Re: Re-emergence of lost features.

["Thomas R. Holtz, Jr." <th81@umail.umd.edu>]

At 06:59 PM 3/13/98 -0000, John Jackson wrote:
>Darren Naish's "Birds of a Feather" article in the "Fortean Times" is
excellent (haven't seen the pics yet, though they're prob. good too) - the
kind of standard that "Sci Am" should have been aiming for!

If it weren't for the first eight words in the sentence above, that would be
frightening message to see posted to a scientific discussion group...

>Are any examples of normal-winged birds with throw-back clawed hands ever
found? 

Did somebody say hoatzin? :-)  Sure, they lose them as they get older, but
they are present in juveniles.  _Opisthocomus_ is deeply nested within the
(otherwise clawless) modern bird clade, so the expression of clawed fingers
in this genus is clearly a reversal.

>And why did the phorusrhacoids lose out to the early carnivorous mammals
when a similar design survived for so long before?

Your time frame is a bit off here.  Phorusrhacoids are amazingly recently
extinct forms.  They were present in South America and North America as
recently as the Plio-Pleistocene.

We don't have any good evidence that they "lost out" to carnivorous mammals,
since a) they coincided for much of their history with the carnivorous
mammals of South America and b) they overlapped in time and space with very
modern style carnivorans during and after the Great American Interchange.
One could argue that their extinction was due to competition with, for
example, sabrecats, but one could argue on pretty much the same evidence
that the extinction of the sabrecats was due to competition with the last
phorusrhacoids.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661