Systematics, phylogeny and palaeobiogeography of the ankylosaurid dinosaurs

<p>The Ankylosauria is a group of herbivorous, quadrupedal, armoured dinosaurs subdivided into at least two major clades, the Ankylosauridae and the Nodosauridae. The most derived members of Ankylosauridae had a unique tail club formed from modified, tightly interlocking distal caudal vertebrae and enlarged osteoderms that envelop the terminus of the tail. We review all known ankylosaurid species, as well as ankylosaurs of uncertain affinities, in order to conduct a revised phylogenetic analysis of the clade. The revised phylogenetic analysis resulted in a monophyletic Ankylosauridae consisting of <i>Ahshislepelta</i>, <i>Aletopelta</i>, <i>Gastonia</i>, <i>Gobisaurus</i>, <i>Liaoningosaurus</i>, <i>Shamosaurus</i> and a suite of derived ankylosaurids (Ankylosaurinae). There is convincing evidence for the presence of nodosaurids in Asia during the Early Cretaceous. In the mid Cretaceous, Asian nodosaurids were replaced by ankylosaurine ankylosaurids. Ankylosaurines migrated into North America from Asia between the Albian and Campanian, where they diversified into a clade of ankylosaurines, here named Ankylosaurini, characterized by arched snouts and numerous flat cranial caputegulae. There is no evidence for any ankylosaurids in Gondwana; Ankylosauridae appears to be completely restricted to Asia and North America. The genus <i>Crichtonpelta</i> gen. nov. is created, type species <i>Crichtonsaurus</i> <i>benxiensis</i> Lü <i>et al</i>.</p> <p><a href="http://zoobank.org/urn:lsid:zoobank.org:pub:EE5B88A3-3353-4FB6-B9A2-FCF0F99770EB" target="_blank">http://zoobank.org/urn:lsid:zoobank.org:pub:EE5B88A3-3353-4FB6-B9A2-FCF0F99770EB</a></p

Tooth measurements of <i>Murusraptor barrosaensis</i>.

<p>Tooth measurements of <i>Murusraptor barrosaensis</i>.</p

Canonical variate analysis of 1047 teeth in 32 categories distinguished by qualitative morphotype and chronostratigraphic unit.

<p>The black star indicates the centroid of the dataset from which the relative orientations of the biplot rays in the upper right were calculated. Canonical axes 1 and 2 indicate the first two axes of maximum discrimination in the dataset.</p

Left Articular of <i>Murusraptor barrosaensis</i>, holotype, MCF-PVPH-41.

<p>Articular in posterior (A), dorsal (B) and ventral (C) views. Abbreviations: ctaf, <i>chorda tympani</i> anterior foramen; ctpf, <i>chorda tympani</i> posterior foraman; dm, insertion area for <i>M</i>.<i>depressor mandibulae</i>; g, vascular groove; ir, interglenoid ridge; mg, medial glenoid; ret, retroarticular process; sac, surangular contact; vr, ventral ridge. Scalebar: 10 cm.</p

Measuring orbit shape, and deforming digital models in Geomagic.

<p>A) Two dimensions were measured for each orbit, the maximum rostrocaudal length, and the perpendicular height, shown here on TMP 1999.58.79, <i>Chelydra serpentina</i>. B) To retrodeform digital skull models in Geomagic, the “Deform Region” tool is selected and placed at the midline of the skull, between the orbits. C) The arrow is adjusted into the desired position, in this case, pointing dorsally. D) The tool is then expanded to encompass the entire skull.</p

<i>Euoplocephalus tutus</i> and the Diversity of Ankylosaurid Dinosaurs in the Late Cretaceous of Alberta, Canada, and Montana, USA

