88 Accepted by J. Goy: 17 Jan. 2014; published: 24 Feb. 2014 ZOOTAXA ISSN 1175-5326 (print edition) ISSN 1175-5334 (online edition) Copyright © 2014 Magnolia Press Zootaxa 3768 (1): 088–094 www.mapress.com/zootaxa/ Article http://dx.doi.org/10.11646/zootaxa.3768.1.6 http://zoobank.org/urn:lsid:zoobank.org:pub:C081C8BF-B536-41F3-9A6B-9A34443009CE A new species of the alpheid shrimp genus Triacanthoneus Anker, 2010 (Crustacea: Alpheidae) from Belize FERNANDO ALVAREZ 1,3 , THOMAS M. ILIFFE 2 & JOSÉ LUIS VILLALOBOS 1 1 Colección Nacional de Crustáceos, Instituto de Biología, Universidad Nacional Autónoma de México, Apartado Postal 70-153, Méx- ico 04510, D.F., México. E-mail: falvarez@unam.mx, hiriart@unam.mx 2 Department of Marine Biology, Texas A&M University at Galveston, Galveston, Texas 77553-1675, U.S.A. E-mail: iliffet@tamug.edu 3 Corresponding author Abstract A new species of the alpheid shrimp genus Triacanthoneus Anker, 2010, is described based on material collected in a ma- rine cave off Caye Chapel, Belize. Triacanthoneus chapelianus sp. nov. is the fifth species in the genus and can be distin- guished from the other four species by the position of the dorsolateral teeth on the carapace, which in the new species have an anterior (= submarginal) position, and by the configuration of the posterior margin of the telson, with a notch in the middle portion and two pairs of spines and one pair of plumose setae. A key to the five species of Triacanthoneus is pro- vided. Key words: Caridea, Alpheidae, Triacanthoneus, Belize, cave shrimp, new species Introduction The genus Triacanthoneus Anker, 2010 is composed by four species of small alpheid shrimps distributed in the coastal waters of the Pacific coast of Colombia and Panama, and in the western Atlantic from the Caribbean coast of Panama to the southern Gulf of Mexico (Anker, 2010; Alvarez et al., 2012). Triacanthoneus is a rarely collected genus, with currently only 11 individuals known, representing four species, T. toro Anker, 2010, T. pacificus Anker, 2010, T. alacranes Anker, 2010, and T. akumalensis Alvarez, Iliffe, Gonzalez & Villalobos, 2012, one of them (T. alacranes) was described based on a single individual. Anker (2010) in the diagnosis of Triacanthoneus stated that the genus was characterized by three teeth on the carapace, one in a mediodorsal position on the posterior half of the carapace and two in post-hepatic position, a pattern that is seen in the four known species so far. Here we describe a new species from Caye Chapel, Belize, in which a different pattern is observed: the mediodorsal tooth is on the anterior half of the carapace and the pair of lateral teeth are in a submarginal position behind the orbits. In addition to the unique position of the teeth on the carapace, the single specimen from Caye Chapel has a distinct posterior margin of the telson with a notch similar to that of T. akumalensis Alvarez, Iliffe, Gonzalez & Villalobos, 2012, but with an additional pair of setae. The holotype of the new species is deposited in the Colección Nacional de Crustáceos, Instituto de Biología, Universidad Nacional Autónoma de México, Ciudad de México, Mexico (CNCR). Abbreviations used in the text are: cl, carapace length; tl, total length. Taxonomy Family Alpheidae Rafinesque, 1815 Genus Triacanthoneus Anker, 2010