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1.3 CORONARCTIDAE Renaud-Mornant, 1974 (emended by Hansen 2007) Arthrotardigrades with cylindrical worm-like body. Trunk cuticle smooth, with folds, bearing three somatic cirri (B, C and E) or only one (E). Eleven cephalic sense organs present, including large flattened secondary clavae (occasionally occurring as indistinct areas). Three or four claws, connected to foot by membranes. 1.3.1 Coronarctus Renaud-Mornant, 1974 (emended by Hansen 2007; Figs 4 B, 10A, B) Coronarctidae with unplated cylindrical body, with more or less pronounced cuticular folds. Three pairs of somatic cirri with accordion-like scapus. Conical head separated into two parts; anterior triangular part with median cirrus and flattened secondary clavae, posterior part narrower, bearing lateral cirri and primary clavae. Four claws on each leg displaying more or less important heterometry6. Buccal apparatus without stylet supports or placoids17. Digestive tract with poorly developed diverticula. Female with two seminal receptacles. Type species: Coronarctus tenellus Renaud-Mornant, 1974 Selected literature for further information: Renaud-Mornant (1974, 1987b) and Romano III et al. (2011). 1.3.2 Trogloarctus Villora-Moreno, 1996 (Figs 4 C, 10C) Coronarctidae with elongated body with cuticular folds. Only one pair of somatic cirri (cirrus E) with accordion-like scapus. Eleven cephalic sense organs. Primary clava, small and globular, inserted separately from cirrus A. Secondary clavae flattened and not pronounced. Small cephalic cirri consisting of two parts: scapus and flagellum. External cirri equally distant from the internal cirri and the primary clavae. Spines on all legs. Three claws on each leg, very long on fourth leg. Buccal apparatus with bar-shaped placoids, but without stylet supports. Type species Trogloarctus trionyches Villora-Moreno, 1996 Selected literature for further information: Villora-Moreno (1996)., Published as part of Fontoura, Paulo, Bartels, Paul J., J��rgensen, Aslak, Kristensen, Reinhardt M��bjerg & Hansen, Jesper Guldberg, 2017, A dichotomous key to the genera of the Marine Heterotardigrades (Tardigrada), pp. 1-45 in Zootaxa 4294 (1) on page 26, DOI: 10.11646/zootaxa.4294.1.1, http://zenodo.org/record/831540, {"references":["Renaud-Mornant, J. (1974) Une nouvelle famille de Tardigrades marins abyssaux: Coronarctidae fam. nov. (Heterotardigrada). Comptes Rendus de l'Academie des sciences, Serie D, 278, 3087 - 3090.","Hansen, J. G. (2007) The deep-sea elements of the Faroe Bank tardigrade fauna with a description of two new species. Journal of Limnology, 66 (Supplement 1), 12 - 20.","Renaud-Mornant, J. (1987 b) Bathyal and abyssal Coronarctidae (Tardigrada), description of new species and phylogenetical significance. In: Bertolani, R. (Ed.), Biology of Tardigrades. Selected Symposia and Monographs U. Z. I. 1. Mucchi Editore, Modena, pp. 229 - 252.","Romano III, F., Gallo, M., D'Addabbo, R., Accogli, G., Bagueley, J. & Montagna, P. (2011) Deep-sea tardigrades in the northern Gulf of Mexico with a description of a new species of Coronarctidae (Tardigrada: Arthrotardigrada), Coronarctus mexicus. Journal of Zoological Systematics and Evolutionary Research, 49 (Supplement 1), 48 - 52. https: // doi. org / 10.1111 / j. 1439 - 0469.2010.00597. x","Villora-Moreno, S. (1996) A new genus and species of deep-sea family Coronarctidae (Tardigrada) from a submarine cave with a deep-sea like condition. Sarsia, 81, 275 - 283."]}

1.7 STYGARCTIDAE Schulz, 1951 (emended by Hansen et al. 2012) Arthrotardigrada with dorsal cuticle forming five dorsal plates (one cephalic plate; three body plates ��� segmental plates I, II and III ��� and one caudal plate ��� segmental plate IV). Dorsal plates sometimes absent. Intersegmental dorsal plates and ventral plates may be present. Head subdivided into lobes; complete set of cephalic cirri and two pairs of clavae. Stylet supports always absent. Legs non-digitate with four, three or two claws. Claws with or without dorsal spurs or long dorsal filaments34; claws attached with dorsal basal membrane. Leg sense organs present only on the fourth pair of legs, as bulb-shaped papillae. Seminal receptacles formed as cuticular pouches with short straight ducts or with long sinuous ducts close to the female gonopore. Selected literature for further information: A key to the Stygarctidae can be found in Morone De Lucia et al. (1984)., Published as part of Fontoura, Paulo, Bartels, Paul J., J��rgensen, Aslak, Kristensen, Reinhardt M��bjerg & Hansen, Jesper Guldberg, 2017, A dichotomous key to the genera of the Marine Heterotardigrades (Tardigrada), pp. 1-45 in Zootaxa 4294 (1) on page 32, DOI: 10.11646/zootaxa.4294.1.1, http://zenodo.org/record/831540, {"references":["Schulz, E. (1951) Uber Stygarctus bradypus n. g., s. p., einen Tardigraden aus dem Kustengrundwasser und seine phylogenetische Bedeutung. Kieler Meeresforschung, 8, 86 - 97.","Hansen, J. G., Kristensen R. M. & Jorgensen, A. (2012) The armoured marine tardigrades (Arthrotardigrada, Tardigrada). Scientia Danica, Series B. Biologica, 2, 1 - 91."]}

