Synonymies, diagnoses, descriptions, illustrations, an identification key and meristic frequency tables are provided for all species of Lonchopisthus. Most of the skeletal anatomy of L. higmani is also illustrated. A new jawfish, Lonchopisthus ancistrus n. sp., is described from the Gulf of Mexico and off Honduras based on 21 specimens 41‒89 mm standard length (SL). It differs from other congeners by the following combination of characters: posterior end of maxilla strongly hooked; membrane connecting maxilla and premaxilla and inner membrane covering posterior part of dentary pale; segmented dorsal-fin rays 1113, with unbranched rays 25; longitudinal body scale rows 33‒39; and very long pelvic fins, 39.4‒75.3 % SL. Lonchopisthus lemur (and its synonym L. meadi) share most characters with L. ancistrus but differ in having shorter pelvic fins, 19.2‒29.9 % SL; fewer longitudinal body scale rows, 26‒33; and five infraorbitals. Both are relatively deep-water species occurring from 100 to at least 375 m, while the other species are found in 3‒139 m. Lonchopisthus micrognathus is unique in having no branched caudal-fin rays at any size and the middle caudal-fin rays with free tips that may be used to maintain tactile contact with the substrate while hovering over its burrow. The western Atlantic Lonchopisthus higmani and eastern Pacific L. sinuscalifornicus are sister species that differ from the other Atlantic species in having the posterior end of the maxilla with a notch instead of a strong hook, opercle with a large dark blotch, and one supraneural (vs. no supraneural).
This data release supports the following publication: Smith-Vaniz, W.F., and Walsh, S.J., 2017, Revision of the jawfish genus Lonchopisthus with description of a new Atlantic species (Teleostei: Opistognathidae): Journal of the Ocean Science Foundation, v. 28, p. 5289, https://doi.org/10.5281/zenodo.1001056