Re: Pelvis of *Avimimus*

["David Marjanovic" <david.marjanovic@gmx.at>]

> <While I am at it, I've finally looked at the fossil, and as expected
*Confuciusornis* has a
> proximally broadened mtIII like *Iberomesornis* and *Yandangornis*.>
>
>   This is the plesiomorphic condition for birds, actually.

Sure. I wanted to know just that, because otherwise it would have been an
autapomorphy of *Yandangornis* in my matrix with its big OTUs.

> the ilia of *Avimimus* are not fused to
> the neural spines, which are also separate from one another and do not
form a lamina, as they do
> in birds.

Ah, sorry. I introduced "fused" today (I look too often at that moa
skeleton) when I just meant "very close".

> The ilia have a slight separation from the ilia

neural spines?

> , in fact, and there are two separate
> features which ally them to the condition in modern birds (see Kurzanov,
1987): the wide lateral
> flare of the postacetabular ala, and the sagittal inclination of the
dorsal margin of the ala.

These are better words for what I tried to describe in wound phrases :-] (if
you mean the preacetabular ala at the end of your sentence).

> Various other animals have a sigmoid curvature of the ilia, including
dromaeosaurids.

In PDW both *Archaeopteryx* and *Velociraptor* are drawn in dorsal view with
)-|-(
- shaped ilia ("|" means the neural spines which are all separate, "-" means
the sacral ribs which are separate, too) and _slight_ sagittal inclination.
Has this been falsified (and is the condition in *Archaeopteryx* known at
all)?

> The lateral
> flare of the ilia caudally has also been proposed for *Archaeopteryx,* and
is present to some
> degree as in dromaeosaurids, oviraptorosaurs, *Caudipteryx,* and
segnosaurs, in spite of the
> lateral flare of the preacetabular alae.

I should be more precise. In dorsal view the pelves of neornitheans and
*Avimimus* have the following shape:

cranial
   ||
   ||
  /\
 /-\ acetabula
/--\
|---|
|---|
\---/
caudal

( "-" means places where sacral vertebrae are visible)
In the taxa you mention (I don't know about segnosaurs) there isn't enough
room for the caudal part of this.

> So you are looking at more than one character.

True: the space between the preacetabular alae became narrower dorsally, and
the space between the postacetabular alae became wider on the whole height.
Thanks for enlighten me on that! :-)