1. ARTHROTARDIGRADA Marcus, 1927 Median cephalic cirrus usually present, rarely absent. Digitate legs with or without claws or non-digitate legs with claws always implanted directly into the legs. Selected literature for further information: An early treatment of the arthrotardigrades can be found in Renaud- Mornant (1982a). Early general keys to marine arthrotardigrades can be found in Pollock (1976) for the northeastern USA, Ramazzotti & Maucci (1983) for all known species at the time of publication, and Morgan & O���Reilly (1988) for Scottish species., Published as part of Fontoura, Paulo, Bartels, Paul J., J��rgensen, Aslak, Kristensen, Reinhardt M��bjerg & Hansen, Jesper Guldberg, 2017, A dichotomous key to the genera of the Marine Heterotardigrades (Tardigrada), pp. 1-45 in Zootaxa 4294 (1) on page 25, DOI: 10.11646/zootaxa.4294.1.1, http://zenodo.org/record/831540, {"references":["Marcus, E. (1927) Zur Anatomie und Okologie mariner Tardigraden. Zoologische Jahrbucher Abteilung fur Systematik, Okologie und Geographie der Tiere, 53, 487 - 558.","Renaud-Mornant, J. (1982 a) Species diversity in marine Tardigrada. In: Nelson, D. (Ed.), Proceedings of the Third International Symposium on Tardigrada. East Tennessee State University Press, Johnson City, Tennessee, 149 - 177.","Pollock, L. W. (1976) Marine flora and fauna of the northeastern United States. Tardigrada. National Oceanic and Atmospheric Administration Technical Report, National Marine Fisheries Service, Circular 394, 1 - 25.","Ramazzotti, G. & Maucci, W. (1983) Il Phylum Tardigrada - III edizione. Memorie dell'Istituto Italiano di Idrobiologia, 41, 1 - 1012.","Morgan, C. I., & O'Reilly, M. (1988) Additions to the Scottish tardigrade fauna, including a description of Megastygarctides setoloso new species, with a revised key for identification of Scottish marine species. Glasgow Naturalist, 21, 445 - 454."]}

1.6 RENAUDARCTIDAE Kristensen & Higgins, 1984 (emended by Hansen et al. 2012) Arthrotardigrades with segmental dorsal and ventral plates, both claws and toes present. Four toes are accompanied by four accessory claw spines19 on each foot in the adults. Primary and secondary clavae, and a complete set of cephalic cirri present. 1.6.1 Renaudarctu s Kristensen & Higgins, 1984 (emended by Hansen et al. 2012) (Figs 5 A, 11C) Renaudarctidae with segmental dorsal plates, two dorsal intersegmental plates, four dorsal intersegmental ridges33, a dorsal plate on each leg, and thin ventral plates. Each body plate with a pair of lateral spines. Caudal 32. In the terminology of this key ���dorsal bristle��� = accessory point. 33. According to Hansen et al. (2012), these intersegmental ridges are prominent cuticular structures forming a ridge rather than a true plate, present between segmental and intersegmental plates. plate with two pairs of lateral spikes, one pair of caudal spikes, and lateral margins continuous with furca-like caudal extensions. Complete set of cephalic sense organs. Leg IV with small ovoid papilla; all other legs lack sensory structures. Cirrus E with cirrophore. Female and male with ovoid gonopore papillae adjacent to terminal anal system. Female with latero-ventral projections containing seminal receptacles. Type species: Renaudarctus psammocryptus Kristensen & Higgins, 1984 Remark: During the publication process of this paper a new genus and species, Nodarctus hallucis Fujimoto &Yamasaki, 2017, of Renaudarctidae have been described and, consequently, the diagnosis of the family has been emended. The genus Nodarctus can be easily distinguished from Renaudarctus in having leg IV with two digits, subdivided dorsal body plates without lateral processes, and a large single caudal spike (see Fujimoto & Yamasaki 2017)., Published as part of Fontoura, Paulo, Bartels, Paul J., J��rgensen, Aslak, Kristensen, Reinhardt M��bjerg & Hansen, Jesper Guldberg, 2017, A dichotomous key to the genera of the Marine Heterotardigrades (Tardigrada), pp. 1-45 in Zootaxa 4294 (1) on pages 31-32, DOI: 10.11646/zootaxa.4294.1.1, http://zenodo.org/record/831540, {"references":["Hansen, J. G., Kristensen R. M. & Jorgensen, A. (2012) The armoured marine tardigrades (Arthrotardigrada, Tardigrada). Scientia Danica, Series B. Biologica, 2, 1 - 91.","Fujimoto, S. & Yamasaki, H. (2017) A new genus and species of Renaudarctidae (Heterotardigrada: Arthrotardigrada) from Ryukyu Archipelago, Japan, Marine Biology Research, 1 - 2. [published online]"]}

