The Jaggermeryx is an extinct genus of semiaquatic ungulate (mammal with hooves), related to the hippopotamus. When scientists first discovered the fossils of a large, hippo-like 'water pig' in Egypt, it didn’t take too long to name their find. They dubbed it ‘Jaggermeryx naida’.

Yes, the genus was named after Mick Jagger, although initially there was a bit of a debate among the team as to whether it should be named after Angelina Jolie instead, as she also has famous lips. The creature is estimated to have been the size of a small chubby deer, and is thought to have looked somewhat like a skinny hippo crossed with a long-legged pig. (Jolie should be grateful she was not honored.)

Both parts of the name, ‘Jagger’ and ‘water nymph', are based upon what scientists have been able to discern about the creature's appearance and habits.

Researchers freely admit that the ‘Jagger’ part is a direct reference to Mick Jagger of The Rolling Stones. They noted that both their water pig and Jagger have what they call large, 'tactile' lips. (That determination was based on the fossilized jawbones, which indicated that the species had very sensitive lips and a mobile snout.)

The 'water nymph' part of the name came about because the area at one time was swampy; they believe their discovery spent much of its time standing in water and foraging for plants along the river bank, sometimes frolicking by, and playing in, the water.

More Info: en.m.wikipedia.org