vertebrae were dorsoventrally tall dorsal vertebrae, based on a few of the more complete vertebrae appearing to have laterally compressed neural canals. All other vertebrae lack open sutural facets for the neural arches. Osteoderms Numerous osteoderms and associated osteoderm fragments were associated with the holotype specimen. Most osteoderms pertain to the thoracic region while others might pertain to the pelvic region and forelimbs. All osteoderms are either keeled or circular with an off-center apex. The distal portion of the right scapula preserves an in situ osteoderm and numerous ossicles. The osteoderm and ossicles of the right scapula and another series of osteoderms preserved in situ display a rosette arrangement of small ossicles surrounding the osteoderms. The largest osteoderm pertains to the thoracic region behind the cervical region based on the similar morphology to the median thoracic osteoderms of the holotype specimen of Scolosaurus. The osteoderm has a length of 15 cm, a width of 12 cm and a height of 10 cm. The smallest ossicle has a diameter of 1 cm. The surface texture of the osteoderms are smooth to uniformly pitted with a sparse patterns of grooves as in Euoplocephalus. One osteoderm has a histological condition typical of that of ankylosaurids. Classification Burns & Sullivan (2011) originally placed Ahshislepelta as an ankylosaurid within the clade Ankylosaurinae, although this was not based on the result of a phylogenetic analysis. Likewise, Arbour & Currie (2015) placed Ahshislepelta as sister taxon to Gastonia at the base of Ankylosauridae, and Wiersma and Irmis (2018) placed it in a polytomy consisting of Euoplocephalus, Oohkotokia, Scolosaurus, Ziapelta, Anodontosaurus, Ankylosaurus and Dyoplosaurus. On the other hand, several other studies have favored a nodosaurid position. Arbour et al. (2016) recovered it in a polytomy with Niobrarasaurus and a juvenile nodosaurid from the Paw Paw Formation, while Zheng et al. (2018) positioned Ahshislepelta in a polytomy containing Tatankacephalus, Silvisaurus, Niobrarasurus, Nodosaurus and more deeply nested taxa. Rivera-Sylva et al. (2018) placed it as sister taxon to Niobrarasurus. A phylogenetic analysis conducted by Rivera-Sylva et al. (2018) is reproduced below, favoringa nodosaurid position. Clade names have been added following Madzia et al. (2021). In contrast, an earlier analysis by Arbour & Currie (2015) favors an ankylosaurid position. Their results are reproduced below. Paleoenvironment Ahshislepelta is known from the Hunter Wash Member of the Kirtland Formation which has been dated to the upper Campanian stage, 74.5 Ma. The Kirtland Formation