Open Paleo

Avimimus

Kurzanov, 1981 AY-vim-EYE-muhs /ˌeɪvɪˈmaɪməs/

From Latin avis meaning 'bird' + Latin mimus meaning 'mimic'; overall meaning 'bird mimic', named for its bird-like characteristics.

83.6–66.0 million years ago Campanian–Maastrichtian, Late Cretaceous
Late Cretaceous stages

Avimimus is a genus of oviraptorosaurian theropod dinosaur, named for its bird-like characteristics, that lived in the late Cretaceous in what is now Mongolia, during the Maastrichtian.

Diagnosis

  1. Minimum 11 cervical vertebrae, exceeding the maximum of 10 found in ornithomimids and other theropods
  2. Hypapophyses present on the last two cervical and first three dorsal vertebrae, absent in all other theropods
  3. Frontal and parietal bones fully fused into a single fronto-parietal, unique among theropods
  4. Ischia directed anteriorly and ventrally (parallel to pubis) rather than posteriorly, rotated ~50° forward relative to the typical theropod condition
  5. Pubis excluded from the acetabular cavity, which is formed solely by the ilium and ischium — unique among all dinosaurs
  6. Additional supracondyle on the external condyle of the femur forming a dedicated articulation surface for the highly reduced fibula — first occurrence among dinosaurs

Species (2)

Avimimus portentosus Kurzanov, 1981

Type species

From Latin 'portentosus' meaning 'monstrous' or 'extraordinary', referring to the unusual bird-like characteristics of the animal.

Holotype
PIN 3907/1 , Paleontological Institute, Russian Academy of Sciences
Material
Incomplete skeleton including skull fragment, vertebrae, pectoral girdle, forelimb elements, pelvis, and hind limbs.
Horizon
Nemegt Formation, Campanian–Maastrichtian, Late Cretaceous , 83.6–66.0 million years ago
Locality
Üüden Sair, Ömnögovi, Mongolia Kurzanov (1981) dated the beds by faunal correlation, from Tarbosaurus teeth at the site, rather than from the section. The expeditions that later worked Üüden Sair place it in the Djadokhta, as Handa and colleagues (2012) and Rougier and colleagues (2016) both report, though neither treats Avimimus and none of the works cited for this taxon has revisited this holotype's horizon.

Avimimus nemegtensis Funston et al., 2018

Named for the Nemegt Formation, where the type material was recovered.

Holotype
MPC-D 102/81 , Paleontological Center, Mongolian Academy of Sciences
Material
Partial skull.
Horizon
Nemegt Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
Nemegt, Ömnögovi, Mongolia
Diagnosis
  1. Exoccipital with a single jugular opening for cranial nerves IX-XII (paired foramina in A. portentosus).
  2. Relatively smaller foramen magnum and wider pterygoids.
  3. Quadratojugal bowed laterally from the quadrate condyle, rather than projecting anteriorly.
  4. Dentary with better-developed symphyseal shelf and shallower lingual ridges.
  5. Ilium and ischium unfused, and ischiadic peduncle lacking an antitrochanter.
  6. Preacetabular blade of ilium dorsally expanded and ventrally hooked, with an extensive sigmoidal brevis shelf lacking suprabrevis ridges.

References

  1. Kurzanov, S. M. (1981). O neobuchnykh teropodakh iz verkhnego mela MNR [An unusual theropod from the Upper Cretaceous of Mongolia]. Fossil Reptiles of Mongolia. Sovmestnaya Sovetsko-Mongol'skaya Paleontologicheskaya Ekspeditsiya, Trudy [The Joint Soviet-Mongolian Paleontological Expedition, Transactions] 24: 39-50. kurzanov1981a
  2. Funston, G. F.; Mendonca, S. E.; Currie, P. J.; Barsbold, R. (2018). Oviraptorosaur anatomy, diversity and ecology in the Nemegt Basin. Palaeogeography, Palaeoclimatology, Palaeoecology 494: 101-120. doi:10.1016/j.palaeo.2017.10.023 funston2018a
  3. Handa, N.; Watabe, M.; Tsogtbaatar, K. (2012). New specimens of Protoceratops (Dinosauria: Neoceratopsia) from the Upper Cretaceous in Udyn Sayr, southern Gobi area, Mongolia. Paleontological Research 16(3): 179-198. doi:10.2517/1342-8144-16.3.179

    Assigns the Üüden Sair beds to the Djadokhta Formation and describes their lithology as eolian cross-laminated sandstone.

    handa2012a
  4. Rougier, G. W.; Sheth, A. S.; Spurlin, B. K.; Bolortsetseg, M.; Novacek, M. J. (2016). Craniodental anatomy of a new Late Cretaceous multituberculate mammal from Udan Sayr, Mongolia. Palaeontologia Polonica 67: 197-248.

    Places Üüden Sair in Ömnögovi, reports that Mongolian law restricts precise coordinates to qualified researchers, and distinguishes a lower fluvial package from the upper red beds.

    rougier2016a