The oldest otter in the world... the Giant Otter

 The Giant Otter (Pteronura brasiliensis) is the oldest living species of otter on Earth. It is believed to have evolved from an extinct genus, Satherium. The clade (definition= branch; in biology the term is used to refer to a group of animals that includes a common ancestor and all of it's descendants) that includes the giant otter split from the rest of the otter species ~5-11 million years ago.

The genetics is still being hammered out, but the following hopefully helps put the development of our modern otter species in to perspective!

The giant otter is the largest (longest) of the current otter species with some males getting over 7' (or 2 m) long (nose to end of tail) and weighing over 70 lbs (32 kg).

The giant otter is listed "Endangered" on IUCN's RedList.
It is very social and lives in the northern and central fresh water regions of South America in family groups up to 20 members (generally 3-10 though).

Research published recently even shows giant otters will mob jaguars!