which is responsible for the powerful bite of the anterior portion of the mouth. The incisors of blesmols are projected forward and protrude from the mouth even when the mouth is closed. This condition allows the animals to burrow with their teeth without getting dirt in their mouths. The number of cheek teeth varies greatly between species, an unusual feature among rodents, so that the dental formula for the family is: Technical characteristics The skull morphology of blesmols sets them apart from all other rodents. As with all members of their suborder, their jaws are hystricognathous, but, unlike their relatives, they have a highly reduced infraorbital foramen. The medial masseter muscle shows only minimal passage through the infraorbital foramen leading most authorities to consider them protrogomorphous. They are therefore the only protrogomorphous hystricognaths. Behavior Blesmols live in elaborate burrow systems and different species exhibit varying degrees of sociality. Most species are solitary, but two species, the damaraland blesmol (Fukomys damarensis) and the naked mole-rat (Heterocephalus glaber) are considered to be the only two eusocial mammals. These species are characterized by having a single reproductively active male and female in a colony where the remaining animals are sterile. These animals prefer loose, sandy soils and are often associated with arid habitats. They rarely come to the surface, spending their entire life underground. Blesmols are herbivorous, and primarily eat roots, tubers, and bulbs. They are even able to pull smaller plants underground by their roots, without having to leave their burrows, enabling them to eat leaves, stems, and other parts of the plant that would otherwise be inaccessible. Blesmols burrow in search of food, and the great majority of their tunnel complex consists of these foraging burrows, surrounding a smaller number of storage areas, nests, and latrine chambers. Most species breed only once or twice during the year, although some breed all year round. They generally have small litters of two to five young, perhaps because their environment is sufficiently safe that they do not need to rapidly replace their population as many other rodents do. However, some species have much larger litters, averaging twelve young in the naked mole rat, and sometimes much larger. Classification The Bathyergidae are monophyletic, with all taxa tracing back to a single common ancestor. Although there is some controversy, the closest living relatives of the blesmols appear to be other African hystricognaths in the families Thryonomyidae