1.2 BATILLIPEDIDAE Ramazzotti, 1962 (emended by Gallo d���Addabbo et al. 2005) Arthrotardigrada with a trapezoid head divided into three parts: two lateroventral triangular lobes bearing all the cephalic cirri (except the medial cirrus) along with the primary and secondary clavae, and a central lobate portion with the medial cirrus. 15. In the terminology of this key ���internal accessory point��� = secondary point. Simple cephalic cirri with lance-like or frayed tips. Tubular primary clavae with or without one or more constrictions; papillar secondary clavae, not always evident. Lipoid eye spots sometimes present. Stylet supports always present. Lateral intermetamerical processes present or absent. Legs digitate with four or six toes, according to the age, bearing terminal adhesive discs. Claws absent. Sense organs present on all the legs. Cirrus E dorsal to the fourth pair of legs. A longitudinal groove generally present between the rosette-like female gonopore and the anus. Single internal seminal receptacle16 sometimes present, opposite the oviduct. Circular male gonopore covered with a crescent fold. Caudal apparatus present or absent. Cuticular punctations, consisting of pillars in the epicuticle, always present. Dorsal cuticular pillars always higher than the ventral ones. 1.2.1 Batillipes Richters, 1909 (Figs 3 E, 7I, 14G) Generic diagnosis as that of the family. Type species: Batillipes mirus Richters, 1909 Selected literature for further information: Pollock (1970) defined patterns of toe length of Batillipes species, and Pollock (1971) included an early key to this genus. McKirdy (1975) summarized and discussed the taxonomic characters within the genus. Kristensen (1978) introduced new characters for the genus Batillipes using the electron microscope. Rho et al. (1999) provided a more recent key, but only covered Korean species. Kristensen & Mackness (2000) suggested a toe formula for all known species at that time. See also J��rgensen et al. (2014), Menechella et al. (2015), Rubal et al. (2016), and Menechella et al. (2017) for a comprehensive key to all known species., Published as part of Fontoura, Paulo, Bartels, Paul J., J��rgensen, Aslak, Kristensen, Reinhardt M��bjerg & Hansen, Jesper Guldberg, 2017, A dichotomous key to the genera of the Marine Heterotardigrades (Tardigrada), pp. 1-45 in Zootaxa 4294 (1) on pages 25-26, DOI: 10.11646/zootaxa.4294.1.1, http://zenodo.org/record/831540, {"references":["Ramazzotti, G. (1962) Il Phylum Tardigrada. Memorie dell'Istituto Italiano di Idrobiologia, 14, 1 - 595.","Gallo d'Addabbo, M., Sandulli, R. & de Zio Grimaldi, S. (2005) New Batillipedidae (Tardigrada, Heterotardigrada) from the Orosei Gulf, Sardinia, Tyrrhenian Sea. Zoologischer Anzeiger, 243, 219 - 225.","Richters, F. (1909) Tardigraden-Studien. Bericht der Senckenbergzischen Naturforschenden Gesellschaft in Frankfurt am Main, 1 - 2, 28 - 49.","Pollock, L. W. (1970) Batillipes dicrocercus n. sp., Stygarctus granulatus n. sp. and other Tardigrada from Woods Hole, Massachusetts, U. S. A. Transactions of the American Microscopical Society, 89 (1), 38 - 52. https: // doi. org / 10.2307 / 3224613","Pollock, L. W. (1971) On some British marine Tardigrada including two new species of Batillipes. Journal of the Marine Biological Association of the United Kingdom, 51, 93 - 103.","McKirdy, D. J. (1975) Batillipes (Heterotardigrada): Comparison of six species from Florida (USA) and a discussion of taxonomic characters within the genus. Memorie dell'Istituto Italiano di Idrobiologia Pallanza, 32, 177 - 223.","Kristensen, R. M. (1978) Notes on marine heterotardigrades. 1. Description of two new Batillipes species, using the electron microscope. Zoologischer Anzeiger, 200, 1 - 17.","Rho, H. S., Min, B. H. & Chang, C. Y. (1999) Taxonomic study of marine tardigrades from Korea. I Genus Batillipes (Heterotardigrada: Batillipedidae). The Korean Journal of Systematic Zoology, 15 (1), 107 - 118.","Kristensen, R. M. & Mackness, B. S. (2000) First record of the marine tardigrade genus Batillipes (Arthrotardigrada: Batillipedidae) from South Australia with a description of a new species. Records of the South Australian Museum, 33, 73 - 87.","Jorgensen, A., Boesgaard, T. M., Mobjerg, N. & Kristensen, R. M. (2014) The tardigrade fauna of Australian marine caves: With descriptions of nine new species of Arthrotardigrada. Zootaxa, 3802 (4), 401 - 443. https: // doi. org / 10.11646 / zootaxa. 3802.4.1","Menechella, A. G., Bulnes, V. N. & Cazzaniga, N. J. (2015) A new Batillipedidae (Tardigrada. Arthrotardigrada) from Argentina. Zootaxa, 4032 (3), 339 - 344.","Rubal, M., Veiga, P., Fontoura, P. & Sousa-Pinto, I. (2016) A new Batillipes (Tardigrada, Heterotardigrada, Batillipedidae) from North Portugal (Atlantic Ocean). Marine Biodiversity. [published online]","Menechella, A. G., Bulnes, V. N. & Cazzaniga, N. J. (2017) Two new species of Batillipes (Tardigrada, Arthrotardigrada, Batillipedidae) from the Argentinean Atlantic coast, and a key to all known species. Marine Biodiversity, 1 - 9. [published online]"]}

1.4 HALECHINISCIDAE Thulin, 1928 (emended by Fujimoto et al. 2016) Arthrotardigrades without sclerotized dorsal segmental plates. The complete set of cephalic appendages usually consist of unpaired median cirrus, three pairs of cirri and two pairs of clavae, buccal clavae may be 16. A spermatheca according Grimaldi de Zio & D���Addabbo Gallo 1975. 17. Three very large droplet-shaped apophyses flank the buccal tube anterior to the pharyngeal bulb. indistinguishable or consist of fused secondary and tertiary clavae. Unmodified papillate sensory organs on leg IV. Adult legs terminate in either four digits with claws or four suction pads with or without claws. Peduncles present only in external digits, or as tarsal cuticular bars or absent. Single-pointed, crescent shaped claws may bear dorsal spurs and/or minute calcars. Rosette-like female gonopore and paired seminal receptacles. Selected literature for further information: Grimaldi de Zio et al. (1990a), J��rgensen & Kristensen (2001). An early key to the Halechiniscidae can be found in Renaud-Mornant (1984)., Published as part of Fontoura, Paulo, Bartels, Paul J., J��rgensen, Aslak, Kristensen, Reinhardt M��bjerg & Hansen, Jesper Guldberg, 2017, A dichotomous key to the genera of the Marine Heterotardigrades (Tardigrada), pp. 1-45 in Zootaxa 4294 (1) on pages 26-27, DOI: 10.11646/zootaxa.4294.1.1, http://zenodo.org/record/831540, {"references":["Thulin, G. (1928) Uber die Phylogenie und das System der Tardigraden. Hereditas Genetiskt Arkiv, 11, 207 - 266. https: // doi. org / 10.1111 / j. 1601 - 5223.1928. tb 02488. x","Fujimoto, S., Jorgensen, A. & Hansen, J. G. (2016) A molecular approach to arthrotardigrade phylogeny (Heterotardigrada, Tardigrada). Zoologica Scripta. [published online]","Jorgensen, A. & Kristensen, R. M. (2001) A new tanarctid arthrotardigrade with buoyant bodies. Zoologischer Anzeiger, 240, 425 - 439.","Renaud-Mornant, J. (1984) Halechiniscidae (Heterotardigrada) de la campagne Benthedi, canal du Mozambique. Bulletin du Museum National d'Histoire Naturelle (Paris), Series 4 e, 6 e (Section A, n ° 1), 67 - 88."]}

