Pregnant Plesiosaur Fossil Provides First Evidence of Live Birth
Posted on August 11, 2011
The fossil of a plesiosaur has been discovered to be the fossil of a mother plesiosaur with a developing fetus. 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, made the discovery. The 78-million-year-old, 15.4-foot-long adult specimen is a Polycotylus latippinus, a giant, carnivorous, four-flippered reptile (also known as plesiosaurs) that lived during the Mesozoic Era.
The embryonic skeleten contained within the fossil shows the developing body of a baby plesiosaur, including ribs, vertebrae, shoulders, hips, and paddle bones. The researchers say the embryonic fossil is the first evidence plesiosaurs gave birth to live young and did not hatch their offspring from eggs on land. Plesiosaurs may also have lived in social groups, like modern dolphins and whales.
Dr. O'Keefe said in a statement, "Scientists have long known that the bodies of plesiosaurs were not well suited to climbing onto land and laying eggs in a nest. So the lack of evidence of live birth in plesiosaurs has been puzzling. This fossil documents live birth in plesiosaurs for the first time, and so finally resolves this mystery. Also, the embryo is very large in comparison to the mother, much larger than one would expect in comparison with other reptiles. Many of the animals alive today that give birth to large, single young are social and have maternal care. We speculate that plesiosaurs may have exhibited similar behaviors, making their social lives more similar to those of modern dolphins than other reptiles."
The specimen is currently on display in the Dinosaur Hall, the new 14,000-square-foot exhibition at NHM in Los Angeles. The Dinosaur Hall features more than 300 fossils and 20 complete mounts of dinosaurs and sea creatures. The pregnant plesiosaur fossil was discovered in 1987 by Charles Bonner on the Bonner Ranch in Logan County, Kansas.