Widanelfarasia, a diminutive placental from the late Eocene of Egypt.

Abstract

The lower dentition of Widanelfarasia (new genus), a diminutive late Eocene placental from the Fayum Depression in Egypt, is described. Widanelfarasia exhibits a complex of features associated with incipient zalambdodonty and at least three unequivocal apomorphies [loss of P(1), an enlarged I(2) (relative to I(3)), and a basal cusp on I(2)], which provide weak support for its placement as a possible sister taxon of either a tenrecid-chrysochlorid clade or of solenodontids. The former hypothesis gains additional support from biogeographical evidence, but both scenarios are currently tenuous as Widanelfarasia is clearly not truly zalambdodont. Phylogenetic hypotheses positing affinities with tenrecids alone or chrysochlorids alone must invoke either convergent acquisition of zalambdodonty in these taxa or autapomorphic reversal in Widanelfarasia. Given these considerations, a relationship with more generalized taxa from the Laurasian Paleogene (e.g., geolabidids, nyctitheriids, leptictids) cannot yet be ruled out. Comparisons with other Paleogene Afro-Arabian forms are generally inconclusive. A relationship with the earlier Eocene Chambilestes from Tunisia-currently represented by a single specimen preserving P(4)-M(3)-seems possible based on the geometry and predicted occlusal relationships of these teeth, but cannot be confidently determined until these two taxa come to be represented by common diagnostic elements. Todralestes (late Paleocene, Morocco) exhibits general phenetic similarities to Widanelfarasia, but it is not yet known whether this taxon shares any of Widanelfarasia's unequivocal dental apomorphies. Pending the recovery of more informative material, we tentatively refer Widanelfarasia to Placentalia incertae sedis. Truly zalambdodont placentals remain conspicuously absent from the Paleogene of Afro-Arabia.