Re: [dinosaur] Gnathovorax, new herrerasaurid (open access)

[Tim Williams <tijawi@gmail.com>]

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

> ...and the silesaurids come out as the basal grade of ornithischians, which 
> will be very familiar to a few of us. Herrerasauridae is found as the 
> sister-group of all other
> saurischians.

The phylogeny retains a rump clade of "core" silesaurids, comprising
_Silesaurus_ and its closest kin.  Meanwhile,
_Lewisuchus_/_Pseudolagosuchus_ remain(s) outside the Ornithischia
(and Dinosauria) entirely.

If silesaurids are ornithischians, then they fill in the gap of
missing ornithischians from the Triassic.  The apparent absence of
ornithischians from the Triassic (assuming _Eocursor_ is Jurassic) has
been perplexing.  It could be an artifact of an imperfect fossil
record.  Or, Triassic ornithischians have already been discovered -
such as silesaurids (e.g., Pacheco &c), or as weird theropods (such as
_Daemonosaurus_).  The latter raises the prospect that all
ornithischians are 'weird' theropods, having originated from among
basal theropods.  I quite liked the idea of a
_Daemonosaurus_-heterodontosaurid nexus.  However, in this analysis,
_Daemonosaurus_ falls out as a saurischian, in between herrerasaurids
and eusaurischians (theropods + sauropodomorphs), and the traditional
Saurischia-Ornithischia dichotomy is preserved.