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Re: Anatomical details



David Marjanovic wrote-

> - Does *Hesperornis* have a pygostyle? Is the end of the tail known at
all?

Yes.  Clarke (2002) says it's approximately two caudals in length.

> - Behind the transition point, most theropods have broad, forward-leaning
> prezygapophyses that stiffen the tail. Some (*Archaeopteryx*, *Rahonavis*)
> have narrow prezygapophyses that do the same. Dromaeosaurs have both pre-
> and postzygapophyses elongated beyond good and evil, and the chevrons,
too.
> Scansoriopterygids... *Epidendrosaurus* is not well enough preserved.
> *Scansoriopteryx*, however... its chevrons are plesiomorphic; but are its
> pre- and postzygapophyses discernible in the first place? In the photos
they
> are seemingly not. I can't tell if only the prezygapophyses are lengthened
> (as the very optimistic drawings show it) or the postzygapophyses, too. I
> remember some fellow listmembers have seen the specimen...?

I find the caudal prezygapophyses quite visible in figure 13 of Czerkas and
Yuan (2002).  They are about 50-60% of the previous centrum's length.
Similarly, the postzygapophyses seem to extend to the tip of the preceding
vertebra's prezygapophysis.

Mickey Mortimer
Undergraduate, Earth and Space Sciences
University of Washington
The Theropod Database - http://students.washington.edu/eoraptor/Home.html