<i>Koristocetus pescei</i> gen. et sp. nov., a diminutive sperm whale (Cetacea: Odontoceti: Kogiidae) from the late Miocene of Peru

Abstract

Abstract. Among odontocetes, members of the family Kogiidae (pygmy and dwarf sperm whales) are known as smallsized and in many respects enigmatic relatives of the great sperm whale Physeter macrocephalus. Most of the still scanty fossil record of Kogiidae is represented by isolated skulls and ear bones from Neogene deposits of the Northern Hemisphere, with the significant exception of Scaphokogia, a highly autapomorphic genus from late Miocene deposits of the Pisco Formation exposed along the southern coast of Peru. Here we report on a new fossil kogiid from Aguada de Lomas, a site where the late Miocene beds of the Pisco Formation are exposed. This specimen consists of an almost complete cranium representing a new taxon of Kogiidae: Koristocetus pescei gen. et sp. nov. Koristocetus mainly differs from extant Kogia spp. by displaying a larger temporal fossa and well-individualized dental alveoli on the upper jaws. Coupled with a relatively elongated rostrum, these characters suggest that Koristocetus retained some degree of raptorial feeding abilities, contrasting with the strong suction feeding specialization seen in Recent kogiids. Our phylogenetic analysis recognizes Koristocetus as the earliest branching member of the subfamily Kogiinae. Interestingly, Koristocetus shared the southern coast of present-day Peru with members of the genus Scaphokogia, whose unique convex rostrum and unusual neurocranial morphology seemingly indicate a peculiar foraging specialization that has still to be understood. In conclusion, Koristocetus evokes a long history of high diversity, morphological disparity, and sympatric habits in fossil kogiids, thus suggesting that our comprehension of the evolutionary history of pygmy and dwarf sperm whales is still far from being exhaustive.

Extensive Diversity and Disparity of the Early Miocene Platanistoids (Cetacea, Odontoceti) in the Southeastern Pacific (Chilcatay Formation, Peru)

“…Following other works already published by us on the platanistoids from the Chilcatay Formation [24][25][26], the fossils here described further support the great diversity and morphological disparity of this clade. On the whole the Eocene-Pliocene sedimentary succession of the East Pisco Basin represents one of the most significant marine vertebrate Lagerstätte of the Cenozoic Era due to the exceptional preservation and the elevated concentration of fossils [21,22,[40][41][42][43][44][45][46] referred to cetaceans (archaeocetes [47][48][49]; odontocetes [24,25,[50][51][52][53][54][55][56][57][58][59][60][61][62]; mysticetes [10,[63][64][65][66][67][68]), pinnipeds [69,70], marine birds [71][72][73][74], marine turtles [75], marine sloths [76][77]…”

Nasal compartmentalization in Kogiidae (Cetacea, Physeteroidea): insights from a new late Miocene dwarf sperm whale from the Pisco Formation

“…The Pisco Formation exposed in the coastal desert of southern Peru (13°–16°S) has been recognized as a major diversification hotspot of sperm whales. In fact, four species of extinct kogiids have been described so far from the Pisco strata, namely: Scaphokogia cochlearis Muizon, 1988; Koristocetus pescei Collareta et al ., 2017; Scaphokogia totajpe Benites‐Palomino et al ., 2020a; and Platyscaphokogia landinii Collareta et al ., 2020. Such a broad taxonomic diversity during the late Miocene and Pliocene was not restricted to kogiids, but also applies to other physeteroids (Lambert et al ., 2016).…”

The awkward record of fossil whales

“…Silhouettes), and beaked whales (superfamily Ziphioidea) are dominant mesopelagic predators, typically diving deep along the continental slope (up to 3000 m), where cephalopods are most abundant, and avoiding the shallow shelf. The Physeteroidea, with the longest geologic history among crown Odontoceti, have included very large (Lambert et al, 2010) and small species (Collareta et al, 2017) that fed by raptorial means, showing a wider range of adaptations. Stem ziphiids probably foraged on fish at shallow depths (Lambert et al, 2015;Ramassamy et al, 2016).…”

“…5), notwithstanding they host a diverse and abundant cetacean fauna since the onset of the Antarctic Circumpolar Current (Fordyce, 2003;Marx et al, 2015). The South-Western Pacific record, with the incredibly rich and well-preserved finds in Peru (Muizon and DeVries, 1985;Gariboldi et al, 2015;Bianucci et al, 2016b) and Chile (Pyenson et al, 2014), and a younger history of research with respect to Europe and North America, reveals a still unexplored potential, where new studies based on single specimens have quickly changed our view of cetacean macroecology and macroevolution (Lambert et al, 2010(Lambert et al, , 2013(Lambert et al, , 2017a(Lambert et al, , 2017bCollareta et al, 2017;Bianucci et al, 2019aBianucci et al, , 2019b, and where much of the record needs to be taxonomically identified (e.g., Esperante et al, 2014;Gariboldi et al, 2017). A well-constrained chronostratigraphic framework has been only recently available for the highly fossiliferous Pisco Formation in the Pisco Basin, in Peru (localities Cerro Colorado and Cerro Los Quesos, Ica Desert: Gariboldi et al, 2017), and the age of the main bone beds of the Sacaco Basin, the first to be described and studied (Muizon and DeVries, 1985;Villafaña and Rivadeneira, 2014), has been lately revised (Collareta et al, 2017), so that available timings of clade divergence (e.g., McGowen et al, 2009;Marx et al, 2015) need to be revised.…”