Abstract
We report the discovery of three isolated primate petrosal fragments from the fossiliferous locality ofChambi (Tunisia), a primate-bearing locality dating from the late early to the early middle Eocene. Thesefossils display a suite of anatomical characteristics otherwise found only in strepsirhines, and as suchmight be attributed either to Djebelemur or/and cf. Algeripithecus, the two diminutive stem strepsirhineprimates recorded from this locality. Although damaged, the petrosals provide substantial informationregarding the ear anatomy of these advanced stem strepsirhines (or pre-tooth-combed primates),notably the patterns of the pathway of the arterial blood supply. Using mCT-scanning techniques anddigital segmentation of the structures, we show that the transpromontorial and stapedial branches of theinternal carotid artery (ICA) were present (presence of bony tubes), but seemingly too small to supplyenough blood to the cranium alone. This suggests that the ICA was not the main cranial blood supply instem strepsirhines, but that the pharyngeal or vertebral artery primitively ensured a great part of thisrole instead, an arterial pattern that is reminiscent of modern cheirogaleid, lepilemurid lemuriforms andlorisiforms. This could explain parallel loss of the ICA functionality among these families. Specificmeasurements made on the cochlea indicate that the small strepsirhine primate(s) from Chambi was(were) highly sensitive to high frequencies and poorly sensitive to low frequencies. Finally, variance fromorthogonality of the plane of the semicircular canals (SCs) calculated on one petrosal (CBI-1-569) suggeststhat Djebelemur or cf. Algeripithecus likely moved (at least its head) in a way similar to that ofmodern mouse lemurs.