1.8 STYRACONYXIDAE Kristensen & Renaud-Mornant, 1983 (emended by Fujimoto et al. 2016) Considered as subfamily Styraconyxinae assigned to the family Halechiniscidae by Kristensen & Renaud-Mornant (1983). Elevated to family level by Fujimoto et al. (2016) as previously suggested by Jørgensen et al. (2010). Arthrotardigrada without sclerotized cuticular plates. Cephalic appendages usually consist of unpaired median cirrus, three pairs of cirri and two pairs of clavae. Buccal clavae may be indistinguishable or third pair of clavae may be present (Angursa Pollock, 1979). Unmodified papillate sensory organs on leg IV. Adult legs terminate in four digits, usually with multipointed claws, rarely single-pointed (Lepoarctus Kristensen & Renaud-Mornant, 1983; Pleocola Cantacuzène, 1951). Peduncles present in all digits, in external digits only with heart-shaped pads on internal digits or absent. Rosette-like female gonopore and paired seminal receptacles. Selected literature for further information: Jørgensen et al. (2014). See Kristensen & Renaud-Mornant (1983) and Kristensen & Higgins (1984a) for keys to this family. 1.8.1 Angursa Pollock, 1979 (emended by Bussau, 1992; Figs 8 I, 12C) Styraconyxidae with four digits. External digits supported by peduncles, internal digits with proximal pads. Claws with two divergent points (hooks), primary hook stronger than secondary hook. Claws retractable into membranous sheath. Dorsal cuticular plates absent. Complete set of cephalic cirri present, sometimes median cirrus may be reduced or absent. Configuration of primary clavae and lateral cirri variable, arising from distinct lateral extension or directly from head. Secondary clavae occasionally present, occurring as indistinct dome-shaped areas. Sometimes tertiary clavae with appearance similar to those of secondary clavae present, situated ventrally to the secondary clavae. Spines present on legs I, II, III or only on legs I. Usually clavoid papillae, mostly with spine, on legs IV. Body smooth and slender. Type species: Angursa bicuspis Pollock, 1979 Selected literature for further information: See Renaud-Mornant (1981b); Bussau (1992) and Villora-Moreno (1998) for keys to this genus. 1.8.2 Bathyechiniscus Steiner, 1926 (emended by Pollock 1983; Fig. 8 B, no drawing of claws) Cylindrical Styraconyxidae with four fully developed toes, each bearing claws with three or more vertically arrayed exposed points, on medial digits at least. Well-developed cephalic cirri present, including median cirrus. Single pair of clavae immediately adjacent to lateral cirri with one or both of these structures arising from a distinct lateral extension of the head, i.e., from a pedestalate base. Spines present on legs I–III and papilla or papilla/spine combination on legs IV. Lateral folds of cuticle or alae absent. Type species: Bathyechiniscus tetronyx Steiner, 1926 Remark: Bathyechiniscus was described by Steiner (1926) as having claws with four points. However, his description was based on only one specimen, and his drawings are rough sketches. Steiner’s Fig. 3 shows four small points, but in his Fig. 5 the fourth point could be interpreted as the posteriormost tip of a crescent-shaped claw (Pollock 1983). The type material for Bathyechiniscus no longer exists, no paper after Steiner ever mentions studying it and no other records of Bathyechiniscus have ever been made. As we cannot determine whether Bathyechiniscus actually has four points or only three, we have not included a drawing for Bathyechiniscus in our illustration of feet (Figs 10–14). 1.8.3 Lepoarctus Kristensen & Renaud-Mornant, 1983 (translated from French; Figs 8 D, 12F) Styraconyxidae with enlarged bell-shaped epicuticle around the body excluding the cephalic region. Complete set of cephalic appendages with cylindrical scapus. Primary clavae retractable into a membranous epicuticular sheath. Secondary clavae indistinct. Cirrus E located in a funnel-shaped epicuticular structure. Spines on legs I; reduced on legs II and vestigial on legs III. Papillae on legs IV with pointed tip. Buccal tube long, stylets and stylet supports very thin, placoids thin. Simple claws retractable into membranous sheath. Type species: Lepoarctus coniferus (Renaud-Mornant, 1975) Selected literature for further information: Kristensen & Renaud-Mornant (1983) transfer Pleocola coniferus Renaud-Mornant, 1975 to Lepoarctus coniferus (Renaud-Mornant, 1975a). 1.8.4 Paratanarctus D’Addabbo Gallo, Grimaldi de Zio, Morone De Lucia & Troccoli, 1992 (Figs 3 C, 9A, 11I) Styraconyxidae with a complete set of cephalic sense organs. Cephalic cirri short and thin; primary clavae tubular. Sense organs of the fourth leg coxal. Cirrus E articulated with an elementary accordion-plated portion. Lance-shaped tarsus with pretarsus. Basal pads on all digits. All claws with external dorsal calcars. Peduncles not present. Type species: Paratanarctus kristenseni D’Addabbo Gallo, Grimaldi de Zio, Morone De Lucia & Troccoli, 1992 Selected literature for further information: D’Addabbo Gallo et al. (1992). 1.8.5 Pleocola Cantacuzène, 1951 (translated from French, following Renaud-Mornant 1979a; Figs 8 C, 12E) Styraconyxidae with strongly convex conical head; Cirri A and clavae implanted in a posterior plan relative to median cirrus. Simple claws. Remark: The original description does not exactly give a diagnosis of the genus: A subsequent incomplete diagnosis has been given by Renaud-Mornant (1979a). Based on the reexamination of Pleocola specimens by Kristensen & Renaud-Mornant (1983) a body smooth and slender; the presence of a complete set of cephalic sense organs; primary clavae short and ovoid; secondary clavae indistinct; spines on legs I, II, III; papillae on legs IV, and cirrus E present are some missing characters characterizing the genus. Type species: Pleocola limnoriae Cantacuzène, 1951. Commensal on the isopod Limnoria lignorum (Rathke, 1799). Selected literature for further information: Kristensen & Renaud-Mornant, 1983. 1.8.6 Raiarctus Renaud-Mornant, 1981 (emended by Jørgensen et al. 2014; Figs 8 G, 12G) Styraconyxidae with the dorso-lateral epicuticular coat supported by long thin pillars 5–6 µm regularly arranged in close parallel lines. With 3-pointed claws42, with or without heart shaped pads on the internal digits. With or without peduncles on every tarsus. Minor primary clava with a cone or tube-like shape; the short, secondary clava either reduced or minor. Body dorso-ventrally flattened. With lateral tube-like openings to the seminal receptacles. Halechiniscid male gonopore (oval papilla with a crescent-shaped opening). Type species: Raiarctus colurus Renaud-Mornant, 1981 Selected literature for further information: see Renaud-Mornant (1981a), D’Addabbo Gallo et al. (1986) and Jørgensen et al. (2014). 1.8.7 Rhomboarctus Renaud-Mornant, 1984 (emended by Hansen et al. 2003a; Figs 8 H, 12D) Styraconyxidae with convex frontal edge; indistinct or lenticular secondary clavae; dorsal cuticle punctated; cuticular fins supported by medium sized pillars, extending on both sides of the body between primary clavae and the fourth pair of legs. More or less evident caudal appendage with cuticular fan with pillars. Peduncles present only on the external digits, proximal pads on the internal ones; all the claws with very thin or vestigial secondary hooks. Type species: Rhomboarctus thomassini Renaud-Mornant, 1984 Remark: Claw bases can appear like a third point. 1.8.8 Styraconyx Thulin, 1942 (emended by Kristensen & Higgins 1984a; Figs 8 A, 12A) Styraconyxidae with four digits. External digits always supported by peduncles; internal digits with proximal pads, peduncles present or absent. Claws with three exposed points (hooks43), may be retracted within claw sheath. Dorsal cuticular plates absent although grid-like pattern of 18–23 folds sometimes present on epicuticle. Complete 42. In the terminology of this key “three points” = primary, secondary and accessory points. 43. In the terminology of this key “three points or hooks” = a primary point and 2 secondary points or an accessory point, primary point and secondary point. set of cephalic cirri always present; configuration of primary clavae and lateral cirri variable, arising from distinct lateral extension or directly from head; secondary clavae occurring as indistinct flat sacs or dome-shaped papillae. Stylet supports, stylets and placoids present. Spines present on legs I–III, clavoid papillae, each with spine, on leg IV. Paired seminal receptacles with ducts opening posterior to the female gonopore present between legs III and IV. Type species: Styraconyx haploceros Thulin, 1942 Selected literature for further information: See Kristensen & Higgins (1984a) and D’Addabbo Gallo et al. (1989) for keys to this genus. See also Chang & Rho (1998) and Bartels et al. (2015) for more recently described species. 1.8.9 Tetrakentron Cuénot, 1892 (emended by van der Land 1975; Figs 8 F, 12H) Styraconyxidae with the body dorsoventrally flattened. Cephalic appendages (including cirrus medianus) very short; only the cephalic papillae are relatively large. Eyes lacking. Mouth opening on buccal cone and anus subterminal. Legs short, with short tibia and digits. Claws compound (with primary and secondary hooks) and with peduncles; those of internal digits with large accessory spine44 on secondary hook; no spurs. Marine, littoral ectoparasitic on burrowing holothurians. Type species: Tetrakentron synaptae Cuénot, 1892 Selected literature for further information: Kristensen (1980). 1.8.10 Tholoarctus Kristensen & Renaud-Mornant, 1983 (emended by Jørgensen et al. 2014; Figs 8 E, 12B) Styraconyxidae with barrell-shaped outer epicuticle surrounding the trunk, the body itself is thin and elongated. Complete set of cephalic appendages. Cone-shaped primary clavae and secondary clavae enlarged surrounding both the internal and external cephalic cirri. Cirri A and E partially surrounded by funnel-shaped epicuticular folds. Leg sense organs always present on the first and fourth pair of legs, though much smaller sense organs may be present on the second and third legs. Flagellum on the sense organ of the first leg always very long. Sense organ on the fourth leg partially enclosed in funnel-shaped epicuticular folds. Females have claws with a main hook, a basal accessory hook and a terminal accessory spur45. Males and larvae migth have simple claws in the external digits. Long buccal tube with two lateral projections at ca. the mid-point. Long and thin stylet supports articulate with the furcae. Placoids consist of a non-calcified cuticular lining, but three small calcified apodemes occur in the anterior part of the pharyngeal bulb. Mouth cone terminal and protruding. Globular coelomocytes seem to be attached to the midgut. Sexual dimorphism in body size and claws. Type species: Tholoarctus natans Kristensen & Renaud-Mornant, 1983

