Re: Reflections on Recent "Dromaeosaurs"

["Timothy Williams" <twilliams_alpha@hotmail.com>]

Jaime A. Headden wrote:


> *Achillobator* [could be] an assemblage of more than one taxa (as
> suggested by Burnham et al., 2000) a dromie, and
> another maniraptoriform, or more.

I just looked at the _Bambiraptor_ paper and, yeah, the authors raise this 
as a possibility. I'm willing to believe that _Achillobator_ is a good 
taxon, just one that doesn't happen to fit neatly into existing cladograms.  
Burnham also suggest that _Utahraptor_ is a chimera too, based as it is on 
scattered bones: "We see little reason to believe that these bones come from 
a single species, let alone a dromaeosaurid )p.7)."

> so Bambi
> may be a distinct taxon from *Saurornitholestes*. This
> is the bulk of Burnham et al.'s differentiation, so
> I'm not too willing to trust it, but it seems a
> likelyhood. At worst, Bambi is a unique "species," if
> not a genus.

So your cladogram below should probably have _Bambiraptor_ and 
_Saurornitholestes_ grouping a lot closer together.  Although the 
_Saurornitholestes_ type material is fragmentary and not a lot can be 
gleaned from it, there is some good stuff for this genus yet to be 
described.

As for _Adasaurus_, the obturator process is about half way down the the 
ischial shaft, so more distally located compared to other dromaeosaurids 
(except _Achillobator_).  This specimen apparently comes from a "pathologic 
individual" (says Norell and Makovicky), but I don't know why.

> |
> `--+--*Achillobator giganticus*
>    `--+--*Ozraptor subotaii*
>       |--*Variraptor mechinorum*
>       `--+--*Dromaeosaurus albertensis*
>          `--+--*Utahraptor ostrommaysi /
> ostrommaysorum*
>             `--+--+--*Bambiraptor feinbergi /
> feinbergorum*
>                |  |--*Adasaurus mongoliensis*
>                |  `--+--*Unenlagia comahuensis*
>                |     `--+--*Rahonavis ostromi*
>                |        `?-+--*Archaeopteryx
> lithographica*
>                |           `--+--*Archaeopteryx
> bavarica?*
>                |              `--Aves
>                |?-*Sinornithosaurus millenii*
>                `--+--*Deinonychus antirrhopus*
>                   `--+--*Velociraptor mongoliensis*
>                      `--*Saurornitholestes langstoni*



Tim
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