Largest otter ever

The largest species of otter ever known to have existed is a prehistoric species – the Ethiopian bear otter Enhydriodon dikikae. It is currently known principally from a single fossilised partial skull (including its snout, orbits and all upper teeth except for the first and second incisors, plus parts of its lower jaw and teeth), which was discovered in the Hadar Formation of Dikika, in Ethiopia's Afar Valley, and dates back to the Pliocene epoch, approximately 5.3–3.6 million years ago. Based upon its size, however, palaeontologists have estimated that the entire creature would have weighed around 200 kg. This very sizeable species was formally described and named in 2011.

Several other Enhydriodon species had also previously been described, and extra-large prehistoric otters belonging to various additional fossil genera are on record too, notably from the Italian island of Sardinia, where no fewer than four such species once existed, but none attained or exceeded the estimated total size of the Ethiopian bear otter.

Postcranial remains of this species have led some researchers to suggest that, unlike typical otters, it may have been predominantly terrestrial rather than aquatic, but the remains are too fragmentary for such suggestions to be anything more than conjectural at present.