Nanocuris

Nanocuris is an extinct genus of Deltatheridiidae from the Cretaceous of Canada (Saskatchewan) and United States (Wyoming - Lance Formation and Hell Creek Formation ). Initially, it was classified in a proper family, Nanocuridae, in the clade Eutheria, but a reanalysis of a new specimen revealed a delthatheroid affinity of the genus.

Size
It was the proportionally largest deltatheroidean. Alongside the similarly sized Didelphodon, it likely replaced earlier Cretaceous eutriconodonts as a large sized predatory mammal.

Classification
Ironically, it's closest relative is the smallest deltatheroidean, Gurbanodelta.