Life, where it is portrayed as preying upon a small ornithischian dinosaur, Nanosaurus agilis. Description Carpenter et al. (2005, pp. 43–44) determined that the holotype of Tanycolagreus represents a subadult individual which measured approximately long in life. However, one of the referred fossils, the premaxilla from the Cleveland-Lloyd Quarry, would have belonged to a larger individual, measuring long. In 2010 Gregory S. Paul estimated the weight of a four-meter-long animal at . It cannot be determined whether or not the Cleveland-Lloyd specimen represents a fully mature adult, so the upper size limit for the taxon remains unknown. The head of Tanycolagreus is large, elongated and rectangular in profile due to a blunt snout. The leg is rather long and lightly built. Carpenter et al. (2005; pp. 27 & 29) diagnosed Tanycolagreus topwilsoni as follows: "Medium-sized tetanuran having short, deep-bodied premaxilla pierced by narial foramen at base of nasal process, orbital process on postorbital, T-shaped quadratojugal, centrodiapophyseal lamina on dorsals. Differs from Coelurus in the absence of pleurocoel on anterior dorsals; posterior caudal prezygapophyses elongated to one-third centrum length, rather than short; straight, rather than sigmoidal, humeral shaft; bowed, rather than straight, radius; flat-bottomed rather than arced pubic foot; straight rather than sigmoidal femoral shaft; metatarsal length subequal to humeral length, rather than 1.75 times humeral length. Differs from Ornitholestes in straight anterior margin of premaxilla, rather than rounded; T-shaped rather than L-shaped quadratojugal; elongate neural spine; posterior caudal prezygapophyses only one-third centrum length, rather than one-half centrum length; bowed, slender radius, rather than straight, robust radius". The single premaxillary tooth preserved with the holotype is badly damaged, but does exhibit the asymmetrical cross-section typical in theropod teeth; the cheek teeth are too poorly preserved to show any detail. In the foot the second toe is slightly hyperextendable but does not carry an enlarged claw. Classification Carpenter e.a. originally assigned Tanycolagreus to the Coeluridae. Carpenter et al. (2005, p. 44) state that, of the other known Morrison theropods, this genus most closely resembles Coelurus, though it retains more "primitive" features. A detailed phylogenetic analysis in 2007 by Philip Senter including Tanycolagreus showed it had a basal position in the Tyrannosauroidea. Later analyses indicated a basal position in the Coelurosauria. References Prehistoric coelurosaurs Late Jurassic dinosaurs of North America Dinosaurs of the Morrison Formation Fossil taxa described in 2005 Taxa named by Kenneth Carpenter Paleontology in Wyoming