Akainacephalus johnsoni is a Cretaceous ankylosaur that offers new evidence of ancient migrations

Akainacephalus johnsoni
Akainacephalus johnsoni

An article published in the journal “PeerJ” describes the study of a dinosaur of the family of ankylosaurids. Named Akainacephalus johnsoni, this armored herbivore was identified by paleontologists Jelle Wiersma and Randall Irmis, the authors of the research, in today’s Utah, in the USA, where it lived about 76 million years ago, towards the end of the Cretaceous period. Its characteristics indicate a closer relationship with the ankylosaurids that lived in today’s Asia than with other family members that lived in today’s North America.

Ankylosaurids (Ankylosauridae) were part of the suborder of the ankylosaurs (Ankylosauria), which appeared in the Jurassic period but spread remarkablly especially during the Cretaceous period. The species in this family were particularly well-equipped with armor and bony clubs at the end of their tail. They lived in the then Gondwana and according to some researchers there were migrations during the Cretaceous that brought species that lived in what’s now Asia to migrate in today’s North America, where they diversified.

In 2008 a partial skeleton was discovered in today’s Utah in the Kaiparowits Formation along with other animal fossils. It was a dinosaur with a length estimated around 4-5 meters and a height at the hips between 1 and 1.5 meters. The top image (courtesy J.P. Wiersma & R. B. Irmis, doi: 10.7717 / peerj.5016. All rights reserved) shows the bones found (A) and reconstructions of Akainacephalus johnsoni skeleton (B and C). The bottom image (courtesy Andrey Atuchin / DMNS 2017. All rights reserved) shows a reconstruction of the dinosaur’s appearance.

The skeleton discovered, cataloged as UMNH VP 20202, is partial but is the most complete member of the ankylosaurid family discovered in the South-East of the USA. After the long task of cleaning up its bones, in 2014 it was subjected to a CT scan to examine its internal anatomy. The skull was prepared by Randy Johnson, a volunteer from the Natural History Museum of Utah, whose work was honored by giving his name to the new species.

Named Akainacephalus johnsoni, the new ankylosaurid showed similarities with the species Nodocephalosaurus kirtlandensis, part of the same family, which lived in the same period in today’s New Mexico. The paleontologists’ examination showed that these two dinosaurs are more closely related to some Asian cousins ​​such as the genera Saichania and Tarchia than to other North American ankylosaurids. In particular, they found similarities in the their skulls’ flat armor.

The Utah area where the Akainacephalus johnsoni skeleton was discovered, called the Grand Staircase-Escalante National Monument (GSENM), in the late Cretaceous was part of an island continent called Laramidia. Between 80 and 75 million years ago the life forms that lived on that continent were very diversified and in recent years many new species have been discovered.

However, the similarities between Akainacephalus johnsoni and the Asian ankylosaurids offer new confirmations that, before that period of isolation, there were periods when the sea level was lower allowing migrations of various species of animals within the then Gondwana. In essence, the study of this species is important because it’s helping to reconstruct at least one of those migrations.

Akainacephalus johnsoni reconstruction
Akainacephalus johnsoni reconstruction

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