Evidence for the Specific Status of the Honduran Lizards Formerly Referred to Ctenosaura palearis (Reptilia: Squamata: Iguanidae)

Ctenosaura melanosterna, a new species of spiny-tailed iguana, is described from the Aguan Valley and the Cayos Cochinos in Honduras. Its closest phylogenetic affinities are with C. palearis from the Motagua Valley in Guatemala with which it has previously been considered conspecific. Previous work on relationships within Ctenosaura presented evidence of a clade consisting of C. palearis (including the species described herein), C. bakeri, and C. oedirhina (de Queiroz, 1987a, 1987b; Kohler, 1995c). Data presented here adds additional support for this clade. Alternative biogeographic scenarios are discussed, with the conclusion that the current range of these species of Ctenosaura in Nuclear Central America probably resulted from the fragmentation of a Caribbean versant distribution. Display behavior of the new Ctenosaura and C. bakeri involves head shaking unlike that seen in other Ctenosaura but similar to Iguana. Because of the highly restricted distributions of C. palearis, C. bakeri, and C. oedirhina and the new form, close monitoring of their conservation status is strongly recommended.