Most Vertebrates have symmetrical skulls, although there are some exceptions to this. The most obvious of these is found in the Flatfish, Pleuronectiformes, where both eyes have migrated to the same side of the head, enabling Fish to lie flat on the seabed. Among Tetrapods, asymmetric skulls have appeared in two groups, and in both is associated with positioning of the ears so that these can be used to locate prey when hunting. Many Owls, Strigiformes, have developed highly asymmetric skulls as part of a suite of adaptations which enable them to fly and hunt in light conditions which other Birds avoid. Among Whales, Cetacea, this trait has evolved at least twice, amongst the early-diverging Archaeocetes, a group known only from fossils and whose behaviour in life we can only speculate about, and in the extant Toothed Whales, Odontoceti, where it is combined with echo-location to give these Marina Mammals a formidable hunting capability.
Cranial asymmetry is found in the earliest known Sperm Whales, Physeteroidea, along with the development of a supercranial basin, which holds the spermaceti organ, which is used to make the clicks used in the echolocation used by these Whales. Only three species of Sperm Whale are alive today, the True Sperm Whale, Physeter macrocephalus, the Dwarf Sperm Whale, Kogia sima, and the Pygmy Sperm Whale, Kogia pusilla. However their fossil record shows they were once a much more diverse group, with considerable morphological variation, and therefore implied ecological variation, developing soon after the group first appeared in the Miocene.
In a paper published in the journal Communications Biology on 9 November 2026, Aldo Benites-Palomino of the GeoZentrum Nordbayern at Friedrich-Alexander-Universität Erlangen-Nürnberg, the Department of Paleontology at the University of Zurich, and the Departamento de Paleontología de Vertebrados at the Museo de Historia Natural-Universidad Nacional Mayor de San Marcos, Marcelo Sánchez-Villagra, also of the Department of Paleontology at the University of Zurich, Florencia Paolucci of the División Paleontología Vertebrados at the Universidad Nacional de la Plata, Jorge Vélez-Juarbe of the Department of Mammalogy at the Natural History Museum of Los Angeles County, Alberto Collareta of the Dipartimento di Scienze della Terra at the Università di Pisa, Apolline Alfsen of the Department of Evolutionary Morphology at the Museum für Naturkunde, Alton Dooley of the Western Science Center, Dan Omura of the Centro de Desarrollo para la Educación Lima Nikko of the Asociación Peruano Japonesa, Mario Urbina, also of the Departamento de Paleontología de Vertebrados at the Museo de Historia Natural-Universidad Nacional Mayor de San Marcos, Rodolfo Salas-Gismondi, again of the Departamento de Paleontología de Vertebrados at the Museo de Historia Natural-Universidad Nacional Mayor de San Marcos, and of the Laboratorios de Investigación y Desarrollo at the Universidad Peruana Cayetano Heredia, and Gabriel Aguirre-Fernández, once again of the Department of Paleontology at the University of Zurich, describe a new species of Pygmy Sperm Whale from the Late Miocene Pisco Formation of southern Peru, with a distinctly asymmetrical skull.
The new species is described from a single partial skull (MSUM 972), lacking the squamosal and lateralmost portion of the frontal on the left side of the cranium. This was excavated from an exposure of the Pisco Formation at Aguada de Lomas in the Bella Unión District of Caravelí Province. The sediments here deposit were laid down during a marine transgression between 6.3 and 5.6 million years ago, close to the end of the Miocene.
The new species is placed in the extinct genus Scaphokogia, which already contains two species, Scaphokogia cochlearis and Scaphokogia totajpe. The genus Scaphokogia is thought to be related, but not ancestral, to the modern genus Kogia, with specimens known from the Late Miocene Pisco Formation in Peru and the Pliocene Tirabuzon Formation of Baja California, suggesting a rather limited geographical range. It is given the specific name huachafo, which in Peru is used to describe something surprising or unusual.
The rostrum of Scaphokogia huachafo is notably more robust than seen in other members of the genus, due to the presence of extensive pachyostotic bone and partial ossification of the mesethmoid (nose) cartilage. It has eight large and well-defined maxillary alveoli (tooth sockets in the upper jaw), but these are filled with spongey bone, but were lost or reabsorbed at some point, possibly associated with maturity.
The facial region is distinctly asymmetric, with both the nares (nostrils) on the left side of the face, and the left nostril being larger than the right. There is a robust antorbital notch on the right side, whereas on the left there is a laminar process which extends both forward and backward of its equivalent on the right. The absence of distortion elsewhere in the skull suggests that this is not the result of injury or post mortem distortion of the skull.
The asymmetric cranian modifications of Scaphokogia huachafo are considered by Benites-Palomino et al. to be too specialised for a role in echolocation. Instead they suggest that they are indicative of a specialised feeding mode, probably hunting benthic prey with one side of the face pressed into the sediment for long periods. The Pisco Formation is noted for an abundance of benthic Invertebrate fauna, and has yielded other Vertebrates which appear to have specialised in feeding on these.
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