Researchers have discovered a new birth story for mosasaurs.
A fierce marine lizard that patrolled the sea more than 65 million years ago wasn't born quite where paleontologists thought it was.
Mosasaurs, once thought to be reared from eggs deposited on land, were instead born out in the open ocean, a new study out of Yale University and the University of Toronto suggests.
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The family of marine reptiles, which could reach some 50 feet in length, lived during the Late Cretaceous, between 66 and 85 million years ago. The top-drawer predators ate fare such as turtles and birds but weren't averse to taking on bigger prey such as sharks and plesiosaurs. They went extinct along with practically everything else in the Cretaceous-Tertiary extinction of 65 million years ago.
While the creature's later stages of life are well known, little is understood about the initial environment it faced.
"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 Yale doctoral candidate in geology and geophysics, Daniel Field, the study's lead author.
Field and Aaron LeBlanc, a doctoral candidate at the University of Toronto at Mississauga, examined mosasaur specimens from the Yale Peabody Museum of Natural History that had been gathered more than a century ago.
The finds in the collection had been identified as belonging to ancient marine birds, but the two scientists saw something else. They noted jaw and teeth features that were unique to mosasaurs and realized they were studying the youngest mosasaur samples ever found. Too, the finds came from open ocean deposits.
"Really, the only bird-like feature of the specimens is their small size," said LeBlanc. "Contrary to classic theories, these findings suggest that mosasaurs did not lay eggs on beaches and that newborn mosasaurs likely did not live in sheltered nearshore nurseries."
The researchers' findings have just been published online in the journal Paleontology.
