Family XENISTHMIDAE

Xenisthmidae

© Copyright Ros Poole.

Xenisthmus clarus from holotype of Xenisthmus proriger

© Copyright Snyder 1912

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Introduction

Xenisthmids are restricted to the tropical regions of the Indian Ocean and western and central Pacific oceans. Six genera are currently recognised (Allomicrodesmus, Gymnoxenisthmus Paraxenisthmus, Rotuma, Tyson and Xenisthmus) and about 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.

General References

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.

Gill, A.C., Bogorodsky, S.V. & Mal, A.O. 2014. Gymnoxenisthmus tigrellus, new genus and species of gobioid fish from the Red Sea (Gobioidei: Xenisthmidae). Zootaxa 3755(5): 491-495

Gill, A.C. & Hoese, D.F. 1993. Paraxenisthmus springeri, new genus and species of gobioid fish from the west Pacific, and its phylogenetic position within the Xenisthmidae. Copeia 1993: 1049-1057

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

Snyder, J.O. 1912. The fishes of Okinawa, one of the Riu Kiu Islands. Proceedings of the United States National Museum 42: 487-519 pls 62-70

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

Springer, V.G. 1988. Rotuma lewisi, new genus and species of fish from the southwest Pacific (Gobioidei, Xenisthmidae). Proceedings of the Biological Society of Washington 101(3): 530-539 figs 1-8

Thacker, C.E. 2009. Phylogeny of Gobioidei and placement within Acanthomorpha, with a new classification and investigation of diversification and character evolution. Copeia 2009(1): 93–104

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

Common Name References

Myers, R.F. 1999. Micronesian Reef Fishes. A comprehensive guide to the coral reef fishes of Micronesia. Guam : Coral Graphics vi 330 pp. 192 pls. [261] (Wrigglers)

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