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A Middle Jurassic (Bajocian) ophthalmosaurid (Reptilia, Ichthyosauria) from the Tuxedni Formation, Alaska and the early diversification of the clade

  • PATRICK S. DRUCKENMILLER (a1) and ERIN E. MAXWELL (a2)
Abstract
Abstract

Ophthalmosauridae is a clade of derived thunniform ichthyosaurs that are best known from Callovian (late Middle Jurassic) to Cenomanian-aged (Late Cretaceous) deposits in both the Northern and Southern Hemispheres. Ophthalmosaurids arose prior to the Early–Middle Jurassic boundary, however, very little is known about their diversity and distribution in the earliest phase of their evolutionary history during the Aalenian–Bathonian (Middle Jurassic) interval. Here we describe new diagnostic ophthalmosaurid material from the Early Bajocian (Middle Jurassic) of Alaska. The specimen, UAMES 3411, is a partial disarticulated skull that was discovered in the Middle Jurassic Tuxedni Formation, which was deposited in shallow marine settings outboard of the then-accreting Wrangellia composite terrane. The new material is significant in that it is the first Jurassic ichthyosaur described from Alaska, one of the oldest ophthalmosaurids known and the only Middle Jurassic ophthalmosaurid described from the Northern Hemisphere. The new material adds to a rapidly growing data set on ophthalmosaurid diversity and suggests that the clade was geographically widespread by the Early Bajocian, very early in its evolutionary history.

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Corresponding author
Author for correspondence: psdruckenmiller@alaska.edu
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This list contains references from the content that can be linked to their source. For a full set of references and notes please see the PDF or HTML where available.

N. Bardet 1994. Extinction events among Mesozoic marine reptiles. Historical Biology 7, 313–24.

M. S. Fernández 2003. Ophthalmosauria (Ichthyosauria) forefin from the Aalenian–Bajocian boundary of Mendoza Province, Argentina. Journal of Vertebrate Paleontology 23, 691–94.

E. E. Maxwell , M. S. Fernández & R. R. Schoch 2012. First diagnostic marine reptile remains from the Aalenian (Middle Jurassic): a new ichthyosaur from southwestern Germany. PLoS ONE 7, e41692. doi:10.1371/journal.pone.0041692.

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Geological Magazine
  • ISSN: 0016-7568
  • EISSN: 1469-5081
  • URL: /core/journals/geological-magazine
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