A new southern Laramidian ankylosaurid, Akainacephalus johnsoni gen. et sp. nov., from the upper Campanian Kaiparowits Formation of southern Utah, USA

A partial ankylosaurid skeleton from the upper Campanian Kaiparowits Formation of southern Utah is recognized as a new taxon, Akainacephalus johnsoni, gen. et sp. nov. The new taxon documents the first record of an associated ankylosaurid skull and postcranial skeleton from the Kaiparowits Formation. Preserved material includes a complete skull, much of the vertebral column, including a complete tail club, a nearly complete synsacrum, several fore- and hind limb elements, and a suite of postcranial osteoderms, making Akainacephalus johnsoni the most complete ankylosaurid from the Late Cretaceous of southern Laramidia. Arrangement and morphology of cranial ornamentation in Akainacephalus johnsoni is strikingly similar to Nodocephalosaurus kirtlandensis and some Asian ankylosaurids (e.g., Saichania chulsanensis, Pinacosaurus grangeri, and Minotaurasaurus ramachandrani); the cranium is densely ornamented with symmetrically arranged and distinctly raised ossified caputegulae which are predominantly distributed across the dorsal and dorsolateral regions of the nasals, frontals, and orbitals. Cranial caputegulae display smooth surface textures with minor pitting and possess a distinct conical to pyramidal morphology which terminates in a sharp apex. Character analysis suggests a close phylogenetic relationship with N. kirtlandensis, M. ramachandrani, Tarchia teresae, and S. chulsanensis, rather than with Late Cretaceous northern Laramidian ankylosaurids (e.g., Euoplocephalus tutus, Anodontosaurus lambei, and Ankylosaurus magniventris). These new data are consistent with evidence for distinct northern and southern biogeographic provinces in Laramidia during the late Campanian. The addition of this new ankylosaurid taxon from southern Utah enhances our understanding of ankylosaurid diversity and evolutionary relationships. Potential implications for the geographical distribution of Late Cretaceous ankylosaurid dinosaurs throughout the Western Interior suggest multiple time-transgressive biogeographic dispersal events from Asia into Laramidia

The basal nodosaurid ankylosaur Europelta carbonensis n. gen., n. sp. from the Lower Cretaceous (lower Albian) Escucha Formation of northeastern Spain.

Nodosaurids are poorly known from the Lower Cretaceous of Europe. Two associated ankylosaur skeletons excavated from the lower Albian carbonaceous member of the Escucha Formation near Ariño in northeastern Teruel, Spain reveal nearly all the diagnostic recognized character that define nodosaurid ankylosaurs. These new specimens comprise a new genus and species of nodosaurid ankylosaur and represent the single most complete taxon of ankylosaur from the Cretaceous of Europe. These two specimens were examined and compared to all other known ankylosaurs. Comparisons of these specimens document that Europelta carbonensis n. gen., n. sp. is a nodosaur and is the sister taxon to the Late Cretaceous nodosaurids Anoplosaurus, Hungarosaurus, and Struthiosaurus, defining a monophyletic clade of European nodosaurids- the Struthiosaurinae

Dorsal vertebrae of <i>Europelta carbonensis</i> n. gen., n. sp. AR-1/31.

<p>Anterior dorsal vertebra with rib fragment AR-1-3662/31 in: (A) posterior view, (B) cranial view. Anterior dorsal vertebra AR-1-3672/31 in: (C) cranial view, (D) posterior view, (E) dorsal view, and (F) ventral view. Medial cervical vertebra AR-1-3633/31 in: (G) cranial view, (H) posterior view, (I) right lateral view, (J) left lateral view, (K) dorsal view, and (L) ventral view. Medial dorsal vertebra AR-1-3674/31 in: (M) cranial view, (N) posterior view, and (O) left lateral view. Medial dorsal vertebra AR-1-3489/31 in: (P) cranial view, (Q) posterior view, (R) right lateral view, (S) left lateral view, (T) dorsal view, and (U) ventral view. Medial dorsal vertebra AR-1-3675/31 in: (V) cranial view, (W) right lateral view, (X) left lateral view, (Y) dorsal view, and (Z) ventral view. Mid-dorsal vertebra AR-1-3704/31 in: (AA) cranial view, (BB) posterior view, (CC) left lateral view, (DD) ventral view, and (EE) dorsal view. Mid-dorsal vertebra AR-1-3673/31 in: (FF) cranial view, (GG) posterior view, (HH) right lateral view, (II) dorsal view, and (JJ) ventral view.</p

