Mesozoic mammals
Early Mammals
The mammals first appeared at the same time as the dinosaurs, in the late Triassic, about 230 million years ago. Their ancestors were the mammal-like reptiles. During the first two thirds of mammalian history, when the dinosaurs ruled the Earth, the mammals were small, nocturnal animals about the size of mice and rats. When the dinosaurs died out 65 million years ago, the mammals were well equipped to exploit the different ecological niches left vacant, and their rapid evolution started.

Triconodonts
The triconodonts were the most primitive mammals. They looked like mammal-like reptiles - cynodonts - but were smaller. Like the cynodonts, they had molars with three cusps in a straight row. Large canines show that the triconodonts were carnivorous, but some may have been insectivores. They died out in the late Cretaceous.

Multituberculates
The multituberculates are an extinct side branch of the mammalian line; the first omnivorous mammals. They had large incisors, looking somewhat like modern rodents, and long multi-cusped molars. They were numerous and diverse in the late Cretaceous and the early Tertiary. They died out in the Oligocene, about 35 million years ago, probably because of competition from the rodents.
The reconstruction of the skeleton of the multituberculates, shows that the legs were not tucked completely under the body as in other mammals. The legs had a slight sprawl, similar to what we see in reptiles today. List of contents in the mesozoic mammals showcase

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