mastodon: extinct elephant-like mammal that flourished worldwide from Miocene through Pleistocene times; differ from mammoths in the form of the molar teeth
placental: mammals having a placenta; all mammals except monotremes and marsupials
mefenamic acid: a nonsteroidal anti-inflammatory and analgesic drug (trade name Ponstel) used to treat mild pain (especially menstrual cramps)