Fossils reveal ancient killer-whalelike reptiles

BANGKOK, Thailand – Scientists have identified two ancient reptiles that swam in icy waters off Australia 115 million years ago, researchers said Friday. They are among the first of their kind to be found from the period soon after the Jurassic era.

The discoveries – dubbed Umoonasaurus and Opallionectes – belonged to a group of animals called plesiosaurs, long-necked marine reptiles that lived during the time of the dinosaurs.

Researchers, led by paleontologist Benjamin Kear and a team from the University of Adelaide and South Australian Museum, identified the new species after piecing together fossils from 30 individuals collected from an opal mine in the past 30 years.

The team’s findings were recently published in both the international journal Paleontology and the online edition of Biology Letters, a periodical published by the prestigious Royal Society of London.

Umoonasaurus was a rhomaleosaurid, a kind of plesiosaur that was the “killer-whale equivalent of the Jurassic” period, Kear said. It was distinguished by its relatively small size of less than 8 feet long and three crestlike ridges on its skull.

“Imagine a compact body with four flippers, a reasonably long neck, small head and short tail much like a reptilian seal,” Kear said.

Opallionectes was also a plesiosaur, but much larger – about 19 feet long with masses of fine, needlelike teeth for trapping small fish and squid. Its name means “the opal swimmer from Andamooka.”

“It’s a missing link between older forms of the Jurassic period found in England about 170 million years ago and the much younger ones found in Antarctica and Patagonia which are about 65 million years old,” Kear said.

Both creatures lived in a freezing polar sea that covered what is now Australia 115 million years ago, when the continent was located much closer to Antarctica. Kear said he expected more discoveries, which together could open a window on a period that he said had been largely unexplored in Australia.