Tomiyamichthys Smith, 1956: 553 (type species Cryptocentrus oni Tomiyama, 1936, by origiNal desigNatioN). Flabelligobius Smith, 1956: 553 (Flabelligobius fourmanoiri Smith, 1956, by origiNal desigNatioN).

Eilatia KlausewitZ, 1974: 206 (type species Eilatia latruncularia KlausewitZ, 1974, by origiNal desigNatioN).

The genus was separated from other gobiid fishes associated with alpheid shrimps by Shibukawa et al. (2005) in having the ventral one-third or more of the lower part of first gill slit closed by membrane; gill rakers on outer surface of first arch rudimentary or relatively short, 11 or fewer in total number; well-developed longitudinal pattern of sensory-papillae rows on cheek and a uniserial transverse row of sensory papillae just behind the chin. The genus is also characterised by having equal number of dorsal and anal rays, numerous small scales, often nonimbricate anteriorly and a moderately narrow gill opening reaching to below the operculum.

Currently 13 species of Tomiyamichthys are known from the Indo-Pacific region. Several species have been described in recent years from a few specimens from small geographical areas. We describe here a species known only from Australia, belonging to the Tomiyamichthys russus complex. That complex is superficially similar to Cryptocentrus and differs from other species of Tomiyamichthys in having a deeper head and body, with the body depth at anal origin varying from 15–19% SL versus less than 15%.

The following species are included in the genus: Tomiyamichthys alleni Iwata, Ohnishi and Hirata, 2000 from Japan and Indonesia; T. dorsostigma Bogorodsky, Kovačić & Randall, 2011 from the Red Sea; T. fourmanoiri (Smith, 1956) from the Western Indian Ocean; T. gomezi Allen and Erdmann, 2012 from the Philippines and Indonesia; T. lanceolatus (Yanagisawa, 1978) from Japan, Great Barrier Reef, New Guinea and Guam; T. latruncularius (Klausewitz, 1974) from the Red Sea to Java and Great Barrier Reef; T. nudus Allen and Erdmann, 2012, only known from Indonesia; T. oni (Tomiyama, 1936) from Japan, New Guinea, Indonesia, Philippines, Sabah, Palau, New Caledonia; T. praealtus (Lachner and McKinney, 1980) from Seychelles; T. russus (Cantor, 1849) from the west Pacific and eastern Indian Ocean; T. smithi Chen and Fang, 2003 from Taiwan, Papua New Guinea, Sabah and Yaeyama Islands, Japan, T. tanyspilus Allen and Erdmann, 2012 from Flores and West Papua, Indonesia and T. zonatus Allen, 2015 from Papua New Guinea. In addition to these, several other undescribed species are under study by Shibukawa.

Both Flabelligobius and Tomiyamichthys were described by Smith (1956) in the same paper. Those names have been considered synonymous for some time, but there is some confusion over application of the Principle of First Reviser under the International Code of Zoological Nomenlature. Shibukawa et al. (2005) indicated that “An explanation is given for regarding Flabelligobius Smith, 1956 as a senior synonym of Tomiyamichthys Smith, 1956 ”, which could suggest application of First Reviser. However later in the paper they indicated that “Although their result has been not yet formally published, we provisionally follow the generic assignment made by Shibukawa and Iwata (2005) ” in a conference abstract, which suggests that their assignment was conditional upon formal revision of the genus. Randall & Chen (2007) added to the confusion by indicating that Shibukawa intended to make Flabelligobius a synonym of Tomiyamichthys thus reversing the previous synonymy. Again that statement by Randall & Chen is regarded here as being conditional on publication by Shibukawa. Bogorodsky et al. (2011) also indicated the intention of Shibukawa to treat Flabelligobius as a junior synonym of Tomiyamichthys. Article 15.1 of the International Code of Zoological Nomenclature states that “Conditional proposal. A new name or nomenclatural act proposed conditionally and published after 1960 is not thereby made available.” Consequently we do not regard that the Principle of First Reviser has been applied to these names. The name Tomiyamichthys has generally been accepted as the correct generic name and to avoid further confusion, we here regard Flabelligobius as a junior synonym of Tomiyamichthys. That synonymy is based on the fact that type species of both genera contain the features that define the genus: partial closure of the first gill slit, longitudinal papilla pattern on the cheek and a truncate mental fraenum with sensory papillae along the margin, rather than running as two parallel rows on the chin.