Middle Miocene Pierolapithecus provides a first glimpse into early hominid pelvic morphology

Here we describe the pelvis from the holotype specimen of Pierolapithecus catalaunicus (IPS-21350), a middle Miocene (11.9 Ma [millions of years ago]) stem hominid from Barranc de Can Vila 1 in Abocador de Can Mata (Catalonia, Spain) for which a partial skeleton is preserved. This skeleton includes the oldest known great ape pelvic materials, which have implications for reconstructing the basal hominid body plan from which later hominids evolved. The P. catalaunicus pelvis is composed of a fragment from the ilium (IPS-21350.38) and one from the ischium (IPS-21350.39). Although the P. catalaunicus ischium consists of just a small fragment from the caudal acetabulum, the preserved morphology is consistent with the basal hominoid Proconsul nyanzae. The ilium is similar to Pr. nyanzae in its concave gluteal surface and linea arcuata form, which suggests much of the iliac and pubic form was primitive. However, the ilium was relatively more flaring than Pr. nyanzae and most monkeys, and could be within the range of extant lesser apes. In addition, the iliac tuberosity width was probably intermediate between extant great apes and monkeys, although maximum and minimum estimates could be accommodated within either group. The P. catalaunicus ilium reflects incipient modifications of the basal hominoid torso for the more frequent use of orthograde behaviors described for this taxon on the basis of other preserved anatomical regions, and also supports claims that extant ape pelvic morphology could be homoplastic given the hypothesized phylogenetic positions of Pierolapithecus.