Re: SICKLE-CLAWED DINOSAURS

["T. Mike Keesey" <tkeese1@gl.umbc.edu>]

On Mon, 9 Mar 1998 darren.naish@port.ac.uk wrote:

> _Noasaurus_, so far as I know, has never been regarded as an 
> abelisaurid - nevetheless it is related to them and considered part 
> of a more inclusive clade called Abelisauroidea by Holtz, Novas, 
> Bonaparte and others.

I said "abelisaur", not "abelisaurid". I think I've heard one person
suggest that _Noasaurus_ and _Abelisaurus_ share a more recent ancestry
with each other than with _Carnotaurus_, but that was a while ago, and it
was, of course, unpublished...
 
> But the Holtz paradigm is not necessarily correct, and other workers 
> - most notably Hans Sues - support a troodont-dromaeosaurid 
> relationship as a result of newer analyses. The idea that 
> Deinonychosauria could be reinstated is therefore possible, but 
> debatable.

If you use (+_Deinonychus_, -Neornithes) as the definition, it can be used
anyway for the stem-group including Dromaeosauridae (as I use it on my
website).
 
> I was unaware that _Vorona_ may have been sickle-clawed. Are you sure 
> about that? AFAIK, the type and only known specimen is represented 
> only by a tibiotarsus, and you can only tell if digit II was 
> sickle-clawed if, surprise surprise, you have bones from digit II. 
> Maybe my memory is at fault and digit II is known for _Vorona_.

I think I may have been confusing it with the unnamed "flying 'raptor"
from Madagascar...
 
> It is tempting, then, to regard this as a primitive feature of the 
> clade which has been inherited by both later phorusrhacoids, and by 
> later cariamids (seriemas). However, last time I looked at photos of 
> one of the best preserved early phorusrhacoids, _Aenigmaornis sapei_  
> from Messel (mid Eocene) (I may have spelt the genus name wrong: note 
> also that the specific name is in honour of SAPE, The Society for 
> Avian Paleontology), I saw no sickle-claw. This _suggests_ that it 
> evolved in parallel in some phorusrhacoids and some seriemas, in 
> which case it appeared in this clade at least twice. 

Perhaps similar to the troodontid-dromaeosaurid phenomenon...
 
> Also, how do you properly define a sickle claw? Cassowaries, as 
> everyone on the list should now be aware, have an elongate, very 
> sharp claw that they use as a slashing/stabbing weapon - it is not 
> kept raised off the ground, and is not sickle-shaped. Meanwhile, a 
> number of birds of prey (true raptors) have an enlarged, 
> sickle-shaped claw on digit II. In falconids this is sometimes kept 
> raised when the bird is perched.

I'd say if it's hyperextendable and significantly larger, it counts. 
Sounds like falconids could be a fifth radiation of "sickle-clawed" 
theropods. 
 
--T. Mike Keesey
tkeese1@gl.umbc.edu
DINOSAUR WEB PAGES -- http://www.gl.umbc.edu/~tkeese1/dinosaur/index.htm