Revueltosaurus Keeps Bouncing Around

Updated December 09, 2014 as Revueltosaurus now nests with Fugusuchus.

Revueltosaurus has revealed itself to us (and to me) a little bit at a time (see below). That is okay. It’s still good science. Best guesses based on limited data are just fine. Better guesses based on more data are better, of course. This doesn’t always happen (see the flap on pterosaur origins), but at least here, now based on virtually complete skeletal material, that little Triassic oddball, Revueltosaurus, may soon stop bouncing around the reptile family tree. It’s a fun and interesting story.

First, Just Teeth – a Basal Ornithischian
When Hunt (1989) first described Revueltosaurus, it was a Triassic dinosaur, based on its teeth alone, which resembled those of basal ornithischians.

Then, Some Crushed Skull Parts, a Pelvis and Scapula – a Pseudosuchian
Parker et al. (2005) redescribed Revueltosaurus as a pseudosuchian based on some skull, pectoral and pelvic bones. Unfortunately they could not place it within any known monophyletic clade.

Reconstruction of Revueltosaurus from Parker et al. 2005.

Figure 1. Reconstruction of Revueltosaurus from Parker et al. 2005.

Third, A Nesbitt Skull Reconstruction – a Basal Aetosaur
Recently Nesbitt (2011) nested Revueltosaurus at the base of the Aetosauria as a sister to Turfanosuchus, Gracilisuchus and Ticinosuchus — all taxa just ouside of the Archosauria. Here, Ticinosuchus is at the base of the aetosauria.

Skull reconstruction of Revueltosaurus traced from Nesbitt 2011.

Figure 2. Skull reconstruction of Revueltosaurus traced from Nesbitt 2011.

Finally, an Overall Reconstruction by Jeffrey Martz – a Fugusuchus Sister
A recent award-winning reconstruction by Jeffrey Martz illustrated the complete skeleton and osteoderm covering of Revueltosaurus. Captions along with this illustration indicate that an aetosaur sisterhood is still favored. Although the skull was very close to the reconstruction offered by Nesbitt, it was distinct enough to cause a phylogenetic shift to a sister to Fugusuchus, a basal erythrosuchid.

Revueltosaurus revised from a tracing by Jeffrey Martz.

Figure 4. Revueltosaurus revised from a tracing by Jeffrey Martz. The limbs and tail have been straightened just a bit.

Is Revueltosaurus a Mini-Fugusuchus?
Not quite. Likely they shared a common ancestor. The teeth of Revueltosaurus indicate a diet of plants, but the small rib cage and the reduced depth of the pubis do not support an herbivorous diet. The shorter hind limbs of Revueltosaurus indicate that it was a full-time quadruped.

Figure 1. Revueltosaurus compared to its big sister, Fugusuchus, a basal erythrosuchid.

Figure 1. Revueltosaurus compared to its big sister, Fugusuchus, a basal erythrosuchid.

The Question Is
What is real?

References
Hunt AP 1989. A new ornithischian dinosaur from the Bull Canyon Formation (Upper Triassic) of east-central New Mexico. In Lucas, S. G. and A. P. Hunt (Eds.), Dawn of the age of dinosaurs in the American Southwest 355–358.
Parker WG., et al. 2005. The Pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs. In Proceedings of the Royal Society London B 272(1566):963–969.

wiki/Revueltosaurus

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