Resumen

SALGADO, Leonardo; FERNANDEZ, Marta  y  TALEVI, Marianella. Histological observations on marine reptiles (Elasmosauridae and Mosasauridae) from the Late Cretaceous of Patagonia and Antarctica. Ameghiniana [online]. 2007, vol.44, n.3, pp.513-523. ISSN 1851-8044.

Bones of two elasmosaurid plesiosaurs (one subadult and one adult) from the Upper Cretaceous of Patagonia (Argentina), and one adult mosasaur from the Upper Cretaceous of Antarctica are histologically described in order to obtain information related to their lifestyles. The bones of the subadult elasmosaurid from Lago Pellegrini (Río Negro, Argentina), display a well developed endosteal compaction or osteosclerosis, the degree of osteosclerosis being higher in the vertebra than in the humerus or pelvic girdle. By contrast, the bones analyzed in the adult elasmosaurid (cf. Mauisaurus from the Salinas de Trapalcó area, Río Negro), display internal vacuities leading to a lightening of the bone (osteoporotic-like bone structure). The distribution of osteosclerotic bone structure in juvenile plesiosaurs and osteoporotic-like structure in adults is similar to the one described in plesiosaurs from New Zealand, and could be related to adaptations to different aquatic environments: estuaries and shallow waters for juveniles, and open seas for adults. Both situations are in agreement with paleoenvironment reconstructions of the Allen and Jagüel Formations in Lago Pellegrini and Salinas de Trapalcó respectively. In the bones of the mosasaur from the López de Bertodano Formation (Upper Cretaceous, Isla Marambio, Antarctica), compact bone is in the inner part of the vertebra, while in the transverse process there is a high degree of osteoporotic tissue.

Palabras clave : Paleohistology; Marine reptiles; Patagonia; Antarctica; Upper Cretaceous.