Desert warthog Phacochoerus aethiopicus was until recently one of the most poorly known and neglected large non-forest mammals in Africa with almost no information available regarding behaviour or ecology. But surely a warthog is a warthog and the suggestion of a second species is just a manifestation of creative taxonomy; yet on further scrutiny it is apparent that the Desert Warthog is a surprisingly different beast from its common cousin.
Identification (from Safaritalk):
There are three consistent and reliable external features which separate the two species of warthog:
1) Desert Warthogs always have distinctively backward curled tips to the ears -a feature never seen in Common Warthogs.
2) Desert Warthogs have a pronounced infra-orbital swelling (a prominent boney ridge below the eye) which is absent in Common Warthogs.
3) Desert Warthogs have pronounced hooked genal/jugal warts (the wart below and to the side of the eye). Common Warthogs have conical-shaped warts.
..and more detailed about the skull.
1) The skull is slightly smaller, but proportionately shorter and broader.
2) Thickened zygomatic arches: the front part of the zygomatic arch is thickened by internal sinuses and swollen into a spherical hollow knob just in front of the jugal-squamosal suture (in the Common warthog, the zygomatic arch may be robust but it is never quite so thickened and there is no formation of a knob).
3) Enlarged sphenoidal pits: In the Common warthog the skull roof behind the internal nares is marked by two deep and distinct “sphenoidal pits”, not found in any other African suid, while in the Desert species, these pits have expanded enormously, disappearing as distinct entities, so as to contribute to two vaults between the pterygoids, separated by a deep vomerine ridge.
4) Absence of incisors: there is never any trace of upper incisors, even in relatively young individuals, and the lower incisors, even if present, are rudimentary and non-functional, and reduced to 2 pairs maximum (whereas the Common Warthog always has two upper incisors, though these may be lost in very old animals, and usually six functional lower incisors in the adult dentition of normal suine form).
5) The large third molars are very different from those of the Common Warthog in that no roots have been formed by the time all the enamel columns have come into wear, so that the columns are able to continue growing and extend the life of the tooth -a feature which markedly prolongs the life of these molars when dealing with tough fibrous foodstuffs.
Here are some Desert from Meru..