Of River Horses and the Sea Pigs of Tonga

Christian Science Monitor reporter Nick Squire recently filed a quirky story headlined In Tonga, pigs fish but don't fly - yet.

TALAFO'OU, TONGA – Travelers who think they have seen it all should head to the island kingdom of Tonga for one of the Pacific's strangest tourist attractions: "fishing pigs."

Hogs on the archipelago's main island, Tongatapu, have conquered their fear of the ocean and now forage at low tide for crabs, mussels, seaweed, and fish marooned in rock pools.

While piglets snuffle around a few yards from the beach, fully grown porkers wade into the turquoise sea up to their waists....

In the coastal village of Talafo'ou, what looks like a miniature hippo is half-submerged in the sea, 100 yards from the beach. In fact it is a huge black sow, that bears closer resemblance to a wild boar than any farm breed, rooting around the reef.

Although the pigs don't swim, they do plunge their heads beneath the water for a few minutes at a time.

I wonder how long it would take for these swine to evolve into hippos--or porpoises. According to Wikipedia:

As indicated by the name, ancient Greeks considered the hippopotamus to be related to the horse. Until 1985, naturalists grouped hippos with pigs, based on molar patterns. However evidence, first from blood proteins, then from molecular systematics, and more recently from the fossil record, show that their closest living relatives are cetaceans – whales, porpoises and the like. Hippopotami have more in common with whales than they do with other artiodactyls (even-toed ungulates), such as pigs. Thus, the common ancestor of hippos and whales existed after the branch-off from ruminants, which occurred after the divergence from the rest of the even-toed ungulates, including pigs. While the whale and hippo are each other's closest living relatives, their lineages split very soon after their divergence from the rest of the even-toed ungulates.

How would one render in taxonomic Greek the 'sea pig' equivalent of hippopotamus 'river horse'? Hyenathalassa?

This reminds me of an article about the initial failures of machine translation that I remember from grad school in linguistics. The example I've never forgotten was translating the Russian for 'guinea pigs' a bit too literally as 'maritime piglets' (or 'sea SVINKI').