Abstract

The fossil record of odontocetes (toothed cetaceans) is relatively scarce during the Oligocene and early Miocene compared with later in the Miocene and Pliocene; most of the odontocete families from these epochs are known by a limited number of species and specimens. Among those, Squalodelphinidae is a family of small- to medium-sized platanistoids with single-rooted teeth, which until now has included only four genera based on diagnostic material, from the early Miocene of Europe, Argentina, and North America. Recent field work in the Pisco-Ica desert, southern coast of Peru, has resulted in the discovery of several marine vertebrate-rich localities in various levels of the late Oligocene–early Miocene Chilcatay Formation. Based on three specimens from Ullujaya and Zamaca, including two well-preserved skulls with periotics, we describe a new squalodelphinid genus and species, Huaridelphis raimondii. This new species increases the early Miocene diversity of the family and is also its smallest known member. It further differs from other squalodelphinids by its thin antorbital process of the frontal, abruptly tapering rostrum, and higher tooth count. A more fragmentary skull, from Zamaca, is referred to Squalodelphinidae aff. H. raimondii. This skull provides information on the morphology of the tympanic, malleus, and incus, currently unknown in H. raimondii. Focusing on platanistoids with single-rooted teeth, our phylogenetic analysis suggests that Squalodelphinidae are monophyletic and confirms the sister-group relationship between the latter and Platanistidae. The relationships within Squalodelphinidae are not fully resolved, but H. raimondii might be one of the earliest diverging taxa.