- The Paleontological Society
The polycotylidae is a family of short-necked (pliosauromorph) plesiosaurs, with examples known from epicontinental marine deposits of every major landmass except Antarctica. Our knowledge of its diversity and distribution has increased tremendously in the last decade, with new material described from North America (Sato, 2005; Albright et al., 2007; Schumacher, 2007; Schmeisser, 2008), South America (Gasparini and de la Fuente, 2000; Salgado et al., 2007), Africa (Bardet et al., 2003; Buchy et al., 2005), and Asia (Sato and Storrs, 2000; Arkhangel'skii et al., 2007). Polycotylid diversity is greatest in the Late Cretaceous, and particularly so in the Turonian; however, knowledge of the group's initial history in the Early Cretaceous is limited to a handful of specimens from North America (Storrs, 1981; Druckenmiller, 2002) and Australia (Kear 2003, 2005).
The specimen described here, TMP (Royal Tyrrell Museum of Palaeontology) 95.87.01, is an Early Cretaceous short-necked (pliosauromorph) plesiosaur discovered in 1995 in an enormous, open-pit oil sands mine near the town of Ft. McMurray, in northeastern Alberta, Canada (Fig. 1). Owing to its serendipitous discovery using heavy machinery, the skeleton, which is contained in a large concretion, was broken into many large fragments. Reassembly of the concretion revealed that approximately 80 percent of the skeleton is present, including much of the axial skeleton, girdle elements, and portions of all four limbs. Although no skull was associated with the skeleton, the postcranial remains can be confidently referred to Polycotylidae, making this the oldest unequivocal remains of the clade in North America.