Archaebalaenoptera eusebioi, a new rorqual from the late Miocene of Peru (Cetacea, Mysticeti, Balaenopteridae) and its impact in reconstructing body size evolution, ecomorphology and palaeobiogeography of Balaenopteridae

Archaebalaenoptera eusebioi is a new late Miocene (Tortonian) balaenopterid species from the Aguada de Lomas locality in the Pisco Formation, Peru. It is dated to 8.85–7.93 Ma and is represented by a nearly complete skull with cervical vertebrae. Its inferred body length and mass are respectively c. 7 m and 7–11 tonnes. Archaebalaenoptera eusebioi is characterized by a short and wide rostrum, outward bowed dentary with typical balaenopterid characters in the posterior portion (posteriorly faced articular surface of the mandibular condyle, comparatively long distance between condyle and coronoid process, vestigial postcoronoid crest and fossa) and wide temporal fossa with scarcely protruding temporal crest and posteriorly placed posterior apex of nuchal crest. Its morphology suggests that it fed similarly to the modern balaenopterid whales but with a comparatively wider gape and, possibly, with a limited number of ventral throat grooves. Palaeobiogeographical analysis shows that Archaebalaenoptera originated in the North Atlantic and the invasion of South Pacific and Mediterranean occurred by subsequent dispersal events. Our results suggest that the North Atlantic acted as a centre of origin for many balaenopterid radiations and as a starting basin for recurrent invasions of other oceanic basins.