lower left jaw is this? That's the question ancient mammal expert
Jaelyn Eberle asked herself when a colleague found this little
lower-left jaw in Late Cretaceous sediments
in Wyoming's Hanna Basin. So she set out on a taxonomic and systematics
journey -- to identify and create a family tree for this "beautiful"
tell a tale so specific that mammal species, both modern and ancient,
can be identified from teeth alone.
At first glance Eberle knew that these teeth were mammalian. Fish
and reptile teeth are most often conical or pointed. In contrast,
the molars and premolars of these teeth are more complex, having
numerous cusps, or bumps. In fact, they have so many that Eberle
judged that the animal was a member of the ancient mammalian order
known as the multituberculates, which means "animals with many
cusps on their teeth". They are an unusual group of rodent-sized
mammals with strange teeth. They went extinct in the Eocene (about
35 million years ago) leaving no modern descendants.