The first pre-Pleistocene cetacean from Madagascar, western Indian Ocean

Abstract

A single lumbar vertebra from a small dolphin (Cetacea: Odontoceti) from the island of Nosy Makamby, is the first cetacean fossil reported from Madagascar. Benthic foraminifera in the associated bioclastic limestone indicate a warm, shallow-water marine setting, and are consistent with a strontium date of 9.7 Ma (early Tortonian, early late Miocene age). The elongate vertebral body is subrhomboidal in anterior section, with obliquely descending transverse processes. The neural spine is transversely narrow, tall, and anteroposteriorly elongate, with a notched posterior margin. There are no close matches with extant species representing the major clades of Odontoceti (Physeteridae, Kogiidae, Ziphiidae, Platanistidae, Inioidea, and Delphinoidea). Amongst fossils, there is some similarity with the much larger stem-platanistid Zarhachis flagellator (marine middle Miocene, Maryland). The Malagasy fossil is one of few Cetacea reported from around the Indian Ocean beyond India, Pakistan and Sri Lanka.