Compiler and date details
9 April 2012 - Douglass F. Hoese
Xenisthmids are restricted to the tropical regions of the Indian Ocean and western and central Pacific oceans. Five genera are currently recognised — Allomicrodesmus, Paraxenisthmus, Rotuma, Tyson and Xenisthmus — and 10 described species. All except Paraxenisthmus and Xenisthmus are regarded as monotypic. Gill (2001) provided a key to genera. In Australia, three genera and seven species have been recorded and an additional species from the Cocos (Keeling) Islands is included. The family is currently under study by A.C. Gill and it is likely that the number of species will exceed 30.
Members of the Xenisthmidae are characterised by having a projecting lower jaw and, apparently, the habit of diving head first into sand. They are all known from coral reefs from the intertidal to depths of over 30 m and are small sized, rarely exceeding 3.5 cm in length.
Relationships of the Xenisthmidae are uncertain, but they have been studied by several workers including Springer (1983, 1988), Hoese (1984) and Gill & Hoese (1993); based on these studies xenisthmids are believed to be closest to eleotrids. Thacker & Hardman (2005), however, provided evidence, based on molecular work, that the group is closest to Gobiidae (as Gobiinae). Subsequently Thacker (2009) placed the group within the Eleotrinae and Agorreta et al. (2013) placed the group close to the Eleotrinae.
Agorreta, A., San Mauro, D., Schliewen, U., Van Tassell, J.L., Kovačić, M., Zardoya, R. & Rüber, L. 2013. Molecular phylogenetics of Gobioidei and phylogenetic placement of European gobies. Molecular Phylogenetics and Evolution 69(3): 619–633
Gill, A.C. 2001. Xenisthmidae. pp. 3605-3606 in Carpenter, K.E. & Niem, T.H. (eds). The Living Marine Resources of the Western Central Pacific. FAO Species Identification Guide for Fisheries Purposes. Rome : FAO Vol. 6 pp. 3381-4218.
Hoese, D.F. 1984. Gobioidei: Relationships. pp. 588-591 in Moser, H.G. et al. (eds). Ontogeny and Systematics of Fishes. American Society of Ichthyologists and Herpetologists. Special Publication 1: 1-760
Springer, V.G. 1983. Tyson belos, new genus and species of western Pacific fish (Gobiidae, Xenisthminae), with discussions of gobioid osteology and classification. Smithsonian Contributions to Zoology 390: 1-40
Thacker, C.E. & Hardman, M.A. 2005. Molecular phylogeny of basal gobioid fishes: Rhyacichthyidae, Odontobutidae, Xenisthmidae, Eleotridae (Teleostei: Perciformes: Gobioidei). Molecular Phylogenetics and Evolution 37: 851-871
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