The Robo-aetosaur Paratypothorax andressorum

On his recent post on the Staatliches Museum für Naturkunde Stuttgart Dave Hone featured a photo of a rare thing, an aetosaur mount. What Dave found so interesting about this mount; however, is that the missing portions of the skeleton have been filled in with burnished metal (see below).

The "robo-aetosaur" as Dave affectionately calls it, is the holotype specimen of Paratypothorax andressorum Long and Ballew 1985, and if I am not mistaken the actual osteoderms are used in the mount and are completely removable for study (Randy, Sterling, or Jeff will have to correct me on this if I am wrong).

The photo below is one of the dorsal paramedian plates of the left side of the holotype. Paratypothorax is a typothoracisine aetosaur and a member of the clade Paratypothoracisini (Parker, 2007). Members of this clade are characterized by paramedian plates that are much wider than long, have a distinct radial patterning, sharp anteromedial and anterolateral projections, a smooth anterior bar, and a medially offset dorsal eminence or boss.

Paratypothorax is also known from Greenland and the western United States. The best skeleton from the Chinle Formation was collected from Petrified Forest National Park by the Field Museum in 1982. The Petrified Forest specimen was described by Hunt and Lucas (1992) and again by Lucas et al. (2006) who assign it to Paratypothorax andressorum; however, this ID has not been accepted by all workers (e.g., Long and Murry, 1995) who suggest that it may be a new taxon.

Surprisingly the holotype specimen, which consists solely of armor, has never been completely described. Just as strange, even though the Petrified Forest specimen was not considered to be the same taxon as the German material by Robert Long and Karen Ballew, the species name given to the German material (collected in the 1800s and originally believed to be a phytosaur) was named for Chris Andress (the chief ranger at Petrified Forest) and his family (Long and Ballew, 1985).

Thanks to Dave Hone who sent me his photos of the Paratypothorax mount and secured permission to post the photos.

REFERENCES

Hunt, A.P. and S.G. Lucas. 1992. The first occurrence of the aetosaur Paratypothorax andressi (Reptilia, Aetosauria) in the western United States and its biochronological significance. Paläontologische Zeitschrift 66:147-157. DOI:10.1007/BF02989485.

Long, R. A., and K. L. Ballew. 1985. Aetosaur dermal armor from the late Triassic of southwestern North America, with special reference to material from the Chinle Formation of Petrified Forest National Park. Museum of Northern Arizona Bulletin 47:45-68.

Long, R. A., and P. A. Murry. 1995. Late Triassic (Carnian and Norian) tetrapods from the southwestern United States. New Mexico Museum of Natural History and Science Bulletin 4:1-254.

Lucas, S.G., Heckert, A.B., and L.F. Rinehart. 2006. The Triassic aetosaur Paratypothorax. New Mexico Museum of Natural History and Science Bulletin 37:575-580

Parker, W. G. 2007. Reassessment of the aetosaur “Desmatosuchus” chamaensis with a reanalysis of the phylogeny of the Aetosauria (Archosauria: Pseudosuchia). Journal of Systematic Palaeontology 5:41–68.