Order Testudines Wagler, 1830 - turtles
   Suborder Cryptodira Cope, 1868
     Superfamily Testudinoidea Batsch, 1788
       Family Emydidae Rafinesque, 1815 - pond turtles
         Subfamily Deirochelyinae Agassiz, 1857
           Genus Trachemys Agassiz, 1857
             Trachemys gaigeae (Hartweg, 1939) - Big Bend slider
               1 Trachemys gaigeae gaigeae (Hartweg, 1939) - Big Bend slider
               2 Trachemys gaigeae hartwegi (Legler, 1990) - Nazas slider