Redescription of the type specimens for the Late Jurassic rhynchocephalian Opisthias rarus and a new specimen of Theretairus antiquus from Quarry 9, Morrison Formation, Wyoming, USA
Jorge A. Herrera-Flores, Thomas L. Stubbs, and Francisco Sour-Tovar
We reexamine and redescribe the type specimens and other associated material of the Late Jurassic rhynchocephalian Opisthias rarus, from Quarry 9 of the Morrison Formation. We rediscover and describe a fragment of rock matrix belonging to the holotype that is presented for the first time, and we also comment on undescribed material from Quarry 9 that possibly belongs to an unnamed species of Opisthias. In addition, we describe a new specimen of Theretairus antiquus that helps to reject its proposed status as a junior synonym of O. rarus, and contributes to increase the knowledge of the microvertebrate fauna of the Late Jurassic of North America.
Key words: Lepidosauria, Rhynchocephalia, Morrison Formation, Jurassic, Wyoming, USA.
Jorge A. Herrera-Flores [jorge.herrera@ciencias.unam.mx] and Francisco Sour-Tovar [fcosour@ciencias.unam.mx], Museo de Paleontología, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, Ciudad de México, Mexico. Thomas L. Stubbs [tom.stubbs@bristol.ac.uk], School of Earth Sciences, University of Bristol, Queens Road, Bristol, BS8 1RJ, UK.
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