4. Macroscelidea

Two incomplete mandibles (plus a third tentatively referred) and an isolated P4 of Rhynchocyon pliocaenicus are reported from Localities 2, 3, and 10E, Upper Laetolil Beds, Laetoli, Tanzania, East Africa. The specimens are dated at ca. 3.7–3.6 Ma. Morphology of this newly recovered material confirms and enhances a diagnosis based previously on only the holotype and paratype. Mean jaw depth and almost all dental measurements of R. pliocaenicus are on average about 21% smaller than those of the extant species R. cirnei, R. petersi, and R. chrysopygus. Rhynchocyon pliocaenicus is diagnosed also by a p2 with a strong posterior heel with a prominent posterior basal cusp, consistent presence of an anterobuccal cingulum on p4-m2, and a posterior cingulum on p4-m1. The protoloph of P4 and M1 of R. pliocaenicus connects to the tip of the paracone. If the habitat preferences of R. pliocaenicus were similar to extant Rhynchocyon, then the presence of this fossil species suggests that closed canopy habitats were present at Laetoli ca 3.7–3.6 Ma, but probably relatively rare.