Key to the species of the genus Menticirrhus

1a. Pored scales along lateral line up to caudal fin base 62 or more ….............................................. 2

1b. Pored scales along lateral line up to caudal fin base 60 or less................................................… 3

2a. Caudal-fin posterior margin concave; pectoral-fin rays 18–20; anal-fin rays 9; pored scales along lateral line up to caudal fin base 63–66 …............................................... M. ophicephalus (eastern Pacific, Ecuador to Chile)

2b. Caudal-fin posterior margin S-shaped; pectoral-fin rays 21–23; anal-fin rays 7; pored scales along lateral line up to caudal fin base 76–98 …........................................... M. paitensis (eastern Pacific, Gulf of California to Chile)

3a. Soft dorsal fin without scales along its base ….............................................................. 4

3b. Soft dorsal fin with scales along its base …................................................................ 6 4a. Gill rakers on first arches 10–15, rarely 9; pectoral-fin tip barely reaching tip of depressed pelvic fin.........................................................................… M. undulatus (eastern Pacific, California, United States)

4b. Gill rakers on first arches 3–9; pectoral-fin tip surpassing tip of depressed pelvic fin ….............................. 5

5a. Body with faint dark streaks along scale rows on back, often with numerous dark spots on flanks; dorsal-fin spines II-IV long …....................................................... M. nasus (eastern Pacific, Gulf of California to Peru)

5b. Body with dusky silver, grayish brown on upper back; dorsal-fin spines II-IV short ….................................................................................... M. panamensis (eastern Pacific, Gulf of California to Chile)

6a. Dorsal-fin rays 18–21 (Table 3) …................... M. gracilis (western Atlantic, Southeast and South Coast of Brazil)

6b. Dorsal-fin rays 22 or more (Table 3) ….................................................................... 7

7a. Pectoral fin pale (Fig. 7A); pectoral-fin tip barely reaching tip of depressed pelvic fin (Fig. 7)…...................... 8

7b. Pectoral fin dusky (Fig. 1A); pectoral-fin tip surpassing tip of depressed pelvic fin (Fig. 1) …......................... 9

8a. Black hue at tip of upper caudal-fin lobe in live and fresh specimens (Figs. 2B, C) …............................................................................... M. littoralis (western Atlantic, United States and Gulf of Mexico)

8b. Caudal fin without darkened area in live and fresh specimens (Fig. 7) …........................................................................................ M. cuiaranensis (western Atlantic, North and East Coast of Brazil)

9a. Body without irregular dark bars ….......................... M. elongatus (eastern Pacific, Gulf of California to Peru)

9b. Body with irregular dark bars........................................................................… 10

10a. Body with seven or eight distinct oblique bars, second and third bars forming a V below spinous dorsal fin, a longitudinal stripe below lateral line extending to tip of caudal fin; spinous dorsal fin high, its tip reaching beyond base of fourth soft dorsal fin ray ….......................................... M. saxatilis (western Atlantic, United States and Gulf of Mexico)

10b. Body with eight or nine diffused bars, second and third bars forming a faint V below nape and spinous dorsal fin; spinous dorsal fin lower, not reaching base of second soft ray …........................................................... 11

11a. Dorsal profile with “hump” behind eye in some specimens (Fig. 1)........................................................................................... M. americanus (western Atlantic, United States and Gulf of Mexico)

11b. Dorsal profile slightly convex, without evident hump (Fig. 5) …............................................................................................... M. martinicensis (western Atlantic, Caribbean and South America).