The holotype and only known specimen of Polyodontosaurus was collected in 1928 by Charles Mortram Sternberg, and includes only a left dentary, lacking any teeth.

Sternberg compared this dentary to one referred to Troodon by Russel in 1948, and decided that they belonged to the same family, and potentially the same genus.

It was found about 37 m (121 ft) below the highest layer of the formation, and comes from the MAZ (Megaherbivore assemblage zone)-2 portion of the fauna, which existed after MAZ-1.

Van der Reest & Currie in 2017 determined that due to the lack of sufficient material in the holotype, and that the dentaries of troodontids to not bear unique, autapomorphic features, Polyodontosaurus was a nomen dubium, and could not be considered senior synonym of Latenivenatrix.

Sinornithoides Urbacodon Gobivenator Latenivenatrix Philovenator Linhevenator Two medicine troodontid Saurornithoides Zanabazar The single specimen of Polyodontosaurus was found in the central level of the Dinosaur Park Formation, and was a member of a diverse and well-documented fauna of prehistoric animals that included such well-known dinosaurs as the horned Centrosaurus, Styracosaurus, and Chasmosaurus, fellow duckbills Prosaurolophus, Gryposaurus, Corythosaurus, and Parasaurolophus, tyrannosaurid Gorgosaurus, and armored Edmontonia and Euoplocephalus.

[3][5] The Dinosaur Park Formation is interpreted as a low-relief setting of rivers and floodplains that became more swampy and influenced by marine conditions over time as the Western Interior Seaway transgressed westward.