Rodrigo B. Salvador

A new species of giant petrel, Macronectes tinae sp. nov., is described from the Pliocene deposits of South Taranaki, New Zealand. The holotype is a near complete skull and the paratype a fragmentary left humerus; both come from the Tangahoe Formation, dating from the late Pliocene (Piacenzian or “Waipipian”; age estimated as ca. 3.36–3.06 Ma). The new species of giant petrel is the first fossil Macronectes ever reported. It is morphologically similar to the two present-day Macronectes spp., but it was a smaller bird. The skull is diagnosed by its overall smaller size, a proportionately longer apertura nasi ossea, and potentially by a shorter os supraocciptale. The humerus is diagnosed from both species by a proportionately less deep shaft, a more prominent medial portion of the epicondylus ventralis, and a larger and fusiform fossa medialis brachialis. The Tangahoe Formation is proving to be a remarkable source of marine vertebrate fossils and an important piece of the puzzle in understanding the evolution and biogeography of seabirds.