The mudskipper (Gobiidae: Oxudercinae) genus Oxuderces Eydoux & Souleyet is re-diagnosed with five putative synapomorphies: (1) a fleshy, dorsal, interorbital trough or slit supported internally by expanded, curved medial margins of the frontal bones and lined with a thick epidermis and thin dermis (vs. no fleshy, interorbital trough, medial margins of the frontal bones expanded but not curved, and epidermis extremely thin and dermis thick); (2) highly thickened epidermis over the eye (vs. thickened dermis); (3) neural spine of the fourth vertebra broad and spatulate (vs. narrow and pointed); (4) anterior ceratohyal posterior to fourth branchiostegal ray insertion elongate and notched (vs. not elongate, or elongate and not notched); and (5) angle between the metapterygoid–symplectic–quadrate strut and the anguloarticular acute (vs. angle obtuse). The fleshy, dorsal, interorbital trough is a unique character for Oxuderces that is not observed in other oxudercine gobies or gobioid fishes. The extremely thick epidermis may help the skin remain moist when exposed to the air and facilitate cutaneous respiration. Two allopatric species are included in the genus Oxuderces: Oxuderces dentatus Eydoux & Souleyet, 1848, from the south-east coast of China, is the type species; Oxuderces nexipinnis (Cantor, 1849), from the Indo-West Pacific, is resurrected from synonymy of O. dentatus sensu Murdy (1989). Apocryptodon wirzi Koumans, 1937, a species classified in Oxuderces by Murdy (1989) is reassigned to Apocryptodon based on a posteriorly directed laminar process on the parapophyses of the fourth vertebra. Oxuderces nexipinnis uniquely has a dermal invagination of unknown function just posterior to the point of attachment of the pelvic-fin base.