Myocastorini members share long upper incisor roots (except Callistomys), and mid- to long-sized lower incisor roots. These five genera share either four (Callistomys, Thrichomys) or five (Hoplomys, Myocastor, Proechimys) lophids on the lower deciduous fourth premolar, three roots anchoring the upper molars, and well-connected lophs on cheek teeth.[1]
Members display a variety of lifestyles including terrestrial (Hoplomys, Proechimys, Thrichomys), arboreal (Callistomys), and amphibious (Myocastor) adaptations.
Phylogeny
On the one hand, the genus Proechimys is the sister group to the genus Hoplomys (armored rats), and both form a clade of lowland rainforest terrestrial spiny rats. On the other hand, Callistomys (painted tree-rats) is the sister group to Myocastor (coypus). In turn, these two pairs of genera share evolutionary affinities with Thrichomys (punaré).
^Galewski, Thomas; Mauffrey, Jean-François; Leite, Yuri L. R.; Patton, James L.; Douzery, Emmanuel J. P. (2005). "Ecomorphological diversification among South American spiny rats (Rodentia; Echimyidae): a phylogenetic and chronological approach". Molecular Phylogenetics and Evolution. 34 (3): 601–615.
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^Upham, Nathan S.; Patterson, Bruce D. (2012). "Diversification and biogeography of the Neotropical caviomorph lineage Octodontoidea (Rodentia: Hystricognathi)". Molecular Phylogenetics and Evolution. 63 (2): 417–429.
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^Fabre, Pierre-Henri; Galewski, Thomas; Tilak, Marie-ka; Douzery, Emmanuel J. P. (2013-03-01). "Diversification of South American spiny rats (Echimyidae): a multigene phylogenetic approach". Zoologica Scripta. 42 (2): 117–134.
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S2CID83639441.
^Upham, Nathan S.; Patterson, Bruce D. (2015). "Evolution of Caviomorph rodents: a complete phylogeny and timetree for living genera". In Vassallo, Aldo Ivan; Antenucci, Daniel (eds.). Biology of caviomorph rodents: diversity and evolution. Buenos Aires: SAREM Series A, Mammalogical Research — Sociedad Argentina para el Estudio de los Mamíferos. pp. 63–120.