Plesiosaurs from the Upper Cretaceous (Cenomanian–Turonian) Tropic Shale of southern Utah, part 1: new records of the pliosaur Brachauchenius lucasi

Abstract

ABSTRACT Recent fieldwork in the Tropic Shale of southern Utah has resulted in the recovery of two new specimens of the short-necked pliosaurid Brachauchenius lucasi Williston, 1903. Both specimens were recovered in Lower Turonian strata a few meters above the Cenomanian-Turonian Stage boundary as determined from molluscan assemblages found in direct association, and both include skull material. The larger of the two also includes pectoral and pelvic elements previously unknown for this taxon. These specimens represent the first records of B. lucasi from the western margin of the Cretaceous Western Interior Seaway; previously recorded specimens were recovered in Kansas and Texas. The Cenomanian through middle Turonian temporal range of B. lucasi, in addition to its geographic range across the seaway, indicates that this taxon suffered few, if any, negative consequences as a result of global scale oceanographic events, including marine extinctions, that transpired during late Cenomanian-early Turonian time.