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PHORUSRHACOIDS: UNFEATHERED HANDS?
On another spinoff from the feathery forearms of coelurosaurian
theropods, Jeff Hecht writes..
>..what about the large secondarily flightless predatory birds of the
> Tertiary? They would presumably have problems similar to 'feathered
> dinosaurs' in maintaining feathers. Have feather remains been found
> with them? If so, what type of feathers?
New material of the North American phorusrhacoid _Titanis_ (not
_Titanus_ [sic]) published by Robert Chandler shows that it had a
stout, clawed digit borne on a modified, possibly monodactyl manus.
This structure has been interpreted as a weapon that could have been
used in pinning down mammalian prey. As Jeff notes, again we come to
the problem with the feathers: if the hand really was used this way,
wouldn't feathers have gotten in the way? A number of artistic
restorations depict large phorusrhacoids kitted out with their new,
clawed hands (an article from _Natural History_ with art by Steve
Kirk comes to mind), and all show the birds with naked-skinned hands.
To their credit, the artists have noted that hand feathers would have
gotten fouled or broken if the hand was used as a weapon.
As for what the fossils say about this, no published phorusrhacoid
with feather impressions is known EXCEPTING _Aenigmavis sapea_, a
grouse-sized form from the middle Eocene Messel deposits. The feather
impressions on the type specimen are not particularly informative,
and furthermore the bird doesn't seem to have a monodactyl, clawed
manus (it's wing is short, but if I remember correctly it's suggested
in Schaal and Zeigler (1988) - the big, fantastically illustrated
volume on the Messel fossils - that it could have been capable of
limited flight). Another Messel fossil, a little thrush-sized
specimen that might be a falconiform or something, has been touted as
a possible _Aenigmavis_ chick by Dieter Peters.
"They come, they eat, they leave"