1

Chapter

Part I Evolution, Taxonomy, and Domestication

1

Evolutionary Relationships and Taxonomy of

Suidae and Tayassuidae

Jaime Gongora, Colin Groves, and Erik Meijaard

Introduction to Suoidea

The Order Artiodactyla includes four suborders: Tylopoda (cam-
els 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 con-
sidered 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 arrange-
ment 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 incor-
porating 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 descrip-
tions 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). The mandibular incisors are
   procumbent (i.e. they slant forward), so that it is their
   lingual surfaces that occlude with the cutting edges of the
   maxillary ones, except that the anterior upper incisors are

over-jetted and only their lingual shelves are in centric

occlusion. The canines are sexually dimorphic. The

premolars are increasingly molariform distally. Both

premolars and molars are low-crowned, bunodont, and

adorned with numerous secondary cuspules. The dental

formula is plesiomorphic, as is the brachyodont and

bunodont general condition of the postcanine dentition,

and probably also the simple structure of the anterior

premolars, but the incisors and the multicuspid condition

of the posterior premolars and molars are apomorphic.

3. There is no fusion of the metapodials, a plesiomorphic
   condition.


4. There are no horns, again plesiomorphic within the
   Artiodactyla.


5. The pelage is sparse, coarse and bristly: probably an
   apomorphic state.

A Brief Evolutionary History of Suoidea

Extant Suoidea are grouped into two living families: Suidae

(suids, hogs or pigs) and Tayassuidae (tayassuids, javelinas or

peccaries). The evolutionary success and ecological adaptability

of these taxa is reflected by the multitude of habitats in which the

extant taxa occur. Suidae are distributed from tropical rainfor-

est to dry open woodlands, grasslands, highlands, deserts and

islands of Africa, Europe, and Asia (Figure 1.1; Meijaard et al.

2011). Tayassuidae occur in deserts, flooded savannas and man-

groves as well as in a range of tropical forests and grasslands in

the Americas (Figure 1.1; Taber et al. 2011).

Overall morphological and DNA studies have shown that

Tayassuidae and Suidae are sister-groups, but taxonomic debate

continues as to the intergeneric relationships within these fami-

lies. Extant Suidae consist of 14–30 species (see below), which

are grouped into six genera: Sus (domestic and wild pigs) from

Eurasia; Porcula (pygmy hog) from the Indian subcontinent;

Babyrousa (babirusas) from South East Asia; Potamochoerus

(bush pigs), Phacochoerus (warthogs) and Hylochoerus (forest

hogs) from sub-Saharan Africa (Groves & Grubb 1993, 2011;

Meijaard et al. 2011; Ruvinsky et al. 2011; Taber et al. 2011). For

Tayassuidae, which are confined to the Americas, three extant

peccary species were traditionally recognized in the same num-

ber of genera: Catagonus wagneri (Chacoan peccary), Tayassu

pecari (white-lipped peccary) and Pecari tajacu (collared pec-

cary) (Groves & Grubb 1993; Ruvinsky et al. 2011; Taber et al.

2011), but it has recently been shown that there are at least two,

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