1.1 ARCHECHINISCIDAE Binda, 1978 (following Kristensen & Higgins 1984b) Considered as subfamily Archechiniscinae assigned to the family Halechiniscidae by Grimaldi de Zio & D���Addabbo Gallo (1987). The family Archechiniscidae was reinstated by J��rgensen et al. (2010). Arthrotardigrades with two internal clawed toes having a hook-like dorsal point. Toes with a short basal pad inserted into a tarsal extension. External strong sessile claws with a powerful internal accessory point15. Median cirrus absent or vestigial, cuticle finely pointed, anterior clava and thin dorsal metameric plates also present. 1.1.1 Archechiniscus Schulz, 1953 (following Chang & Rho 1998a) (Figs 4 A, 12I) Archechiniscidae with two external claws directly inserted on the tarsus, and internal claws supported by fingers; median cephalic cirrus very small or absent. Papillate primary clavae and lenticular secondary clavae. Tubular seminal receptacles present. Type species Archechiniscus marci Schulz, 1953 Selected literature for further information: Miller et al. (2012) provides a key to all currently known species of this genus., Published as part of Fontoura, Paulo, Bartels, Paul J., J��rgensen, Aslak, Kristensen, Reinhardt M��bjerg & Hansen, Jesper Guldberg, 2017, A dichotomous key to the genera of the Marine Heterotardigrades (Tardigrada), pp. 1-45 in Zootaxa 4294 (1) on page 25, DOI: 10.11646/zootaxa.4294.1.1, http://zenodo.org/record/831540, {"references":["Binda, M. G. (1978) Risistemazione di alcuni tardigradi con l'istituzione di un nuovo genere di Oreellidae e della nuova famiglia Archechiniscidae. Animalia, 5, 307 - 314.","Kristensen, R. M. & Higgins, R. P. (1984 b) A new family of Arthrotardigrada (Tardigrada: Heterotardigrada) from the Atlantic Coast of Florida, U. S. A. Transactions of the American Microscopical Society, 103 (3), 295 - 311. https: // doi. org / 10.2307 / 3226191","Jorgensen, A., Faurby, S., Hansen, J. G., Mobjerg, N. & Kristensen, R. M. (2010) Molecular phylogeny of Arthrotardigrada. Molecular Phylogenetics and Evolution, 54, 1006 - 1015.","Schulz, E. (1953) Ein neue Tardigraden-Gattung von der pacifischen Kuste. Zoologischer Anzeiger, 151, 306 - 310.","Chang, C. Y. & Rho, H. S. (1998 a) Three new tardigrade species associated with barnacles from the Thai coast of Andaman Sea. The Korean Journal of Biological Sciences, 2, 323 - 331.","Miller, W. R., Clark, T. & Miller, C. (2012) Tardigrades of North America: Archechiniscus biscaynei, nov. sp. (Arthrotardigrada, Archechiniscidae), a marine tardigrade from Biscayne National Park, Florida. Southeastern Naturalist, 11 (2), 279 - 286. https: // doi. org / 10.1656 / 058.011.0209"]}

