Ankylosaur club evolution

Several years ago, Victoria Arbour authored a study on ankylosaur club evolution. In her view, the club was unknown prior to the late Cretaceous, and only began to appear in the Turonian. Gobisaurus, which lived then, possessed a tail handle i.e. stiffened caudal vertebrae but no terminal bludgeon. In Arbour's judgment, the club (or knob) came later. The Baynshiree taxon Talarurus had a small club which, although not preserved, is indicated by breakage at the tail tip. The earliest preserved club, Arbour wrote, belonged to the Campanian Pinacosaurus. This is almost certainly incorrect because, as I showed, Dyoplosaurus, which has a preserved club, is somewhat older than Pinacosaurus (roughly 76 million years vs 75 or less for Pinacosaurus). But that was a minor error. As a discovery in China clearly shows, Arbour's thesis requires modification.

 Jinyunpelta possessed a tail club in Albian-Cenomanian time--eons before its predicted first occurrence in Arbour's thesis. Whereas Gobisaurus existed 92 million years ago, Jinyunpelta already had advanced caudal armament 100 Ma, or several million years before the putative forerunner of such armament.

Clearly, Gobisaurus did not represent an intermediate phase in club evolution. Almost certainly, the weapon already existed in the late early Cretaceous.

References

V. Arbour, P. Currie 2015 Ankylosaurid dinosaur tail clubs evolved through stepwise acquisition of key features. Journal of Anatomy.

Zheng, Jin et. al. 2018 The most basal ankylosaurine dinosaur from the Albian-Cenomanian of China, with implications for the evolution of the tail club. Scientific Reports.