A newly recognized family from the H orn of A frica, the H eterocephalidae ( R odentia: C tenohystrica)

The C tenohystrica is one of the three major lineages of rodents and contains diverse forms related to gundis, porcupines, and guinea pigs. Phylogenetic analyses of this group using mitochondrial and nuclear gene sequences confirm the monophyly of the infraorder H ystricognathi and most of its recognized subclades, including both the N eotropical caviomorphs and the A frican phiomorphs, which are recovered as sister groups. Molecular timetrees calibrated with 22 securely placed fossils indicate that hystricognath superfamilies originated in the E ocene and O ligocene and most families had appeared by the end of the O ligocene, ∼23  M ya. Divergences leading to hystricognath genera took place in the M iocene and Pliocene, with a single exception. The naked mole‐rat ( H eterocephalus ) diverged from other A frican mole‐rats ( B athyergidae) in the early O ligocene (∼31.2  M ya), when the four caviomorph superfamilies ( E rethizonoidea and C avioidea at 32.4  M ya, C hinchilloidea and O ctodontoidea at 32.8  M ya) were first appearing in S outh A merica. The extended independent evolution of H eterocephalus suggested by this analysis prompted a closer examination of mole‐rat characters. H eterocephalus indeed shares many characters with bathyergids, befitting their joint membership in the parvorder B athyergomorphi and superfamily B athyergoidea as well as their shared exploitation of subterranean lifestyles. However, a diverse array of cranial, dental, postcranial, external, and ecological characters distinguishes H eterocephalus from other A frican mole‐rats. These differences equal or exceed those used to diagnose caviomorph families and justify recognizing the naked mole‐rat in its own family, H eterocephalidae L andry, 1957. This taxonomic arrangement poses questions for the inter‐relationships of fossil and extant mole‐rats and brings time equivalence to the ranks assigned to the major clades of hystricognaths. © 2014 The Linnean Society of London