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Re: dino-lice

On 4/23/2011 3:56 PM, Jason Brougham wrote:
I just read about anatomical features that indicate that the hand of
Mononykus lost the ability to flex strongly relative to the ancestral
condition in Haplocheirus. This reduction of flexor ability is evidence
against any hypothesis that relies on strong flexion, including digging,
propulsion, and cracking termite mounds.

You certainly won't hear argument from me on termite mounds... :)

I am not clear that flexing is necessary for propulsion in this limited case, but that could be ignorance on my part.

I am clear on my watermelons needing water (that might be why they call them "watermelons") and this being Saturday Evening though, so this will likely be my last post this weekend...

Did you guys know that the ungual of Mononykus has no flexor tubercle? It
is not merely reduced, it is completely absent. Senter (2005) did not
mention this.

There is a robust, proximal, dorsal process on Ph I 1. This must be a
highly developed extensor process, right? Therefore, Mononykus may have
been specialized for strong extension, but lost the ability to flex
strongly. Senter also found a huge range of motion in the ungual (162

Strong extension, I like that! "Must pull head out of here... Unphh!"

Just kidding.

The distal radius and ulna do not articulate with the carpometacarpus.
Perle and Senter both assumed from this that there must have been
cartilaginous or otherwise un-preserved carpal elements. If the wrist
lacked tight - fitting, ossified, joints, this may indicate that the wrist
never bore large loads, as it must in digging.

I will have to think about that -- I know I can dig w/out loading my wrists, but...


All of these features are consistent with my hypothesis that the hands
bore a tuft of long plumes, and that the pectoral anatomy was specialized
to flutter them in threat or sexual display.

In the cases of species recognition, threat display, and etc., sexual dimorphism may not be an issue, but it is in sexual display. Can dimorphism be ruled out (or in) w/ confidence?

My sources are Perle et al. (Skeletal Morphology of Mononykus oelcranus
(theropoda: Avialae) from the Late Cretaceous of Mongolia, Amer. Mus.
Novitates, no. 3105, 1994), and Senter (Function in the stunted forelimbs
of Mononykus olecranus (Theropoda), a Dinosaurian anteater. Paleobiology,
Vol. 31, No. 3, 2005).

Jason Brougham
Senior Principal Preparator
Department of Exhibition
American Museum of Natural History
81st Street at Central Park West
212 496 3544