Genus description from Pollock 1976: “Oreellidae with four claws each on the first three pairs of legs and three claws each on the fourth pair of legs; claws with accessory basal spurs.”
Genus description from Bartels et al. 2018: “Echiniscoididae with four claws on each of the first pairs of legs and three claws on the fourth pair of legs in adults. Paired basal spurs on all claws. Median cirrus present but reduced.”
Genus description from Møbjerg et al. 2020: “Unplated, interstitial, marine heterotardigrades. Four claws inserted directly on each of the first three leg pairs, and three claws inserted directly on the fourth pair of legs (in adults). Paired basal hooks on all claws, with the two hooks oriented at right angles to one another. Median cephalic cirrus is always present, but can be reduced. Cephalic appendages include internal and external cirri, lateral cirri (cirri A) and generally also primary clava and flat, often indistinct, secondary clava. Cirri E is always present. Papillae on leg IV are often present, and sensory structures on legs I–III may also be present (presently seen in only one species, Anisonyches mauritianus Grimaldi de Zio, D’Addabbo Gallo, Morone De Lucia & D’Addabbo, 1987). Black eyes are present. Stylets are long, with stylet sheaths; stylet supports are lacking. The three placoids are CaCO3 incrusted. Paired seminal receptacles are present in females. The coiled receptacles open relatively distant from the six-lobed female gonopore. The anal system consists of two lateral lobes connected by a median zig-zag structure, with the anus formed by a small terminal pore.”
Species key: Bartels PJ, Fontoura P, Nelson DR. 2018. Marine tardigrades of the Bahamas with the description of two new species and updated keys to the species of Anisonyches and Archechiniscus. Zootaxa. 4420(1): 43-70.
Citations:
Bartels, P.J., Fontoura, P. & Nelson, D.R. (2018) Marine tardigrades of the Bahamas with the description of two new species and updated keys to the species of Anisonyches and Archechiniscus. Zootaxa, 4420(1), 43–70.
Møbjerg, N., Jørgensen, A. & Kristensen, R.M. (2020) Ongoing revision of Echiniscoididae (Heterotardigrada: Echiniscoidea), with the description of a new interstitial species and genus with unique anal structures. Zoological Journal of the Linnean Society, 188 (3), 663–680.
Pollock, L.W. (1975) Observations on marine Heterotardigrada, including a new genus from the western Atlantic ocean. Cahiers de biologie marine, 16, 121-132.
