Revision of Saurorhynchus (Actinopterygii: Saurichthyidae) from the Early Jurassic of England and Germany

摘要

Saurichthyidae is a speciose group of fishes, ranging from the Late Permian to the Middle Jurassic. Early Jurassic saurichthyids are usually considered morphologically less disparate and taxonomically less diverse than their Triassic counterparts, consisting of only two valid species. These were historically differentiated almost entirely based on cranial ratios, and both had stratigraphic ranges spanning the Early Jurassic. Here, we revise the Early Jurassic saurichthyid fishes of Europe based on restudy of the type material of Saurorhynchus brevirostris (Woodward, 1895) and S. acutus (Agassiz, 1844). We identify four species based on cranial osteology: S. acutus , S. brevirostris , S. anningae sp.?nov., and S. hauffi sp. nov. Saurorhynchus brevirostris and S. anningae sp. nov. are known from the Sinemurian of England only, whereas S. acutus and S.?hauffi sp. nov. share a broad European distribution during the Toarcian, from southwestern Germany to England. Saurorhynchus anningae sp. nov. and S.?brevirostris , in particular, show disparity in such ecomorphologically important traits as cranial fineness, and tooth and jaw morphology. In contrast, S.?acutus and S. hauffi sp. nov. show much lower levels of disparity, differing from each other in nostril morphology, dermal ornamentation, and position of the lateral extrascapular. The new species do not increase diversity estimates for Saurorhynchus in either the Sinemurian or Toarcian interval.