Key to the species of Cathorops from the Mesoamerica and Caribbean Sea

1. Lateral and mesial surfaces of first and second gill arches with fleshy papillae intercalated with the gill rakers, papillae more developed on second arch (Fig. 3b); 14-16 gill rakers on first arch; 13-16 gill rakers on second arch ..................................... 2

1’. Lateral and mesial surfaces of first and second gill arches without fleshy papillae intercalated with the gill rakers (Fig. 3a); 16 to 23 gill rakers on first arch; 16 to 22 gill rakers on second arch ............................................................................................ 3

2. Snout length 9.3-11.6% SL (Fig. 4); distance from tip of snout to dorsal-fin origin 39.0-40.7% SL (Fig. 5) .... Cathorops aguadulce

2’. Snout length 6.0-8.6% SL (Fig. 4); distance from tip of snout to dorsal-fin origin 33.1-38.0% SL (Fig. 5).... Cathorops kailolae

3. Head length 22.3-23.0% SL; distance from tip of snout to posterior margin of dorsomedian groove of neurocranium 17.9- 19.1% SL; pelvic and pectoral fins with intense black pigmentation; posterior margin of pectoral-fin spine with conspicuous and long serrations (Fig. 20) .......................................................................................................................... Cathorops melanopus

3’. Head length 23.3-31.9% SL; distance from tip of snout to posterior margin of dorsomedian groove of neurocranium 20.2- 27.3% SL; pelvic and pectoral fins with pale pigmentation; posterior margin of pectoral-fin spine with inconspicuous and short serrations (Figs. 8 and 13)......................................................................................................................................................... 4

4. Dorsal-fin spine 15.9-17.6% SL (Fig. 9); dorsal-fin spine length 29.4-33.3% of distance from tip of snout to pelvic-fin origin; dorsal-fin spine as long as pectoral-fin spine................................................................................................ Cathorops belizensis

4’. Dorsal-fin spine 18.6-24.2% SL (Fig. 9); dorsal-fin spine length 35.1-48.3% of distance from tip of snout to pelvic-fin origin; dorsal-fin spine longer than pectoral-fin spine................................................................................................................................ 5

5. Cephalic shield with very few granules (Fig. 13); supraoccipital process length 22.3-32.6% of maxillary barbel length (Fig. 14); supraoccipital process length 32.8-48.3% of external mental barbel length........................................ Cathorops higuchii

5’. Cephalic shield densely granulated; supraoccipital process length 35.5-51.4% of maxillary barbel length (Fig. 14); supraoccipital process length 51.5-81.2% of external mental barbel length...................................... Cathorops mapale species group