New Evidence for That Huge Dinosaur Family Tree Rewrite

[muriel_volestrangler]

Chilesaurus, which roamed the planet about 145-150 million years ago, was originally grouped with the theropods, those bipedal carnivores that include, most famously, T. rex and velociraptors (as well as the lineage that eventually led to modern birds).

There was just one problem: the small size of its head, its leaf-shaped teeth, plus a keratin-covered, beak-like feature called a rhamphotheca at the end of its snout, all screamed “plant-eater.”
...
It turns out, according to today’s study, that when Baron and Barrett added Chilesaurus to their dataset of early dinosaurs and dinosauromorphs, the animal fit rather well as a very early ornithischian, or even a possible “transitional” species leaving the theropod trunk to branch off into Ornithischia.
...
Accepting it as an early ornithischian, right at the ornithischian-theropod split within Ornithoscelida, means that paleontologists still have to reconcile what it was doing running around more than 90 million years after the split actually occurred.

http://blogs.discovermagazine.com/deadthings/2017/08/15/new-evidence-for-that-huge-dinosaur-family-tree-rewrite/#.WZPwFDOGPIU

More coverage:

http://www.sciencemag.org/news/2017/08/scientists-struggle-fit-strange-vegetarian-dinosaur-family-tree

http://www.newsweek.com/chilesaurus-dinosaur-evolution-t-rex-650964

http://www.bbc.co.uk/news/science-environment-40890714

https://phys.org/news/2017-08-dinosaur-link.html

The paper:

http://rsbl.royalsocietypublishing.org/content/13/8/20170220

I think the use of "missing link" isn't justified; as that last excerpted paragraph says, Chilesaurus was from long after everyone agrees the big split happened, whichever side you put the theropods on (universally recognised ornithischians like Fabrosaurus and Scutellosaurus were between 200 and 190 million years ago). If they're right, Chilesaurus is a descendant of the 'missing link' between theropods and the established definition of ornithischians.

Earlier thread on the possible rewrite of the family tree: https://www.democraticunderground.com/122851107

[Bernardo de La Paz]

1. Interesting. I'll have to read in detail later. Thanks for posting! . . . nt