Abstract
Nowadays, the odontocete family Kogiidae is monotypic and only includes two species of diminutive relatives of the great sperm whale Physeter Linnaeus, 1758. Conversely, a growing body of extinct species indicates that kogiids were diverse and disparate during the late Neogene. The fossil record of Kogiidae is, to date, represented by several cranial specimens from Mio-Pliocene localities of the Northern Hemisphere, with the significant Southern Hemisphere exception of the Pisco Formation of Peru, from which two genera were known so far, including Scaphokogia Muizon, 1988, a highly idiosyncratic form characterised by a distinctly spoon-shaped dorsal surface of the neurocranium and a downturned semicylindrical rostrum, which is even placed in its own subfamily Scaphokogiinae. Here, we report on two skulls of Kogiidae from the Messinian (upper Miocene) portion of the Pisco Formation exposed in the East Pisco Basin. These two skulls are referred to the new taxon Platyscaphokogia landinii n. gen., n. sp., which our phylogenetic analysis recovers as sister group of Scaphokogia, within the subfamily Scaphokogiinae. Although Platyscaphokogia n. gen. shares with Scaphokogia a remarkably spoon-like dorsal aspect of the neurocranium, it retains a non-pachyostotic, dorsoventrally thin rostrum that distinctly points anteriorly; as such, Platyscaphokogia n. gen. might be regarded as testifying an early stage in the evolution of the scaphokogiine cranial anatomy. Morphofunctional and palaeoecological considerations allow for hypothesising that Platyscaphokogia n. gen. was a raptorial physeteroid that foraged along the water column in relatively open-sea palaeoenvironments. In conclusion, our finds expand the palaeodiversity of Kogiidae, as well as our knowledge on the late Miocene sperm whales of the southeastern Pacific, and further suggest that the fossil content of the East Pisco Basin is crucial for reconstructing the Neogene evolutionary history of physeteroids.
Highlights
IntroductionThe family Kogiidae (Cetacea: Odontoceti: Physeteroidea) is currently represented by two species of physeteroid toothed whales, namely, Kogia sima (Owen, 1866) (the dwarf sperm whale) and Kogia breviceps (de Blainville, 1838) (the pygmy sperm whale)
The family Kogiidae (Cetacea: Odontoceti: Physeteroidea) is currently represented by two species of physeteroid toothed whales, namely, Kogia sima (Owen, 1866) and Kogia breviceps
Two genera and species of kogiids – namely, Koristocetus pescei Collareta, Lambert, Muizon, Urbina & Bianucci, 2017 and Scaphokogia cochlearis Muizon, 1988 – are currently known from the upper Miocene portion of the Pisco Formation of southern Peru; whereas the former has been recognized as an early-branching representative of the extant subfamily Kogiinae (Collareta et al 2017a), the latter is a highly idiosyncratic form, characterised by a downturned semicylindrical rostrum and a spoon-shaped dorsal surface of the neurocranium, assigned to its own subfamily Scaphokogiinae (Muizon 1988)
Summary
The family Kogiidae (Cetacea: Odontoceti: Physeteroidea) is currently represented by two species of physeteroid toothed whales, namely, Kogia sima (Owen, 1866) (the dwarf sperm whale) and Kogia breviceps (de Blainville, 1838) (the pygmy sperm whale) These small-sized and largely elusive relatives of the great sperm whale Physeter macrocephalus Linnaeus, 1758 are known as deep-diving marine mammals that inhabit tropical to temperate open-sea environments worldwide (McAlpine 2017). These specimens were discovered in upper Miocene beds exposed at the localities of Cerro Hueco la Zorra and Cerro los Quesos, in the East Pisco Basin. An analysis of the phylogenetic relationships of this new taxon and a discussion of its palaeoecological and evolutionary significance are undertaken
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