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Falcarius utahensis

Falcarius utahensis is a newly exposed dinosaur species found in east-central Utah, in the United States, in 2005. Its name is resulting from the word sickle (a "falcarius" being in Latin a sickle cutter), which scientists have used to explain its unwieldy clawed hands. This find, along with the recently exposed therizinosauroid Beipiaosaurus from the Early Cretaceous of China, may clarify the group's relationship with the better family of theropod dinosaurs.

The discovery site, in a 0.8 ha (2 acre) area of Utah's Cedar Mountain Formation, includes the leftovers of hundreds, perhaps thousands, of specimens of the new species. Only a small number of the obtainable fossils have been excavated. From examining fossilized bones from more than a few individual animals, scientists describe the dinosaurs as feathered, rotund, sickle-clawed creatures. Falcarius utahensis averaged 3.7-4 m (12-13 ft) in length and just over 1.2 m (4 ft) tall. With its long neck, it could it seems that reach about 1.5 m (5 ft) off the ground to munch leaves or fruit. Its leaf-shaped teeth and 10-13 cm (4-5 inch) claws indicate that it inspired both meat, quite probably small animals such as lizards, and plant material.

Falcarius utahensis lived about 125-130 million years ago, in the early Cretaceous period, and closely resembles dinosaurs belonging to a collection called Therizinosauridae, part of the Maniraptora. Probably Falcarius itself does not belong to this former group, though it might more unclearly be called a "therizinosaur" and probably belongs to the more including Therizinosauroidea. The group is characterized by bird-like wide hips, a moderately large brain case and long necks with hollow bones typical of plant eaters. The less-primitive Asian specimens were enclosed in shaggy feathers; this is unspecified for Falcarius as well. A larger member of the group, a sloth-like therizinosaur called Nothronychus, was described in 2001, based on discoveries made in the late 1990s in New Mexico. It, however, was predictable to be only 90 million years old.

An article about Falcarius utahensis was in turn out in the May 2005 issue of the journal Nature. Co-authors of the study comprise Scott Sampson, chief curator at the University of Utah's Utah Museum of Natural History, and Lindsay Zanno, a doctoral student at the University. Dr. Sampson is quoted as saying that this class "...is the missing link between greedy dinosaurs and the bizarre plant-eating therizinosaurs". A skeletal mount of Falcarius utahensis went on show at the Utah Museum of Natural History on 29 June 2005.