<div><p>Few ankylosaurs are known from more than a single specimen, but the ankylosaurid <i>Euoplocephalus tutus</i> (from the Late Cretaceous of Alberta, Canada and Montana, USA) is represented by dozens of skulls and partial skeletons, and is therefore an important taxon for understanding intraspecific variation in ankylosaurs. <i>Euoplocephalus</i> is unusual compared to other dinosaurs from the Late Cretaceous of Alberta because it is recognized from the Dinosaur Park, Horseshoe Canyon, and Two Medicine formations. A comprehensive review of material attributed to <i>Euoplocephalus</i> finds support for the resurrection of its purported synonyms <i>Anodontosaurus lambei</i> and <i>Scolosaurus cutleri</i>, and the previously resurrected <i>Dyoplosaurus acutosquameus</i>. <i>Anodontosaurus</i> is found primarily in the Horseshoe Canyon Formation of Alberta and is characterized by ornamentation posterior to the orbits and on the first cervical half ring, and wide, triangular knob osteoderms. <i>Euoplocephalus</i> is primarily found in Megaherbivore Assemblage Zone 1 in the Dinosaur Park Formation of Alberta and is characterized by the absence of ornamentation posterior to the orbits and on the first cervical half ring, and keeled medial osteoderms on the first cervical half ring. <i>Scolosaurus</i> is found primarily in the Two Medicine Formation of Montana (although the holotype is from Dinosaur Provincial Park), and is characterized by long, back-swept squamosal horns, ornamentation posterior to the orbit, and low medial osteoderms on the first cervical half ring; <i>Oohkotokia horneri</i> is morphologically indistinguishable from <i>Scolosaurus cutleri</i>. <i>Dyoplosaurus</i> was previously differentiated from <i>Euoplocephalus</i> sensu lato by the morphology of the pelvis and pes, and these features also differentiate <i>Dyoplosaurus</i> from <i>Anodontosaurus</i> and <i>Scolosaurus</i>; a narrow tail club knob is probably also characteristic for <i>Dyoplosaurus</i>.</p></div

Right lacrimal and postorbital of <i>Murusraptor barrosaensis</i>, holotype, MCF-PVPH-41.

<p>Lacrimal in lateral (A) and medial (B) views. Postorbital in lateral (C) and medial (D) views. Abbreviations: ap, anterodorsal process; fp, frontal process; gr, groove from pneumatopores to antorbital fenestra; js, jugal suture; ld, lacrimal duct; lns, nasal suture limit; lr; lacrimal recess; lsc, laterosphenoid contact; ms, maxillary suture; msv, posterior limit of ventral contact with posterodorsal process of maxilla; ns, nasal suture; pdp, posterodorsal process; pn, pneumatopores; prf, prefrontal contact; pro, preorbital process; sp, squamosal process; ss, squamosal suture; sur, anterior tip of surangular; vl, ventral limit of prefrontal in lateral view; vp, ventral process. Scale bar: 10 cm.</p

External and internal structure of ankylosaur (Dinosauria, Ornithischia) osteoderms and their systematic relevance

<div><p>ABSTRACT</p><p>Ankylosaurian systematics can be assessed using morphological, textural, and histological characters of osteoderms. Archosaur osteoderms have cortices surrounding cancellous cores. Ankylosaurs are united by an external cortex distinguishable from the core and by the presence of mineralized structural fibers. Nodosaurid osteoderms lack a well-developed basal cortex and have dense external cortical fibers. Ankylosaurid osteoderms are thinner than those of other ankylosaurs. Polacanthine osteoderms have a cancellous core, but share this feature with other derived and primitive taxa. Cortical thickness overlaps among groups, so a thick cortex is not diagnostic for polacanthines. Specialized elements diverge histologically from the primitive condition to suit their specific functions. Some shapes and external textures are diagnostic for specific taxa, such as <i>Ankylosaurus</i> and <i>Glyptodontopelta</i>. Parsimony analyses suggest osteodermal support for a monophyletic Polacanthinae (excluding <i>Mymoorapelta</i>) and Shamosaurinae.</p><p>SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at <a href="http://www.tandfonline.com/UJVP" target="_blank">www.tandfonline.com/UJVP</a></p></div

Hit ratios for each pairwise discriminant function analysis (DFA) of theropod tooth categories showing the percentage of correctly identified elements.

<p>Bolded numbers indicate a non-significant differences in MANOVA; * indicates analyses with only three variables. [full page width].</p

Manual ungual of <i>Murusraptor barrosaensis</i>, Holotype, MCF-PVPH-411 side views.

<p>Abbreviations: at, anterior tip; vg, vascular groove. Scale bar: 1 cm.</p