Ashorocetus Temporal range: Oligocene, Chattian PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Artiodactyla
Infraorder:	Cetacea
Family:	†Aetiocetidae
Genus:	†Ashorocetus Barnes et al. 1995
Species
†A. eguchii (type) Barnes et al. 1995

Ashorocetus is a monotypic genus of an extinct primitive baleen whale of the family Aetiocetidae. It was named by Barnes et al. 1995, and contains one species, A. eguchii. Fossils of this whale are found from the Chattian Morawan formation, near Ashoro, of upper Oligocene (28.4 to 23.03 million years ago) Hokkaido, Japan (43°18′N 143°48′E / 43.3°N 143.8°E / 43.3; 143.8, paleocoordinates 44°36′N 141°24′E / 44.6°N 141.4°E / 44.6; 141.4).^[1][2] Ashorocetus eguchii was described based on a partial skull and is named after the type locality and Kenichiro Eguchi of the Ashoro Museum of Paleontology.^[3]

Barnes et al. 1995 described four new aetiocetid species, of whom Ashorocetus eguchii was the most primitive. It has a neatly telescoped skull and is closely related to Chonecetus, another primitive aetiocetid. Barnes et al. also described Morawanocetus yabukii, a more derived species with a foreshortened braincase, intermediate between Chonecetus and Aetiocetus; Aetiocetus tomitai, the most primitive Aetiocetus discovered; and Aetiocetus polydentatus, the most derived Aetiocetus with a highly telescoped cranium and both homodont and polydont dentition. Barnes et al. also proposed three subfamilies for Aetiocetidae (Chonecetinae, Morawanocetinae, and Aetiocetinae) to reflect this proposed evolution within the family.^[4] The placement of A. polydentatus in Aetiocetus has, however, been questioned, as has the monophyly (and therefore the proposed subfamilies) of Aetiocetidae.^[5]

• Aetiocetus
• Chonecetus
• Morawanocetus
• Willungacetus

• Barnes, L. G.; Kimura, M.; Furusawa, H.; Sawamura, H. (1995). "Classification and distribution of Oligocene Aetiocetidae (Mammalia; Cetacea; Mysticeti) from western North America and Japan". The Island Arc. 3 (4): 392–431. doi:10.1111/j.1440-1738.1994.tb00122.x.
  • "L. G. Barnes et al. 1995". Fossilworks. Archived from the original on 5 July 2022.
• Deméré, T. A.; Berta, A. (2008). "Skull anatomy of the Oligocene toothed mysticete Aetioceus weltoni (Mammalia; Cetacea): implications for mysticete evolution and functional anatomy" (PDF). Zoological Journal of the Linnean Society. 154 (2): 308–352. doi:10.1111/j.1096-3642.2008.00414.x.
  • "†Ashorocetus Barnes et al. 1995 (whale)". Fossilworks.
• Rose, Kenneth David; Archibald, J. David (2005). The Rise of Placental Mammals. JHU Press. p. 236. ISBN 0-8018-8022-X.