索齿兽

索齿兽属; 化石时期：渐新世至中新世 PreЄ Є O S D C P T J K Pg N
科学分类
界：	动物界 Animalia
门：	脊索动物门 Chordata
纲：	哺乳纲 Mammalia
目：	†索齿兽目 Desmostylia
科：	†索齿兽科 Desmostylidae
属：	†索齿兽属 Desmostylus; Marsh, 1888
种
	金星索齿兽 †D. hesperus (模式种) Marsh 1888; †D. coalingensis; Reinhart 1959; †D. japonicus; Tokunaga & Iwasaki 1914;
异名
	†Vanderhoofius coalingensis;

索齿兽（学名：Desmostylus^[1]），又名戴斯莫兽或束齿兽，是已灭绝的草食性哺乳动物，生存于 28.4 - 7.250 百万年前^[2]的渐新世晚期（恰特期）。

描述

索齿兽像河马，长约1.8米（6英尺）及重200千克（440英磅）。牠有短的尾巴及强壮的四肢，肢上有四蹄。牠们的颚部较长，有向前的獠牙，是较长的犬齿及门齿^[3]。索齿兽可能是完全水栖的，最早被认为生活在沿岸水深少于 30 米深的浅水区^[4]；不过近年来针对索齿兽化石同位素的分析研究显示，牠们其实多半栖息于淡水或河口流域，以水草为食^[5]。

索齿兽具有较低的骨质密度，这代表牠们可能是很活跃的水生生物，会在水面与水中游动寻找食物；这与其他索齿兽目的物种有很大的区别，其他索齿兽目的物种多半仅能进行缓慢的游泳或是在海床上行走^[6]。

物种

目前索齿兽属正式成立的物种共有 3 种：D. hesperus（异名与无效名：D. watasei、D. cymatias、D. californicus、D. mirabilis、D. minor、Desmostylella typica^[2]）、D. coalingensis（异名：Vanderhoofius coalingensis^[7]^[8]）与 D. japonicus。

Marsh 1888根据在美国加利福尼亚州费利蒙地区（座标：37°36′N 121°54′W / 37.6°N 121.9°W / 37.6; -121.9、古座标：36°48′N 117°36′W / 36.8°N 117.6°W / 36.8; -117.6）^[9]所找到的部分牙齿化石将模式种命名为 D. hesperus。马什爵士认为这个样本属于海牛目，并认为属于 Metaxytherium（英语：Metaxytherium）属（已绝种的儒艮近亲）或是 Halicore属（儒艮的过时名）^[10]。

在这之后许多索齿兽的新物种根据牙齿的特征差异而被发表。不过在这之后都被认为仅是 D. hesperus 的异名，因为同种之间的牙齿比起不同物种间本身就能具有很大的牙齿型态差异^[11]。

D. japonicus 由 Yoshiwara & Iwasakai 1902 根据完整保存的部分颅骨进行发表并由 Tokunaga & Iwasaki 1914 进行命名，由于颅骨型态的差异而被确立为一新种^[11]。

化石分布

索齿兽的化石在北环太平洋地区均有发现，包括下加利福尼亚半岛、加利福尼亚州、俄勒冈州、华盛顿州、库页岛、北海道、岛根县^[2]。

参考文献

^ "Bound pillar", from Greek δεσμός (desmos), bond, and στῦλος (stulos), pillar, referring to the shape of the molars.
^ ^2.0 ^2.1 ^2.2 Desmostylus. Paleobiology Database. . Retrieved March 2013.
^ Palmer 1999，第228页
^ 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.
^ Clementz, Hoppe & Koch 2003
^ Hayashi, S.; Houssaye, A.; Nakajima, Y.; Chiba, K.; Ando, T.; Sawamura, H.; Inuzuka, N.; Kaneko, N.; Osaki, T. Bone Inner Structure Suggests Increasing Aquatic Adaptations in Desmostylia (Mammalia, Afrotheria). PLoS ONE. 2013, 8 (4): e59146. OCLC 837402105. PMC 3615000 . PMID 23565143. doi:10.1371/journal.pone.0059146.
^ Tomida & Ohta 2007，第60页
^ Inuzuka, Domning & Ray 1984
^ Mission San Jose, east (Miocene of the United States). Fossilworks. [December 2013]. （原始内容存档于2016-03-04）.
^ Marsh 1888，第96页
^ ^11.0 ^11.1 Uno & Kimura 2004，第1页

