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Willo, dinosaur with a heart
"Not only does this specimen have a heart, but computer-enhanced images of its chest strongly suggest it is a four-chambered, double-pump heart with a single systemic aorta, more like the heart of a mammal or bird than a reptile," says Dr. Dale Russell, a paleontologist at NC State University and a senior research curator at the N.C. Museum of Natural Sciences. The finding suggests the dinosaur's circulatory system was more advanced than that of reptiles, and supports the hypothesis that dinosaurs were warm-blooded, Russell says. "This challenges some of our most fundamental theories about how and when dinosaurs developed," he says. Russell is director of the newly created Center for the Exploration of the Dinosaurian World, a joint project of the museum and the university. The dinosaur, a 66-million-year-old Thescelosaurus (THESS-uh-loh-SAWR-us) about the size of a short-legged pony, was found in 1993 in northwest South Dakota. It was acquired by the museum in 1996 and is on permanent display in the museum's new "Prehistoric North Carolina" exhibit. Scientists have nicknamed the 663-pound, 13-foot-long herbivore Willo, after the wife of the rancher on whose property it was found. Images of the fossil, a video, and further information is available on the Web at www.dinoheart.org, a free site maintained jointly by the university and museum. "Willo's ventricles and aorta indicate it had completely separate pulmonary and body circulation systems, which suggests it had a metabolic rate higher than we generally see in living reptiles," explains Dr. Michael Stoskopf, professor of wildlife and aquatic medicine and environmental toxicology at NC State, and an expert on the comparative anatomy of mammals, reptiles and birds. College of Veterinary Medicine Biomedical Imaging Resource FacilityWorking with Russell and Stoskopf, imaging specialists at NC State's College of Veterinary Medicine created enhanced 3-D composite images of Willo's thoracic cavity from a series of two-dimensional computerized tomography (CT) scans. These images confirmed that a grapefruit-sized reddish-brown clump visible in Willo's partially exposed chest was, indeed, a fossilized heart. "When we looked at the two-dimensional images, there was something in the thoracic cavity that resembled a heart, but we couldn't tell for certain. The skeleton was compressed and not in precise anatomical order due to being buried for 66 million years in sandstone," says Paul Fisher, director of the vet school's Biomedical Imaging Resource Facility. "But once the computer software put all the 2-D images together into a 3-D model, it became very apparent that, yeah ? this was the real deal. You could see both ventricles and the aorta." Dr. Reese Barrick, an NC State paleobiologist, and graduate student William Straight conducted X-ray diffraction analyses that confirmed the presence of iron in Willo's heart but not in the sediments surrounding the heart or skeleton. This corroborated Russell, Stoskopf and Fisher's findings that the fossilized concretion in Willo's chest was a heart. The research team's co-authors on the Science paper are Michael Hammer of Hammer & Hammer Paleotek of Jacksonville, Ore., and Dr. Andrew Kuzmitz of Ashland, Ore. Hammer and his son Jeff found Willo in the Hell Creek Formation near Buffalo, South Dakota, in 1993. Kuzmitz, a family practitioner and amateur paleontologist, did the first CT scans on the fossil. Thescelosaurus means "marvelous lizard." Scientists have not yet conclusively identified which species of Thescelosaurus Willo is, but Russell and Hammer believe it is most likely T. neglectus. Neglectus translates as "neglected one" -- so named because though the first fossil was found in 1891, it was considered so unremarkable that it sat, unidentified and unstudied, in its packing crate at the Smithsonian Institution for 22 years. It wasn't until 1913 that paleontologist Charles Gilmore examined the fossil and discovered it to be a previously undescribed type. "Thescelosaurus neglectus, the marvelous neglected lizard," Russell says. "Marvelous -- Yes. But I don't think this one is going to be neglected any more." Remarkably well-preserved, Willo is the only Thescelosaurus ever found with a complete skull and with soft tissues usually lost to decay. Tendons are still connected to its spine, and fossilized cartilage remains attached to its ribs. Shadows and shapes revealed by the 3-D images suggest Willo may contain other fossilized organs as well, Russell notes. Because of the dinosaur's scientific importance and fragile condition, the museum is displaying it in its original posture, still embedded in the sandstone in which it has rested for 66 million years. The right side of its skull, spinal column, ribs and sections of the tail are partially exposed. The left side and extremities were lost to erosion. "We got lucky. If it hadn't been discovered when it was, it could all have eroded within six months," Russell says. He speculates Willo's soft tissues were preserved by a process called saponification, in which soft tissues are converted into a soap-like substance when submerged in wet, oxygen-free environments, allowing them to petrify rather than decay. "This specimen was apparently buried in waterlogged sand," he says. "The cellular structure of the soft tissue was lost but its form was retained." Thescelosaurus was an ornithischian, or "bird-hipped," dinosaur that lived at the end of the Cretaceous period, about 1 million years before the end of the dinosaur era. Native to North America, its range extended from Wyoming and the Dakotas northward into Alberta, Canada. Since using the 3-D software to reveal Willo's heart, Fisher has also used it to create 3-D images of the fossil's skull, and of remains from other specimens in the museum's collection. It's the first time the software -- developed for medical imaging at the Mayo Clinic -- has been used on dinosaurs, he says, but likely not the last time. "This gives us a nondestructive way to look inside specimens that are still embedded, as two-thirds of Willo is, in stone," he says. "It's an amazing use of the technology." The Willo research team will collaborate with scientists and educators from NC State, the N.C. Museum of Natural Sciences and other institutions worldwide to conduct continuing research on dinosaurs and dinosaurian ecosystems through the newly formed Center for the Exploration of the Dinosaurian World.
This information was derived from Photo at the top of this page was taken by Jim Page, MCMNS
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