News: AAAS 2013 Annual Meeting News
Long Necks and Fabulous Feathers From China's Prehistoric Past
“What it did with this long neck I can only speculate,” said Olivier Rieppel, Curator of Evolutionary Biology at the Field Museum in Chicago, who led the team that identified the Dinocephalosaurus skeleton.
This 5-meter-long creature might have splayed out the ribs in its neck to create suction for drawing prey into its mouth, Rieppel proposed at the AAAS Annual Meeting.
Dinocephalosaurus is just one of the reptiles that moved from land into the shallow seas over what is now southern China during the Triassic period approximately 250 to 200 million years ago.
Illustration of Dinocephalosaurus Orientalis showing the body proportions, including its long neck. Credit: Courtesy of The Field Museum/artist Marlene Donnelly
China has been the source of many exquisite fossils, including some beautifully preserved feathered dinosaurs, plus other important geological finds, experts said in the symposium “Dragons of the East: China's Paleontological Riches.” Like all good scientific discoveries, each of these finds has opened new questions.
For example, the feathered Archaeopteryx has long been considered the ancestor to modern birds. Xing Xu of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing called it “an icon” that researchers have looked to for clues about how flight evolved and how birds developed from non-avian dinosaurs.
Working in northeastern China, Xu and his colleagues discovered a feathered specimen that resembles Archaeopteryx in some ways but is actually a theropod dinosaur. Because Archaeopteryx now appears to have so much in common with relatives outside the bird lineage, Xu hypothesizes that it belongs instead to the group Deinonychosauria, which includes the well-known Velociraptor. If further research supports this hypothesis, it may re-open the search for modern birds' prehistoric ancestor.
Findings from a third Chinese team are casting new light on an extinction event that preceded the rise of the dinosaurs, roughly 250 million years ago.
Shu-zhong Shen of the Nanjing Institute of Geology and Paleontology in Nanjing and colleagues have pared down the likely duration of the greatest mass extinction in history, the Permian-Triassic extinction. This event, known as the “Great Dying,” killed off 95 percent of marine species and 75 percent of the species on land.
This extinction period was generally thought to have lasted more than five million years, but new geological evidence indicates that it happened much faster -- in less than 200,000 years, Shen said.
What could have wiped out so many species, so quickly? The evidence from Shen's team offers some clues. Geochemical isotopes and other data suggest that the event happened simultaneously on land and at sea, and that the oceans both warmed and acidified rapidly. And, sediment layers rich in charcoal, soot and clumps of rock fragments indicate widespread wildfires and catastrophic soil erosion on land, according to Shen. Pinpointing exactly what happened will require more research.
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