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August 12, 2011
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Ancient sea monster may have cared for its young
Aug. 12, 2011
Courtesy of the Natural History
Museum of Los Angeles County
and World
Science staff
Some of the monstrous reptiles that lorded it over the oceans during the Age of Dinosaurs might have cared for their young, and even interacted a bit like dolphins, researchers are reporting. Artist's concept of a
mother and juvenile plesiosaur. (Courtesy U.S. Nat'l Science
Foundation)
The claim is based on a fossil of a pregnant member of a reptilian lineage known as plesiosaurs. Details of the object suggest the beast would have given birth to a single, live offspring, the scientists say.
With long necks, small heads, dagger-like teeth and paddle-shaped limbs, plesiosaurs prowled the seas snapping up smaller creatures for millions of years before dying out along with the dinosaurs some 65 million years ago.
Other lineages of aquatic reptiles from this era are known to have birthed live young. But whether plesiosaurs also did so has been unknown, paleontologists say. Robin O’Keefe of Marshall University in Huntington, W. Va. and Luis Chiappe of the Natural History Museum of Los Angeles County analyzed the fossil, discovered in 1987 and archived at the museum. Their
findings are published in the Aug. 12 issue of the research journal
Science.
The fetus’ large size suggests that rather than giving birth to multiple smaller young, as other live-bearing marine reptiles of the age did, plesiosaurs made one, large baby, the researchers propose. Other marine species that give birth this way, such as whales, care for their young extensively, they noted. Though more evidence is needed, they continued, plesiosaurs may also have done so.
The 78-million-year-old, 15.4-foot-long adult specimen is identified as a species of plesiosaur called
Polycotylus latippinus. The embryonic skeleton within shows much of the developing body, including ribs, 20 vertebrae, shoulders, hips, and paddle bones.
"Scientists have long known that the bodies of plesiosaurs were not well suited to climbing onto land and laying eggs in a nest," O'Keefe said. "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."
Plesiosaurs have no known living relatives, thought they were common in their day. They are thought to have ranked among the top predators in the Western Interior Seaway, a vast body of water that split North America during the Cretaceous era when waters from the Arctic Ocean and the Gulf of Mexico flooded onto the continent and met.
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Some of the monstrous reptiles that lorded it over the oceans during the Age of Dinosaurs might have cared for their young, and even interacted a bit like dolphins, researchers are reporting. The claim is based on a fossil of a pregnant member of a reptilian lineage known as plesiosaurs. Details of the object suggest the beast would have given birth to a single, live offspring, the scientists say. With long necks, small heads, dagger-like teeth and paddle-shaped limbs, plesiosaurs prowled the seas snapping up smaller creatures for millions of years before dying out along with the dinosaurs some 65 million years ago. Other lineages of aquatic reptiles from this era are known to have birthed live young. But whether plesiosaurs also did so has been unknown, paleontologists say. Robin O’Keefe of Marshall University in Huntington, W. Va. and Luis Chiappe of the Natural History Museum of Los Angeles County analyzed the fossil, discovered in 1987 and archived at the museum. The fetus’ large size suggests that rather than giving birth to multiple smaller young, as other live-bearing marine reptiles of the age did, plesiosaurs made one, large baby, the researchers propose. Other marine species that give birth this way, such as whales, care for their young extensively, they noted. Though more evidence is needed, they continued, plesiosaurs may also have done so. The 78-million-year-old, 15.4-foot-long adult specimen is identified as a species of plesiosaur called Polycotylus latippinus. The embryonic skeleton within shows much of the developing body, including ribs, 20 vertebrae, shoulders, hips, and paddle bones. "Scientists have long known that the bodies of plesiosaurs were not well suited to climbing onto land and laying eggs in a nest," O'Keefe said. "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." Plesiosaurs have no known living relatives, thought they were common in their day. They are thought to have ranked among the top predators in the Western Interior Seaway, a vast body of water that split North America during the Cretaceous era when waters from the Arctic Ocean and the Gulf of Mexico flooded onto the continent and met.