Late Cretaceous (Maastrichtian)
Hell Creek Formation
Powder River County, Montana, USA

Fine 2mm P4

Mammal, Multituberculate.

Mesodma is a genus of the Order Multituberculata, a branch of Jurassic-Eocene mammals quite unrelated to any mammal groups that live today.  Some paleontologists once thought they laid eggs.  They would have resembled rodents and probably had much the same lifestyle but their teeth were different.  Mesodma was one of the multituberculates that survived into the Early Paleocene after the K/T mass extinction.