Multigene phylogeny and taxonomic revision of American shrimps of the genus Cryphiops Dana, 1852 (Decapoda, Palaemonidae) implies a proposal for reversal of precedence with Macrobrachium Spence Bate, 1868

The freshwater shrimp genus Cryphiops Dana, 1852 has a disjunct distribution in North (Mexico) and South (Brazil, Chile) America, and is composed of only six species. The current classification of genera in the Palaemonidae is controversial, based on variable morphological characters, and still far from a clear definition. Cryphiops differs from the speciose genus Macrobrachium Spence Bate, 1868 only by the absence of the hepatic spines on the carapace. Previous studies with a limited dataset suggested the necessity to link morphology and phylogeny to create an internal rearrangement in the genus to resolve the paraphyletic status. Through a molecular phylogenetic approach, the evolutionary relationships are inferred based on four (mitochondrial and nuclear) genes, among all recognized species of Cryphiops and, in combination with a taxonomic revision, a rearrangement in the systematics of the genus is suggested. The absence of hepatic spines on the carapace, the only character used to separate the genus Cryphiops, is subjective and should be considered as a homoplasy. This implies that Cryphiops and Macrobrachium are subjective synonyms and, because the latter genus is much more diverse and widely known, with several economically important species, to avoid confusion and disturbance in nomenclatural stability and keep universality, a proposal for the priority of the older synonym (Cryphiops) to be partially suppressed in favor of maintaining the prevailing use of the younger synonym (Macrobrachium) is presented. As the species of Cryphiops should be accommodated in the genus Macrobrachium, new names to replace three preoccupied specific names that, by this action, resulted to be secondary homonyms are offered.