Ashoroa

Ashoroa Temporal range: Chattian ~28–23  Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Mounted skeleton in Hokkaido University Museum
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	† Desmostylia
Family:	† Paleoparadoxiidae
Genus:	† Ashoroa Inuzuka, 2000 [1]
Species:	†A. laticosta
Binomial name
†Ashoroa laticosta Inuzuka, 2000

Ashoroa (named after its type locality Ashoro, Hokkaido) is an extinct genus of desmostylian, aquatic, herbivorous mammal. Fossils of Ashoroa have been found in the Morawan Formation on Hokkaido, Japan ( 43°18′N143°48′E / 43.3°N 143.8°E / 43.3; 143.8 , paleocoordinates 44°36′N141°24′E / 44.6°N 141.4°E / 44.6; 141.4 ) and were dated to the late Oligocene. ^[2]

Description

Skeletal diagram

Ashoroa is the smallest and one of the oldest desmostylians with an estimated body length of 168 cm (66 in). It is known from a rib, a humerus, a femur, and three vertebrae of the single species and holotype, Ashoroa laticosta. ^[3]

Ashoroa had pachyosteosclerotic (large and dense) bones. ^[4] The ribs are broader than in other desmostylians, similar to sirenian ribs, and very dense, like those of Behemotops and Paleoparadoxia ; and extant, semi-aquatic mammals such as Eurasian beaver and hippopotamus, but not as dense as in sirenians. The recovered long bones lack inner cavities, like in Paleoparadoxia and Desmostylus , and the trabecular pattern is different from that in Behemotops. ^[5]

Hayashi et al. 2013 interpreted Ashoroa, together with Behemotops and Paleoparadoxia. as a "shallow water swimmer, either hovering slowly at a preferred depth, or walking on the bottom". ^[4]

References

1. Ashoroa laticosta in the Paleobiology Database. Retrieved March 2013
2. Morawan (Lower Hard Shale Member) (Oligocene of Japan) in the Paleobiology Database. Retrieved March 2013.
3. Hayashi et al. 2013 , p. 2
4. Hayashi et al. 2013 , Abstract
5. Hayashi et al. 2013 , pp. 7–9, 15

Bibliography

• Inuzuka, N. (2000). "Primitive late Oligocene desmostylians from Japan and Phylogeny of the Desmostylia". Bulletin of the Ashoro Museum of Paleontology. 1: 91–123.
• Hayashi, Shoji; Houssaye, Alexandra; Nakajima, Yasuhisa; Kentaro, Chiba; Ando, Tatsuro; Sawamura, Hiroshi; Inuzuka, Norihisa; Kaneko, Naotomo; Osaki, Tomohiro (2013). "Bone Inner Structure Suggests Increasing Aquatic Adaptations in Desmostylia (Mammalia, Afrotheria)". PLOS ONE. 8 (4) e59146. Bibcode:2013PLoSO...859146H. doi: 10.1371/journal.pone.0059146 . OCLC   837402105. PMC   3615000 . PMID   23565143.