Monday, January 12, 2009

Whoa: Therinizosaurs with Simple Feathers?


Ed Young at Not Exactly Rocket Science has the scoop.

That would it feathers even further down as a basal trait for theropods, right? Therinizosaurs and maniraptors aren't that closely related are they?

12 comments:

Zach said...

Therizinosaurs ARE maniraptors. They're usually grouped with oviraptors (in a monophyletic "Oviraptorosauria"), but Zanno's research at SVP last year suggests that while still maniraptors, therizinosaurs are decoupled from oviraptors and instead sit at the base of the Maniraptora.

Either way, they're maniraptors, and it's no surprise that they have feathers. And we've known that Beipaiosaurus has feathers since it was discovered...

Will Baird said...

Oops.

For some reason I thought they'd been split off into their own clade towards the base of the theropods. My stupid.

Zach said...

That's the very old thinking. Paul considered them basal saurischians that were extremely close to the saurischian/ornithischian split. They've also been thought of as derived prosauropods.

It wasn't until a reasonbly complete postcranial skeleton (Alxsaurus) was discovered in the 90's that the group finally fell into the higher Theropoda.

Will Baird said...

I probably hybridized what I read: basal dinosaur and derived maniraptor.

Something kewl was happening in the Cretaceous that maniraptors were going herbivorous! Too bad we can't see what the next era would have been like zoologically if the dinos had survived.

Zach said...

I know. At least three groups of theropods (therizinos, ornithomimids, probably oviraptors) developed herbivory to some degree. However, all three groups originated in Asia during the Cretaceous, and there was a dearth of large-bodied herbivorous competition.

Will Baird said...

Query: when did the dearth of uber herb munchers disappear in Asia?

Zach said...

Well, nodosaurs and ankylosaurs were the resident low-browsers, as were basal ceratopsians. I don't think stegosaurs got very big over there. I imagine that therizinosaurs, which had tilted bodies and long necks, were able to browse at a level unreachable by the resident ornithischians.

I know there were some ornithopods over there, but they were probably eating tougher food material than the stegosaurs or therizinos. Niche partitioning, my friend.

Will Baird said...

Right but previously there had been sauropods there, right? When did they vanish?

Zachary said...

I don't know if sauropods were ever that prevalent in Asia...

Will Baird said...

huh.

I'll have to look up the Jurassic fauna of asia then.

Dr. Vector said...

There were sauropods in Asia during both the Jurassic and Cretaceous: Opisthocoelicaudia and Nemegtosaurus, for example. But they don't seem to have been very diverse or abundant, at least not in Mongolia. Of course there is a question of whether they were really thin on the ground, or we're just not finding them.

I find it interesting that the herbivorous maniraptors seem to have diversified bigtime around the time that angiosperms were on the rise.

Will Baird said...

I find it interesting that the herbivorous maniraptors seem to have diversified bigtime around the time that angiosperms were on the rise..

Two things. First that the KTR I thought was shown to be decoupled from dino diversity. Is this not correct?

Second, in a bit of spec-bio, could we see a rise of maniraptor derived high browsers taking over from the sauropods during or after the Mesozoic alt-Neogene?