Open Paleo

Dyslocosaurus

McIntosh et al., 1992 dis-LOK-o-SAWR-us

From Greek dys-, 'hard/difficult', + Greek lokos (topos), 'place', + Greek sauros, 'lizard'; means 'hard-to-place lizard', reflecting difficulty classifying it taxonomically

154.8–143.1 million years ago Kimmeridgian–Tithonian, Late Jurassic
Late Jurassic stages

Dyslocosaurus is an extinct genus of diplodocoid sauropod dinosaur from the Late Jurassic Morrison Formation of Wyoming, United States. The type and only species, Dyslocosaurus polyonychius, was described by McIntosh, Coombs, and Russell in 1992 from fragmentary remains including limb bones and a partial manus.

Under dispute

Dyslocosaurus is known only from fragmentary appendicular material, originally described as a diplodocid (McIntosh and colleagues, 1992), and the association of that material has been questioned. Wilson and Sereno (1998) argued that two pedal phalanges and a small ungual are non-sauropod bones that do not belong with the specimen, while Tschopp and colleagues (2015) separately judged one pes phalanx to have been collected apart from the rest and excluded it. Both nonetheless retained the remainder as a valid taxon; Tschopp and colleagues (2015) found it diagnostic — uniting apatosaurine, diplodocine, and dicraeosaurid traits — and recovered it as the most basal dicraeosaurid.

Diagnosis

  1. Proximodistal length of astragalus equal to about 50% of transverse breadth, a higher percentage than in other diplodocids.
  2. Metatarsals with greater shaft circumference relative to length than in other diplodocids.

Species

Dyslocosaurus polyonychius McIntosh et al., 1992

Type species

From Ancient Greek 'polys' meaning 'many' and 'onyx' meaning 'claw', referring to the interpretation that this dinosaur had four or possibly five claws on the foot, more than other diplodocids.

Holotype
AC 663 , Beneski Museum of Natural History, Amherst College
Material
Distal ends of left(?) ulna and radius, partial head of left femur, proximal end of left tibia, distal end of right tibia, left astragalus, left Mt I-IV (proximal half of Mt IV only), phalanges I-1, III-1, IV-1, unguals of digits I-IV, possible ungual of digit V.
Horizon
Morrison Formation, Kimmeridgian–Tithonian, Late Jurassic , 154.8–143.1 million years ago
Locality
vicinity of Lance Creek, Wyoming, United States McIntosh and colleagues (1992) favor the Morrison Formation for the holotype, but Loomis recorded no horizon and the Lance Formation remains a candidate, its type area being the same ground. Which unit the specimen came from is unsettled.

References

  1. McIntosh, J. S.; Coombs, W. P.; Russell, D. A. (1992). A new diplodocid sauropod (Dinosauria) from wyoming, U.S.A. Journal of Vertebrate Paleontology 12(2): 158-167. Informa UK Limited. doi:10.1080/02724634.1992.10011446 mcintosh1992a
  2. Paul, G. S. (2024). The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton University Press.

    Source of the body length and mass estimates.

    paul2024a
  3. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Sauropods. Princeton University Press.

    Source of the appearance features.

    jones2026b
  4. Tschopp, E.; Mateus, O.; Benson, R. B. J. (2015). A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda). PeerJ 3: e857. PeerJ. doi:10.7717/peerj.857

    Found the holotype diagnostic and Dyslocosaurus a valid taxon, recovering it as the most basal dicraeosaurid.

    tschopp2015a
  5. Wilson, J. A.; Sereno, P. C. (1998). Early evolution and higher-level phylogeny of sauropod dinosaurs. Memoir (Society of Vertebrate Paleontology) 5: 1-68. doi:10.2307/3889325

    Argued that two pedal phalanges and a small ungual of the Dyslocosaurus holotype are non-sauropod bones and should not be associated with it, while accepting the remainder.

    wilson1998a