Saturday, September 27, 2014

[Paleontology • 2014] Ziapelta sanjuanensis • A New Ankylosaurid Dinosaur from the Upper Cretaceous (Kirtlandian) of New Mexico with Implications for Ankylosaurid Diversity in the Upper Cretaceous of Western North America


Ziapelta sanjuanensis
Arbour,  Burns, Sullivan, Lucas, Cantrell, Fry & Suazo, 2014

Abstract
A new ankylosaurid (Ankylosauria: Dinosauria), Ziapelta sanjuanensis, gen. et sp. nov., is based on a complete skull, an incomplete first cervical half ring, a possible fragment of the second cervical half ring, and additional fragmentary osteoderms. The holotype specimen is from the Upper Cretaceous (Upper Campanian, Kirtlandian Land-Vertebrate Age) Kirtland Formation (De-na-zin Member) at Hunter Wash, San Juan Basin, in northwestern New Mexico, USA. Diagnostic characters of Ziapelta include: a large, prominent triangular median nasal caputegulum; a mixture of flat and bulbous frontonasal caputegulae; ventrolaterally oriented squamosal horns with a sharp, prominent dorsal keel; and the ventral surface of basicranium with three prominent anteroposteriorly oriented fossae. A phylogenetic analysis suggests that Ziapelta is not closely related to the other ankylosaurid from the De-na-zin Member, Nodocephalosaurus, but allies it to the northern North American ankylosaurids Ankylosaurus, Anodontosaurus, Euoplocephalus, Dyoplosaurus, and Scolosaurus.


Figure 2. Ziapelta sanjuanensis, gen. et sp. nov., (holotype NMMNH P-64484), complete skull.
A, dorsal view; B, ventral view; C, anterior view; D, occipital view; and E, left lateral view.
Abbreviations: asca, anterior supraorbital caputegulum; bas, basioccipital; ch, choana; fm, foramen magnum; j, jugal; laca, lacrimal caputegulum; loca, loreal caputegulum; ltf, laterotemporal fenestra; mnca, median nasal caputegulum; nar, external naris; oc, occipital condyle; orb, orbit; pal, palatine; par, parietal; parocc, paroccipital process; pmx, premaxilla; psca, posterior supraorbital caputegulum; pt, pterygoid; q, quadrate; qj, quadratojugal; qjh, quadratojugal horn; snca, supranarial caputegulum; socc, supraoccipital; sqh, squamosal horn; tr, tooth row; v, vomer. doi: dx.doi.org/10.1371/journal.pone.0108804.g002

Speculative life restoration of Ziapelta sanjuanensis
Illustration: Sydney Mohr

Systematic Paleontology

Dinosauria Owen, 1842 
Ornithischia Seeley, 1888  

Thyreophora Nopcsa, 1915  

Ankylosauria Osborn, 1923 
Ankylosauridae Brown, 1908 

Ziapelta gen. nov. 

Type and only known species. Ziapelta sanjuanensis sp. nov. 

Etymology. Zia, after the Zia sun symbol, a stylized sun with four groups of rays, having religious significance to the Zia people of New Mexico, and the iconic symbol on the state flag of New Mexico; pelta (Latin), a small shield, in reference to the osteoderms found on all ankylosaurids; sanjuanensis, In reference to San Juan County and the structural basin from which the specimen was derived.


Figure 4. Cervical half rings of Ziapelta sanjuanensis.
A) Incomplete first and second cervical half rings of NMMNH P-64484 (holotype), with isolated post-cervical osteoderm, as preserved in situ. First cervical half ring is in posterior view. B) Dorsal view of left medial osteoderm showing smaller interstitial osteoderms, anterior is up. C) Isolated first cervical half ring NMMNH P-66930 (referred specimen) in anterior view.
Abbreviations: b, band; g, groove; i, interstitial osteoderm; ld, left distal osteoderm; ll, left lateral osteoderm; lm, left medial osteoderm; mid, midline of the cervical half ring; os, osteoderm; pc os, post-cervical osteoderm; rl, right lateral osteoderm; rm, right medial osteoderm. doi: dx.doi.org/10.1371/journal.pone.0108804.g004


Victoria M. Arbour,  Michael E. Burns, Robert M. Sullivan, Spencer G. Lucas, Amanda K. Cantrell, Joshua Fry and Thomas L. Suazo. 2014. A New Ankylosaurid Dinosaur from the Upper Cretaceous (Kirtlandian) of New Mexico with Implications for Ankylosaurid Diversity in the Upper Cretaceous of Western North America. PLoS ONE. 9, 9: e108804. doi: dx.doi.org/10.1371/journal.pone.0108804


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