From its incisors and size, Kimbetopsalis simmonsae would have looked something like a fully-terrestrial beaver. You’d have to look into its mouth and see the ludicrous number of cusps on its cheek teeth to immediately spot it as a multituberculate. And if you really knew your anatomy, as Williamson and coauthors do, you’d eventually work out that Kimbetopsalis is a taeniolabidoid – a subset of particularly large multis whose bones and teeth have been found in Palaeocene rocks through western North America and Asia.

Those teeth may have been what made Kimbetopsalis and its relatives so successful in the wake of the Cretaceous mass-extinction. The anatomy of taeniolabidoid jaws, Williamson and coauthors write, gave them “a grinding-focused chewing stroke”,