pinacosaurus

Ziapelta sanjuanensis is a new ankylosaurid from the Kirkland Formation of New Mexico. The holotype consists of a complete skull, two partial cervical half rings (neck armour plates), and miscellaneous osteoderms. It was contemporary with the Kaiparowits formation, however Ziapelta shows little resemblance to what ankylosaur remains have been found there. What’s really interesting about this ankylosaur is where phylogenetic analysis has recovered it - Ziapelta is much closer to other North American ankylosaurs such as Euoplocephalus and Scolosaurus than its contemporary, Nodocephalosaurus. Astonishingly, Nodocephalosaurus recovers within a clade of Asian ankylosaurs including Tarchia and Pinacosaurus. What this exactly implies for the radiation of derived ankylosaurids is currently not clear. 

The PalaeoFellows only just heard about this and did not feel like drawing an ankylosaur (well no, I admit, it’s just me), so we didn’t produce a reconstruction for Ziapelta. Reconstruction up top by Sidney Mohr.

The Plank lizard, Pinacosaurus (1933)

Phylum : Chordata
Class : Reptilia
Order : Ornithischia
Family : Ankylosauridae
Subfamily : Ankylosaurinae
Genus : Pinacosaurus
Species : P. grangeri, P. mephistocephalus

  • Late Cretaceous (80 - 75 Ma)
  • 5 m long and 1 000 kg (size)
  • Djadokhta formation, Mongolia (map)

Considering how many fossils have been discovered of this medium-sized, late Cretaceous ankylosaur, Pinacosaurus doesn’t get nearly the attention it deserves–at least not compared to its more famous North American cousins, Ankylosaurus and Euoplocephalus. This central Asian armored dinosaur pretty much adhered to the basic ankylosaur body plan–blunt head, low-slung trunk, and clubbed tail–except for one odd anatomical detail, the as-yet-unexplained holes in its skull behind its nostrils.

The “type fossil” of Pinacosaurus was discovered in the 1920’s, on one of the numerous expeditions to inner Mongolia sponsored by the American Museum of Natural History. Because so many remains have been found in such close proximity–including the bones of juveniles that were apparently huddling together at the time of their death–paleontologists speculate that Pinacosaurus may have roamed the central Asian plains in herds. This would have afforded some protection from predators, as would the fact that the only way a tyrannosaur or raptor could have killed this dinosaur was by flipping it over onto its armored back and digging into its soft belly.

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I’m a Dinosaur - Pinacosaurus