Re: New basal dinosauriform

[Tim Williams <tijawi@gmail.com>]

David Marjanovic <david.marjanovic@gmx.at> wrote:


> Oh yes, and it makes me happy that it's finally out after about 60 years.


To put this in a historical context, when _Nyasasaurus_ was first
described (but not formally named), there was not yet a Tanzania.  It
was still the British territory of Tanganyika.


> :-) And the beastie has an interesting phylogenetic position (or two), too!


Indeed.  It also emphasizes just how rare dinosaurs (and dinosaur-like
dinosauriforms) were in the Middle Triassic.  Not as rare as Middle
Triassic pterosauromorphs though (zero discoveries so far).


_Thecodontosaurus alophos_ (named by Haughton, 1932) is referred by
Nesbitt et al. to their new taxon _Nyasasaurus parringtoni_.  So
shouldn't the name be _Nyasasaurus alophos_...?  (Unless _T. alophos_
is a nomen nudum.)


Also, _Nyasasaurus_ is diagnosed based on a unique combination of
characters, some of which may be plesiomorphic for clades "just
outside or within Dinosauria" (Nesbitt et al., 2012).  This is fine by
me, because a genus can be diagnosed in the absence of autapomorphies;
so _Nyasasaurus_ is a valid genus in my book.  However, _Lagosuchus
talamapeyensis_ was regarded as a nomen dubium for much the same
reason (Sereno & Arcucci, 1994): the holotype of _Lagosuchus_ has no
autapomorphies, and its combination of characters (which can
distinguish it from other basal dinosauriforms, like _Marasuchus_) are
plesiomorphic for various ornithodiran clades.  So if _Nyasasaurus_ is
a valid genus (and I have no doubt that it is), then so is
_Lagosuchus_ (contra Sereno & Arcucci, 1994).







Cheers

Tim