Untangling the Echiniscus Gordian knot: Stellariscus gen. nov. (Heterotardigrada : Echiniscidae) from Far East Asia
Piotr Gąsiorek![https://orcid.org/0000-0002-2814-8117](/media/client/orcid_16x16.png)
![https://orcid.org/0000-0002-3027-7110](/media/client/orcid_16x16.png)
![https://orcid.org/0000-0001-9549-1188](/media/client/orcid_16x16.png)
![https://orcid.org/0000-0001-9072-1677](/media/client/orcid_16x16.png)
![https://orcid.org/0000-0002-2912-4870](/media/client/orcid_16x16.png)
A Department of Entomology, Institute of Zoology and Biomedical Research, Jagiellonian University, Gronostajowa 9, 30-387 Kraków, Poland.
B Department of Biology, Keio University, Yokohama 223-8521, Japan.
C Section of Biosystematics, Natural History Museum of Denmark, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark.
D Corresponding author. Email: piotr.lukas.gasiorek@gmail.com
Invertebrate Systematics 32(5) 1234-1247 https://doi.org/10.1071/IS18023
Submitted: 10 March 2018 Accepted: 22 May 2018 Published: 17 October 2018
Abstract
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.
Additional keywords: cuticle, Echiniscoidea, morphology, phylogeny, polyphyly, sexual dimorphism, ventral plates.
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