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  • Cited by 3
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    This chapter has been cited by the following publications. This list is generated based on data provided by CrossRef.

    Li, Lüzhou Li, Qiang Lu, Xiaoyu and Ni, Xijun 2017. Morphology of an Early Oligocene beaver Propalaeocastor irtyshensis and the status of the genus Propalaeocastor. PeerJ, Vol. 5, Issue. , p. e3311.

    Samuels, Joshua X. Albright, L. Barry and Fremd, Theodore J. 2015. The last fossil primate in North America, new material of the enigmaticEkgmowechashalafrom the Arikareean of Oregon. American Journal of Physical Anthropology, Vol. 158, Issue. 1, p. 43.

    Calede, Jonathan Jean-Michel 2014. Skeletal Morphology of Palaeocastor peninsulatus (Rodentia, Castoridae) from the Fort Logan Formation of Montana (early Arikareean): Ontogenetic and Paleoecological Interpretations. Journal of Mammalian Evolution, Vol. 21, Issue. 2, p. 223.

  • Print publication year: 1996
  • Online publication date: July 2010

20 - Castoridae



North American Eocene-Oligocene beavers compise 18 species in 7 genera, including one new genus (Nannasfiber) and 5 new species (Capacikala parvus, Capatanka minor, Euhapsis luskensis, Nannasfiber ostellatus, and Nannasfiber osmagnus). They can be divided into three groups. The first includes only Agnotocastor; the second group consists of Palaeocastor and Capacikala; the third group includes Capatanka, Euhapsis, Nannasfiber, and Fossorcastor. Differences among the three groups are recognized from skull, mandible, and dental patterns. During their evolution in the Chadronian through the Arikareean, dental pattern becomes simpler, and skull shape becomes diversified.

The only beaver represented in the Chadronian and Orellan is Agnotocastor, which survived into the carliest Arikareean. Palaeocastor first appeared in the Whitneyan, but was most abundant in the early Arikareean. A radiation of beavers took place in the early Arikareean when 4 castorid genera (Capacikala, Capatanka, Euhapsis, and Fossorcastor) first appeared. The rapid evolution and radiation of the Arikareean beavers make them excellent biochronological correlation tools. Palaeocastor and Capatanka are significant references for the early early Arikareean; Capacikala comes from the early Arikareean; Nannasfiber implies an early late Arikareean age; Euhapsis and Fossorcastor are known from the late early through late late Arikareean.


The North American Eocene-Oligocene beavers range from the Chadronian through the Arikareean. Previously described genera include Agnotocastor, Palaeocastor, Capacikala, Capatanka, Euhapsis, Pseudopalaeocastor, and Fossorcastor (Stirton, 1935; Wilson, 1949a, b; Emry, 1972; J. Macdonald, 1963, 1970; L. Macdonald, 1972; Martin, 1987).

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The Terrestrial Eocene-Oligocene Transition in North America
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