Ankylosauridae

Reconstruction of Bissektipelta archibaldi an ankylosaurid dinosaur from the Late Cretaceous of Uzbekistan

Huaxiazhoulong is a fairly large ankylosaurid dinosaur, at around 6 m in length. It was a robust quadruped with a beak and teeth adapted for processing its herbivorous diet. Huaxiazhoulong had an armor of osteoderms, and the characteristic ankylosaurid tail club which was likely used in defense against predators, as well as intraspecific combat.

Skeletal reconstruction of Ahshislepelta minor, a small ankylosaur from the Late Cretaceous Kirtland Formation of New Mexico. While originally recovered as an ankylosaurid related to Gastonia, later analyses favored a nodosaurid position which this is based on. Based on the holotype SMP VP-1930, consisting of fragmentary shoulder, forelimb, and vertebral elements as well as several osteoderms. Unknown material filled in using Niobrarasaurus, Pawpawsaurus, Silvisaurus, Sauropelta, and Borealopelta. Total length is approximately 4.9 m through the centra. Notes: Osteoderm placement somewhat speculative, not all osteoderms and vertebral fragments are figured. References: Burns & Sullivan, 2011.

Phylogenetic position of Akainacephalus johnsoni in (A), a strict consensus of 21 equally most parsimonious trees, including the wildcard taxon Ahshislepelta minor, placing A. johnsoni within a large polytomy, consisting of crown group taxa that include Asian and all Laramidian ankylosaurids; and (B), the resulting strict consensus of six equally most phylogenetic trees, from which the wildcard taxon Ahshislepelta minor has been pruned. The crown group taxa are slightly better resolved in the pruned analysis, in which Akainacephalus johnsoni forms a clade with its sister taxon Nodocephalosaurus kirtlandensis, nested within the clade that also includes the Asian taxa Minotaurasaurus ramachandrani, Tarchia kilanae, and Shanxia tianzhenensis, suggesting a close taxonomic relationship with Nodocephalosaurus kirtlandensis and Asian taxa.

Phylogenetic position of Akainacephalus johnsoni in (A), a strict consensus of 21 equally most parsimonious trees, including the wildcard taxon Ahshislepelta minor, placing A. johnsoni within a large polytomy, consisting of crown group taxa that include Asian and all Laramidian ankylosaurids; and (B), the resulting strict consensus of six equally most phylogenetic trees, from which the wildcard taxon Ahshislepelta minor has been pruned. The crown group taxa are slightly better resolved in the pruned analysis, in which Akainacephalus johnsoni forms a clade with its sister taxon Nodocephalosaurus kirtlandensis, nested within the clade that also includes the Asian taxa Minotaurasaurus ramachandrani, Tarchia kilanae, and Shanxia tianzhenensis, suggesting a close taxonomic relationship with Nodocephalosaurus kirtlandensis and Asian taxa.

Phylogenetic position of Akainacephalus johnsoni in (A), a strict consensus of 21 equally most parsimonious trees, including the wildcard taxon Ahshislepelta minor, placing A. johnsoni within a large polytomy, consisting of crown group taxa that include Asian and all Laramidian ankylosaurids; and (B), the resulting strict consensus of six equally most phylogenetic trees, from which the wildcard taxon Ahshislepelta minor has been pruned. The crown group taxa are slightly better resolved in the pruned analysis, in which Akainacephalus johnsoni forms a clade with its sister taxon Nodocephalosaurus kirtlandensis, nested within the clade that also includes the Asian taxa Minotaurasaurus ramachandrani, Tarchia kilanae, and Shanxia tianzhenensis, suggesting a close taxonomic relationship with Nodocephalosaurus kirtlandensis and Asian taxa.

Simple drawing of Ankylosaurus magniventris, a North American Cretaceous ankylosaurid. Based on skeletal reconstruction in Paul 2010.

An Ankylosaurus head (cast of specimen AMNH 5214), on display at the Museum of the Rockies in Bozeman, Montana. This is from a specimen collected in Custer County, Montana. The Ankylosauria were armored dinosaurs that lived from 122 million years ago to 66 million years ago in western North America, Europe, and East Asia. There were two subgroups: The Nodosauridae and Ankylosauridae. The Ankylosauridae contained six species, and a single subfamily -- the Ankylosaurinae. There 18 genus within the subfamily, of which Ankylosaurus is the best known. Ankylosaurus as the last of these, and lived 65.5 to 66.5 million years ago. Ankylosaurus was about 20.5 feet long, 5 feet wide, and 5.5 feet tall at the hip. It walked on all fours, with the rear legs longer than the front ones. They ripped vegetation, and swallowed it whole. Their defining feature was their armor. They body was covered in thick, heavy bony plates, and most of the plates were fused together to make them even stronger. Embedded in the skin were more knobs of bone, and the outer skin above these knobs covered in keratin (the same stuff fingernails are made of). Ankylosaurus had a tail club, which consisted of several large osteoderms fused to the last few tail vertebrae. Ankylosaurus was discovered in 1908.