Amtosaurus magnus

Amtosaurus () is a genus of ornithischian dinosaur based on a fragmentary skull collected from the Late Cretaceous (Cenomanian to Turonian) Bayanshiree Formation of Mongolia and originally believed to represent an ankylosaurid. Hadrosaurid affinities have also been suggested. However, according to 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.

==Discovery and species== The Soviet-Mongolian Paleontological Expedition of 1975 discovered two partial ankylosaur in the Baynshire Formation of the Late Cretaceous of Mongolia, one from the locality Bayshin Tsav and the other from Amtgai. In 1978, Soviet paleontologists Sergei Kurzanov and Tatiana Tumanova described these braincases, which represented the first description of the region of the skull in ankylosaurs since the description of Silvisaurus in 1960. While the braincase from Bayshin Tsav, PIN 3780/1, was referred to the existing taxon Talarurus plicatospineus, the braincase from Amtgai (PIN 3780/2) was named as the new taxon Amtosaurus magnus, with the genus name referencing the type locality and the species name derived from the Latin word magnus for "large". While the location, age, and general anatomy of Amtosaurus was most similar to Talarurus, it could be separated from it and other ankylosaurs by details of the .