They can be distinguished from other therizinosauroids by means of several features of the skeleton (particularly the hands and feet) which were intermediate between early therizinosaurs such as Falcarius and Beipiaosaurus, and more "advanced" members of the group like therizinosaurids.

The deep and homogeneous hand claws clearly differ from the case in early therizinosauroids, but the foot has not yet acquired the robust morphology of therizinosaurids.

The holotype specimen, UMNH VP 21400, hails from the Hayden-Corbett site of the Cedar Mountain Formation of Utah, approximately eight miles southeast from the city of Green River.

The generic name, Martharaptor, is in honor to the paleontologist assistant Martha C. Hayden who helped in the discovery of the site, and the specific name, greenriverensis, is a reference to the Green River.

Manual and pedal morphology show that the specimen is distinct from other theropods from the Cedar Mountain Formation and from other previously described therizinosauroids.

[2] Phylogenetic analysis placed Martharaptor within Therizinosauroidea as the sister taxon to the Alxasaurus + Therizinosauridae group, although support for this placement is weak.