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[Ngala]

A new ankylosaurine dinosaur from the Judith River Formation of Montana, USA, based on an exceptional skeleton with soft tissue preservation 
Zuul crurivastator Arbour & Evans, 2017

*This image is copyright of its original author

Reconstruction credits: Danielle Dufault

*This image is copyright of its original author

Zuul crurivastator’s skull. Credits: Brian Boyle/Royal Ontario Museum

*This image is copyright of its original author

Figure 2.
Holotype of Zuul crurivastator, ROM 75860, skull in (a) left lateral, (b) anterior, © posterior and (d) oblique left anterodorsal views. (a′–d′) are digital models of the skull. Diagnostic characters for Z. crurivastator include (1) imbricated frontonasal caputegulae, (2) peaked, pyramidal prefrontal and middle supraorbital caputegulae and (3) prominent apicobasal furrows on the squamosal horns. Abbreviations are as follows: asca, anterior supraorbital caputegulum; fm, foramen magnum; laca, lacrimal caputegulum; loca, loreal caputegulum; mnca, median nasal caputegulum; mx, maxilla; na, external naris; nuca, nuchal caputegulum; oo, ocular osteoderm; oc, occipital condyle; pa, parietal; pmx, premaxilla; pnca, postnarial caputegulum; poc, paroccipital process; poca, postocular caputegulum; prfca, prefrontal caputegulum; psca, posterior supraorbital caputegulum; q, quadrate; qjh, quadratojugal horn; snca, supranarial caputegulum; sqh, squamosal horn.

Abstract:
"The terrestrial Judith River Formation of northern Montana was deposited over an approximately 4 Myr interval during the Campanian (Late Cretaceous). Despite having been prospected and collected continuously by palaeontologists for over a century, few relatively complete dinosaur skeletons have been recovered from this unit to date. Here we describe a new genus and species of ankylosaurine dinosaur, Zuul crurivastator, from the Coal Ridge Member of the Judith River Formation, based on an exceptionally complete and well-preserved skeleton (ROM 75860). This is the first ankylosaurin skeleton known with a complete skull and tail club, and it is the most complete ankylosaurid ever found in North America. The presence of abundant soft tissue preservation across the skeleton, including in situ osteoderms, skin impressions and dark films that probably represent preserved keratin, make this exceptional skeleton an important reference for understanding the evolution of dermal and epidermal structures in this clade. Phylogenetic analysis recovers Zuul as an ankylosaurin ankylosaurid within a clade of Dyoplosaurus and Scolosaurus, with Euoplocephalus being more distantly related within Ankylosaurini. The occurrence of Z. crurivastator from the upper Judith River Formation fills a gap in the ankylosaurine stratigraphic and geographical record in North America, and further highlights that Campanian ankylosaurines were undergoing rapid evolution and stratigraphic succession of taxa as observed for Laramidian ceratopsids, hadrosaurids, pachycephalosaurids and tyrannosaurids."

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