Myocastoridae Ameghino 1904

Wilson, Don E. & Reeder, DeeAnn, 2005, Order Rodentia - Family Myocastoridae, Mammal Species of the World: a Taxonomic and Geographic Reference (3 rd Edition), Volume 2, Baltimore: The Johns Hopkins University Press, pp. 1593-1593 : 1593

Myocastoridae Ameghino 1904

Myocastoridae Ameghino 1904 , Anales Soc. Cient. Argentina, 56-58: 103.

Genera: 1 genus with 1 species:

Genus Myocastor Kerr 1792 (1 species with 4 subspecies)

Discussion: The higher-level classification of Myocastor remains unresolved. Myocastorids presumably evolved in the Oligocene of South America from an echimyid of the subfamily Adelophomyinae ( Woods et al., 1992) . The myocastorids have been included in Capromyidae by Hall (1981), Corbet and Hill (1991), and others, included in the Echimyidae ( McKenna and Bell, 1997) , and placed in the family Myocastoridae by Ameghino (1904), Woods and Howland (1979), and Woods (1993). Patterson and Pascual (1968 b) and Patterson and Wood (1982) considered both myocastorids and capromyids to be subfamilies of the Echimyidae , based on the retention of the deciduous premolar in these taxa. Sequence data support this placement, as Leite and Patton (2002) suggested the inclusion of Myocastor and Capromys within the Echimyidae . Although Leite and Patton (2002) identified Capromys as the sister taxon of Myocastor , their placement within the Echimyidae clade is not well supported and is in need of further examination. Though myocastorids are related to echimyids and capromyids, Woods (1972, 1982) and Woods and Howland (1979) concluded that there are too many morphological differences to unite myocastorids with either of these taxa in the same family.