Barry Cox, Colin Harrison, R.J.G. Savage, and Brian Gardiner. (1999): The Simon & Schuster Encyclopedia of Dinosaurs and Prehistoric Creatures: A Visual Who's Who of Prehistoric Life. Simon & Schuster.

Clementz, Mark T.; Hoppe, Kathryn A.; Koch, Paul L. A paleoecological paradox: the habitat and dietary preferences of the extinct tethythere Desmostylus, inferred from stable isotope analysis. Paleobiology. 2003, 29 (4): 506–519. OCLC 211272891. doi:10.1666/0094-8373(2003)029<0506:APPTHA>2.0.CO;2.
Inuzuka, Norihisa; Domning, Daryl P.; Ray, Clayton E. Summary of taxa and morphological adaptations of the Desmostylia. Island Arc. 1984, 3 (4): 522–537. doi:10.1111/j.1440-1738.1994.tb00131.x.
Marsh, O. C. Notice of a new fossil sirenian, from California. American Journal of Science. 1888, 25 (8): 94–96 [December 2013]. OCLC 79838746. 简明摘要 (December 2013).
Palmer, Douglas. The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. 1999. ISBN 1-84028-152-9. OCLC 313633743.
Reinhart, Roy Herbert. A review of the Sirenia and Desmostylia. University of California Publications in Geological Sciences. 1959, 36 (1): 1–146. OCLC 3474601.
Tokunaga, S.; Iwasaki, C. Notes on Desmostylus japonicus (PDF). 1914 [December 2013].
Tomida, Yukimitsu; Ohta, Toshikazu. Discovery of a desmostylian tooth from Kitami City, northeastern Hokkaido, Japan (PDF). Memoir of the Fukui Prefectural Dinosaur Museum. 2007, 6: 57–61 [December 2013].
Uno, Hikaru; Kimura, Masaichi. Reinterpretation of some cranial structures of Desmostylia hesperus (Mammalia, Desmostylia): A new specimen from the Middle Miocene Tachikaraushinai Formation, Hokkaido, Japan (PDF). Paleontological Research. 2004, 8 (1): 1–10 [December 2013]. doi:10.2517/prpsj.8.1.
Yoshiwara, S.; Iwasaki, J. Notes on a New Fossil Mammal (PDF). Journal of the College of Science, Imperial University, Tokyo, Japan. 1902, 16 [December 2013].

[1] "Bound pillar", from Greek δεσμός (desmos), bond, and στῦλος (stulos), pillar, referring to the shape of the molars.

[Paleodb36958-2] 2.0 ^2.1 ^2.2 Desmostylus. Paleobiology Database. . Retrieved March 2013.

[EoDP-3] Palmer 1999，第228页

[4] 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.

[5] Clementz, Hoppe & Koch 2003

[Hayashi2013-6] Hayashi, S.; Houssaye, A.; Nakajima, Y.; Chiba, K.; Ando, T.; Sawamura, H.; Inuzuka, N.; Kaneko, N.; Osaki, T. Bone Inner Structure Suggests Increasing Aquatic Adaptations in Desmostylia (Mammalia, Afrotheria). PLoS ONE. 2013, 8 (4): e59146. OCLC 837402105. PMC 3615000 . PMID 23565143. doi:10.1371/journal.pone.0059146.

[Tomida-7] Tomida & Ohta 2007，第60页

[Inuzuka-8] Inuzuka, Domning & Ray 1984

[9] Mission San Jose, east (Miocene of the United States). Fossilworks. [December 2013]. （原始内容存档于2016-03-04）.

[10] Marsh 1888，第96页

[Uno-Kimura-11] 11.0 ^11.1 Uno & Kimura 2004，第1页

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