''Zarhinocetus'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

whale Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...

from the Early to Middle

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

of the eastern North Pacific.

Description

''Zarhinocetus'' is a member of Allodelphinidae, a family of primitive dolphins related to the

South Asian river dolphin South Asian river dolphins are toothed whales in the genus ''Platanista'', which inhabit fresh water habitats in the northern Indian subcontinent. They were historically considered to be one species (''P. gangetica'') with the Ganges river dolp ...

, measuring in length. The rostrum is narrow and elongated, and the teeth are both polydont and heterodont. ''Zarhinocetus'' is distinguished from other allodelphinids in having a depressed medial part of dorsal surface of proximal part of rostrum, enlarged tubercle present on dorsolateral surface of maxilla anterior to antorbital notch, supraorbital process of frontal thicker dorsoventrally, anteroposteriorly-oriented crest present on dorsal surface of supraorbital process of maxilla, bony orbit of larger diameter, dorsal exposures of frontals on cranial vertex asymmetrical with midline suture located to left of cranial midline, zygomatic process of squamosal nearly rectangular in lateral view rather than arc shaped, nuchal crest curving anteriorly at apex posterior to cranial vertex, occipital shield larger and more vertically oriented, occipital condyles proportionally larger; petrosal more massive, with anterior process more robust, posterior process shorter, posterior articular facet for tympanic bulla smaller; tympanic bulla with outer lip more inflated.Toshiyuki Kimura and Lawrence G. Barnes (2016). "New Miocene fossil Allodelphinidae (Cetacea, Odontoceti, Platanistoidea) from the North Pacific Ocean". Bulletin of the Gunma Museum of Natural History 20: 1–58.

Taxonomy

The type species, ''Zarhinocetus errabundus'', was originally described as a new species of ''

Squalodon ''Squalodon'' is an extinct genus of whales of the Oligocene and Miocene epochs, belonging to the family Squalodontidae. Named by Jean-Pierre Sylvestre de Grateloup in 1840, it was originally believed to be an iguanodontid dinosaur but has since ...

'', ''S. errabundus''. Later authors recognized it as generically distinct from ''Squalodon'', and in 2009 the name ''Zarhinocetus'' was coined for ''S. errabundus''.Barnes, L. G. and Reynolds, R. E. (2009): A new species of Early Miocene allodelphinid dolphin (Cetacea, Odontoceti, Platanistoidea) from Cajon Pass, southern California, U.S.A. Museum of Northern Arizona Bulletin, 65:483-507.

Biology

The nature of the sediments in which ''Zarhinocetus'' has been found denotes a neritic environment for the genus. The advanced degree of telescoping in the cranium shows that it could track prey using echolocation.

References

{{Taxonbar, from=Q24915049 Prehistoric toothed whales Miocene cetaceans Prehistoric cetacean genera Fossil taxa described in 2009