Trimma charon, a new species of pygmygoby (Teleostei, Gobiidae) from the Red Sea with a key to the Red Sea species of the genus.

Trimma charon sp. nov. is described based on two specimens collected at 30 m depth from the northern Red Sea, Saudi Arabia. The new species can be distinguished from its congeners by the following combination of characters: predorsal midline with scales; fifth pelvic-fin ray unbranched and 41-43% length of the fourth ray; cheek and opercle scaleless; 14 pectoral-fin rays, all unbranched; dorsal fins VI + I,8, with no elongate spines; anal-fin I,8; bony interorbital width 55-62% of pupil diameter; and 6 papillae in row c. In life, T. charon sp. nov. is translucent with a distinct, broad, orange-red midlateral stripe extending from the eye to the caudal-fin base and interrupted by three narrow pale bars, and with conspicuous golden spots on the caudal fin that extend onto the caudal peduncle; the iris is divided into four uneven white/orange sectors. The species is known from two specimens collected at the entrance of a cave on a steep outer-reef slope. Trimma charon sp. nov. was compared with congeners, especially with the very similar T. anaima and co-occurring Red Sea species. An illustrated dichotomous key to all Trimma currently known from the Red Sea is provided. With the description of T. charon sp. nov., the number of valid species in the Red Sea rises to 11.