Cymbospondylus nichollsi, Fröbisch & Sander & Rieppel, 2006

Fröbisch, Nadia B., Sander, P. Martin & Rieppel, Olivier, 2006, A new species of Cymbospondylus (Diapsida, Ichthyosauria) from the Middle Triassic of Nevada and a re-evaluation of the skull osteology of the genus, Zoological Journal of the Linnean Society 147 (4), pp. 515-538 : 517-519

CYMBOSPONDYLUS NICHOLLSI SP. NOV.

Diagnosis: Medium-sized Cymbospondylus . Differs from Cymbospondylus petrinus in having a longer cheek region: the ratio between length posterior to nares and length of cheek region is 1.85 in C. nichollsi vs. 2.11 in C. petrinus . The parietal foramen is about 4.5 cm posterior to the fronto-parietal suture within the parietal, but is very close to the fronto-parietal suture in C. petrinus . Autapomorphies of C. nichollsi are: nasals have a long posterior process entering the upper temporal opening; the postorbital reaching far dorsally to the border of the temporal opening, whereas it is restricted to the medial portion of the cheek region in C. petrinus and C. buchseri ; the long, slender supratemporal extends beyond the back of the skull; the quadratojugal is short and restricted to the lateral side of the skull and does not make contact with the quadrate at the back of the skull; as a result, the squamosal takes part in the posterior border of the lateral embayment, in contrast to the condition seen in C. petrinus and most other ichthyosaurs.

The preserved postcranial parts are very similar to C. petrinus and C. buchseri , but the clavicle is more robust in C. nichollsi .

C. nichollsi possesses 8–10 cervical vertebrae in comparison with 12 in C. petrinus and six in C. buchseri .

Holotype and only specimen: Specimen FMNH PR2251 . Anterior half of an articulated skeleton, comprising the skull without the rostrum, articulated vertebral column with neural arches and ribs, extending to the middle dorsal region, and parts of the shoulder girdle.

Type locality: Augusta Mountains, Pershing County, Nevada (T25N, R39E; Section 14; USGS Cain Moutain 7.5′ quadrangle, 1990 provisional edition, exact locality on file at the FMNH).

Horizon and distribution: Fossil Hill Member, Favret Formation, Anisian, Middle Triassic.

Etymology: Named in memory and honour of Dr Elizabeth L. Nicholls, curator of marine reptiles at the Royal Tyrrell Museum, Drumheller, Canada, for her work on Triassic ichthyosaurs, which greatly contributed to the increased knowledge and understanding of the group.