Reverse Taxonomy and Phylogenetic‐Phylogenomic Inferences Clear the Fog on the Northeastern Atlantic‐Mediterranean Eurynome and Resurrect the Family Eurynomidae (Decapoda: Majoidea)

ABSTRACT

Spider crabs of the genus Eurynome have complex taxonomic, phylogenetic, and biogeographic histories worldwide. Using newly generated molecular data, including the characterization of complete mitochondrial genomes, we addressed several unresolved questions surrounding the genus and its two Atlantic‐Mediterranean representatives, the type species Eurynome aspera and its sympatric Eurynome spinosa . DNA‐barcoding and reverse taxonomy demonstrated conspecificity between Atlantic and Mediterranean samples, confirmed the occurrence of E. spinosa in the Mediterranean Sea sensu stricto , and contradicted most diagnostic characters previously proposed in the literature. In their place, a set of 10 molecularly validated morphological traits, regardless of sex and developmental stage, was proposed and accompanied by high‐resolution imagery. The DNA‐assayed material was then used to investigate the phylogenetic position of Eurynome through various inferences (multilocus and mitochondrial genome trees, and mitochondrial gene orders), which suggested that these taxa form a distinct, early‐diverging clade, for which the family Eurynomidae Neumann, 1878 is resurrected here. This was also supported by high similarity with the ancestral Brachyura mitochondrial gene order and strong dissimilarities with other majoid ones. Although several questions remain open, the present results resolve debates on two pseudo‐cryptic species, elevate Eurynome to one of the most molecularly characterized majoid genera, and lay a solid foundation for proceeding with the study of allied taxa and the entire superfamily through modern integrative approaches.