Late Jurassic (Tithonian)
Morrison Formation
Bone Cabin Quarry, Albany County, Wyoming, USA

Ultra-rare 1mm mammal tooth.

Mammal,

The mammals of the Jurassic would have looked like rodents to us but they lived at least 85 million years before the earliest true rodents appeared.  These animals belong to groups not far removed from the earliest mammals of the Late Triassic. Today, only the last of the monotreme mammals still lay eggs but in the Late Jurassic several forms were laying eggs. Unfortunately, many Jurassic mammals are known only from teeth and jaw sections but they have become more of a focus of research in the past 50 years.

This kind of tooth appeals to the completist collector who wants whatever is available from the Morrison Formation or who wants a example of as many mammal groups as possible.