RE: If an Asteroid wiped out the Dinosaurs how did Evolution continue?
July 10, 2013 at 5:08 pm
(This post was last modified: July 10, 2013 at 5:12 pm by The Grand Nudger.)
(July 10, 2013 at 3:38 pm)Chuck Wrote: The foraging dinosaurs of middle Cretaceous certainly did, and it might just be possible that Jurassic dinosaurs also didLatest word says that whatever would eventually become grass was likely already around by 129mya. Pop her a couple more my and genetics and speculations about what fossilized evidence we may some day find have a rough parity, again. We still can't find the damned grass though, and that's a shame. Again, leads to caution about speculating herds of grazing dinosaurs as opposed to dinosaurs that -could- eat grass.
Cretaceous evidence:
1. There was a major change in the composition of foraging dinosaurs population around 120 mya. Big herding quadrupedal herbavores built for browsing very low to the ground, and dentition showing adaptations for, and signs of, working with highly abrasive plant material (such as grass with their intra-cellular silicate crystals) became much more numerous. High browsers became comparative much less well represented. This change does not require any anatomicaly breakthrough on the part of dinosaurs, so it must be an adaptation to the composition of available plant material. There must have a been a major increase in neutritious ground hugging plants around 120 million years ago.
2. Some of the low browsers may have eaten woody brush like plants, but others like hedrosaurs and titanosaurs have cow like adaptations that seem specifically targets ground hugging, abrasive, but not tough, plants like grass.
Jurrasic evidence:
The late cretaceous grass evidence has been found in dinosaurs dung fossils from India and Africa. These evidence points to existence of diversified grass during late cretaceous that had already some evolutionary distance from any original ancesteral grass. How far is suggested by India and Africa have been separated during the break up anf Pangea 140 million ago. This suggests the original ancesteral had already existsed 140 million years ago. That's so close to Jurrasic that it might as well be jurrasic.
http://www.nature.com/ncomms/journal/v2/...s1482.html
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