The mustelids probably evolved from the miacids (above) during the Early Tertiary. Modern members of this family include the weasel, stoat, badger, skunk and otter. They are all slim, long-bodied hunters, living mainly in temperate latitudes throughout the world. In the tropics, their place is taken by the civets, genets and mongooses (the viverrids, see p. 225).
name: Potamotherium time: Early Miocene locality: Europe (France) size: 5 ft/1.5 m long
Potamotherium is the earliest-known otter, and like its modern counterpart it had a long, sinuous body and short legs. It probably ran through the riverside undergrowth in a series of leaps, its back arched and its head close to the ground. Its sense of smell was not well developed, but its hearing and sight seem to have been acute, helping it to hunt its fish prey in the water.
Potamotherium was without a doubt an excellent swimmer — its sleek, streamlined shape would have cut through the water, and its flexible back-
bone enabled it to dive and dart about easily underwater.
The otters are the only mustelids that are well represented in the fossil record. This is probably because they lived near water, and so were more likely to become buried in sediments and subsequently fossilized. Paleontologists believe that the true seals, or phocids, evolved from a mustelid ancestor (see p. 228).
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