Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical (2121); Hypsibius-type claw pairs; AISM hooked (or, if the buccal tube is elongated, AISM can be broad ridges).”
Hypsibioidea from Bertolani et al. 2014: “Double claws asymmetrical with respect to the median plane of the leg (2121), the external (or posterior) claw often with flexible main branch; double claws different in size and shape on the same leg (Hypsibius and Ramazzottius type, or modified), or very reduced in size (Calohypsibius and Microhypsibius type); buccal tube often very narrow”
Hypsibioidea from Gąsiorek et al. 2018: “Eutardigrades with asymmetrical claws (2-1-2-1) and pseudolunulae at claw bases or without any cuticular structures under the basal parts. Hooked or broad-ridged apophyses for the insertion of the stylet muscles. Herbivorous or microbivorous (Guidetti et al. 2012).”
Microhypsibiidae from Pilato 1998: “Eutardigrades having claws arranged asymmetrically with respect to the median plane of the legs. Claws of Microhypsibius type: the claws have a narrow basal portion continuous with the primary branch; the secondary branch is rigidly joined to the primary branch. The internal claws cannot rotate on their bases.”
Hypsibiidae from Bertolani et al. 2014: “Double claws of the Microhypsibius type (small, rigid, with an evident thin basal tract continuous with the primary branch); buccal tube completely rigid; double claws similar in size and shape on the same leg; apophyses for the insertion of the stylet muscles on the buccal tube asymmetrical with respect to the frontal plane. Pharynx with a septulum in some species.”
Genus description from Thulin 1928: “Krallen vom ersten Typus. Placoidenreihen des Schlundkopfes verhältnismässig lang, jede aus drei Macroplacoiden zusammengesetzt.
Mundröhre nicht besonders eng, beinahe gerade. Körperoberfläche glatt.”
Translated: Claws of the first [Microhysibius] type. Placoid rows of the pharynx relatively long, each composed of three macroplacoids.
Buccal tube not particularly narrow, almost straight. Body surface smooth.
Genus description from Pilato 1998: “Microhypsibiidae; cephalic elliptical organ absent; buccal tube rigid; ventral lamina absent; apophyses for the insertion of the stylet muscles asymmetrical with respect to the frontal plane; ventral apophysis in the shape of a ridge with an evident ‘blunt hook’; dorsal apophysis split into two portions: the anterior in shape of ‘semilunar hook’; the caudal portion is a little, short, thickening. Both the dorsal and ventral apophyses with two very slender caudal processes pointing posteriorly and laterally. Peribuccal lamellae and peribuccal papulae absent (?); pharyngeal apophyses and placoids present; the two branches of the furcae of the stylets have thickened, swollen and rounded apices. Lunulae absent in the known species. Smooth eggs laid in the exuviae.”
Citations:
Bertolani R, Guidetti R, Marchioro T, Altiero T, Rebecchi L, Cesari M. 2014. Phyloeny of Eutardigrada: New molecular data and their morphological support lead to the identification of new evolutionary lineages. Molecular Phylogenetics and Evolution. 76: 110-126.
Gąsiorek P, Stec D, Morek W, Michalczyk Ł. 2018. An integrative redescription of Hypsibius dujardini (Doyère, 1840), the nominal taxon for Hypsibioidea (Tardigrada: Eutardigrada). Zootaxa. 4415 (1): 45-75.
Marley NJ, McInnes SJ, Sands CJ. 2011. Phylum Tardigrada: A re-evaluation of the Parachela. Zootaxa. 2819: 51-64.
Pilato G. 1969. Schema per una nuova sistemazione delle famiglie e dei generi degli Eutardigrada. Bollettino delle Sedute della Accademia Gioenia di Scienze Naturali in Catania, Series IV. 10 (277): 181-193.
Pilato G. 1998. Microhypsibiidae, new family of eutardigrades, and description of the new genus Fractonotus (Tardigrada). Spixiana. 21 (2): 129-134.
Thulin G. 1928. Über die phylogenie und das system der tardigraden. Zoologisches Institut, Lund.
