Early Holocene fauna from a new subfossil site: A first assessment from Christmas River, south central Madagascar

Abstract

We report on faunal remains recovered during recent explorations at ‘Christmas River’, the only subfossil locality known from Madagascar’s south central plateau. Recovered remains of several extinct taxa date to approximately 10,000 14 C years before present (BP), including crocodiles, tortoises, the elephant bird Aepyornis, the carnivoran Cryptoprocta spelea, the lemurs Archaeolemur majori, Pachylemur insignis, and Megaladapis edwardsi, and abundant remains of the dwarf hippopotamus, Hippopotamus lemerlei. The presence of southern - limited, forest - dependent species at Christmas River supports the hypothesis that forest once extended, perhaps discontinuously, across the central highlands towards the west. One theory is that sites in the north central highlands, which are higher in elevation, maintained more mesic conditions during Plio - Quaternary climate shifts than those of the lower elevation sites of the south central highlands. Thus, elevation above sea level may have acted as a filter that limited species dispersal across the island in the past. Such a scenario would explain the distinction between more humid, higher elevation, northern highland subfossil communities versus more arid, lower elevation, southern subfossil communities. Continued exploration at Christmas River thus provides a remarkable opportunity for deciphering ecological changes that have taken place in south central Madagascar during the Holocene.