Abstract Marine turtle fossils are extremely rare in the Muwaqqar Chalk Marl Formation of the Harrana Fauna in comparison to the relatively rich variety of other vertebrate fossils collected from this locality. This paper reports and describes the remains of an extinct marine turtle (Chelonioidea) which will be tentatively assigned to a new genus and species of marine turtles (Cheloniidae Bonaparte, 1835) Gigantatypus salahi n.gen., n.sp.. The new genus represented by a single well–preserved right humerus, reached remarkably large proportions equivalent to that of Archelon Wieland, 1896 and represents the first to be found from this deposit and from the Middle East. The specimen, which exhibits unique combinations of features is characterized by the following morphological features not found in other members of the Cheloniidae: massive species reaching over 12 feet in length; a more prominently enlarged lateral process that is situated more closely to the head; a ventrally situated capitellum; a highly laterally expanded distal margin. The presence of these features may warrant the placement of this new species in a new genus. The specimen also retains some morphological features found in members of advanced protostegids indicating close affinities with the family. Several bite marks on the ventral surface of the fossilized humerus indicate shark–scavenging activities of possibly Squalicorax spp.

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