Open Paleo

Laosaurus

Marsh, 1878 LAY-oh-SAWR-us Nomen dubium

From Greek laas (stone or fossil) and sauros (lizard); meaning "stone or fossil lizard"

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

Laosaurus is a genus of neornithischian dinosaur. The type species, Laosaurus celer, was first described by O.C. Marsh in 1878 from remains discovered in the Upper Jurassic (Kimmeridgian) Morrison Formation of Wyoming. The validity of this genus is doubtful because it is based on fragmentary fossils. A second species also from the Morrison Formation, L. gracilis, and a species from the Upper Cretaceous Allison Formation of Alberta, Canada, L. minimus, are also considered dubious.

Under dispute

Laosaurus is a nomen dubium based on fragmentary Late Jurassic material from the Morrison Formation; its species have been variously reassigned or considered indeterminate (Galton, 1977).

Species

Laosaurus celer Marsh, 1878 Nomen dubium

Type species

From Latin 'celer' meaning 'swift' or 'fast', in reference to the inferred agility of this small ornithischian.

Holotype
YPM 1874 , Yale Peabody Museum of Natural History
Material
Fragmentary caudal material, described by Marsh (1878) as a median caudal vertebral centrum, the proximal end of an ulna, and pedal phalanges.
Horizon
Morrison Formation, Kimmeridgian–Tithonian, Late Jurassic , 154.8–143.1 million years ago
Locality
Como Bluff, Wyoming, United States

References

  1. Marsh, O. C. (1878). Notice of new dinosaurian reptiles. American Journal of Science s3-15(87): 241-244. American Journal of Science (AJS). doi:10.2475/ajs.s3-15.87.241

    Gives the provenance only as the Atlantosaurus beds of the Rocky Mountains, naming neither a state nor a locality.

    marsh1878a
  2. Galton, P. M. (1977). The ornithopod dinosaur Dryosaurus and a Laurasia–Gondwanaland connection in the Upper Jurassic. Nature 268(5617): 230-232. doi:10.1038/268230a0

    Treated Laosaurus species as reassigned or indeterminate.

    galton1977a
  3. Galton, P. M. (1983). The cranial anatomy of Dryosaurus, a hypsilophodontid dinosaur from the Upper Jurassic of North America and East Africa, with a review of hypsilophodontids from the Upper Jurassic of North America. Geologica et Palaeontologica 17: 207-243.

    Gives the holotype as YPM 1874 (fragmentary caudal material) and the type species as an indeterminate nomen dubium. Traces it to Como Bluff, the source of the locality, but not to any quarry there.

    galton1983a
  4. Barrett, P. M.; Maidment, S. C. R. (2025). A review of Nanosaurus agilis Marsh and other small-bodied Morrison Formation ornithopods. Bulletin of the Peabody Museum of Natural History 66(1): 25-50. Bulletin of the Peabody Museum of Natural History. doi:10.3374/014.066.0102

    Re-examines the holotype at first hand and gives its quarry as unknown, the Peabody Museum records having never tied it to one.

    barrett2025a