Friday, 14 January 2011

A new, very early dinosaur

This BBC article is about a new dinosaur fossil found in the foothills of the Andes in Argentina in 1996 and only now published in the journal Science.

The almost complete skeleton took so long to prepare because it was embedded in ironstone, which was incredibly hard and difficult to remove.  Jenny and I are well familiar with that, since many of her Greenland fossils are in extremely hard matrix which can only be prepared by hand.

Christened Eodromaeus, it was about 1.2m long, so pint-sized, and hails from 230 million years ago, when the land was dominated by large mammal-like reptiles very different from the later dinosaurs.  At the end of the Triassic period, an extinction event wiped out about half of the known species, including most of the mammal-like reptiles, leaving the way clear for the dinosaurs to expand and take over the world.

This one is thought to be an early ancestor of the theropod line, leading ultimately to things like Velociraptor and T. rex.  Another beastie from the same timeframe, misfortunately named Eoraptor, is thought to be an early example of one of the other major lineages of dinosaurs, the sauropods.  Since the sauropods were herbivorous, a moniker meaning "early predator" is hardly appropriate.  However, it's been so named, and the name will stick, I think.  Them's the rules!  I think the people that published its description didn't realise it was more closely related to sauropods than theropods.  Well, it was very early in dinosaur evolution, so both these animals were pretty similar to the earliest dinosaur of all, so probably not a hard mistake to make.

No comments: