page_title: Scolosaurus
section_title: Classification
hierarchical_section_title: Scolosaurus / Classification
caption_attribution_description: English: Skull of specimen AMNH 5404, referred to Scolosaurus cutleri (formerly referred to Euoplocephalus tulus) from the American Museum of Natural History, New York, U.S.
context_page_description: Scolosaurus is an extinct genus of ankylosaurid dinosaurs within the subfamily Ankylosaurinae. It is known from either the lower levels of the Dinosaur Park Formation or upper levels of the Oldman Formation in the Late Cretaceous of Alberta, Canada. It contains two species, S. cutleri and S. thronus.
context_section_description: In 1928, Nopcsa assigned the specimen to the family Ankylosauridae, and drew morphological comparisons with the fossil material known from Dyoplosaurus. In 1971, Walter Coombs concluded that there was only one species of ankylosaurid during the Campanian age of the Late Cretaceous of North America. He synonymized the species Anodontosaurus lambei, Dyoplosaurus acutosquameus, and Scolosaurus cutleri with Euoplocephalus tutus but did not provide any justification for these synonymies. The synonymization of Scolosaurus cutleri and Euoplocephalus tutus was generally accepted and thus NHMUK R.5161 was assigned to E. tutus. However, a redescription of Scolosaurus published in 2013 in the Canadian Journal of Earth Sciences by Paul Penkalski and William T. Blows suggested that the genus is a valid taxon. They concluded that Scolosaurus can be distinguished from Euoplocephalus by the form of their cervical armour, the details of other armour and the structure of the forelimb. They also concluded that Scolosaurus and Dyoplosaurus are distinct, due to differences noted in the pelvis and armour. Due to its completeness, the holotype of Scolosaurus has formed the basis for most Euoplocephalus reconstructions since 1971; therefore, most images of Euoplocephalus actually depict Scolosaurus instead.
  A 2013 study found that the ankylosaurine Oohkotokia was indistinguishable from Scolosaurus, and was therefore considered a junior synonym. However, this synonymization is contentious as Oohkotokia was subsequently recognized as valid. Thus, much of the material illustrated as belonging to Scolosaurus may actually pertain to Oohkotokia.
   
   
  The following cladogram is based on a 2015 phylogenetic analysis of the Ankylosaurinae conducted by Victoria Arbour and Phillip J. Currie. The cladogram follows the biogeographical family tree provided by that study, which is a fusion of the study's 50% majority rule tree as well as the maximum agreement subtree. The study's 50% majority rule tree was a cladogram formed by a collection of clades, although it only included clades that appear in more than 50% of the family trees found during the analysis. The maximum agreement subtree is the cladogram that results from an algorithm which attempts to maximize the amount of taxa included in the result while also retaining the fundamental shape of all other trees in the sample. Some controversial taxa thus had to be omitted by the subtree in order for the resulting cladogram to fulfill the second requirement. The biogeographical tree (i.e. the following cladogram) is basically the 50% majority rule tree, except with some of the polytomies resolved according to the results of the maximum agreement subtree:
  The following cladogram is based on a 2017 phylogenetic analysis of the Ankylosaurinae conducted by Victoria Arbour and David Evans. The cladogram depicts the majority rule (average result) of 10 most parsimonious trees, which each are considered to have the fewest evolutionary steps, thus being the most accurate under the principle of Occam's razor:
caption: Referred S. cutleri skull, AMNH 5404
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