The Leg Is Different

Alectrosaurus has a leg that has certainly led to some of the debate and confusion surrounding its placement in the tyrannosaur family. The reasons for this are that the leg, foot, and ankle are all of lengths that are atypical for tyrannosaurs. The tibia and femur are of nearly equal lengths. The normal condition in tyrannosaurs are tibia lengths that exceed those of the femur. Additionally, the foot and ankle are typically longer than the tibia length in tyrannosaurs, but again, Alectrosaurus differs from this trend by having a hind foot and ankle that are nearly equal to the tibia length. The implications of this change the movement of the dinosaur overall. Long tibiae have been used to indicate swifter running speeds in ornithomimids and the long tibia of Alectrosaurus may have been a useful tool in running at greater speed than other tyrannosaurs. Swifter running speeds may have allowed Alectrosaurus to out compete Gigantoraptor and other predators in pursuing ornithopods like Bactrosaurus and Gilmoreosaurus. A more complete fossil would enable more in depth studying of the gait, but for now the gait of Alectrosaurus is what it is and it appears to be a fairly swift gait also.

This appears to be partially based on a Ryan Lewis drawing, but has no clear attribution.