Chuck Bednar for redOrbit.com – @BednarChuck
The large, extinct marine reptiles known as mosasaurs gave birth to their young while in the water, not on land or near the shore as previously believed, according to new research published online Friday in the journal Palaeontology.
In the study, Daniel Field from the Yale University department of geology and geophysics, and his colleagues examined the fragmentary cranial remains of two neonatal mosasaurs, which were recovered from the open sea, and concluded that they were likely born in that setting.
Youngest mosasaurs fossils ever found in the open ocean
According to the authors, the fossils they analyzed are the youngest mosasaur specimens ever discovered. Field reportedly found them in the collection at Yale’s Peabody Museum, and said that they had been collected more than a century ago and misidentified as birds.
The cranial remains were originally recovered from the pelagic zone of the Niobrara Formation in North America, and their presence in waters located so far from shore indicate that even the youngest mosasaurs occupied oceanic habitats, and probably began their lives there.
“Mosasaurs are among the best-studied groups of Mesozoic vertebrate animals, but evidence regarding how they were born and what baby mosasaur ecology was like has historically been elusive,” said Field, who is also affiliated with the Smithsonian National Museum of Natural History’s Department of Vertebrate Zoology in Washington DC.
No on-shore nurseries
Based on their findings, they concluded that these ancient reptiles (which could grow to lengths of more than 50 feet) gave birth to their young in the open ocean, not near land. The discovery will help answer long-standing questions about the early environment of the mosasaur, which roamed the waters in the era of the dinosaurs before dying out 65 million years ago.
Co-author Aaron LeBlanc, a doctoral candidate at the University of Toronto at Mississauga, and Field concluded that the specimens also showed a wide variety of different teeth and jaw features found only in mosasaurs. He explained that, despite previous theories, these marine predators did not lay eggs on beaches, and probably did not have on-shore nurseries for newborns.
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