Proximal posterior vertebrae of holotype of <i>Europelta carbonensis</i> n. gen., n. sp. AR-1/10.

<p>Proximal posterior vertebra (2 or 3) AR-1-635/10 in: (A) anterior view, (B) posterior view, (C) right lateral view, (D) left lateral view, (E) dorsal view, and (F) ventral view. Proximal chevron AR-1-4451/10 in: (G) anterior view, (H) lateral view, and (I) posterior view. Proximal posterior vertebra (4 or 5) AR1-1-562/10 in: (J) anterior view, (K) posterior view, (L) right lateral view, (M) left lateral view, (N) dorsal view, and (O) ventral view. Proximal chevron AR-1-569/10 in: (P) anterior view, (Q) lateral view, and (R) posterior view. Proximal chevron AR-1-10/560 in: (S) anterior view, (T) lateral view, and (U) posterior view. Proximal posterior vertebra (5 or 6) AR-1-636/10 in: (V) anterior view, (W) posterior view, (X) right lateral view, (Y) left lateral view, (Z) dorsal view, and (AA) ventral view.</p

Distribution of polacanthids and nodosaurid ankylosaurs in Europe vs. that of North America.

<p>Dashed gray line indicates interval of ankylosaur fauna turnover.</p

Paleogeographic reconstruction of the Escucha outcrop belt during deposition of coal under freshwater conditions in the Ariño area.

<p>Modified after Querol and others <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080405#pone.0080405-Querol1" target="_blank">[44]</a> with salinity data based on ostracods from Tibert and others <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080405#pone.0080405-Tibert1" target="_blank">[58]</a>.</p

Generalized stratigraphy.

<p>(A) General Lower Cretaceous stratigraphy in the area of the Oliete sub-basin with the relative distribution of thyreophoran dinosaurs in Spain and southern England indicated. (B) General stratigraphy of the Escucha Fm. in the area around Ariño, Aragón, Spain showing approximate position of dinosaur locality AR-1. Stratigraphic nomenclature following Rodríguez-López and others <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080405#pone.0080405-RodrguezLpez2" target="_blank">[53]</a>.</p

<i>Europelta carbonensis</i> n. gen., n. sp. mandible from AR-1/31.

<p>Fused dentary and splenial AR-1-3698/31: Isolated splenial in (A) medial view. Dentary in: (B) medial view, (C) dorsal view with splenial inverted in medial view, and (D) dorso-medial view with splenial inverted in medio-ventral view, and (E) latero-ventral view with posterior splenial visible in dorsal view. Angular AR-1-2945/31 in: (F) lateral view and (G) medial view. Abbreviations: if = intermandibular foramen. s = mandibular symphysis, sc = splenial contact.</p

Dorsal vertebrae of <i>Europelta carbonensis</i> n. gen., n. sp. AR-1/31.

