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Re: JFC-Bloodiest Battle ??
I have not seen the Longrich and Currie paper, so I am speaking from a
bit of ignorance here, but that has not stopped me before. Forelimb
analysis can provide insight into strength, planes of movement, etc.
Its a further step to what those movements were used for by the
organism. When confronted with something as bizarre as alvaresaurids
and the desire to make sense of them, getting them to fit into a known
niche, such as myrmecophagy, can be satisfying. And it may even be
correct. I would maintain that we should be circumspect because the
world of the past may have offered opportunities different and more
diverse than the present. I guess I don't see a problem with saying
these are damn weird beasts and we have no real understanding of what
the hell they were doing.
To return to a long abandoned thread, when the flight analysis of
Microraptor showed that the feather arrangement as preserved did not
give the expected gliding path, re-examination of the feathers yielded
an arrangement that did give the expected path and was viewed as
success. Maybe the new arrangement was correct, or maybe it just
satisfied expectations. Maybe a much more vertical drop WAS the hunting
strategy of Microraptor and not too relevant to the origin of flight.
Or maybe gliding developed from such a death from above hunting technique.
My arms are tired from waving, so I shall retreat until a future time.
Tim Williams wrote:
Dan Chure wrote:
I remain agnostic on the myrmecophagus habits of Mononykus. The
forelimbs are very short and I can't see how that would work
functionally with the long neck.
The alvarezsaur bauplan is certainly unlike any modern myrmecophagous mammal. However,
between them I think Senter (2005) and Longrich & Currie (2008) present a strong
case for considering alvarezsaur forelimbs as being specialized for breaking into
insect nests. The combination of a long neck and short forelimbs might make sense if
(as Longrich & Currie propose) alvarezsaurs fed on wood-nesting termites. So as
the claws tore into rotting trees, the alvarezsaurid jaws would snatch up the termites
scurrying up the surface of the trunk. A long and flexible neck would help in this
Nevertheless, the shortness of the alvarezsaur forelimbs is especially weird. Even if the forelimbs were used for digging, why were they so short? It's possible/lilely that alvarezsaurids evolved from theropods in which the forelimbs were already reduced (as in compsognathids - or maybe compsognathids themselves were the ancestors of alvarezsaurids). Perhaps alvarezsaurids inherited forelimbs that were on the way to being vestigial? Then, for one reason or another (maybe to do with the shift to a myrmecophagous diet), the forelimbs acquired a new function in digging. But by this point the alvarezsaurs were stuck with their puny forelimbs, and had to make the best of them. And, for some reason, the forelimbs could not be re-enlarged - although fortunately a strong upper arm musculature was retained. Carnotaurines have tiny forelimbs that were probably useless, but the scapula and coracoid are still very large and (presumably) well-muscled. So alvarezsaurid ancestors ma
similarly have drastically shortened the forelimb (associated with loss of function), but left the arm musculature mostly untouched (?to promote ribcage and pectoral girdle mobility, as suggested for _Carnotaurus_). This gave the alvarezsaurid forelimb 'wiggle room' to take on a novel function, although in a less-than-ideal way given how short the forelimbs had become.
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