[D] Euoplocephalus tutus [Su] [sG] [T]
Cretaceous Late, Campanian Maastrichtian
Ornithischia Thyreophora Eurypoda Ankylosauria Ankylosauridae
Judith River Formation (Wedge), Two Medicine Formation, Montana, US; Judith River Group (Wedge), Horseshoe Canyon Formation, Oldman Formation, Alberta, Canada
Genus - Typespecies - Skull
Euoplocephalus tutus (Lambe, 1902) = Stereocephalus tutus (Lambe, 1902) >> Palaeoscincus asper (Lambe, 1902) Dyoplosaurus acutosquameus (Parks, 1924) Scolosaurus cutleri (Nopcsa, 1928) Anodontosaurus lambei (Sternberg, 1929)
More than 40 specimens, including 15 complete or partial skulls, isolated teeth, and 1 nearly complete skeleton with in situ armor.
Euoplocephalus tutus is a medium- to large-sized ankylosaurid (length 6-7 m; skull length to 460 mm; width to 475 mm) that is represented by more skulls tan any other ankylosaur.
Diagnosis of genus (as for the type species)
Cranial elements only: Medium to large-sized ankylosaurids having unique pattern of cranial sculpturing across preorbital area; teeth small, flutting not corresponding to position of denticles along apical carina; no cingulum; modified palpebral located whitin orbital cavity; nasal vestibule shallow; similar to Ankylosaurus magniventris in having small teeth; distinct pattern of three or more flat polygons forming cranial sculpturing across dorsal surface of preorbital area; and caudal margin of prterygoid process of quadrate differing from Ankylosaurus in premaxilla being virtyally devoid of cranial ornamentation; intranarial cranial sculpturing forming more than one polygon in transverse plane; external naris proper vissible in rostral view; and quadrate-paroccipital process contact not fused; differing from other ankylosaurines (except Tsagantegia longicranialis) in having certical process of premaxilla forming intranarial septum; differing from all other ankylosaurines in that maxillary tooth rows converge medially, diverge rostrally and caudally (Vickaryous and Russell, 2003)