Diagnostic key for six nominal species of Luciogobius from Taiwan and the Matsu Islands, ROC:

1a Vertebral count 3................................................................. L. newtaipeiensis sp. nov.

1b Vertebral count more than 36........................................................................... 2

2a Pectoral fin with 1 or more upper free ray(s)............................................................... 3

2b Pectoral fin without any upper free rays....................................... L. opisthoprotus Chen & Liao 2024

3a Pectoral fin with 1 upper free ray........................................................................ 4

3b Pectoral fin with more than 1 upper free ray................................................................ 5

4a Pectoral fin modally 16; vertebral count 37–38..................................... L. matsuensis Chen et al. 2024

4b Pectoral fin modally 13; vertebral count 41............................................. L. chaojinensis sp. nov.

5a Second dorsal fin modally I/15; pectoral fin with 4 upper free rays; vertebral count 39.......... L. huatungensis sp. nov.

5b Second dorsal fin I/16; pectoral fin with 3 upper free rays; vertebral count 41........... L. dongyinensis Chen et al. 2024