Specimens of Tyrannosaurus - Peck's Rex

Peck's Rex

Peck's Rex (also known as "Peckrex", "Rigby's rex" and Tyrannosaurus "imperator") is the nickname (specimen number MOR 980) given to a fossil specimen found in Montana in 1997. The excavation was led by J. Keith Rigby, and the fossil got its nickname after Fort Peck, which is located close to the place of discovery. Peck's Rex has been part of several exhibitions on dinosaurs, and is specifically famous because it was the first specimen of its species to have Metacarpal III preserved.

The fossil of Peck's Rex is relatively well preserved. The skeleton includes a relatively complete skull with jaws, multiple vertebrae of the back and tail, a well preserved gastralium, and hipbone with complete ischium and pubis. The left hindleg is relatively complete, missing only some toe bones. The forelimbs include the scapula and furcula, both humeri and right hand phalanges, as well as metacarpal III. Because the skeleton is of the gracile morphotype, Peck's Rex is believed to be a male, although the hypothesis which suggests that the sex of Tyrannosaurus specimens can be determined by the degree of skeletal sturdiness has been debated in recent years. Peck's Rex has been the subject of research regarding parasitic infections in dinosaurs. The forelimbs of Peck's Rex have also been studied as they show evidence of use. This evidence includes the construction of metacarpal III, as well as repeated fractures in the furcula - possibly caused by heavy loads or pressure (Carpenter and Lipkin, 2005).

Casts of Peck's Rex have been featured at several museums including the Maryland Science Center, the Fort Peck Interpretive Center and Museum (beside a lifesized model), and the Carnegie Museum of Natural History as part of the exhibit: Dinosaurs in Their Time where it is mounted in a "face off" position against the holotype Tyrannosaurus skeleton (CM 9380). Cast pieces and skeletons of Peck's rex (like forelimbs, teeth, and parts of the jaws and feet) are also for sale.