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re: "Mega-raptors" and the high frequency of undescribed dromaeosaurs in lists.



T. Mike Keesey wrote:
>Ever since I started listing unnamed species on my dinosaur pages, I've
>noticed that the Dromaeosauridae seems to have more than its share.
>There're ones from Africa, France, Japan, Mongolia, and, until recently,
>Argentina. Also the possible close relatives from Madagascar (flying
>sickle-claw) and the U.S.A. ("Linsterosaurus"). And there's also one from
>Australia? Why are there so many?


Mostly from teeth, as you surmised.  The Hell Creek Formation
dromaeosaur is based on such material.
The high frequency in reporting could be a reflection of
any one of the following:

1) reporting bias ("raptors" are hot these days). Thus,
any scrappy dromaosaurid teeth found in a study are reported
(this is unlikely, as dromaeosaurid teeth have been
widely reported from studies published WAY before Jurassic Park
came out).

2) unwillingness of researchers to study very incomplete material
(also doubtful, considering how many good dromaeosaur comparative
specimens there are; it would make the research easy, even on
scrappy material).

3) the commonness of teeth could be a reflection of a real numerical
superiority of these theropods in the rocks (perhaps dromaeosaurs had
a high "critical reproductive population").

4) possibly these beasts had a vastly higher tooth-replacement
rate than other theropods, hence, the greater number of
isolated teeth.

5) dromaeosaur teeth and pedal claws are taphonomically-
and diagentically-durable;
other dromaeosaur bones are light, hollow, and fragile.
This is the most likely explaination for the large number of
undescribed "Dromaeosaurid" sp.'s occurrences in faunal lists.

However, dinosaur tooth taxa are still being described, although it is
frowned-on by some workers.  Currie et. al (in _Dinosaur Systematics_)
described a new genus of theropod found in Campanian through
Maastrichtian rocks (_Richardoestesia_) based on a scrappy
jaw and some isolated teeth.  I don't remember if the
jaw was part of the holotype, or was instead a paratype (or was simply
a referred specimen), but I do remember that the genus diagnosis was
mostly on the teeth.

                         <pb>