by Playfuls Staff |
12th December 2006
Scientists working in a remote area on the frozen southern continent have made a remarkable discovery: the well-preserved skeleton of a baby plesiosaur.[more]
Plesiosaurs (Greek: plesios meaning 'near' or 'close to' and sauros meaning 'lizard') were carnivorous aquatic (mostly marine) reptiles. Plesiosaurs first appeared at the very start of the Jurassic Period and thrived until the mass extinction which allegedly occured at the end of the Cretaceous Period, caused probably by a giant meteorite. While they were Mesozoic reptiles that lived at the same time as dinosaurs, they were NOT dinosaurs.
Typical plesiosaurs had a broad body and a short tail. They retained their ancestral two pairs of limbs, which evolved into large flippers. Plesiosaurs were probably relatively slow swimmers. It is likely that they cruised slowly below the surface of the water, using their long flexible neck to move their head into position to snap up unwary fish or cephalopods.
Now, a group of scientists from Argentina and the US is reporting the discovery of a well preserved skeleton of plesiosaur, in the Vega Island region of Antarctica.
A massive volcanic eruption in Antarctica (probably similar to the one that occurred in 1980, when Mount St. Helens erupted) likely killed and preserved the long-necked, diamond-finned marine reptile 70 million years ago, said Judd Case, a field researcher for UC Berkeley's Museum of Paleontology and former St. Mary's College dean.
The team of paleontologists knew from the beginning that the icy skeleton was an amazing breakthrough, but it wasn’t until they reached a warmer climate that they realized the importance of their discovery. During the period when it stood covered in ash and ice, the head eroded but the other parts of the body were remarkably well preserved in the volcanic material, including cartilages too.
The fossil is what remained of a baby plesiosaur, less than 1.5 meters long. An adult plesiosaur could reach more than 32 feet in length. The animal's stomach area was wonderfully preserved. Stomach ribs span the abdomen, and rather than being long, straight bones like those of most plesiosaurs, these are forked, sometimes into three prongs.
Experienced paleontologist James Martin, from the South Dakota School of Mines, called it an "exceedingly unique" find. Tony Fiorillo, a paleontologist at the Dallas Museum of Nature and Science, Texas, also points out that infant fossils are hard to find because juvenile bones are not as well ossified as adult bones, and fall apart more easily over time.
"Baby plesiosaurs are super rare," says Benjamin Kear of the University of Adelaide in Australia who studies plesiosaurs of all ages. "To get a really good one is just fantastic."
"It's rare to get even a bone out. To get a complete skeleton was fabulous," Martin said during Monday's press conference at the National Science Foundation. "It's rare to find a baby and then to find this, this animal that lived and died here — there was a whole bunch of 'gee whiz' moments."
It was a return trip for the American-Argentinean expedition, which had found a duck-billed hadrosaur on the same bluff in 1998. This time, the scientists came across a different type of sediment: layers of sticky ash, pumice and glassy material from a massive, ancient volcanic eruption.
"That's where we found the baby plesiosaur," said Case. "It was probably a near-shore environment, but that young individual got trapped in a volcanic explosion."
Vega Island is a small island to the northwest of James Ross Island, on the Antarctic Peninsula. Vega Island has a rich trove of fossils, located in deposits which span the Cretaceous and Tertiary periods. This includes the Cretaceous-Tertiary extinction event, which wiped out all non-avian dinosaurs, and it is one of the best such in the world.
Plesiosaurs lived for millions of years in the southern ocean around Antarctica, which, back then, was warm. Adults could be more than 30 feet long, and the creatures had fins with which they could move through the water much the way penguins do.
Scientists believe the area where the fossil and other partial plesiosaur remains were found may have been a shallow area where marine reptiles gave birth and where young remained until they were big enough to go into open waters.
Getting the cold bones out of the rigid permafrost was really an adventure for the scientists, who were confronted with extreme weather conditions. The wind tossed gravel into the researchers' faces and made unearthing the fossil a great challenge. "We would uncover a few vertebrae and the wind would cover them back up," says Martin, who is at the South Dakota School of Mines and Technology's Museum of Geology. One week the wind speed reached 110 kilometers per hour. "And then it got cold," he adds.
"At the end of the work, icy temperatures turned water to slush before plaster could be mixed to encase the fossil for transportation."
"The ground was so frozen, a digging tool snapped in half during the excavation. Finally, a jackhammer had to be carried up to the site in backpacks along with gasoline, plaster, and water," the statement said.
The fossils were transported in Argentina using a helicopter of the Argentinean Air Force, because they were too heavy.
The fossil is one of the most-complete plesiosaur skeletons found and is believed to be the best-articulated fossil skeleton ever recovered from Antarctica. The creature would have inhabited Antarctic waters during a period when the Earth and oceans were far warmer than they are today.
