Xenotoca lyonsi

Xenotoca lyonsi, the Tamazula redtail splitfin, is a bony fish species in the goodeid family. Until 2016 it was considered to be a variant of the redtail goodeid, X. eiseni. A 2016 study by Omar Dominguez-Dominguez, et al. split the redtail goodeid into three separate species: X. eiseni, X. doadrioi and X. lyonsi.

The IUCN lists Xenotaca lyonsi as critically endangered.

Xenotoca lyonsi is endemic to the Coahuayana River drainage in Jalisco, Mexico.

Xenotoca lyonsi reaches a standard length of 5 cm. Males are more colorful than females, with red caudal fin and caudal peduncle, and blue area in front of the red. Females are brownish or brownish grey, and sometimes have a horizontal dark band across the middle of the body.