<p>Anterior dorsal vertebra with rib fragment AR-1-3662/31 in: (A) posterior view, (B) cranial view. Anterior dorsal vertebra AR-1-3672/31 in: (C) cranial view, (D) posterior view, (E) dorsal view, and (F) ventral view. Medial cervical vertebra AR-1-3633/31 in: (G) cranial view, (H) posterior view, (I) right lateral view, (J) left lateral view, (K) dorsal view, and (L) ventral view. Medial dorsal vertebra AR-1-3674/31 in: (M) cranial view, (N) posterior view, and (O) left lateral view. Medial dorsal vertebra AR-1-3489/31 in: (P) cranial view, (Q) posterior view, (R) right lateral view, (S) left lateral view, (T) dorsal view, and (U) ventral view. Medial dorsal vertebra AR-1-3675/31 in: (V) cranial view, (W) right lateral view, (X) left lateral view, (Y) dorsal view, and (Z) ventral view. Mid-dorsal vertebra AR-1-3704/31 in: (AA) cranial view, (BB) posterior view, (CC) left lateral view, (DD) ventral view, and (EE) dorsal view. Mid-dorsal vertebra AR-1-3673/31 in: (FF) cranial view, (GG) posterior view, (HH) right lateral view, (II) dorsal view, and (JJ) ventral view.</p

External osteoderms of <i>Europelta carbonensis</i> n. gen., n. sp. AR-1/31.

<p>Type C armor AR-1-3449/31 in: (A) external view and (B) basal view. Type C armor AR-1-3608/31 in: (C) external view and (D) basal view. Type B-C armor AR-1-3491/31 in: (E) external view and (F) basal view. Type B-C armor AR-1-3492/31 in: (G) external view and (H) basal view. Type D armor AR-1-3590/31 in: (I) external view and (J) basal view. Type D armor AR-1-3587/31 in: (K) external view and (L) basal view. Type D armor AR-1-3438/31 in: (M) external view and (N) basal view. Type D armor AR-1-3390/31 in: (O) external view and (P) basal view. Type D armor AR-1-3030/31 in: (Q) external view and (R) basal view. Type D armor AR-1-3209/31 in: (S) external view and (T) basal view. Type D-F armor AR-1-3572/31 in: (U) external view and (V) basal view. Type F armor AR-1-3681/31 in: (W) external view and (X) basal view. Type F armor AR-1-3340/31 in: (Y) external view and (Z) basal view. Type F armor AR-1-3448/31 in: (AA) external view and (BB) basal view. Type F armor AR-1-3228/31 in: (CC) external view and (DD) basal view. Type F armor AR-1-3447/31 in: (EE) external view and (FF) basal view. Type F armor AR-1-3226/31 in: (GG) external view and (HH) basal view. Type F armor AR-1-3080/31 in: (II) external view and (JJ) basal view. Type F armor AR-1-3576/31 in: (KK) external view and (LL) basal view. Type F armor AR-1-3638/31 in: (MM) external view and (NN) basal view. Type F armor AR-1-3658/31 in: (OO) external view and (PP) basal view. Type F armor AR-1-3683/31 in: (QQ) external view and (RR) basal view. Type F armor AR-1-3573/31 in: (SS) external view (TT) and basal view. Type F armor AR-1-3574/31 in: (UU) external view and (VV) basal view. Type F armor AR-1-3597/31 in: (WW) external view and (XX) basal view. Type F armor AR-1-3610/31 in: (YY) external view and (ZZ) basal view. Type F armor AR-1-3682/31 in: (AAA) external view and (BBB) basal view. Type F armor AR-1-3339/31 in: (CCC) external view and (DDD) basal view. Type F armor AR-1-3180/31 in: (EEE) external view and (FFF) basal view. Type F armor AR-1-3687/31 in: (GGG) external view and (HHH) basal view. Type F armor AR-1-3609/31 in: (III) external view and (JJJ) basal view. Type F armor AR-1-3680/31 in: (KKK) external view and (LLL) basal view. Type F armor AR-1-3684/31 in: (MMM) external view and (NNN) basal view. Small type D armor AR-1-3575/31 in: (OOO) external view and (PPP) basal view. Type F armor AR-1-3074/31 in: (QQQ) external view and (RRR) basal view. Type F armor AR-1-3708/31 in: (SSS) external view and (TTT) basal view. Type F armor AR-1-3720/31 in: (UUU) external view and (VVV) basal view.</p