection even
if they didn't rely on their parents for food, not that they could
effectively compete with natural low browsers for what was left.