PHORUSRHACOIDS: UNFEATHERED HANDS?

[darren.naish@port.ac.uk]

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"

DARREN NAISH
darren.naish@port.ac.uk