this study, Carano et al. found that although it was very unusual, Segisaurus was firmly a coelophysoid, and probably a close relative of Procompsognathus. Distinguishing anatomical features A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism or group. According to Rauhut (2003), Segisaurus can be distinguished based on the following features: the dorsal centra are not very constricted ventrally the scapula is slender the humeral shaft has stronger torsion (~50 degrees) than does that of Coelophysis the presence of a large ischial fenestra (according to Carrano et al., 2005) the humeral deltopectoral crest is rectangular History of discovery In 1933, Max Littlesalt, a Navajo Indian, discovered the holotype in Tsegi Canyon of the Navajo Sandstone of Coconino County, Arizona. The specimen was found in calcareous sandstone, which was deposited during the Pliensbachian - Toarcian stages of the Jurassic, approximately 190 to 174 million years ago. After discovering the remains, Littlesalt, who kept livestock inside the canyon, pointed out the fossils to archeologists who were on an expedition inside the canyon. Other than the first finding of Segisaurus, no other specimens have been discovered. When the specimen of Segisaurus was discovered, Camp likened its posture to that of a "sitting hen", due to the position the dinosaur's remains were in. Other theropods used this positions to sleep or stay sheltered during sand and ash storms. Taphonomy The Segisaurus holotype was found in a bed of sandstone, suggesting that the dinosaur had been buried in a layer of sand and died. This is still only a hypothesis, as no nest or den materials were discovered with the specimen. Geological features of the Navajo Sandstone Formation suggest that this genus lived in an environment resembling modern sand dunes. References External links Segisaurus in the Dino Directory Coelophysoids Early Jurassic dinosaurs of North America Jurassic Arizona Paleontology in Arizona Fossil taxa described in 1936 Taxa named by Charles Lewis Camp