Open Paleo

Martharaptor

Senter et al., 2012 mar-thuh-RAP-tuhr

Named in honor of Martha C. Hayden, the paleontologist assistant who helped discover the Hayden-Corbett site in the Cedar Mountain Formation of Utah where the specimen was found, combined with Latin 'raptor' meaning 'thief'.

125.8–121.4 million years ago Barremian, Early Cretaceous
Early Cretaceous stages

Martharaptor is a genus of therizinosaur from the Early Cretaceous of the Cedar Mountain Formation in Utah. They can be distinguished from other therizinosaurs 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.

Under dispute

Martharaptor is a poorly known basal therizinosaur whose precise position is unresolved. Its describers (Senter and colleagues, 2012) recovered it near the base of Therizinosauroidea, but with weak support, and Hartman and colleagues (2019) found it to occupy several equally parsimonious positions as a therizinosaur less derived than Alxasaurus. It is therefore placed conservatively within Therizinosauria rather than at a finer node.

Diagnosis

  1. Manual unguals without proximodorsal lips, with prominent flexor tubercles and strong curvature
  2. Manual unguals with total length perpendicular to articular facet subequal to total height parallel to facet
  3. Manual ungual of digit III nearly as large as that of digit II
  4. Distal end of scapula expanded
  5. Metatarsal I proximally attenuated and distally reduced in transverse width
  6. All metatarsals distally non-ginglymoid; fourth metatarsal beveled distally

Species

Martharaptor greenriverensis Senter et al., 2012

Type species

Named for Green River, the city in Utah near which the holotype was excavated from the Cedar Mountain Formation.

Holotype
UMNH VP 21400 , Utah Museum of Natural History
Material
Fragmentary skeleton including vertebral fragments, scapula, forelimb and hindlimb bones, ischium, and well-preserved manual unguals
Horizon
upper Yellow Cat Member, Cedar Mountain Formation, Barremian, Early Cretaceous , 125.8–121.4 million years ago
Locality
Hayden-Corbett Site (Gr287v), Utah, United States

References

  1. Senter, P.; Kirkland, J. I.; DeBlieux, D. D. (2012). Martharaptor greenriverensis, a New Theropod Dinosaur from the Lower Cretaceous of Utah. PLoS ONE 7(8): e43911. Public Library of Science (PLoS). doi:10.1371/journal.pone.0043911 senter2012a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Source of the body length, mass, and hip height estimates.

    jones2026c
  3. Hartman, S.; Mortimer, M.; Wahl, W. R.; Lomax, D. R.; Lippincott, J.; Lovelace, D. M. (2019). A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight. PeerJ 7: e7247. PeerJ. doi:10.7717/peerj.7247

    Found Martharaptor in several equally parsimonious positions less derived than Alxasaurus

    hartman2019a