Untangling the Echiniscus Gordian knot: Stellariscus gen. nov. (Heterotardigrada : Echiniscidae) from Far East Asia.

Species constituting the family Echiniscidae are highly derived, armoured and inhabit terrestrial habitats, in contrast to other heterotardigrades that are predominantly marine. The genus Echiniscus C.A.S. Schultze, 1840, nominal for the family Echiniscidae, is currently the most speciose tardigrade genus. However, the great morphological variability, in comparison with other heterotardigrade genera, suggests the polyphyletic character of the genus. Here, we analyse new specimens of Echiniscus pseudelegans Séméria, 1994 collected in Japan and conclude that the species as well as two other related taxa, E. elegans Richters, 1907 and E. latifasciatus Dudichev and Biserov, 2000, represent a new genus, Stellariscus , gen. nov. The new genus is characterised by a mixture of peculiar morphological apomorphies: black eyes, star-like dorsal plate sculpturing, no trunk appendages (only cephalic cirri present), two types of ventral plates, and striking sexual dimorphism in both qualitative and quantitative traits. Morphological phylogeny of the family Echiniscidae suggests a close affinity between Stellariscus , Hypechiniscus Thulin, 1928 and Pseudechiniscus Thulin, 1911. The polyphyletic status of both Echiniscus and Testechiniscus Kristensen, 1987 is also inferred. The taxonomic significance of ventral armature in echiniscid phylogeny and taxonomy is discussed. Many tardigrades can be easily found in garden mosses, but the members of the family Echiniscidae are quite rare, thus poorly known. This paper presents morphological clues for an artificial character of the largest echiniscid genus Echiniscus , by erecting new genus restricted to Asia. Therefore, by demonstrating the value of cuticular pattern in the systematics, further changes can be made to elucidate echiniscid classification. [ABSTRACT FROM AUTHOR]