Osteology of a perinatal aristonectine (Plesiosauria; Elasmosauridae)

• Autores: O'gorman, José P.; Talevi, Marianella; Fernández, Marta S.
• Año de publicación: 2016
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Marine Reptile; Aristonectinae; Perinatal; Upper Cretaceous; Weddellian Province
• Institución: Universidad Nacional de Río Negro

Fil: O'gorman, José P. Consejo Nacional de Investigaciones Científicas y Técnicas. Buenos Aires, Argentina.
Fil: Talevi, Marianella. Consejo Nacional de Investigaciones Científicas y Técnicas. Buenos Aires, Argentina.
Fil: Fernández, Marta S. Consejo Nacional de Investigaciones Científicas y Técnicas. Buenos Aires, Argentina.
Fil: O'gorman, José P. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados. Buenos Aires, Argentina.
Fil: Talevi, Marianella. Universidad Nacional de Río Negro. Instituto de Investigación en Paleobiología y Geología. Río Negro, Argentina.
Fil: Fernández, Marta S. Universidad Nacional de La Plata. Museo de La Plata. División Paleontología de Vertebrados. Buenos Aires, Argentina.
Perinatal specimens give valuable information about the first stages of vertebrate ontogeny. Here, the morphology and palaeohistology of an aristonectine perinatal specimen from Seymour Island (Isla Marambio), López de Bertodano Formation are analysed. The palaeohistological analysis shows incomplete endochondral ossification (retention of a calcified cartilaginous core in the medullary region), predominance of primary bone tissue without secondary remodelling, lack of primary or secondary osteons and of growth marks in the cortical bone, and open vascular spaces not surrounded by a thin coat of lamellar bone tissue. General lines of morphological changes were inferred from comparing the fossil with an adult aristonectine specimen indicating i) a tendency of relatively high and broad posterior cervicals to decrease during ontogeny, ii) a decrease of relative size of the dorsolateral process and an increase of the glenoid ramus and iii) the existence of two separate stages in propodial growth divided into an initial elongation followed by a distal expansion. The presence of a perinatal specimen in the James Ross Archipelago indicates that the region was used as a breeding area by the aristonectines during the last part of the Cretaceous.
Perinatal specimens give valuable information about the first stages of vertebrate ontogeny. Here, the morphology and palaeohistology of an aristonectine perinatal specimen from Seymour Island (Isla Marambio), López de Bertodano Formation are analysed. The palaeohistological analysis shows incomplete endochondral ossification (retention of a calcified cartilaginous core in the medullary region), predominance of primary bone tissue without secondary remodelling, lack of primary or secondary osteons and of growth marks in the cortical bone, and open vascular spaces not surrounded by a thin coat of lamellar bone tissue. General lines of morphological changes were inferred from comparing the fossil with an adult aristonectine specimen indicating i) a tendency of relatively high and broad posterior cervicals to decrease during ontogeny, ii) a decrease of relative size of the dorsolateral process and an increase of the glenoid ramus and iii) the existence of two separate stages in propodial growth divided into an initial elongation followed by a distal expansion. The presence of a perinatal specimen in the James Ross Archipelago indicates that the region was used as a breeding area by the aristonectines during the last part of the Cretaceous.