sacral transverse processes on the third sacral vertebra, forming a butterfly-like arrangement of the sacral fenestrae, and in having ischia that articulate with the ilia at right angles. The holotype specimen of Dyoplosaurus preserves ossified tendons on the tail club. The tail club preserves three series of tendons on the dorsolateral sides of the handle, and four on the distal, ventral side of the tail. These tendons are more readily grouped into two sets on the dorsolateral sides. Arbour, 2009 conducted a study to determine the impact force of ankylosaurids and used ROM 784. Arbour found that Dyoplosaurus could generate an impact force of 797–1127 N and a more realistic tensions of 571 N, an impact force that isn’t enough to puncture bone. This is mainly due to the knob being smaller in comparison to that of other ankylosaurids. The small size of the tail club of suggests that ankylosaurid knobs were not primarily used as defensive weapons, as a weapon that is not functional until very late in life would probably not have a selective advantage over a weapon that is of use earlier in life. The holotype specimen preserves remnants of fossilized skin and osteoderms on the left side. These skin impressions are punctuated by a nearly unbroken mosaic of small (0.50–1.0 cm), sub-angular to subrounded osteoderms. The skin imperssions on the right side have been lost via erosion. Classification In 1971, Walter Coombs synonymized Dyoplosaurus, along with Scolosaurus and Anodontosaurus, into Euoplocephalus as one of the four mandibles assigned to Dyoplosaurus was identical to those of other Euoplocephalus specimens, but did not offer any other characteristics to support the synonymization. However, a re-description of Dyoplosaurus published in 2009 by Victoria Arbour, Michael Burns and Robin Sissons considered it as a valid taxon and proposed that the synonymy was due to the fragmentary nature of the holotype and other referred specimens of Euoplocephalus. Thompson et al., 2011 confirmed its separation and recovered it as sister taxon to Pinacosaurus mephistocephalus. A cladistic analysis conducted by Arbour and Currie, 2015 recovered Dyoplosaurus as sister taxon to a clade containing Ankylosaurus, Euoplocephalus, Anodontosaurus and Scolosaurus, while an analysis conducted by Arbour and Evans, 2017 recovered it as sister taxon to Zuul. A phylogenetic analysis conducted by Arbour & Evans, 2017 is reproduced below. The results of an earlier analysis by Arbour & Currie, 2015 is reproduced below. Paleoenvironment The holotype specimen