MORPHOLOGICAL DIVERSITY IN CRONOPIO (MAMMALIA, DRYOLESTOIDEA) AT THE LA BUITRERA PALEONTOLOGICAL AREA (CENOMANIAN, RÍO NEGRO PROVINCE)

LUCAS APPELLA GUISCAFRE; SEBASTIÁN APESTEGUÍA; GUILLERMO W. ROUGIER

Zapala y El Chocón

Jornada; XXVIII Jornadas Argentinas de Paleontologia de Vertebrados; 2014

museo juan olsacher , museo bachmann y fundacion Azara

The knowledge on South American Cretaceous mammals has substantially improved in the last decades. New remains include cladothere forms from the northern Patagonian latest Cretaceous Los Alamitos, La Colonia and Allen formations, which shared paleoenvironmental conditions with Gondwanatherians. The early Late Cretaceous mammalian fauna was unknown until some few years ago, when the first mammals were described from the Candeleros Formation in La Buitrera Paleontological Area, Río Negro Province. Cronopio dentiacutus Rougier, Apesteguía and Gaetano is a dryolestoid, phylogenetically close to both the latest Cretaceous forms as well as the Neogene dryolestoids. A revision of the holotype (MPCA-PV454) and hypodigm of Cronopio shows that some specimens differ slightly. For example, in MPCA-PV453 and 456 the distance between P3 and P2 is substantially larger than in other specimens. The P3 in MPCA-PV468 lacks an anterior accessory cusp and the specimen is more bunodont, robust and 25% larger than the remaining. In MPCA-PV453, which is also a large specimen, the posterior heel is more developed, and a valley separates the main cusps from the posterior accessory one. In relation to molars, MPCA 454 shows the small conical parastyle positioned as small cingular cusp on the mesiolabial corner, but it is absent in 456 and present only in the M1 of the type. These differences suggest strong polymorphisms, a sexual dimorphism, or perhaps low level systematic differences that are yet to be explored.