Open Paleo

Limusaurus

Xu et al., 2009 LIM-oo-SOR-us

From Latin 'limus' meaning 'mud' or 'mire' and Greek 'sauros' meaning 'lizard', hence 'mire lizard', referring to the specimens appearing to have died after being mired in mud.

165.3–154.8 million years ago Callovian–Oxfordian, Middle Jurassic–Late Jurassic
Middle Jurassic and Late Jurassic stages

Limusaurus is a genus of theropod dinosaur that lived in what is now China during the Late Jurassic, around 161 to 157 million years ago. The type and only species Limusaurus inextricabilis was described in 2009 from specimens found in the Upper Shishugou Formation in the Junggar Basin of China. The genus name consists of the Latin words for "mud" and "lizard", and the species name means "impossible to extricate", both referring to these specimens possibly dying after being mired. Limusaurus was a small, slender animal, about 1.7 m (5 ft 7 in) in length and 15 kg (33 lb) in weight, which had a long neck and legs but very small forelimbs (with reduced first and fourth fingers). It underwent a drastic morphological transformation as it aged: while juveniles were toothed, these teeth were completely lost and replaced by a beak with age. Several of these features were convergently similar to the later ornithomimid theropods as well as the earlier non-dinosaurian shuvosaurids.

Diagnosis

  1. Short skull, half as long as the femur
  2. Skull and mandible toothless
  3. Nasal with lateral shelf
  4. Short and wide nasal less than one-third of skull roof length
  5. Metacarpal I highly reduced and carrying no phalanges
  6. Metacarpal II much more robust than other metacarpals
  7. Large external mandibular fenestra about 40% of mandibular length
  8. Metatarsus forming strong transverse arch

Species

Limusaurus inextricabilis Xu et al., 2009

Type species

From Latin 'inextricabilis' meaning 'impossible to extricate', referring to the specimens' likely fate of dying after becoming mired in mud pits created by the footprints of giant sauropods.

Holotype
IVPP V15923 , Institute of Vertebrate Paleontology and Paleoanthropology
Material
Articulated nearly complete skeleton.
Horizon
Shishugou Formation, Callovian–Oxfordian, Middle Jurassic–Late Jurassic , 165.3–154.8 million years ago
Locality
TBB2005, Wucaiwan, Xinjiang, China Xu and colleagues (2009) give the horizon as the "Oxfordian upper part of the Shishugou Formation" without tying it to the dated tuffs, which on the ICS chart v2024/12 straddle the base of the Oxfordian.

References

  1. Xu, X.; Clark, J. M.; Mo, J.; Choiniere, J.; Forster, C. A.; Erickson, G. M.; Hone, D. W. E.; Sullivan, C.; Eberth, D. A.; Nesbitt, S.; Zhao, Q.; Hernandez, R.; Jia, C. K.; Han, F. L.; Guo, Y. (2009). A Jurassic ceratosaur from China helps clarify avian digital homologies. Nature 459(7249): 940-944. Springer Science and Business Media LLC. doi:10.1038/nature08124 xu2009a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026c
  3. Eberth, D. A.; Xu, X.; Clark, J. M. (2010). Dinosaur death pits from the Jurassic of China. PALAIOS 25(2): 112-125. Society for Sedimentary Geology. doi:10.2110/palo.2009.p09-028r

    Reports the holotype from the TBB2005 bonebed, one of three in the upper half of the formation at Wucaiwan.

    eberth2010a