Mosasaurs, a humongous marine lizard that lived in every ocean around the world during the age of the dinosaur, did not head inland when it came time to deliver offspring.

New research reveals the Mesozoic vertebrate animal gave birth out in open ocean waters and not near shorelines. Such insight will help scientists understand more about the predator that often grew to 50 feet long. The lizards went extinct 65 million years ago.

"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 Daniel Field, a doctoral candidate in Yale's Department of Geology and Geophysics.

Field is lead author of the new research published online in the journal Palaeontology on April 10. The study, "Pelagic neonatal fossils support viviparity and precocial life history of Cretaceous mosasaurs," was co-authored by Adam Behlke and Adrienne Gau and funded by the Smithsonian Institution and the Natural Sciences and Engineering Research Council of Canada.

The research focused on the youngest mosasaur specimens found in the extensive fossil collection at the Yale Peabody Museum of Natural History. Field's discovery then led to the research effort.

"These specimens were collected over 100 years ago," Field said. "They had previously been thought to belong to ancient marine birds."

The baby fossils were on record as being found in open ocean deposits.

"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 near-shore nurseries," stated Aaron LeBlanc, a doctoral candidate at the University of Toronto at Mississauga and a member of the research team.

The research team's investigation showed that the baby fossils' varied jaw and teeth were found only in mosasaurs.

"Really, the only bird-like feature of the specimens is their small size," LeBlanc said.

The data sheds new light on the ecology of neonatal mosasaurs and the understanding of the early life history of iconic marine reptiles.