Extremely Long-necked, Oddly Proportioned Sauropod Reported By American Museum Of Natural History Paleontologists
Daniel T. Ksepka
Credit: Roderick Mickens, AMNH
Two American Museum of Natural History paleontologists have described a new species of sauropod, Erketu ellisoni, that had an extremely elongated neck, one of the longest necks proportional to trunk height of all known sauropods. E. ellisoni belongs to the Sauropoda, a group of four-legged herbivorous dinosaurs that includes the largest land animals ever on Earth. While certainly a giant compared to living land animals, E. ellisoni was actually modest-sized for a sauropod, smaller than DiplodocusÂ--one of the longer sauropods. The truly impressive feature of this dinosaur was not its bulk or overall length, but the length of its neck-especially in comparison to the rest of its body. Most sauropods had long necks extending from large bodies, but E. ellisoni took this to an extreme. A single neck vertebra from E. ellisoni measures more than half a yard (nearly two feet) long and is comparable in size to about two loaves of bread. Based on the partial neck recovered from this specimen, the Museum team estimates that the full neck was more than eight yards long. The known vertebrae for E. ellisoni are longer than the same vertebrae in the well-known mounted skeleton of Diplodocus carnegii.
The new finding is described in the peer-reviewed journal American Museum Novitates by Daniel T. Ksepka, a graduate student enrolled at Columbia University who studies at the American Museum of Natural History, and Mark A. Norell, Curator in the Museum's Division of Paleontology.
The fossil, which also includes a chest plate, two lower leg bones, and a potato-sized anklebone, was discovered in 2002 during the exploration of a new site, Bor Guvas part of the Museum's annual joint paleontological expeditions to the great fossil beds of Mongolia's Gobi Desert with the Mongolian Academy of Sciences. Bor Guvas a floodplain when the rocks bearing the new fossil were deposited 100 to 120 million years ago. The generic name for the new sauropod, which was an adult when it died, is derived from Erket of 99 deities chronicled from pre-Buddhist Mongolian shamanistic tradition. Erketthe god of might. The species name honors Mick Ellison, Senior Principal Artist at the Museum, whose work has made a significant contribution to dinosaur research.
Mr. Ksepka and Dr. Norell's research included a new genealogical analysis of the relationships among sauropods, now including E. ellisoni. The new family tree revealed that this specimen occupies a branch of the sauropod evolutionary tree close to the advanced sauropod group Titanosauria. Titanosaurs are considered the most successful group of sauropods by many paleontologists because they managed to spread throughout the world and survive until the end of the Cretaceous Period. Titanosaur fossils have been reported from every continent. Despite their wide geographical distribution, there are many gaps in scientists' understanding of early titanosaur evolution. E. ellisoni helps to fill one of these gaps.
"The discovery of this unusually proportioned sauropod is providing new insights into the complex evolutionary relationships among Asian sauropods and the success of Titanosauria," Mr. Ksepka said. "We hope to examine additional sauropod bones and teeth that have been found at this location to help resolve the questions raised by our study of this unique animal."
The neck vertebrae of E. ellisoni illustrate some of the interesting evolutionary strategies sauropods used to reduce the burden of their long, cumbersome necks. The sides of the bones feature large concavities where air sacs would have existed. Computed tomography (CT) scans of the bones performed at Stony Brook University Hospital reveal that the vertebrae are not solid, but instead are filled with numerous small pneumatic chambers that would reduce their weight. Also, spines along the top of some of the vertebrae were split into two parallel tracks rather than one, as with the human spine. The channel between the two spine rails probably allowed room for a ligament to help support the neck.
With the exception of a few previous discoveries, sauropod material from Mongolia has been scarce and fragmentary. The E. ellisoni discovery adds a new and important dimension to Mongolian sauropod diversity. "The American Museum of Natural History's joint expeditions to the Gobi Desert continue to yield remarkable fossils, such as this new sauropod which had one of the longest necks proportionately of any dinosaur," Dr. Norell said. "The excavation of sauropod fossils is quite time-consuming as it requires digging out massive body parts. Further work at Bor Guvill give us even more insight into the diversity and evolution of highly derived sauropods."
The work on E. ellisoni was funded by the National Science Foundation and the American Museum of Natural History.
Paleontology at the American Museum of Natural History
Home to the world's largest collection of vertebrate fossils, totaling nearly one million specimens, the American Museum of Natural History has had a long and distinguished history of paleontological research in almost all areas of the globe. Since 1990, Michael J. Novacek, Provost, Senior Vice President, and Curator in the Division of Paleontology, and Dr. Norell have been the co-leaders of the Museum's annual joint paleontological expeditions to the great fossil beds of Mongolia's Gobi Desert with the Mongolian Academy of Sciences. These expeditions, which have yielded spectacular discoveries of dinosaurs, birds, and mammals, continue the work begun by Museum paleontologist Roy Chapman Andrews and his team in the 1920s when they first discovered these fossil beds during the Museum's groundbreaking Central Asiatic Expeditions. The Gobi has preserved a broad spectrum of creatures, from towering dinosaurs to lizards that fit in the palm of your hand, all in exquisite detail. Museum scientists will return this summerÂ--for the 17th consecutive yearÂ--to explore this vast desert with their colleagues from the Mongolian Academy of Sciences.
American Museum of Natural History
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