In Part 2, ichthyosaur taxa of the Late Jurassic are described; three taxa are considered valid: Brachypterygius extremus, Nannopterygius enthekiodon, and Macropterygius sp. indet. (Ichthyosauria: Ophthalmosauridae). These taxa are best represented from the Kimmeridge Clay Formation. Grendelius mordax is rejected as a junior subjective synonym of Brachypterygius extremus based on skull and limb morphology. Material referred to Macropterygius is too incomplete to erect a species, but is considered different enough to retain the genus as separate. Ichthyosaurus aequalis, Ichthyosaurus dilatatus, Ichthyosaurus ovalis, Ichthyosaurus thyreospondylus, and Ichthyosaurus trigonus are considered nomina dubia. Ichthyosaurus advena, Ichthyosaurus chalarodeirus, Ichthyosaurus hygrodeirus, and Ichthyosaurus megalodeirus are considered nomina nuda. Comparisons are drawn with other ichthyosaur taxa, focusing particularly on Neoichthyosauria and Ophthalmosauridae. Evidence is presented for Ophthalmosaurus in the Kimmeridge Clay Formation, but the material is not complete enough to be certain of its specific affinities. Ophthalmosaurus icenicus and Ophthalmosaurus natans are considered separate species, but within the same genus based on several shared autapomorphies. However, reevaluation of the material of Ophthalmosaurus natans is required.
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Moon, B. C., 27 Sep 2016
Student thesis: Doctoral Thesis › Doctor of Philosophy (PhD)File