First evidence of cryptic diversity in mud dragons (kinorhyncha) and description of Echinoderes quasae sp. nov. from the northeastern pacific coast

The genus Echinoderes, currently consisting of over 150 known species, has seen a surge in new descriptions since 2015. Species identification traditionally relies on morphological traits and morphometrics, but distinguishing closely related species is more and more challenging due to overlapping features and character variability. Cryptic diversity, where species are genetically distinct but morphologically identical, is common in meiofauna and suspected in kinorhynchs, though not previously confirmed. This study examines the northeastern Pacific Echinoderes fauna, using newly collected material and historical collections of the Smithsonian National Museum of Natural History. We describe a new species, Echinoderes quasae sp. nov., using a molecular and morphological approach and provide the first evidence of cryptic diversity in kinorhynchs, revealing at least two new species within a previously unrecognized cryptic complex.