Abstract

A large ichthyosaur, with a total length in excess of 7 m, is described from the Lower Jurassic (Sinemurian) of Dorset, England. Like Leptopterygius tenuirostris the new species, named Leptopterygius solei, has a long slender snout armed with slender teeth that are remarkably small for the large size of the skull. There are also similarities in the forefin: the humerus is widely expanded distally, and the phalanges are rounded rather than polygonal and are probably well spaced distally. However, in contrast to L. tenuirostris, there is no notch on the leading edge of the radius. The snout is also relatively shorter and the orbit smaller. Thus in the holotype the estimated values for the snout and orbital ratios are 0.68 and 0.15 respectively, compared with observed ranges for L. tenuirostris of 0.71–0.76 (n = 7) and 0.18–0.24 (n = 7). Leptopterygius solei also has a somewhat higher prepelvic vertebral count, being at least 50 in the holotype compared with an observed range of 44–48 (n = 9) for L. tenuirostris. Furthermore, the ischium is considerably wider than the pubis, whereas these elements have approximately similar widths in L. tenuirostris. The possibility that the new material might merely represent the upper end of a growth series of L. tenuirostris is dismissed. Based on skull length, the holotype of L. solei is 66% larger than the largest specimen of L. tenuirostris.

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