Myocastor Kerr, 1792 . In Linnaeus, Anim. Kingdom, p. 225.

TYPE SPECIES: Mus coypus Molina, 1782 .

SYNONYMS: Mastonotus, Myopotamus, Potamys.

COMMENTS: Myocastor is not a capromyid and was referred to the family Myocastoridae by Ameghino (1904) and Woods and Howland (1979:114). Although Patterson and Pascual (1968b:6) included Myocastor and several fossil forms as the subfamily Myocastorinae of the Echimyidae, it is generally agreed that Myocastor is not an echimyid.