Featured Fossil: A New Species of Thalattosaur from the Triassic of North-Central Oregon

by Eleanor Gardner via Aaron Currier and Greg & Gloria Carr of North America Research Group (NARG)

In the spring of 2011, during a geology class field trip to a road cut near Suplee, Oregon, Gloria Carr and her father Greg found bone fragments from a large vertebrate preserved in concretions of conglomerate rock. The father-daughter pair, who are members of North America Research Group (NARG), did a quick survey of the area and realized that the bone-bearing concretions were tumbling downhill from an immense block containing disarticulated skeletal material. They marked the spot on a map and then went about the process of seeking permission to excavate, which required working with county lawyers, local landowners, and the University of Oregon (recipient of the donated fossils).

On Memorial Day of 2012, a team of 22 NARG members excavated the fossils – they unearthed over 1000 pounds of rock during the dig and named the skeletal material “Bernie” in honor of the landowners, Gene & Miriam Bernard.

Initially, the bones were thought to be from ichythyosaurs, but that identification was only tentative due to the limited number of diagnostic bones visible at the time. Because the fossils were imbedded in solid rock, the fossil preparation process was very slow-going; for example, it took 5 months to prepare one half of a skull.

Over time and with great care in preparation at the Paleo Lab of the Oregon Museum of Science and Industry, Greg Carr and fellow museum volunteers realized that the bones were not from ichythyosaurs but rather thalattosaurs. Thalattosaurs (“ocean lizards”) are a group of extinct marine reptiles from the Triassic period, of undetermined evolutionary affinity: some experts group them near ichythyosaurs, some group them near archosaurs, and others group them near lepidosaurs. See related image here. Thalattosaur material has been found in California, Alaska, as well as British Columbia; the rocks from which the Bernie bones were recovered are part of the Brisbois Member of the Vester Formation, representing a deltaic environment and dating to the Upper Triassic. Therefore, Bernie’s skeletal elements may be the oldest bones in the state of Oregon.

More than 60 separate bones have been recovered, including limb bones, ribs, shoulder girdle elements, vertebrae, fragmentary premaxillae and maxillae (upper jaw), a partial mandible (lower jaw), and the entire right half of a skull.

Based on the number of limb bones, skull pieces, and girdle elements, researchers estimate that the Bernie fossils actually come from at least seven different disarticulated individuals. The bones are three-dimensional and tightly packed on top of each other in indurated rock, making removal very difficult. With the slow but steady recovery of more and more material, it became clear that these thalattosaur fossils were new to science, so in 2014 diagnostic specimens were sent to the University of Alaska at Fairbanks for expert analysis.

In December 2015, preparation revealed an extremely large chevron bone (an arch-like bone that is part of the caudal vertebrae in reptile tails). This specimen, measuring 18 cm, is three times as big as all other previously-found thalattosaur chevron bones.

According to University of Alaska graduate student Eric Metz, who presented at the 2015 Society of Vertebrate Paleontology meeting in Dallas, Texas, the Bernie material represents a new species of thalattosaur which also happens to be the largest discovered thus far in North America. A paper describing the new species is forthcoming, with publication anticipated in the spring of 2017. After publication, the diagnostic fossils will be returned to the University of Oregon’s paleontology research collection and preserved as holotype specimens. In the future, NARG hopes to share the 3D data from this discovery through online repositories such as MorphoSource and to create traveling exhibit displays to help educate the public about Oregon’s ancient ocean lizards.