Scientists identify two ancient reptiles that swam in Australian waters

On Friday, July 28, 2006, scientists finally identified the skeletons of two ancient reptiles that swam in the icy waters surrounding Australia up to 115 million years ago.  They are some of the first reptiles to be categorized into the time period shortly after the Jurassic era; this period is estimated to have been about 90 million to 130 million years ago.

Paleontologist Benjamin Kear and a team of researchers from the University of Adelaide and South Australian museum identified the two skeletons after piecing together fossils from 30 individuals, all of which had been collected from an opal mine for the last 30 years.  Both reptiles are thought to be juvenile animals, which leads to the theory that the lake was a breeding and nursery ground.  These scientists have named these plesiosaurs, or long-necked marine reptiles that lived alongside dinosaurs, Umoonasaurus demoscyllus and Opallionectes andamookaensis.

Umoonasauras demoscyllus

This plesiosaur was a rhomaleosaurid, which was known as the Jurassic era’s equivalent of the killer whale today. The reptile was about 2.4 meters (7.2 feet) long and had crests on its head. Kear describes it as a small, sturdy body with four flippers, a long neck, a diminutive head and a short tail, comparing it to a reptilian seal.

Opalionectes andamookaensis

Opallionectes, whose name means “the opal swimmer from Andamooka,” was a much larger plesiosaur than Umoonasaurus – it spanned about 16-19 feet long (4-6 meters). However, the only descriptive factor that seems to be unique is its masses of fine, needle-like teeth that it used to trap small fish and squid. Both the Opallionectes and the Umoonasauras are thought to have developed mechanisms to cope with the harsh climate, including a faster metabolic rate.

The identification of these two creatures is the “missing link” connecting older creatures from about 170 million years ago that lived during the Jurassic period, found in England, and the younger ones from about 65 million years ago that were found in Antarctica and Patagonia.

Both the Umoonasaurus and the Opallionectes lived in frigid waters that covered what are now known as Australia 115 million years ago.  Back then, Australia was much closer to Antarctica.  According to Kear, this discovery could be the beginning of revealing this time period that had previously been mostly unexplored in Australia. The identification fills a time frame not often represented in the world’s ancient history, since scientists have found older fossils from Europe and younger fossils in North America, but fossils from the time frame sometime between these time periods are far and few between.

The University of Newcastle’s Colin McHenry only slightly disagrees, stating that the discovery was not revolutionary in that it overturns our idea of the Earth’s history, but he agrees that the discovery would help scientists better understand what was going on during the period from 90 million to 140 million years ago.  Rather than opening a window, as Kear believes, McHenry states that these animals represent a new chapter in scientific understanding of the current marine ecosystem’s roots.