Daemonosaurus a Plant Eater?

Updated February 28, 2015, with a revised skull for Daemonosaurus and an updated cladogram.

A Bizarre New “Theropod” Dinosaur was Recently Reported
Daemonosaurus (Sues et al., 2011) was named for its very large and wickedly curved fangs, quite beyond those of sister taxa like Eoraptor (Sereno et al. 1993) and Tawa. The skull was also unique…for a meat eater. So unique, in fact, that it’s closest comparisons in the large reptile tree were to plant eaters with premaxillary fangs (see below). Unfortunately, these two, Heterodontosaurus and Jeholosaurus were not included in the original phylogenetic analysis. We’ve seen a priori exclusion ruin other nestings, as in Vancleavea.

We remedy that oversight here.

Figure 2 Daemonosaurus skull in 4 views.

The Daemonosaurus Story.
Dinosaur precursors, among the rauisuchia and basal archosauria, were all meat eaters. Vjushkovia, Decuriasuchus and Trialestes are examples. Basal dinosaurs (theropods), like Herrerasaurus and Eoraptor (see below) continued to eat meat. In pre-dinosaurs, like Turfanosuchus, the premaxilla sent out a process posterior to the naris. This was reduced in theropods, including Herrerasaurus, which has a traditional error in that area described here (and see below, note similarity to Eoraptor). This postnarial process is enlarged in ornithischians, like Lesothosaurus and Heterodontosaurus, and in paraornithischians, such as Silesaurus. The process is also enlarged in Daemonosaurus. In Massospondylus the great enlargement of the naris appears to have reduced the postnarial process.

Meat eaters have a long set of jaws. Daemonosaurus doesn’t.

The rostrum of Daemonosaurus is short and convex, as in Heterodontosaurus and Massospondylus (see below), not long and pointed, like a theropod. We could go on and on. Ask for the dataset.

Figure 2. Click to enlarge. Sisters to Daemonosaurus, including Leyesaurus and Jeholosaurus. The postfrontal (in light red) is not fused in most of these taxa (Heterodontosaurus is the exception), contra current dinosaur paradigms. Note the resemblance of Daemonosaurus to the basal sauropodomorph, Leyesaurus. The increase in tooth size in Daemonosaurus was not derived from theropods, but was a unique character trait, shared, more or less with its sister, Jeholosaurus and to a lesser extent in Heterodontosaurus.

Phylogenetic Analysis
The large tree of 238 (now 504) taxa nests Daemonosaurus at the base of the Ornithischia.

Figure 3. Portion of the large reptile tree focusing on dinosaurs and the nesting of Daemonosaurus

Daemonosaurus is the first dinosaur to link theropods with plant eaters.
It’s appearance in the Late Triassic appears to have been some sort of relic, because more derived plant-eaters were also present then.

I Have Never Seen the Original Fossil
So, once again, the use of DGS (Digital Graphic Segregation) AND a greatly enlarged dataset (see tree above) has enabled a more accurate nesting of a “bizarre” or “atypical” taxon than first-hand observation and a traditional small dataset, not yet validated by a larger set.

References:
Sereno PC, Forster CA, Rogers RR and Monetta AM 1993. Primitive dinosaur skeleton from Argentina and the early evolution of Dinosauria.
Sues H-D, Nesbitt SJ, Berman DS and Henrici AC 2011. A late-surviving basal theropod dinosaur from the latest Triassic of North America. Proceedings of the Royal Society B, published online