Amer. Malac. Bull. 29: 51-62 (2011) 51 Multi-data set revision of two uncommon species of Chromodorididae (Nudibranchia) from the Gulf of Mexico Ángel Valdés 1 , Ulysses Gatdula 1 , Nancy Sheridan 2 , and Joan Herrera 2 1 Department of Biological Sciences, California State Polytechnic University, 3801 West Temple Avenue, Pomona, California 91768, U.S.A. 2 Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, 100 8 th Avenue SE, St. Petersburg, Florida 33701, U.S.A. Correspondence, A. Valdés: aavaldes@csupomona.edu Abstract: Morphological and molecular data are used to address the taxonomic status of two uncommon species of opisthobranch molluscs from the Gulf of Mexico. Chromodoris fentoni is a new species closely related to other Atlantic and eastern Pacific congeneric species. It is characterized by having a whitish background color almost completely covered with irregular red pigment. Glossodoris punctilucens Bergh, 1890 is a rare species known from only a handful of specimens. Morphological and molecular data confirm that it is distinct from other similarly colored species from the eastern Atlantic. Key words: Chromodoris, Glossodoris, morphology, COI, H3 Several species of Chromodorididae have been described from the Caribbean and Gulf of Mexico. Most of the historic descriptions are based on preserved material and therefore lack information on the color of the living animals (Valdés et al. 2006). Modern publications generally include both descriptions of the living animals and anatomical data (Valdés et al. 2006), greatly improving the possibility of other authors identifying these species. However, it has become evident that color and anatomical information alone are not always sufficient to provide a solid framework for solving complex taxonomic issues involving closely related species. Pola et al. (2006) illustrated how molecular information combined with anatomical data can be used to effectively address problems of color variation and species boundaries in an eastern Pacific opisthobranch species complex, opening the door for applying this methodology to other groups of species. In this paper, we attempt to clarify the systematics of two uncommon species using a combination of external morphology, anatomy, biology, and sequence data from a mitochondrial and a nuclear gene, and comparing this information with other closely related species. MATERIALS AND METHODS Collection and preservation The specimens were collected from the Gulf of Mexico, west Florida shelf. This area consists of a hard-bottom habitat of low relief carbonate structures, commonly called reef ledges. These discontinuous ledges are generally oriented north-south, rise from less than one meter to several meters off the sandy bottom, and support a diverse community of marine organisms. On 30 March 2009, while scuba diving at a depth of 9 m, commercial aquarium trade fisher, Daniel Fenton, collected by hand a specimen of the red sponge Igernella notabilis, which contained two specimens of Chro- modoris fentoni. The sponge and nudibranchs were placed into plastic bags with seawater and transported to the Florida Fish and Wildlife Conservation Commission’s (FWC), Fish and Wildlife Research Institute (FWRI). Features of these living organisms were digitally photographed in a photo- graphic plexiglass aquarium at the FWRI. On two subsequent field trips with Daniel Fenton, FWRI scientific research scuba divers, at a depth of 9-10 m, searched along ledges for Igernella notabilis where Chromodoris fentoni had been previously collected. While conducting the search for C. fentoni on 21 June 2009, Glossodoris punctilucens Bergh, 1890 was found traversing the substrate. On 21 July 2009, C. fentoni was found on I. notabilis. On each occasion, FWRI scientific divers digitally photographed the specimens in situ and then collected them by hand, placed them into a plastic bag while underwater, and then transferred them from the bag into a five gallon bucket of seawater for transport back to the FWRI. While at the FWRI, the specimens were digitally photographed in a photographic plexiglass aquarium. During subsequent field trips by D. Fenton more specimens of G. punctilucens were collected: on 28 January 2010 two specimens were found on an unidentified sponge and on 3 June 2010 two more specimens were collected on the same species of sponge. This time the sponge was collected and tentatively identified as Ircinia cf. campana. On a separate occasion D. Fenton (pers. comm.) observed G. punctilucens feeding on