Qatranilestes oligocaenus, Seiffert, 2010

Seiffert, Erik R., 2010, The oldest and youngest records of afrosoricid placentals from the Fayum Depression of northern Egypt, Acta Palaeontologica Polonica 55 (4), pp. 599-616 : 607-608

Qatranilestes oligocaenus sp. nov.

Figs. 10 , 11B .

Holotype: YPM 24203 , a right mandibular fragment preserving the talonids of m2–3 ( Fig. 10B ).

Etymology: In reference to the Oligocene age of the species.

Type locality: Quarry I, northern Egypt.

Type horizon: Late early Oligocene, upper sequence of Jebel Qatrani Formation, northern Egypt (~29.5–30 Ma).

Diagnosis.—Small species (about 65% the size of Dilambdogale gheerbranti ) that differs from other Fayum afrosoricids ( Dilambdogale , Widanelfarasia , and Jawharia ) in having relatively reduced talonid basins and capacious hypoflexids on m2–3 ( Figs. 9, 10 ); differs from Dilambdogale in having very reduced molar entoconids.

Description.— Qatranilestes is only known from very fragmentary material, notably the holotype mandible preserving doi:10.4202/app.2010.0023

the talonids of m2–3, the horizontal ramus distal to p4, and the base of the ascending ramus ( Fig. 10B ). A complete but badly abraded and worn m3 is implanted in another partial mandible (YPM 24200, Fig. 10A ). Even from such poorly preserved material, it is clear that Qatranilestes is unique among Fayum tenrecoids in having very reduced talonids ( Figs. 9, 11 ) and capacious hypoflexids (m2 talonid width = 0.45 mm; m3 talonid width = 0.45 mm). The m2 talonid preserves a concave cristid obliqua and small hypoconid, hypoconulid, and entoconid cusps. The trigonid of m3 on YPM 24200 is very worn, but clearly would have had well−developed metaconid, paraconid, and protoconid cusps, and was elevated high above the very low and mediolaterally narrow talonid basin, which shows little clear differentiation of cusps aside from the hypoconid. The m3 of the holotype specimen is not as worn and damaged, but similarly shows only very small and indistinct talonid cusps, with the hypoconid and hypoconulid closely approximated. Relative to trigonid breadth, the m3 talonid of Qatranilestes is very reduced relative to those of Widanelfarasia and Jawharia . Seiffert et al. (2007) noted that Widanelfarasia exhibits slight external rotation of the long axis of the lower molar crowns, leading to an arrangement in which the lower molar paraconids are situated distal to the hypoconulid (rather than the entoconid) of the adjacent molar. This orientation decreases the size of the trough for the occluding upper molar metacone, and increases the buccal exposure of the paracristid for occlusion with the upper molar postmetacrista. Judging from the orientation of the m2 talonid, Qatranilestes had a similar external rotation of the molar crowns. The preserved morphology and orientation of Qatranilestes ’ m2–3 suggests that the occluding M2 would have had a greatly enlarged paracone (to occlude in the large hypoflexid), a reduced metacone, and an elongate postmetacrista, and probably more closely approximated the “euzalambdomorph” occlusal pattern than did any of the older species that have been recovered thus far.

Figures

Fig. 10. Dental morphology of the afrosoricid placental Qatranilestes oligocaenus, gen. et sp. nov., from the late early Oligocene (late Rupelian) Quarry I, upper sequence of the Jebel Qatrani Formation, northern Egypt. A. YPM 24200, right mandibular fragment with crown of m3 in occlusal (A1) and lingual (A2) views. B. YPM 24203, holotype right mandible with talonids of m2–3 in occlusal stereo view (B1 and B2).

Fig. 11. Comparison of talonid morphology, in lingual view of two Egyptian afrosoricid placentals.A. Dilambdogale gheerbranti (DPC 24103A), from the earliest late Eocene (earliest Priabonian; ~37 Ma) locality BQ−2, Birket Qarun Formation, Fayum Depression, northern Egypt. B. Qatranilestes oligocaenus (YPM 24203), from the late early Oligocene (late Rupelian; ~30 Ma) Quarry I, upper sequence of the Jebel Qatrani Formation, northern Egypt. Specimens are scaled to the same approximate m2–3 length to facilitate comparison.Note the much larger hypoconid and relatively capacious and concave talonid basin in Dilambdogale. Also note that the m2 entoconid is broken in DPC 24103A, but is relatively well−developed in other specimens.