Just dug up; Ornitholestes

16 08 2007

I thought I would share another old paleo-image with you all. Here’s Ornitholestes hermanni, looking much the same as it does today in the AMNH’s Hall of Saurischian Dinosaurs.

Ornitho
From Osborn, 1903 “Ornitholestes hermanni, a new compsognathoid dinosaur from the Upper Jurassic.” Bulletin of the AMNH ; v. 19, article 12.


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7 responses

16 08 2007
Zach Miller

Ah, Ornitholestes. It and Coelurus are two theropods whose position in the Theropoda is forever changing. They’re always centered right around the Tetanurine-Maniraptora transition, though, as either incredibly derived tetanurines or very basal maniraptors. It doesn’t help that both animals are poorly preserved, with just one specimen each. And the question of Ornitholestes’ nasal “horn” comes and goes as well. Some say there is a horn, others say that the nasals were just crushed and squashed into a horn-like shape.

I also like Ornitholestes because of its name. If nothing else, Osborn is fantasically imaginative, thinking that the shape of the hands as well as the “balancing power of the tail” suggest that this creature was distinctly adapted to hunt Jurassic birds. Of which none were actually known in North America at the time (actually, that’s still the case).

I also like that it’s being called a compsognathid. This is not really the fault of Osborn–it’s just that small theropods were virtually unknown back then, and the only comparisons were Compsognathus and Coelurus.

17 08 2007
laelaps

Thanks for the comment Zach! I always appreciate your insights. I remember this dinosaur being in nearly every dinosaur book I got as a child (usually in the same pose as above), but it has disappeared over the years. I guess it’s just too problematic to stick in one section or the other. I would prefer my Ornitholestes with a horn, although preference says nothing for whether it really did or didn’t. In the AMNH display, it’s in the little maniraptoran cul-de-sac, facing the Archaeopteryx replicas, so I guess that’s the AMNH’s take on where it should be (then again, the exhibit was revised in the mid-90’s and things have certainly changed since then).

17 08 2007
johannes

> Tetanurine-Maniraptora transition

It might be nitpicking, but the clade Tetanurae includes, among other things like spinosaurs and tyrannosaurs, maniraptorans. In other words: maniraptorans are, by definition, members of the Tetanurae. So technically, there aren’t such things as a Therapsida-Mammalia transition or an Tetanurine-Maniraptora transition, because mammals ARE therapsids and maniraptorans ARE tetanurans. Sometimes cladistics can drive you mad… : )
(especially if you had grown up with the linnean system, like I did).

But where to put Ornitholestes? Olsen places it within Coelurosauria but outside of Maniraptora, as does Mikko Haaramo. Ironically, this is pretty close to compsognathids – so perhaps Osborn got it quite right in the first place…

17 08 2007
laelaps

Thanks for the information johannes; that does make a lot of sense (I have to admit that I need to brush up on the “big picture” of dinosaur evolutionary relationships). I do find cladistics a bit maddening, though, mostly because I don’t particularly care for cladograms, but I know I can’t avoid familiarizing myself with the science behind it if I’m going to have any understanding these days.

17 08 2007
Zach Miller

I know that maniraptors are tetanurines! That’s just the best way I can describe where Ornitholestes sits on the Theropoda family tree.

20 08 2007
johannes

Zach,

perhaps basal or stem Tetanurine – Maniraptora transition will be the best compromise.

20 08 2007
Zach Miller

Yeah, that works.

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