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

The "compromise" hypothesis, of course, which I don't believe has ever been supported quantitatively, would be that (Ornithischia + Silesauridae) is the sister group of Theropoda within Ornithoscelida. I don't know is this is at all plausible, but the silesaurid *Eucoelophysis* was initially described as a neotheropod... Notably, Pacheco et al. (2019) seem to be the first study to recover *Pisanosaurus* closer to Ornithischia than to Silesauridae, after taking into account the studies that find it as a silesaurid.

Etymologically, is *Gnathovorx* the "devouring jaw," or the "devourer of jaws"?

Brad


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From: [email protected] <[email protected]> on behalf of Tim Williams <[email protected]>
Sent: November 10, 2019 9:04 PM
To: [email protected] <[email protected]>
Subject: Re: [dinosaur] Gnathovorax, new herrerasaurid (open access)

David Marjanovic <[email protected]> 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.