The new genus Decorosa Opitz, known only from the Dominican Republic, and its four new species are described: D. aladecoris, D. iviei, D. limatula, and D. neiba. Reduction of the seventh row of elytral punctations and filiform funicular antennomeres distinguish Decorosa specimens from other epiphloeines with antennae composed of 10 antennomeres. Aside from the conventional components of generic revisions this treatise also includes a review of Greater Antillean and Hispaniolan paleogeography, and comments about phylogenetics and zoogeographic considerations.
Distributional records, in conjunction with analysis of intrageneric relationships suggest that Decorosa evolved in northern Hispaniola. Available specimens of Decorosa were collected from mountain forests of the Cordillera Central (1160–2885 m), Sierra de Neiba, (1856–1874 m), and from eastern terrain prehistorically considered part of the northern element of ancient Hispaniola. Compelling evidence from geology and biology suggests that extant Hispaniola was prehistorically composed of a northern and southern island. It is suggested that ancestral Decorosa split into the limatula-iviei and decorosa-neiba stocks in the more northern ancient terrain of Hispaniola. Subsequently, each of two ancestral lineages yielded at least two sister species. It is further postulated that there occurred two dispersal events that brought one species of each sister pair to more southern Hispaniola; limatula from the limatula-iviei lineage and neiba from the aladecoris-neiba lineage.