Dracoraptor: a scrappy new earliest Jurassic theropod from Wales

Revised January 30, 2016. Additional taxa and revisions to Compsognathus now nest Dracoraptor with Coelophysis in the large reptile tree. 

Revised again March 11, 2016 with a rearrangement of the manual elements to match those of sister taxa.

A new paper
by Martill et al. 2016 describes a Late Triassic/Early Jurassic slender, mid-sized theropod, Dracoraptor hanigani, (NMW 2015.5G.1–2015.5G.11, Figs. 1-4).

Figure 1. Dracoraptor manus. Like its sisters, metacarpals 2 and 3 are similar in length.

Figure 1. Dracoraptor manus. Like its sisters, metacarpals 2 and 3 are similar in length.

From the Martill et al. paper:
“Diagnosis. A basal neotheropod with the following autapomorphies and unique combination of plesiomorphies: Three teeth in the premaxilla, slender maxillary process of jugal, large narial opening with slender subnarial bar, anteriorly directed pubis considerably longer than ischium, and large dorsal process on distal tarsal IV.”

Figure 2. Dracoraptor premaxillae compared to one another. Almost hard to believe they came from the same plate/counterplate. Together they present a better basis for scoring.

Figure 2. Dracoraptor premaxillae compared to one another. Almost hard to believe they came from the same plate/counterplate. Together they present a better basis for scoring.

Martill et al nested
Dracroraptor (with long manual digit 3 interpretation, Fig. 3) between Tawa and Coelophysis. Tawas also has a longer manual digit 3. I could not confirm the longer manual digit 3.

Figure 3. Original interpretation of Dracoraptor with color codes for known bones. Above: putting the bones together. Ghosted image represents the jugal/lacrimal impression along with, perhaps two posterior teeth flipped. The reconstruction of the foot on the overall skeletal figure is at an odd tippy-toe angle. It should have more phalanges planted on the substrate and the metatarsus should be angled forward somewhat more.

Figure 3. Original interpretation of Dracoraptor with color codes for known bones. Above: putting the bones together. Ghosted image represents the jugal/lacrimal impression along with, perhaps two posterior teeth flipped. The reconstruction of the foot on the overall skeletal figure is at an odd tippy-toe angle. It should have more phalanges planted on the substrate and the metatarsus should be angled forward somewhat more.

In the large reptile tree (subset Fig. 4) Dracoraptor now nests with Coelophysis among tested taxa.

Figure 2. Here Dracoraptor nests with Coelophysis, another basal theropod.

Figure 2. Here Dracoraptor nests with Coelophysis, another basal theropod.

Scattered digits
One of the problems with scattered digits is producing scores in analysis. The best practice, IMHO, is to nest the taxon first without scoring the scattered digits, then use phylogenetic bracketing to reassemble the scattered phalanges based on sister taxa patterns.

Generally it is problematic
to score scrappy taxa like this. Basal taxa are always interesting. Happily, enough is known to nest Dracoraptor without losing resolution.

As you can see
(Fig. 3), the published drawing does not accurately reflect the shapes of the published skull bones. In addition, the published tracing of the phalanges had to be warped to fit the published photograph. I wish tracings were taken from published photos so there would be a one-to-one correspondence.

References
Martill DM, Vidovic SU, Howells C and Nudds JR 2016. The Oldest Jurassic Dinosaur: A Basal Neotheropod from the Hettangian of Great Britain. PLoS ONE 11(1): e0145713. doi:10.1371/journal.pone.0145713

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One thought on “Dracoraptor: a scrappy new earliest Jurassic theropod from Wales

  1. I have a post going up about Dracoraptor today or tomorrow, once I finish adding its codings to my version of Nesbitt et al.’s matrix. Part of it is on Martill et al.’s misidentifications, and you correctly identified the second metacarpal at least.

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