Genus Batillipes Richters, 1909 Diagnosis. The generic diagnosis is the same as that for the family. Type-species. Batillipes mirus Richters, 1909 Additional 25 species: Batillipes acaudatus Pollock, 1971; B. adriaticus Grimaldi de Zio, Morone De Lucia, D���Addabbo Gallo & Grimaldi, 1979; B. africanus Morone De Lucia, D���Addabbo Gallo & Grimaldi de Zio, 1988; B. annulatus de Zio, 1962; B. bullacaudatus McGinty & Higgins, 1968; B. carnonensis Fize, 1957; B. caudatus Hay, 1917; B. crassipes Tchesunov & Mokievsky, 1995; B. dicrocercus Pollock, 1970; B. friaufi Riggin, 1962; B. gilmartini McGinty, 1969; B. lesteri Kristensen & Mackness, 2000; B. littoralis Renaud-Debyser, 1959; B. longispinosus Chang & Rho, 1997; B. marcelli Morone De Lucia, D���Addabbo Gallo & Grimaldi de Zio, 1988; B. noerrevangi Kristensen, 1978; B. orientalis Chang & Rho, 1997; B. pennaki Marcus, 1946; B. philippinensis Chang & Rho, 1997; B. phreaticus Renaud-Debyser, 1959; B. roscoffensis Kristensen, 1978; B. rotundiculus Rho, Min & Chang, 1999; B. similis Schulz, 1955; B. spinicauda Gallo D���Addobbo, Sandulli & de Zio Grimaldi, 2005; B. tridentatus Pollock, 1989; B. tubernatis Pollock, 1971 Remarks. See the discussion of the status of the type-species Batillipes mirus in Kristensen & Mackness (2000). Batillipes caudatus was incorrectly synonymised with B. mirus by Marcus (1929) and is still recognized as a junior synonym by Guidetti and Bertolani (2005)., Published as part of J��rgensen, Aslak, Boesgaard, Tom M., M��bjerg, Nadja & Kristensen, Reinhardt M., 2014, The tardigrade fauna of Australian marine caves: With descriptions of nine new species of Arthrotardigrada, pp. 401-443 in Zootaxa 3802 (4) on page 405, DOI: 10.11646/zootaxa.3802.4.1, http://zenodo.org/record/252490, {"references":["Richters, F. (1909) Tardigraden-Studien. Bericht der Senckenbergischen Naturforschenden Gesellschaft in Frankfurt am Main, 1909, 28 - 48.","Pollock, L. W. (1971) On some British marine Tardigrada, including two new species of Batillipes. Journal of the Marine Biological Association of the United Kingdom, 51, 93 - 103. http: // dx. doi. org / 10.1017 / s 0025315400006482","Morone De Lucia, R. M., D'Addabbo Gallo, M. & Grimaldi de Zio, S. (1988) Descrizione di due nuove specie di Batillipedidae (Tardigrada: Arthrotardigrada). Cahiers de Biologie Marine, 29, 361 - 373.","de Zio, S. (1962) Descrizione di Batillipes annulatus n. sp. e note su Batillipes pennaki Marcus, nuovo rinveniento nel Mediterraneo (Heterotardigrada). Annuario dell'Istituto e Museo di zoologia dell'Universita di Napoli, 16, 1 - 7.","McGinty, M. M. & Higgins, R. P. (1968) Ontogenetic variation of taxonomic characters of two marine tardigrades with the description of Batillipes bullacaudatus n. sp. Transactions of the American Microscopical Society, 87 (2), 252 - 262. http: // dx. doi. org / 10.2307 / 3224449","Fize, A. (1957) Description d'une especie nouvelle de Tardigrade, Batillipes carnonensis n. sp. Bulletin de le Soci zoologique de France, 82, 430 - 433.","Hay, W. P. (1917) A new species of bear-animalcule from the coast of North Carolina. Proceedings of the United States National Museum, 5, 251 - 254.","Tchesunov, A. V. & Mokievsky, V. O. (1995) A new marine tardigrade, Batillipes crassipes sp. nov., from the Japan Sea (Tardigrada, Arthrotardigrada, Batillipedidae). Cahiers de Biologie Marine, 36, 153 - 157.","Pollock, L. W. (1970) Batillipes dicrocercus n. sp., Stygarctus granulatus n. sp., and other Tardigrada from Woods Hole, Massachussetts USA. Transactions of the American Microscopical Society, 89, 38 - 52.","Riggin, G. (1962) Tardigrada of Southwest Virginia: with the addition of a description of a new marine species from Florida. Virginia Agricultural Experiment Station Technical Bulletin, 1952, 1 - 145.","McGinty, M. M. (1969) Batillipes gilmartini, a new marine tardigrade from a California beach. Pacific Science, 23, 394 - 396.","Kristensen, R. M. & Mackness, B. S. (2000) First record of the marine tardigrade genus Batillipes (Arthrotardigrada: Batillipedidae) from south Australia with a description of a new species. Records of the South Australian Museum, 33 (2), 73 - 87.","Renaud-Debyser, J. (1959) Etudes sur la faune interstitielle des iles Bahamas. III. Tardigrades. Vie et Millieu, 10, 297 - 302.","Chang, C. Y. & Rho, H. S. (1997) Two new marine tardigrades of genus Batillipes (Heterotardigrada: Batillipedidae) from Korea. Korean Journal of Systematic Zoology, 13, 93 - 102.","Kristensen, R. M. (1978) Notes on Marine Heterotardigrades. 1. Description of two Batillipes species, using the electron microscope. Zoologischer Anzeiger, 200, 1 - 17.","Marcus, E. (1946) Batillipes pennaki, a new marine tardigrade from the North and South American Atlantic coast. Comunicaciones Zoologicas del Museo de Historia Natural de Montevideo, 2, 1 - 3.","Rho, H. S., Min, B. H. & Chang, C. Y. (1999) Taxonomic study of marine tardigrades from Korea. I Genus Batillipes (Heterotardigrada, Batillipedidae). Korean Journal of Systematic Zoology, 15, 107 - 118.","Schulz, E. (1955) Studien an marinen Tardigraden. Kiel Meeresforschung, 9, 73 - 79.","Pollock L. W. (1989) Marine interstitial Heterotardigrada from the Pacific Coast of the United States, including a description of Batillipes tridentatus n. sp. Transactions of the American Microscopical Society, 108, 169 - 189.","Marcus, E. (1929) Tardigrada. In: Bronn's Klassen und Ordnunden des Tierreichs, 5, 608 pp.","Guidetti, R. & Bertolani, R. (2005) Tardigrade taxonomy: an updated check list of the taxa and a list of characters for their identification. Zootaxa, 845, 1 - 46."]}

Subfamily Florarctinae Renaud-Mornant, 1982 Diagnosis (following Kristensen 1984): Arthrotardigrades of the family Halechiniscidae Thulin, 1928 with cuticular aliform expansions. Complete cephalic sense organs with secondary clavae transformed to dome-shaped papillae or H-shaped flat sacs. Four digits with claws present in adults; digitus externus with a hook-shaped pedunculus; uncus with a calcar externum. Females with two seminal receptacles, each consisting of a spheroid vesicle and an S-shaped genital duct. Type genus: Florarctus Delamare Deboutteville & Renaud-Mornant, 1965. Additional genera: Ligiarctus Renaud-Mornant, 1982; Wingstrandarctus Kristensen, 1984.

