[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Questions



Steven Mahon wrote-

> > Tyrannosaurids lack an ischial foot.
>
> What?! Do they or do they not?! Does Eotyrannus have
> it or not!?

Well, the holotype of Tyrannosaurus has an ischial foot.  But RTMP 81.61 and
AMNH 5027 lack one (Carpenter, 1990).  The holotype of Gorgosaurus also
lacks a foot (Lambe, 1907), as does juvenile specimen AMNH 5664 (Matthew and
Brown, 1922), and Tarbosaurus (PIN 551-2; Maleev, 1974).  So much like
ornithomimids are coded as having a foot because all but one specimen (a
Dromiceiomimus) has it, tyrannosaurids are coded as lacking a foot because
all but one specimen does.
Eotyrannus doesn't preserve an ischium, Dryptosaurus' is too poorly
preserved to tell, and other basal tyrannosauroids lack described ischia as
well.

> > Sinovenator has only five sacrals (Xu et al., 2002),
> > as do tyrannosaurids
> > (Makovicky, 1995).  Other taxa with over five
> > sacrals include some
> > segnosaurs, Chirostenotes, some dromaeosaurs, some
> > non-pygostylian avians,
> > Avimimus, alvarezsaurids and (depending on how you
> > define "sacral")
> > Nomingia.
>
> So could 5 sacrals up be a coelurosaurian character?

No, it's an avipod character.  Coelophysoids, ceratosaurs, megalosauroids
and carnosaurs also have at least five sacrals.

> >  But also known in a
> > couple basal taxa (Coelurus, Scipionyx), and missing
> > in several
> > maniraptorans (eg. some segnosaurs, Caudipteryx,
> > Noguerornis).
>
> which segnosaurs?

Erlianosaurus (Zhang et al., 2002), Therizinosaurus (Barsbold, 1979) and
apparently Alxasaurus (Xu et al., 1999).  But Nothronychus is reported to
have it (Kirkland and Wolfe, 2001).

Mickey Mortimer