A key to known species of Microphysogobio in the Yangtze River Basin

1a. Lip papillae system undeveloped........................... Microphysogobio microstomus (middle and lower reaches)

1b. Lip papillae system developed.......................................................................... .. 2

2a. Width of cutting edge on upper jaw larger than half mouth width, midventral region scaleless before pelvic-fin insertion................................................................... Microphysogobio nudiventris (middle reaches)

2b. Width of cutting edge on upper jaw smaller than half mouth width.............................................. 3

3a. Midventral region scaleless before two-thirds of the distance from the pectoral-fin insertion to the pelvic-fin insertion............................................................ Microphysogobio kiatingensis (upper and middle reaches)

3b. Midventral scaleless region only before pectoral-fin insertion.................................................. 4

4a. Air-bladder length smaller than eye diameter............................................................... 5

4b. Air-bladder length equal to eye diameter, central anterior papillae equal or slightly larger than all other papillae on upper lip, vertebral counts 4+32................................................. Microphysogobio bicolor (middle reaches)

5a. Vertebal counts 4+30–31, lateral-line scales 35–37.......................... Microphysogobio zhangi (middle reaches)

5b. Vertebal counts 4+34, lateral-line scales 38–39............................................................................................. Microphysogobio tungtingensis (rivers of Lake Dongting System in the middle reaches)