[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
On the one hand, Morokweng was said to be relatively innocuous because
it struck so far south, on the other, it supposedly wiped out NA diplodocids
and Allosaurus (while Gondwana titanosaurs, stegosaurs, dicraeosaurs, etc.
survived!) If a Chicxulub-size blast can create a global dust cloud,
location of impact should be an irrelevancy. As a huge, benign event,
Morokweng may do more damage to the impact theory than it did to the
dinosaurs. Shivas is another possibility, but it seems an odd coincidence
that an impact occurred in the same area as massive Deccan volcanism unless
it triggered the latter, in which case it struck 1-3 Ma prior to the K-T and
therefore is of no relavance to it.
Fires started by lava can spread far so K-T ferns need not be atop
Unlike Tyrannosaurus, ceratopsids always seemed endemic to Cordillera.
Anchiceratops didn't migrate to Mongolia with Saurolophus. T-rex evolved
when the regression began, but probably couldn't spread until it was far
advanced c. 65 Ma. Overrun by chasmosaurines, the Lancian ecosystem may have
collapsed when many T-rexes migrated, easing predation pressure and causing
ceratopsid numbers and food demands to increase even more. The replacement
of overgrazed, good vegetation with ferns doomed the Lancian herbivores,
which were too large or specialized to live elsewhere when their rich habitat
So Pararhabdodon could run away fast? T-rex was also fast! No
lambeosaur survived alongside T-rex in Cordillera, despite exposure to
earlier tyrannosaurs. Foreign prey wouldn't have stood a chance.
Dinosaurian prey was more vulnerable to extermination than many extant forms
because it was relatively large and easy to find, and had smaller
populations. Moreover, T-rex had extremely acute senses and was very adept
at finding prey. Perhaps certain crocodilians, turtles, pterosaur nests,
etc. helped sustain the T-rex population long enough for it to complete the
elimination of non-Cordilleran dinosaurs. Also, if lands were connected,
incoming prey from remoter ecosystems may have sustained T-rex while it
annihilated the nearest non-Cordilleran quarry, a process repeated as it
continued to migrate until nothing but the nondinosaurian substitutes were
left (some of which also disappeared.) The brown tree snake soon outnumbered
Guam prey as it annihilated the latter, even mammals.
There is ample evidence that small theropods were nest raiders e.g.
Troodon teeth associated with hadrosaur nests. Oviraptorids evolved as
specialized egg eaters (see Currie.) Ornithomimids probably relied on
dinosaur hatchlings for the bulk of their diet. As edentulous carnivores,
they bolted down small prey whole. And there wasn't much alternative to
nests. No small theropod could have survived for long without other
dinosaurs. Mammals were mostly inaccessible (nocturnal, arboreal, burrowing)
as were many birds and reptiles. Insects and worms were woefully inadequate.
Crocodilians, varanids and turtles could probably withstand small theropods,
at least. So could pterosaurs.
K-T sea levels may have fallen 100m. In any event, there was a big
difference between Mesozoic and Cenozoic sea life: the former was far more
thermophilic. Long before the Ice Age, sea life was adapted to Cenozoic
cold. That was the key difference between a whale and a mosasaur. Even a
modest fall in ocean temperature might've doomed Mesozoic marine life. And
regression could have contributed to cooler temperatures, since it meant the
oceans had less surface area to be warmed by the sun.