Evolutionary relationships and taxonomy of suidae and tayassuidae

Introduction to Suoidea The Order Artiodactyla includes four suborders: Tylopoda (camels and llamas), Suoidea (also known as Suina or Suiformes), Whippomorpha (hippos and cetaceans), and Ruminantia (ruminants). While Tylopoda are a sister-group to the rest, and Suoidea are a sister-group to Whippomorpha and Ruminantia, the splits seem to have happened very rapidly in evolutionary time, and there would be little point in recognizing them at separate taxonomic ranks. Others have named the joint group as Cetartiodactyla (Cetacea and Artiodactyla), but this is considered to be nomenclaturally incorrect (Asher & Helgen 2010) because Whippomorpha form a monophyletic clade deeply nested within the phylogeny of Artiodactyla. As little as 20 years ago, the prevailing taxonomic arrangement was very different. The Cetacea (whales, dolphins and porpoises) were regarded as a separate order, and within the restricted Artiodactyla the major split was between Suiformes (pigs, peccaries and hippos) and Ruminantia, the latter incorporating the Tylopoda. Molecular data accumulated since then have without exception united the hippos and Cetacea into a monophyletic group, as a sister-group to the ruminants, while the Tylopoda, not the pigs and peccaries, are now seen as a sister-group to the rest of the Artiodactyla. Such conditions as stomach complexity, metapodial fusion and dental reduction are now seen as having arisen independently in camelids and ruminants. Unless otherwise noted, the taxonomic arrangement used here is derived from Groves & Grubb (2011) while the descriptions are either from the same source or from Groves (1981). Diagnostic conditions of the Suoidea are as follows: 1.Snout disk. The tip of the snout is flattened to form a naked, forward-facing disk, supported by cartilage, penetrated by the nostrils. The disk is outlined dorsally and laterally by a raised rim, but inferiorly is continuous with the mucous membrane of the palate. It is movable by specialized muscles originating in the deep preorbital fossae. This whole complex is a clear apomorphic condition of the Suoidea. 2.The dentition is the full eutherian complement of 3143/3143, except in a few species where some reduction has occurred (notably Phacochoerus aethiopicus, with its loss of upper incisors).