A new inioid (Cetacea, Odontoceti, Delphinida) from the Miocene of Peru and the origin of modern dolphin and porpoise families

Abstract

In this paper we describe Brujadelphis ankylorostris gen. nov., sp. nov., a new delphinidan (Cetacea,
\nOdontoceti, Delphinida), based on a well-preserved skull with ear bones, associated mandibles, most of the teeth
\nin situ and a fragment of the atlas, from the late middle to early late Miocene (Serravallian to early Tortonian) of
\nthe Pisco Formation, Pisco Basin, Peru. The new taxon differs from all other delphinidans in the following unique
\ncombination of character states: partial ankylosis of the thickened premaxillae above the mesorostral groove;
\npresence of premaxillary eminences; premaxilla does not contact nasal; inflated nasals with a transversely convex
\ndorsal surface; presence of an internasal fossa; and a longitudinal crest on the vertex formed by transversely
\npinched frontals. Our cladistic analyses of a supermatrix that includes molecular and morphological data
\nidentifies B. ankylorostris as an inioid (Iniidae + Pontoporiidae) that is more closely related to Inia than to
\nPontoporia. This result persists even if a molecular scaffold based on published Bayesian analyses is used. The
\ninclusion of a large sample (12 taxa) of ‘kentriodontids’ allows us to confirm the paraphyly of this group of
\narchaic Miocene delphinidans but contradicts the prevailing views in placing all of these taxa outside of
\nDelphinoidea (Delphinidae + Monodontidae + Phocoenidae). In our unconstrained analysis ‘kentriodontids’ are
\nsplit into five separate clades that occur along the stem of Inioidea + Delphinoidea. Based on our most
\nparsimonious trees, we discuss published calibration points for molecular divergence estimates within Odontoceti
\nand propose one new point: 18 Ma for an unnamed clade including Delphinida + Ziphiidae.