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1a. Dorsal fin long, more than 20 rays.............................................................2

1b. Dorsal fin of 18 or fewer rays..................................................................7

2a. Body long, slender, standard length more than 4 times the body depth; lateral line scales more than 50....................................................................Cycleptus elongatus Blue Sucker

2b. Body short, compressed, standard length less than 4 times the body depth; lateral line scales less than 50..........................................................................................3

3a. Anterior portion of dorsal fin protrudes into a moderate lobe with the first ray about 3 times as long as the shortest dorsal ray; mouth large, maxillary 2 times as big as eye diameter, caudal fin with no V-indentation...........................................................................4

3b. Anterior portion of dorsal fin protrudes into a long pointed lobe with the first ray about 5 times as long as the shortest dorsal ray; small mouth, maxillary equal to the diameter of the eye; caudal fin with deep fork...........................................................................5

4a. Mouth large; tip of upper lip below lower edge of eye; upper jaw shorter than snout; big lips with striated lines.................................................Ictiobus bubalus Smallmouth Buffalo

4b. Mouth large; tip of upper jaw horizontal with lower edge of eye; upper jaw as long as snout....................................................................Ictiobus cyprinellus Bigmouth Buffalo

5a. Small protuberance on tip of lower jaw; tip of lower jaw a little in front of anterior nostril; lateral line scales between 33-37.............................................................6

5b. Small protuberance absent on tip of lower jaw; tip of lower jaw in advance of anterior nostril; lateral line scales between 36-40..............................Carpiodes cyprinus Quillback

6a. Longest ray in dorsal fin in adults longer than fin base; body in adult more elongate, depth about 1/3 standard length...........................................Carpiodes velifer Highfin Carpsucker

6b. Longest ray in dorsal fin in adults less than 2/3 the length of the fin base; body in adult deep and compressed, depth about 1/2 standard length.........Carpiodes carpio River Carpsucker 

7a. Lateral line incomplete or absent in adult.......................................................8

7b. Lateral line well-developed in adult............................................................10

8a. Lateral line absent; mouth horizontal and inferior; each scale has a black spot................ Minytrema melanops Spotted Sucker

8b. Lateral line absent; mouth oblique; no regular pattern of spotted scales but may have bars or blotches on body......................................................................................9

9b. Lateral scale rows about 38; scales not crowded near head..............Erimyzon sucetta Lake Chubsucker

10a. Lateral line scales 55 or more.................................................................11

10b. Lateral line scales 50 or fewer................................................................12

11a. Snout projecting far beyond upper lip; lower lips broad and extending posteriorly beyond vertical line drawn through nostrils; more than 85 scales in lateral line...Catostomus catostomus Longnose Sucker

11b. Snout scarcely projecting beyond upper lip with lower lips thinner; less than 85 scales in lateral line..........................................................Catostomus commersoni White Sucker

12a. Head depressed between eyes (fig. 1)...Hypentelium nigricans Northern Hogsucker

12b. Head convex between eyes (fig. 2).........................................................13

13a. Scale rows around caudal fin usually 15 or 16.......................Moxostoma anisurum Greater Redhorse

13b. Scale rows around caudal fin usually 12 or 13...............................................14

14a. Lower surface of lips have fine ridges; papillae; posterior margins of lower lip meet into an acute angle (fig. 3)..............................................Moxostoma anisurum Silver Redhorse

14b. Lower surface of lips plicate (fig. 4); posterior margins of lower lip meet in an obtuse angle......................................................................................................15

15a. Pharyngeal arch short, with squarish teeth (fig. 5)..................Moxostoma carinatum River Redhorse

15b. Pharyngeal arch light, with comb-like teeth (fig. 6).........................................16

16a. Head small and short about 5 times standard length.........Moxostoma macrolepidotum Shorthead Redhorse

16b. Head longer, about 4 times in standard length...............................................17

17a. Lateral line scales 44-47; body relatively long and skinny; pelvic rays 10 in one or both fins...........................................................................Moxostoma duquesnei Black Redhorse

17b. Lateral line scales 40-42; body short and staulky; pelvic rays 9 in both fins................. Moxostoma erythrurum Golden Redhorse

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