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. 2021 Dec;600(7888):259-263.
doi: 10.1038/s41586-021-04147-1. Epub 2021 Dec 1.

Bizarre tail weaponry in a transitional ankylosaur from subantarctic Chile

Sergio Soto-Acuña  1   2 , Alexander O Vargas  3 , Jonatan Kaluza  4   5   6 , Marcelo A Leppe  4   7 , Joao F Botelho  4   8 , José Palma-Liberona  4   8 , Carolina Simon-Gutstein  4 , Roy A Fernández  4   9 , Héctor Ortiz  4   10 , Verónica Milla  4   9 , Bárbara Aravena  4 , Leslie M E Manríquez  4   11 , Jhonatan Alarcón-Muñoz  4   12 , Juan Pablo Pino  4   12 , Cristine Trevisan  4   7 , Héctor Mansilla  4   7 , Luis Felipe Hinojosa  4   12 , Vicente Muñoz-Walther  4 , David Rubilar-Rogers  4   13
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Bizarre tail weaponry in a transitional ankylosaur from subantarctic Chile

Sergio Soto-Acuña et al. Nature. 2021 Dec.

Abstract

Armoured dinosaurs are well known for their evolution of specialized tail weapons-paired tail spikes in stegosaurs and heavy tail clubs in advanced ankylosaurs1. Armoured dinosaurs from southern Gondwana are rare and enigmatic, but probably include the earliest branches of Ankylosauria2-4. Here we describe a mostly complete, semi-articulated skeleton of a small (approximately 2 m) armoured dinosaur from the late Cretaceous period of Magallanes in southernmost Chile, a region that is biogeographically related to West Antarctica5. Stegouros elengassen gen. et sp. nov. evolved a large tail weapon unlike any dinosaur: a flat, frond-like structure formed by seven pairs of laterally projecting osteoderms encasing the distal half of the tail. Stegouros shows ankylosaurian cranial characters, but a largely ancestral postcranial skeleton, with some stegosaur-like characters. Phylogenetic analyses placed Stegouros in Ankylosauria; specifically, it is related to Kunbarrasaurus from Australia6 and Antarctopelta from Antarctica7, forming a clade of Gondwanan ankylosaurs that split earliest from all other ankylosaurs. The large osteoderms and specialized tail vertebrae in Antarctopelta suggest that it had a tail weapon similar to Stegouros. We propose a new clade, the Parankylosauria, to include the first ancestor of Stegouros-but not Ankylosaurus-and all descendants of that ancestor.

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References

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