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Rise of dinosaurs not so rapid at all

Narrator: A team of paleontologists from the University of California, Berkeley, the American Museum of Natural History and The Field Museum discovered fossils in northern New Mexico that show for the first time that dinosaurs coexisted with their non-dinosaur ancestors for tens of millions of years towards the end of the Triassic Period. This discovery, made at the Hayden Quarry in Ghost Ranch, New Mexico, disproves previous notions that dinosaurs rapidly replaced their supposedly outmoded predecessors.

Randy Irmis, Graduate Student, UC Berkeley: We found a new species here at the Hayden Quarry called Dromomeron romeri and it means Romer's running femur. Al Romer was a famous paleontologist. And the species is what is called the basal dinosauromorphin. It's one of these dinosaur precursors and previously, similar species were only known from much older rocks in Argentina . So, this if the first time such a animal has been found in North America and the first time it's been found in the late Triassic. So, this really extends the range of this group of animals.

Narrator: The Triassic Period lasted from 250 to 200 million years ago, during which time arose a variety of animals including dinosaurs and crocodile relatives. The Hayden Quarry site is between 210 and 220 million years old.

Randy Irmis: In 2005, I visited here with colleagues Sterling Nesbit from the American Museum of Natural History and we saw some of the bones that had been excavated and realized that quite a few of them were early dinosaurs. And this was really exciting because there are very few early dinosaurs known from the Triassic, so we immediately realized this was something very special and decided it would be worth it to come back here and do a large excavation.

Narrator: Altogether, the researchers found thirteen hundred fossil specimens, including several complete bones and they are continuing to excavate at three sites in the quarry, sifting through the debris for smaller fossils of mammals, lizards and fish.

Nate Smith, Graduate Student, UC Berkeley: Most of what we're looking for here is small vertebrae, some teeth, things that might have gotten chipped off or that we lost and we're actually collecting up at Hayden Creek. But there's plenty of small vertebrates that we wouldn't otherwise get the way we're quarrying through. So, stream washing is a great way to increase the known taxonomic diversity of any single site. You almost always find more critters than you started out with. Already we found a couple of important teeth from a Silosaur-like animal, which is only otherwise known from Europe right now in the late Triassic. We know we've got some at that Hayden quarry and so it's great to find some isolated teeth because that's going to get us a bigger sample size for the animal and it's going to allow us to look at microstructure and wear on those teeth. The nice thing about that is this is a group of animals that is probably the most closely related animals to dinosaurs. And it seems to be that they were probably herbivorous, so very different than what we thought early dinosaurs and their relatives were like before.

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