Английская Википедия:Desmostylus

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Desmostylus[1] is an extinct genus of herbivorous mammal of the family Desmostylidae living from the Chattian stage of the Late Oligocene subepoch through the Late Miocene subepoch (28.4 mya–7.250 Mya) and in existence for approximately Шаблон:Mya.[2]

Description

Файл:Desmostylus2DB.jpg
Restoration of D. hesperus
Файл:Desmostylus Skull.jpg
Skull of D. japonicus at the National Museum of Nature and Science, Tokyo, Japan. Holotype

Desmostylus was a large, hippopotamus-like creature, with the adult Keton specimen of D. hesperus measuring Шаблон:Cvt in length, Шаблон:Cvt in height and Шаблон:Convert in body mass; the largest known humerus which is 1.3 times that of the Keton specimen in length probably belonged to an individual with a mass of Шаблон:Convert.[3] It had a short tail and powerful legs with four hooves. The animal's jaws were elongated and sported forward-facing tusks, which were elongated canines and incisors.[4]

Most likely fully aquatic, Desmostylus is thought to have lived in shallow water in coastal regions, usually less than 30 meters deep.[5] Recent isotope work indicates that Desmostylus more likely lived (or spent a large amount of time) in freshwater or estuary ecosystems foraging for aquatic freshwater plants.[6]

Its less dense bone structure suggests that Desmostylus had a lifestyle of active swimming and possibly feeding at the surface, unlike other desmostylians that were primarily slow swimmers and/or bottom walkers and sea grass feeders.[7]

Species

Desmostylus hesperus (synonyms and invalid names: D. watasei, D. cymatias, D. californicus, D. mirabilis, D. minor, Desmostylella typica),[2] D. coalingensis (syn. Vanderhoofius coalingensis),[8][9] and D. japonicus.

Шаблон:Harvnb named the type specimen D. hesperus based on a set of isolated teeth that he had found near Mission San Jose, California (type locality: Шаблон:Coord, paleocoordinates Шаблон:Coord).[10] Marsh described his specimen as a sirenian and proposed affinities with Metaxytherium (a genus of extinct dugongs) and Halicore (an obsolete name for dugong).[11]

Several other species were later described based on minor differences in tooth morphology. Most or all of these species have been synonymized with D. hesperus since variation in tooth morphology between individuals assigned to one of these species has proven to be to greater than the differences between species.[12]

Desmostylus japonicus was described by Шаблон:Harvnb based on a well-preserved partial skull and named by Шаблон:Harvnb. It has been reproposed as distinct species based on cranial morphology.[12]

Fossil distribution

Fossils have been discovered from along the northern Pacific Rim from Baja California Peninsula northward along the coast of California, Oregon, Washington and west to Sakhalin Island, Hokkaido, Japan, and south to the Shimane Prefecture, Japan.[2]

Notes

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References

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Шаблон:Paenungulata Шаблон:Taxonbar Шаблон:Authority control

  1. "bound pillar", from Greek Шаблон:Lang (desmos), bond, and Шаблон:Lang (stulos), pillar, referring to the shape of the molars.
  2. 2,0 2,1 2,2 Шаблон:Paleodb. Retrieved March 2013.
  3. Inuzuka, N. (1996). Body size and mass estimates of desmostylians(Mammalia). The Journal of the Geological Society of Japan, 102(9), 816–819. https://doi.org/10.5575/geosoc.102.816
  4. Шаблон:Harvnb
  5. Kumiko Matsui; Katsuo Sashida; Sachiko Agematsu; Naoki Kohno (2017). "Habitat preferences of the enigmatic Miocene tethythere Desmostylus and Paleoparadoxia (Desmostylia; Mammalia) inferred from the depositional depth of fossil occurrences in the Northwestern Pacific realm". Palaeogeography, Palaeoclimatology, Palaeoecology. 471: 254–265. doi:10.1016/j.palaeo.2017.02.005.
  6. Шаблон:Harvnb
  7. Шаблон:Cite journal
  8. Шаблон:Harvnb
  9. Шаблон:Harvnb
  10. Шаблон:Cite web
  11. Шаблон:Harvnb
  12. 12,0 12,1 Шаблон:Harvnb