A paper to be published on August 12, 2011 in Science reveals that Dr. F. Robin O'Keefe of Marshall University in Huntington, W.Va. and Dr. Luis Chiappe, Director of the Natural History Museum's Dinosaur Institute, have determined that a unique specimen now displayed in the Natural History Museum of Los Angeles County is the fossil of an embryonic marine reptile contained within the fossil of its mother.
The 78-million-year-old, 15.4-foot-long adult specimen is a Polycotylus latippinus, one of the giant, carnivorous, four-flippered reptiles known as plesiosaurs that lived during the Mesozoic Era. The embryonic skeleton contained within shows much of the developing body, including ribs, 20 vertebrae, shoulders, hips, and paddle bones. The research by Dr. O'Keefe and Dr. Chiappe establishes that these dual fossils are the first evidence that plesiosaurs gave birth to live young, rather than hatching their offspring from eggs on land.
Although live birth (or viviparity) has been documented in several other groups of Mesozoic aquatic reptiles, no previous evidence of it has been found in the important order of plesiosaurs. Drs. O'Keefe and Chiappe have also determined that plesiosaurs were unique among aquatic reptiles in giving birth to a single, large offspring, and that they may have lived in social groups and engaged in parental care.
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Cheers,
Bob-C
