Ziapelta is an extinct genus of ankylosaurid. Its fossils have been found in the Hunter Wash and De-na-zin members of the Kirtland Formation of Upper Cretaceous (Campanian) New Mexico. It was named in 2014, in a research paper led by ankylosaur researcher Victoria Arbour. There is a single species in the genus, Ziapelta sanjuanensis. The genus is named 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, and pelta (Latin), a small shield, in reference to the osteoderms found on all ankylosaurids. The specific name is in reference to San Juan County and the San Juan basin, where the fossils were found. Multiple specimens have been described to date, though the fossils are mostly from the front part of the animal.
The adult length of Ziapelta is estimated at between and long, depending on whether the holotype was full-grown. It was quadrupedal, with a wide, robust body. The front part of the jaws was covered in a beak, with rows of small, leaf-shaped teeth farther behind it. It was most likely covered in armor plates, or osteoderms, and had bony half-rings covering the neck. It is thought that Ziapelta might have had a large club on the end of its tail, although this club has not been found fossilized. Bones in the skull and other parts of the body were fused, thus increasing their strength.
Ziapelta is a member of the family Ankylosauridae, and its closest relative appears to be either Scolosaurus or Nodocephalosaurus, depending on what cladistic model is used. Ziapelta is thought to have been a slow-moving animal like other ankylosaurids, due to its squatted stance and extensive body armor. Ziapelta lived alongside animals like Parasaurolophus, Pentaceratops and Sphaerotholus.
Discovery
An expedition from the New Mexico Museum of Natural History and Science and the State Museum of Pennsylvania, led by Robert Michael Sullivan, discovered a number of Z. sanjuanensis fossils in the Kirtland Formation in 2011. The specimens were found in the Hunter Wash and De-na-zin Members of the formation in the Bisti/De-Na-Zin Wilderness in New Mexico. Z. sanjuanensis was identified as a new species from a number of fossils including the holotype NMMNH P-64484 found from the De-na-zin Member and consisting of a complete skull lacking the lower jaws, parts of the first two cervical half-rings, and a number of partial osteoderms; and a referred specimen NMMNH P-66930 from the older Hunter Wash Member, consisting of a first cervical half-ring. By argon dating of ash layers the age of the holotype skull has been determined at between 72.98 and 72.62 million years old, the late Campanian. It was initially prepared by Amanda K. Cantrell and Thomas L. Suazo; later by Larry Rinehart.
In 2014 Victoria Megan Arbour, Michael Burns, Robert Sullivan, Spencer Lucas, Amanda Cantrell, Joshua Fry and Thomas Suazo named the type species Ziapelta sanjuanensis. The genus (Ziapelta) was named after the Zia sun symbol, a religious image for the Zia people and an element of the flag of New Mexico, and the Latin word pelta ("shield"), referring to ankylosaurids' osteoderms. The specific name (sanjuanensis) comes from San Juan County, where the fossils were discovered.
Description
The adult length of Ziapelta is estimated at between 15 feet (4.6 m) and 20 feet (6.1 m) long, depending on whether the holotype was full-grown. It was quadrupedal, with a wide, robust body. The front part of the jaws was covered in a beak, with rows of small, leaf-shaped teeth farther behind it. It was most likely covered in armor plates, or osteoderms, and had bony half-rings covering the neck. It is thought that Ziapelta might've had a large club on the end of its tail, although this club has not been found fossilized. Bones in the skull and other parts of the body were fused, thus increasing their strength.
Distinguishing traits
Ziapelta sanjuanensis showed three unique derived traits or autapomorphies. The (middle bone plate), of the snout was large, prominent and roughly triangular in shape. Ziapelta had deep, anteriorly curved squamosal horns (measuring from the base to the tip). The rear base of the skull featured three deep grooves. A further possible distinguishing trait is the mixture of concave, flat and convex caputegulae on the skull top.