Alisphenoid-mastoid region comparisons in lateral view in four species of Thomasomys: A T. otavalo sp. nov. (MECN 6912, holotype); B T. ucucha (MECN 7937); C T. igor sp. nov. (MECN 702, holotype); D T. silvestris (MECN 4928). Arrow in (B) illustrated to upper edge of the mastoid that exceed the edge of the subsquamosal fenestra; while the oblique dotted line indicates the suture between the squamosal and parietal. Abbreviations: hp, hamular process of squamosal; exo, exoccipital; ip, interparietal; pa, parietal; lpp, lateral parietal portion; mas, mastoid; mf, mastoid fenestra; pgf, postglenoid foramen; sq, squamosal; ssf, subsquamosal fenestra; zps, zygomatic process of the squamosal bone. For ease of comparison are not included to scale