Suina - Classification

Classification

The suborder Suina includes Suidae (pig family) and Tayassuidae (peccary family).

Some morphological studies have also identified the hippopotamus family Hippopotamidae among the Suina.

The oreodonts, a branch of the tylopoda, were often considered suines due to the popular, though inaccurate, description of them as "ruminating hogs". Oreodonts were not suines, they were more closely related to camels. Similarly, the precursors of the oreodonts, the entelodonts, had long been classified as members of the Suina. Spaulding et al. have found them to be closer to whales, than to pigs in his Cetacodontamorpha.

Hippopotamuses were once thought to be part of the Suina, but a growing body of morphological and genetic evidence has suggested that they share a common ancestor not with the Suina, but with Cetaceans—the Order which includes whales and dolphins. Whales and artiodactyls form a clade called Cetartiodactyla.

The most recent research into the origins of hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other Artiodactyls around 60 million years ago. Descendants of this hypothesized ancestor likely split into two branches around 54 million years ago. One branch would evolve into cetaceans, possibly beginning with the proto-whale Pakicetus from 52 million years ago and other early whale ancestors, known as Archaeoceti, which eventually underwent aquatic adaptation into the almost completely aquatic cetaceans.