[1] It contains two extant and one fossil species, found in Argentina, Brazil and Paraguay.

They are as follows: The genus name Euryzygomatomys derives from the three Ancient Greek words εὐρύς (eurús, or eury), meaning "wide, or which extends in width", ζύγωμα or ζύγωματος (zúgōma, zúgōmatos), meaning "a part of the forehead, or the zygomatic bone", and μῦς (mûs), meaning "mouse, rat".

Analyses of craniodental characters proposed that Euryzygomatomys — and also Clyomys — may be associated with Carterodon.

[5][6] However, molecular data suggest the polyphyly of this assemblage of fossorial genera.

[7] Trinomys (Atlantic spiny rats) Clyomys Euryzygomatomys (guiaras) Carterodon (Owl's spiny rat) Plagiodontia Geocapromys Capromys (Desmarest's hutia) Mesocapromys Mysateles