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

Excellent 2mm m2 with roots.

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.  They were considered so primitive that some paleontologists once thought they laid eggs.  They would have resembled rodents and probably had much the same lifestyle but their teeth testify to a separate ancestry.

Mesodma was one of the multituberculates that survived into the Early Paleocene after the K/T mass extinction.  They became less common during the Eocene and died out around the end of that epoch.