''Amtosaurus'' (; " Amtgai lizard") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of ornithischian

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

based on a fragmentary skull collected from the Upper

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

Bayan Shireh Formation The Bayan Shireh Formation (also known as Baynshiree/Baynshire, Baynshirenskaya Svita or Baysheen Shireh) is a geological formation in Mongolia, that dates to the Cretaceous period. It was first described and established by Vasiliev et al. 1959. ...

( Cenomanian to

Santonian The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya (million years ago) and 83.6 ± 0.7 mya. ...

) of

Mongolia Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million, ...

and originally believed to represent an

ankylosaurid Ankylosauridae () is a family of armored dinosaurs within Ankylosauria, and is the sister group to Nodosauridae. The oldest known Ankylosaurids date to around 122 million years ago and went extinct 66 million years ago during the Cretaceous–Pal ...

.Kurzanov, S. M., & Tumanova, T. A. 1978. n the structure on the endocranium in some ankylosaurs from Mongolia Paleontol. Zh. 1978:90-96. Hadrosaurid affinities have also been suggested. However, per Parish and Barrett, this specimen is too fragmentary to be reliably classified beyond an indeterminate ornithischian. A second species assigned to the genus, ''A. archibaldi'', has become the basis of a valid ankylosaurid taxon, ''

Bissektipelta ''Bissektipelta'' (meaning "Bissekty Formation, Bissekty shield") is a genus of ankylosaurine Thyreophora, thyreophoran dinosaurs that lived in Asia during the Late Cretaceous in what is now the Bissekty Formation of Uzbekistan. ''Bissektipelta'' ...

''.

References

Ornithischian genera Late Cretaceous dinosaurs of Asia Cenomanian life Santonian life Fossils of Mongolia Fossil taxa described in 1978 Nomina dubia {{ornithischian-stub