SVP 4 – new data coming in for Scutellosaurus

Figure 1. Scutellosaurus is a small armored ornithischian transitional between Lesothosaurus and Stegosaurus.

Figure 1. Scutellosaurus is a small armored ornithischian transitional between Lesothosaurus and Stegosaurus.

From the abstract
“While rare in Upper Triassic strata, the Ornithischia had achieved a global distribution by the Early Jurassic. The oldest ornithischian fossils from North America have been found in the Silty Facies of the Kayenta Formation in northeastern Arizona. These include the thyreophoran Scutellosaurus lawleri, an unnamed heterodontosaurid, and osteoderms and rib fragments tentatively attributed to the thyreophoran genus Scelidosaurus. I report here new Scutellosaurus material preserving anatomy that is poorly known or not previously reported for the taxon, including the nasal, maxilla, lacrimal, postorbital, quadratojugal, squamosal, opisthotic, scapula, ilium, and metatarsus. Both specimens were mechanically prepared until risk of damaging the fossil bone was deemed too high, at which point the specimens were scanned at The University of Texas High Resolution X-ray Computed Tomography Facility. This approach results in three-dimensional volumetric models of individual bones.”

It is good to see
that more data is coming in for Scutellosaurus. It will be interesting to see if the new material (which I have not seen) fits the best guess offered above (Fig. 1).

In the large reptile tree, Scutellosaurus nests closer to Lesothosaurus not closer to the much larger and more primitive armored Scelidosaurus, which was basal to ankylosaurs and nodosaurs. Earlier the clade Thyreophora was shown to not be monophyletic. Scutellosaurus developed armor independently and was basal to stegosaurs. The long torso and short legs suggest a quadrupedal posture, rather than the traditional bipedal one.

Breeden BT and Rowe TB 2015. New specimens of the threophoran dinosaur Scutellosaurus lawleri from the lower Jurassic Kayenta formation of northern Arizona. Journal of Vertebrate Paleontology Abstracts 2015.


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