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RE: _Microraptor zhaoianus_




Could we look at this from the BCF point of view, and say that this form could be a bird descendant whose foot is reverting back for ground-dwelling, and that the feathers are "degenerating" being no longer needed for flight. Or would this be a "just-so" story that is too unparsimonious? Seems like you could look at it either way, but perhaps other evidence imparts some directionality here, one way or the other.
Just speculating, Ken
*******************************************************
From: "Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>
Reply-To: tholtz@geol.umd.edu
To: <jhecht@world.std.com>, "Dinosaur mailing list" <dinosaur@usc.edu>
Subject: RE: _Microraptor zhaoianus_
Date: Thu, 7 Dec 2000 09:57:55 -0500

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Jeff Hecht
>
> Tom Holtz wrote
> >*The metatarsal I and pedal digit I are very distally placed, and the penultimate phalanx of each of the toes is elongate: Xu et al. interpret this as indicating a climbing habit.
>
> Xu says that the foot structure indicates a ground-living ancestry.


(Specifically, Xu was referring to the arctometatarsalian nature of the foot in this context).

> Suppose the common ancestor was a Microraptor-like animal adapted for predation both on the ground and in trees, so it never truly gave up ground-dwelling but spent a significant part of its life in the trees. The ability to glide down from the trees might offer an evolutionary benefit, giving an advantage to any dino-bird with flight feathers. Perhaps it started by extending pouncing range from tree limbs.
>
> It's just a thought, but I think Xu may be onto something.


Indeed. Wish I had proposed something like that back at SVP 1994. Oh, wait... :-)

(To be fair, others have thought of similar aspects too: recent studies of
the proportiopns of the toes and fingers of maniraptorans near or just past
the origin of birds show a decidedly intermediate aspect to their proportions: neither fully arboreal nor fully cursorial).


              Thomas R. Holtz, Jr.
              Vertebrate Paleontologist
Department of Geology          Director, Earth, Life & Time Program
University of Maryland         College Park Scholars
              College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone: 301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661      Fax (CPS-ELT): 301-405-0796

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