Subfamily Styraconyxinae Kristensen & Renaud-Mornant, 1983 Diagnosis (emended from Kristensen & Higgins 1984): Halechiniscids with two or four peduncles on four digits; either internal peduncles absent or heart-shaped proximal pad present. Three to four hooks present on each claw, sometimes secondarily reduced to only one or two hooks. Claws can be retracted into membranous sheath. Secondary clavae normally reduced or lacking. Cirrus A [lateral cirrus] and Cirrus E similar; primary clavae and sense organs of the fourth leg also similar. The cuticle is variable but dorsal cuticular plates are never present.

Jørgensen, Aslak, Boesgaard, Tom M., Møbjerg, Nadja, Kristensen, Reinhardt M. (2014): The tardigrade fauna of Australian marine caves: With descriptions of nine new species of Arthrotardigrada. Zootaxa 3802 (4): 401-443, DOI: http://dx.doi.org/10.11646/zootaxa.3802.4.1

Subfamily Dipodarctinae Pollock, 1995 Diagnosis (emended): Halechiniscids with primary clavae much longer than, and ventral to, the lateral cirri; indistinct secondary clavae present as kidney- or sausage-shaped elevations between internal and external cephalic cirri. Feet on legs I–III with at least three (digits I–III) of the four digits short and of equal length; digit IV is more dorsal and can be very long. Two short horizontal strengthening bars (peduncles) inside the tarsus. Foot on leg IV differs strongly from feet of leg I–III. It is of Tanarctus - type, i.e., with two long, thin, flexible medial digits (digits II and III) with small crescent claws with accessory spines, and two shorter lateral digits (digits I and IV) without accessory spines. Calcar can be present in all claws. Leg IV sensory organ differ from the spines of legs I–III. The leg IV sense organ is an ovoid to club-shaped papilla with a terminal spine. Type genus: Dipodarctus Pollock, 1995. Additional genera: No additional genera in the subfamily.

Genus Wingstrandarctus Kristensen, 1984 Diagnosis (following Kristensen 1984): Alae present in all stages except for Halechiniscus - type two-clawed larvae, without procuticular hooks or expansions. Unci simple or with a calcar externum; uncus externus formed from a single piece; uncus internus with accessory spine. Hook-shaped pedunculae present on digitus externus. With two, three or no cephalic vesicles containing bacteria. Seminal receptacles and spermatozoa of the florarctid type. Segmental glands and unicellular epidermal glands present in all segments. Type species: Wingstrandarctus corallinus Kristensen, 1984. Additional species: W. intermedius (Renaud-Mornant, 1967) and W. crypticus Renaud-Mornant, 1989. Remarks. The genus Wingstrandarctus was described by Kristensen (1984) from sediment samples taken along the coastline of One Tree Island, Queensland, Australia at a depth of 2 meters. Apart from the new species of Wingstrandarctus several species of the closely related genus Florarctus were found in the fine coral sand. Since the description of W. corallinus several known but undescribed species of Wingstrandarctus have been found in so different areas as Troms��, Norway and the Faroe Bank (North Atlantic Ocean), the Mediterranean Sea and in various tropical seas (R.M. Kristensen pers. obs.). Apart from the type species W. corallinus the genus consist of W. crypticus and W. intermedius. Both species were found in coralline sediment from New Caledonia in the south Pacific (Renaud-Mornant 1989). Wingstrandarctus intermedius was first described as Halechiniscus intermedius (see Renaud-Mornant 1967). Features like the lack of procuticular expansion supports found in the ala of most Florarctus allowed Kristensen (1984) to include it as a member of the genus Wingstrandarctus. In most species of Wingstrandarctus and Florarctus the cuticular expansions (alae) are so thin that they are easily overlooked in conventional light microscopy. Although there are only four lateral alae, there appear to be 6, because the first lateral ala is subdivided by a large fold or constriction just anterior to the second pair of legs. All alae are transparent with a fine punctuation. The punctuation represents the pillars inside two layers of outer epicuticle. The tiny pillars are oriented dorsoventrally. This position of pillars is very different from the lateral arrangement of the long pillars in the alae of Actinarctus or Raiarctus., Published as part of J��rgensen, Aslak, Boesgaard, Tom M., M��bjerg, Nadja & Kristensen, Reinhardt M., 2014, The tardigrade fauna of Australian marine caves: With descriptions of nine new species of Arthrotardigrada, pp. 401-443 in Zootaxa 3802 (4) on page 416, DOI: 10.11646/zootaxa.3802.4.1, http://zenodo.org/record/252490, {"references":["Renaud-Mornant, J. (1967) Tardigrades de la Baie Saint-Vincent, Nouvelle-Caledonie. In: Expedition francaise sur les recifs coralliens de la Nouvelle-Caledonie. Fondation Singer-Polignac, Paris, 12, 103 - 118.","Renaud-Mornant, J. (1989) Especes nouvelles de Florarctinae de l'Atlantique Nord-Est et du Pacifique Sud (Tardigrada, Arthrotardigrada). Bulletin du Museum National d'Histoire Naturelle, Paris, Serie 4 e, 11, 571 - 592."]}

Genus Tholoarctus Kristensen & Renaud-Mornant, 1983 Diagnosis (emended): Styraconyxinae with a barrel-shaped outer epicuticle surrounding the trunk, the body itself is thin and elongated. Complete set of cephalic appendages. Cone-shaped primary clavae and secondary clavae enlarged surrounding both the internal and external cirri. Cirri A and E partially surround by funnel-shaped epicuticle folds. Leg sense organs always present on the first (se 1) and fourth (se 4) legs, though much smaller sense organs may be present on the second (se 2) and third (se 3) legs. Flagellum on the sense organ of the first leg always very long. Sense organ of the fourth leg partially enclosed in funnel-shaped epicuticular folds. Females have claws with a main hook, a basal accessory hook and a terminal accessory spur. Males and larvae might have simple claws in the external digits. Long buccal tube with two lateral projections at ca. the mid-point. Long and thin stylet supports articulate with the furcae. Placoids consist of a non-calcified cuticular lining, but three small calcified apodemes occur in the anterior part of the pharyngeal bulb. Mouth cone is terminal and protruding. Globular coelomocytes seem to be attached to the midgut. Sexual dimorphism in body size and claws. Type species: Tholoarctus natans Kristensen & Renaud-Mornant, 1983. Additional species: The genus is currently monotypic. However a sub-species from Italy, Tholoarctus natans pedunculatus D’Addabbo Gallo, de Zio Grimaldi, Morone De Lucia & Troccoli, 1992, has been described (D’Addabbo Gallo et al. 1992).

