Phiomyidae

Abstract: The fossil record of phiomorph hystricognathous rodents from the Afro-Arabian Paleogene is important for understanding the origins and dispersal routes of the early crown hystricognaths. Here, we describe a “new” basal phiomorph genus and species, Acritophiomys bowni, based on complete upper and lower dentitions, mandibular fragments, and partial crania from the terminal late Eocene (~34 Ma) Locality 41 (L-41) in the Fayum Depression of northern Egypt. Acritophiomys bowni is the oldest and largest representative of the family “Phiomyidae”, being more or less the same size as contemporaneous gaudeamurids, and is one of the most abundant hystricognaths at L-41. The genus exhibits a mosaic of primitive and derived features, the former shared with primitive hystricognaths, such as Waslamys and Protophiomys from the earliest late Eocene, and the latter shared with Metaphiomys from early Oligocene (~31–29 Ma) sites in the upper sequence of the Jebel Qatrani Formation. Phylogenetic analysis of craniodental features, scored across a number of different hystricognathous groups, consistently places Acritophiomys bowni and members of the genus Phiomys as basal members of the phiomorph stem lineage, implying that the commonly used family “Phiomyidae” is a paraphyletic assemblage. Among other things, this material shows that basal members of the phiomorph clade consistently replaced dP4/4 with permanent P4/4, and suggests an African origin of stem and crown Phiomorpha.

Abstract: Early hystricognathous rodents from Africa are primarily documented by two basal and extinct groups, the paraphyletic “Phiomyidae” and the Gaudeamuridae, which were particularly well diversified through the late Eocene and the early Oligocene. However, in the absence of a comprehensive late Oligocene fossil record, the evolutionary history of African hystricognathous rodents during the end of the Paleogene is unclear. Continuing field efforts in the Lokichar Basin of Kenya (western Turkana Basin) have led to the discovery of dental remains of a ‘phiomyid’ from the Lokone site LOK 13. The dental pattern of this rodent is unusual among ‘phiomyids,’ which led us to propose here a new taxon: Turkanamys hexalophus, gen. et sp. nov. Turkanamys shares a similar dental bauplan with early Afro-Asian hystricognaths (early ‘phiomyids’ and ‘baluchimyines’), and as such appears evolutionarily conservative with respect to some Oligocene and all the Miocene hystricognaths. Conversely, Turkanamys is also highly ...

Abstract: Until recently, the ancient fossil family Phiomyidae (suborder Hystricognathi) was recorded only from the early Oligocene site of the Fayum, Egypt (Andrews, 1906; Osborn, 1908; Schlosser, 1910, 1911; Wood, 1968). As defined by Lavocat (1973), the infraorder Phiomorpha includes many other representatives that occurred in the middle or late Oligocene of the Balearic islands (Adrover and Hugueney, 1975; Adrover et al., 1978), in the Miocene of Africa (Stromer, 1926; Lavocat, 1973), of India and Pakistan (Black, 1972; Flynn and Jacobs, 1982; Flynn et al., 1983; Jaeger et al., 1980), and of the eastern Mediterranean (Chios, Greece) (Tobien, 1968). Phiomorphs are still represented in Africa by two living families: the Thryonomyidae and Petromyidae (or Petromuridae). At the Fayum site, Wood (1968) described five new genera and nine species of phiomyids, showing a great variety of dental patterns (three to six crests in upper and lower molars, for example), but possessing already in the Oligocene all the characteristics of the modern representatives of the thryonomyoids: retention of dP4/4; hystricomorphy; hystricognathy; and multiserial enamel on the incisors.

Abstract: [Extract] The evolutionary history of the living African rodent families is a topic of considerable debate, yet it is generally agreed that the modern cane rats (Thryonomys Fitzinger, 1867) and dassie rats (Petromus Smith, 1831) have an evolutionary history within the infraorder Phiomorpha (e.g., Wood, 1968). Phiomorphs possess hystricognathous mandibular morphology, multiserial incisor enamel, and hystricomorphous attachment of the masseteric musculature (e.g., Lavocat, 1978; Holroyd, 1994). In his initial work on the group, Wood (1968) placed all phiomorph taxa into a single family, and named a handful of morphologically diverse species based mainly on size. Lavocat (1978) later revised the taxonomy of the group, raising many of the differences among species to the family level. More recently, Holroyd (1994) observed that these contrasting views likely stemmed from the fact that Wood's phiomorph work emphasized the overall similarity of Paleogene specimens from the Fayum of Egypt, whereas Lavocat endeavored to explain the diverse Miocene rodent faunas from East Africa, envisioning that each of the Miocene forms had an ancestor among the Paleogene taxa. In this paper we adopt Holroyd's (1994) revised version of family-level relationships among the phiomorphs. A variety of well-preserved specimens pertaining to phiomorph evolutionary history have been described from the Paleogene of northern Africa and Oman (Osborn, 1908; Wood, 1968; Jaeger et al., 1985; Fejfar, 1987; Holroyd, 1994) and Asia (e.g., Flynn et al., 1986; Jaeger, 1988; Marivaux et al., 2002; Marivaux and Welcomme, 2003). However, Paleogene terrestrial deposits in sub- Saharan Africa are extremely rare, hence this constitutes the earliest phiomorph record from East Africa. Here we announce a new microsite in the Mbeya Region of southwestern Tanzania, preserving Metaphiomys Osborn, 1908, a rodent taxon previously described exclusively from the early Oligocene of Egypt, Libya, and Oman (Wood, 1968; Fejfar, 1987; Thomas et al., 1989). Not only does this represent a significant geographic extension of the taxon, it also constitutes the first rodent material described from the Paleogene of East Africa.