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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
Sent from Outlook From: dinosaur-l-request@usc.edu <dinosaur-l-request@usc.edu> on behalf of Tim Williams <tijawi@gmail.com>
Sent: November 10, 2019 9:04 PM To: dinosaur-l@usc.edu <dinosaur-l@usc.edu> Subject: Re: [dinosaur] Gnathovorax, new herrerasaurid (open access) 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. |