Amphiorycteropus, Lehmann, 2009

Lehmann, Thomas, 2009, Phylogeny and systematics of the Orycteropodidae (Mammalia, Tubulidentata), Zoological Journal of the Linnean Society 155 (3), pp. 649-702 : 665-666

GENUS AMPHIORYCTEROPUS GEN. NOV.

Diagnosis: Medium-sized Orycteropodidae (about 65–90% of the general size of the extant aardvark) showing the following apomorphies on the skull: a V-shaped nuchal line; an anterior border of the orbit situated above the M 2; a slender palate; a curved post-palatine torus, moreover situated at the level of the M 3; crests on the lateral wall of the pterygoid; an interorbital constriction, including the palatine; a tubercle on the craniomandibular articulation facet; and molars trapezoidal in shape. On the mandible, a concave craniomandibular articulation surface and a mandibular angle superior to 73°. On the postcranium, a blunt oblique rim as well as a pointed radial (or bicipital) tuberosity on the radius, and a ventrally positioned articular facet for the sesamoid bone of the gastrocnemius muscle on the femur. The genus is also characterized by high temporal lines on the cranium, reduced diastema between the premolars, a short scapular neck, a proximodistally elongated talus, feet longer than hands, and metapodes as well as phalanx more slender, proportionally, than in Orycteropus . Amphiorycteropus species exhibit a triangular olecranon fossa on the humerus, as in L. guilielmi , and a continuous border between the tibial tuberosity and the fibula on the proximal epiphysis of the tibio-fibula, as in O. djourabensis . Additionally, they present the following features: a post-palatine foramina situated at the level of the M 3, the absence of an incisura mandibulae, a shallow lingual groove on the upper molar, an articulation axis of the semilunar notch oblique to the diaphysis of the ulna, five sacral vertebrae, no falciform process on the tibiofibula, a short tibial tuberosity, a tibia longer than the femur, and a short tibial crest merging abruptly with the diaphysis.

Remarks: The general size of Amphiorycteropus is based on the limb-bone dimensions. The tibia and the cranial elements cannot be taken into consideration here, as their proportions vary between species.

Type species: Amphiorycteropus gaudryi ( Major, 1888)

Other forms: In Africa, Amphiorycteropus abundulafus ( Lehmann et al., 2005) , Amphiorycteropus mauritanicus ( Arambourg, 1959) , Amphiorycteropus sp. Rooilepel ( Pickford, 1996, but see below), Amphiorycteropus sp. Saitune Dora ( Lehmann, 2008a); and in Eurasia, Amphiorycteropus browni ( Colbert, 1933) , Amphiorycteropus depereti ( Helbing, 1933) , Amphiorycteropus cf. gaudryi Monticino ( Rook & Masini, 1994), Amphiorycteropus cf. gaudryi Chobruchi ( Pavlova, 1915) , Amphiorycteropus cf. gaudryi Maragheh ( Major, 1893) , as well possibly as aff. Amphiorycteropus pottieri ( Ozansoy, 1965) , aff. Amphiorycteropus cf. pottieri Sinap ( Fortelius et al., 2003), aff. Amphiorycteropus seni ( Tekkaya, 1993) , aff. Amphiorycteropus cf. seni Paşalar ( Fortelius, 1990) , and aff. Amphiorycteropus cf. seni Sinap ( Fortelius et al., 2003).

Etymology: The genus name derives from the Greek ‘ amphi ’, meaning ‘on both sides’, and ‘ orycteropus ’, literally ‘digging foot’, but also from the genus name of the extant aardvark. This name – ‘the aardvark from both sides’ – denotes that this genus is for now the only genus of Tubulidentata known from both sides of the Mediterranean sea, i.e. Africa and Eurasia.

Geographic distribution: Kossom Bougoudi ( Chad); Bou Hanifia ( Algeria); Samos Island, Ditiko, and Euboea Island ( Greece); Kemiklitepe, Akgedik-Bayir, Sinap, and Çandir ( Turkey); Perpignan ( France); Brisighella ( Italy); Chobruchi ( Moldavia); Maragheh ( Iran); Potwar Plateau ( Pakistan); as well possibly as Rooilepel ( Namibia) and Saitune Dora ( Ethiopia).

Temporal distribution: Middle Miocene to Early Pliocene.

Discussion: As noticed by Colbert (1941: 326), the hands of A. gaudryi are shorter than its feet: ‘... the third digit in the manus of [ Amphiorycteropus ] gaudryi is considerably shorter than the third digit of the pes of that same animal, whereas in Orycteropus erikssoni faradjius the length of the third digit of the manus is approximately equal to that of the same digit in the pes’. This is also the case in A. abundulafus : the ratio ‘length of the longest finger (metapode to intermediate phalanx) on the longest toe’ is about 0.82 in the Chadian species, whereas in O. afer the ratio is 0.90 ± 0.01 (n = 10) ( Lehmann et al., 2006: 702). Unfortunately, it cannot be confirmed for A. mauritanicus and A. depereti because the material is insufficient. Likewise, there exists a difference in the proportion of the metapodes and phalanx between those genera. These elements of the feet and the hands are proportionally broader in Orycteropus than in Amphiorycteropus (see Lehmann et al., 2005: tables 15, 16). Besides, the length of the metatarsal I and V in A. abundulafus and A. gaudryi is almost similar to the length of their counterpart in O. afer (see Lehmann et al., 2005: table 15).

The creation of a new genus, distinct from genus Orycteropus , helps to clarify the relationships between the Miocene species and the Plio–Pleistocene ones. Indeed, as Patterson (1975: 216) described: ‘Relationships between the described species of Orycteropus are not clear. Tubulidentates first reached Eurasia at some time in the Miocene [...] and there may have been independent evolution within the genus in the north. I doubt if [A.] gaudryi was involved in the ancestry of [O.] afer , which conceivably could have come from [A.] mauritanicus , but whether [A.] depereti descended from [A.] gaudryi or, as such, reached Eurasia from Africa is uncertain. Progress here must await the discovery of more complete material in both continental areas’. The present phylogenetic systematics analysis highlights the high number of apomorphies supporting the redefined Orycteropus and Amphiorycteropus . Therefore, it is unlikely that these two genera are ancestral to one another. It would thus contradict the assumption that A. gaudryi (or any of the new genus members) gradually evolved into O. afer ( van der Made, 2003) . Moreover, the parsimony analysis implies that A. depereti is an early offshoot of the new genus, rather than a descendant of A. gaudryi . For more comments about that genus, see the section ‘T he dichotomy within the genus Orycteropus s.l. ’.