"Compared to all extant mammals, the braincase in Nemegtbaatar and Chulsanbaatar is primitive."

The following taxonomy of extant and recently extinct mammals is from Vaughan et al. 2000.

Bats are the only extant native terrestrial mammals in Puerto Rico.

Similar to all non-avian dinosaurs studied to date, Plateosaurus grew in a pattern that is unlike that of both extant mammals and birds.

However, the bone microstructure indicates rapid growth, as in sauropods and extant mammals, which suggests endothermy.

Males of the species are unique among extant mammals in that they possess four permanent horns.

The most distinctive feature of the animal is the presence of four horns; a feature unique among extant mammals.

This implies that it is due to morphological convergence, because they are not closely allied to any other family of extant mammals (Bronner).

Below is a partial list of extinct and extant mammals with their scientific names included on the right.

Zapus are the only extant mammals with a total of 18 teeth (Schwartz and Schwartz, 1997).