Fictional species: The Lagyll Brushtail (Caudipilus sardus)

The Lagyll Brushtail or Caudipilus sardus is a proboscidean with only little relation to modern elephants. Instead, its origins date back to Gomphotherium [real species] which lived during the palaeogene period 25 million years ago. The placement of the Brushtail's tusks also reminds of Deinotherium [real species] and it is believed that their mutual anchestor is, in fact, Gomphotherium.
While the earliest proboscideans lived in or near water, their evolved descendants specialized in living on firm ground - while so, they retained an everlasting liking towards water. Continuing with Deinotherium, the proboscideans more and more became what we today know als elephants. The second branch, parting from the aforementioned, returned to a water-based lifestyle.
While standing, the Brushtail's trunk does not reach the ground. Feeding on dry land would pose quite an exercise for the animal, but while diving, the trunk makes an excellent plant-grasping device. To further push its swimming abilities, its toes are slightly webbed. The vertically pronounced tail serves as a rudder. At first glance, its hairy tip gives the impression of incomplete shaving, but in fact it is used to determine water flow and speed. As with various water-dwelling mammals, the Brushtail can fold its ears to prevent water from entering.