Dinosaurs are archosaurs, a group that includes crocodiles, birds, and all the descendants of their most recent common ancestor. The closest relatives of dinosaurs, which evolved with them in the Middle and Late Triassic (about 225 million years ago), include the flying pterosaurs and agile, rabbit-sized forms such as Lagosuchus and Lagerpeton. The common ancestor of all these forms was small, lightly built, bipedal, and probably an active carnivore or omnivore. Somewhat larger, with skulls ranging 15–30 cm (6–12 in.) in length, were Eoraptor and Herrerasaurus from the Late Triassic of Argentina, and Staurikosaurus from the early Late Triassic of Brazil. They were thought to be primitive saurischian dinosaurs, but it was later determined that they were outside the group formed by Saurischia plus Ornithischia, a view generally followed. In reconsidering these genera plus the more recently discovered Eoraptor, it has been argued that all three are both saurischians and theropods. However, they lack some features of both groups, so their position remains controversial. This testifies to a burst of evolutionary change at this very interesting time in vertebrate history, and it shows that there are a variety of taxa that are very close to the origin of dinosaurs. The first definite ornithischians and saurischians appear at almost the same time as these taxa, though dinosaurs remained generally rare and not very diverse components of terrestrial faunas until the beginning of the Jurassic Period (about 200 million years ago).
2006-11-10 02:59:28
·
answer #1
·
answered by Anonymous
·
0⤊
0⤋
Unless you're a psycho creationist that believes the earth is only 6,000 years old and that dinosaur bones were hidden to test our faith in God.
Hopefully you don't buy into that. Yes, dinosaurs ruled the earth for many millions of years....well, not like they had a government, but the earth was crawling with them...in all shapes and sizes.
2006-11-10 00:51:24
·
answer #2
·
answered by Shaun 4
·
0⤊
0⤋
yep, everyone agrees that the dinosaurs did reign supreme at one point. the issue is when and what happened to them
2006-11-10 00:07:07
·
answer #3
·
answered by mRNA 2
·
0⤊
0⤋
YES because there is archaeology proofs for this
2006-11-10 03:43:33
·
answer #4
·
answered by genius sonia 3
·
0⤊
0⤋
Y..E..S!! yes yes yes...fossiles fossiles fossiles
2006-11-10 05:16:27
·
answer #5
·
answered by elucidiamia 2
·
0⤊
0⤋