Genus Tanarctus Renaud-Debyser, 1959 Diagnosis (following J��rgensen & Kristensen 2001): Tanarctinids without dorso-lateral epicuticle long rodshaped pillars. All four digits with simple external claws without dorsal spurs, internal claws with microscopic spurs or without spurs. The internal digits may be fused proximal and form a pretarsus. The external digits have a basal cuticular fold. The primary clava, when present, is very long and similar to the IV leg appendages, or the IV leg appendages are strongly modified with long spines, leaf-like appendages or balloon-like ampullae. The buccal clavae may consist of fused secondary and tertiary clavae and then appear H-shaped around the mouth, or they can be located rostrally as club-shaped clavae (secondary clavae?). Finally the buccal clavae may be absent or indistinct as a dome- or lens-shaped structure. FIGURE 16. LM of Tholoarctus oleseni nov. sp. A���D. Allotypic female. A. Overview. B. Close-up of the head. C. Close-up of the buccal apparatus. D. Close-up of the fourth pair of legs. E. Overview of the holotypic male. Abbreviations: bt���buccal tube; cE���cirrus E; ec���external cirrus; ed���external digit; ic���internal cirrus; id���internal digit; oe���outer epicuticle; pb���pharyngeal bulb; pc���primary clava; pi���cuticular pillars; sc���secondary clava; se 3 ���leg sense organ 3; ss���stylet support; st���stylet; ta���tarsus. Type species: Tanarctus tauricus Renaud-Debyser, 1959. Additional species: Tanarctus arborspinosus Lindgren, 1971; Tanarctus bubulubus J��rgensen & Kristensen, 2001; Tanarctus dendriticus Renaud-Mornant, 1980; Tanarctus diplocerus Fujimoto, Miyazaki & Suziki, 2013; Tanarctus gracilis Renaud-Mornant, 1980; Tanarctus helleouetae Renaud-Mornant, 1984; Tanarctus heterodactylus Renaud-Mornant, 1980; Tanarctus longisetosus Grimaldi de Zio, D'Addabbo Gallo, Morone De Lucia, Vaccarella & Grimaldi, 1982; Tanarctus minotauricus Renaud-Mornant, 1984; Tanarctus ramazzottii Renaud-Mornant, 1975; Tanarctus tauricus Renaud-Debyser, 1959; Tanarctus velatus McKirdy, Schmidt & McGinty-Bayly, 1976. Remarks. Several new species of tanarctids with unknown phylogenetic relationships have been reported from the coarse shell gravel of the Faroe Bank (Hansen et al. 2001). These species might represent a North Atlantic radiation, and together with the common occurance of Tanarctus in subtidal samples (R.M. Kristensen pers. obs.), suggest that this genus is much more numerous than the current number of described species. If all the undescribed species residing in various tardigrade collections were examined, the number of known Tanarctus species would greatly increase; as shown with the descriptions of several new species of stygarctids (Hansen et al. 2012)., Published as part of J��rgensen, Aslak, Boesgaard, Tom M., M��bjerg, Nadja & Kristensen, Reinhardt M., 2014, The tardigrade fauna of Australian marine caves: With descriptions of nine new species of Arthrotardigrada, pp. 401-443 in Zootaxa 3802 (4) on pages 432-434, DOI: 10.11646/zootaxa.3802.4.1, http://zenodo.org/record/252490, {"references":["Renaud-Debyser, J. (1959) Etudes sur la faune interstitielle des iles Bahamas. III. Tardigrades. Vie et Millieu, 10, 297 - 302.","Lindgren, E. W. (1971) Psammolittoral marine tardigrades from North Carolina and their conformity to worldwide zonation patterns. Cahiers de Biologie Marine, 12, 481 - 496.","Renaud-Mornant, J. (1980) Description de trois especies nouvelles du genre Tanarctus Renaud-Debyser, 1959, et creation de la sous-famille des Tanarctinae subfam. nov. (Tardigrada, Heterotardigrada). Bulletin du Museum National d'Histoire Naturelle, Paris, Serie 4 e, 2, 129 - 141.","Renaud-Mornant, J. (1984) Halechiniscidae (Heterotardigrada) de la campagne Benthedi, canal du Mozambique. Bulletin du Museum National d'Histoire Naturelle, Paris, Serie 4 e, 6, 571 - 592.","Renaud-Mornant, J. (1975) Occurrence of the genus Tanarctus Renaud-Debyser, 1959 in North eastern Atlantic waters with a description of T. ramazzotti n. sp. (Arthrotardigrada). Memorie dell'Istituto Italiano di Idrobiologia, Pallanza, 32, 325 - 332.","McKirdy, D. J., Schmidt, P. & McGinty, M. (1976) Interstitielle Fauna von Galapagos. XVI. Tardigrada. Mikrofauna des Meeresbodens, 58, 409 - 448.","Hansen, J. G., Jorgensen, A. & Kristensen, R. M. (2001) Preliminary studies of the tardigrade fauna of the Faroe Bank. Zoologischer Anzeiger, 240, 385 - 393. http: // dx. doi. org / 10.1078 / 0044 - 5231 - 00046","Hansen, J. G., Kristensen, R. M. & Jorgensen, A. (2012) The armoured marine tardigrades (Arthrotardigrada, Tardigrada). Scientia Danica. Series B. Biologica, The Royal Danish Academy of Sciences and Letters, 2, 8 - 91."]}

Subfamily Tanarctinae Renaud-Mornant, 1980 Diagnosis (following Jørgensen & Kristensen 2001): Halechiniscids with strongly telescopic legs that have lance-like tibia and conical tarsus. External claw always simple with a prominent calcar; the internal claw may have a small dorsal spur. Leg I–III sense organs are spines; leg IV sense organs strongly modified to long clava-like or bifurcate appendages. Epicuticle may have small dorso-lateral ‘hour-glass’ or very long rod-like pillars. The two dorso-lateral spherical seminal receptacles with spindle-shaped ventral ducts open close to or lateral for the female gonopore. Type genus: Actinarctus Schulz, 1935 Additional genera: Tanarctus Renaud-Debyser, 1959; Zioella Renaud-Mornant, 1987.