Online Tardigrada Key

Modified from Nelson DR, Guidetti R, Rebecchi L. 2009. Tardigrada. Ch. 14 in Ecology and Classification of North American Freshwater Invertebrates, Thorp JH, Covich AP (eds.), 3rd ed.

Lateral Cirri A Absent

Austeruseus

Genus Austeruseus Eohypsibioidea from Bertolani & Kristensen 1987 in Marley et al. 2011: “Parachela;

Lateral Cirri A Absent

Isohypsibius

Genus Isohypsibius Isohypsibioidea from Marley et al. 2011: “Parachela. Claws asymmetrical (2121); Isohypsibius-type

Armoured

Hypechiniscus

From Thulin 1928: “Echiniscidae with armor containing five median plates.

Armoured

Pseudechiniscus

Genus Pseudechiniscus From Ramazzotti & Maucci: “After the second paired

Armoured

Proechiniscus

Genus Proechiniscus From Kristensen 1987: “Echiniscidae with black eyes, flexible

Lateral Cirri A Absent

Calohypsibius

Genus Calohypsibius Hypsibioidea from Pilato 1969 in Marley et al.

Lateral Cirri A Absent

Dastychius

Genus Dastychius Isohypsibioidea from Marley et al. 2011: “Parachela. Claws

Lateral Cirri A Absent

Doryphoribius

Genus Doryphoribius Isohypsibioidea from Marley et al. 2011: “Parachela. Claws asymmetrical (2121); Isohypsibius-type

Lateral Cirri A Absent

Diphascon

Subfamily Diphasconinae Hypsibioidea from Pilato 1969 in Marley et al.

Lateral Cirri A Absent

Platicrista

Subfamily Itaquasconinae Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Lateral Cirri A Absent

Haplomacrobiotus

Isohypsibioidea from Marley et al. 2011: “Parachela. Claws asymmetrical (2121); Isohypsibius-type claw pairs;

Armoured

Novechiniscus

Genus Novechiniscus From Kristensen 1987: “Echiniscidae with flexible buccal tube,

Lateral Cirri A Absent

Apodibius

Genus Apodibius Isohypsibioidea from Marley et al. 2011: “Parachela. Claws asymmetrical (2121); Isohypsibius-type

Lateral Cirri A Absent

Sarascon

Subfamily Itaquasconinae Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Armoured

Bryodelphax

Genus Bryodelphax From Ramazzotti & Maucci 1983 (tr. Beasley 1995):

Lateral Cirri A Absent

Thalerius

Genus Thalerius Isohypsibioidea from Marley et al. 2011: “Parachela. Claws asymmetrical (2121); Isohypsibius-type

Lateral Cirri A Absent

Meplitumen

Subfamily Itaquasconinae Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Lateral Cirri A Absent

Paradiphascon

Genus Paradiphascon Isohypsibioidea from Marley et al. 2011: “Parachela. Claws asymmetrical (2121); Isohypsibius-type

Lateral Cirri A Absent

Hypsibius

Subfamily Hypsibiinae Hypsibioidea from Pilato 1969 in Marley et al.

Lateral Cirri A Absent

Parhexapodibius

Genus Parhexapodibius Isohypsibioidea from Marley et al. 2011: “Parachela. Claws asymmetrical (2121); Isohypsibius-type

Lateral Cirri A Absent

Minilentus

Genus Minilentus Macrobiotoidea from Marley et al. 2011: “Parachela; claw pairs symmetrical

Lateral Cirri A Absent

Famelobiotus

Genus Famelobiotus Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Lateral Cirri A Absent

Fractonotus

Genus Fractonotus Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Cephalic Filaments

Limmenius

Genus Limmenius From Horning et al. 1978: “Head without normal buccal lamellae,

Armoured

Echiniscus

From Schultze 1840: “The body ovate-elongated, with armor plates, in

Lateral Cirri A Absent

Astatumen

Subfamily Itaquasconinae Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Armoured

Testechiniscus

From Kristensen 1987: “Echiniscidae with black/brownish or ‘lipoid’ granular eyes;

Armoured

Mopsechiniscus

Genus Mopsechiniscus From Ramazzotti & Maucci: “The plates are as

Lateral Cirri A Absent

Eohypsibius

Genus Eohypsibius Eohypsibioidea from Bertolani & Kristensen 1987 in Marley

Cephalic Filaments

Milnesium

Genus Milnesium From Doyère 1840: “Téte portant à sa partie

Lateral Cirri A Absent

Ramazzottius

Genus Ramazzottius Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Lateral Cirri A Absent

Itaquascon

Subfamily Itaquasconinae Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Cephalic Filaments

Milnesioides

Genus Milnesioides From Claxton 1999: “Semi-terrestrial eutardigrade belonging to the

Lateral Cirri A Absent

Acutuncus

Incerta Subfamily Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Lateral Cirri A Absent

Pilatobius

Subfamily Pilatobiinae Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Lateral Cirri A Absent

Mixibius

Incerta Subfamily Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Armoured

Antechiniscus

Genus Antechiniscus Antechiniscus, from Kristensen 1987: Echiniscidae with black eyes,

Armoured

Acanthechiniscus

Genus Acanthechiniscus Acanthechiniscus, from Vecchi et al. 2016: “Echiniscid with pseudosegmental cuticular

Lateral Cirri A Absent

Parascon

Subfamily Itaquasconinae Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Lateral Cirri A Absent

Pseudobiotus

Genus Pseudobiotus Isohypsibioidea from Marley et al. 2011: “Parachela. Claws asymmetrical (2121); Isohypsibius-type

Lateral Cirri A Absent

Hexapodibius

Genus Hexapodibius Isohypsibioidea from Marley et al. 2011: “Parachela. Claws asymmetrical (2121); Isohypsibius-type

Lateral Cirri A Absent

Ramajendas

Isohypsibioidea from Marley et al. 2011: “Parachela. Claws asymmetrical (2121); Isohypsibius-type claw pairs;

Lateral Cirri A Absent

Borealibius

Subfamily Hypsibiinae Hypsibioidea from Pilato 1969 in Marley et al.

Lateral Cirri A Absent

Mesocrista

Subfamily Itaquasconinae Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Lateral Cirri A Absent

Paramacrobiotus

Genus Paramacrobiotus Macrobiotoidea from Marley et al. 2011: “Parachela; claw pairs symmetrical

Armoured

Multipseudechiniscus

Genus Multipseudechiniscus From Miller, Schulte, Johansson 2012: “Echiniscidae with dorsal

Armoured

Diploechiniscus

From Vicente et al. 2013: “Echiniscids with dorsal plates I,

Jointed Legs

Arthrotardigrada

Arthrotardigrada, from Marcus 1927: “those tardigrade genera that develop folds

Lateral Cirri A Absent

Bertolanius

Genus Bertolanius: Eohypsibioidea from Bertolani & Kristensen 1987 in Marley

Lateral Cirri A Absent

Cryoconicus

Genus Cryoconicus Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Lateral Cirri A Absent

Biserovus

Genus Biserovus Macrobiotoidea from Marley et al. 2011: “Parachela; claw pairs symmetrical

Lateral Cirri A Absent

Bindius

Subfamily Itaquasconinae Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Lateral Cirri A Absent

Adropion

Subfamily Itaquasconinae Hypsibioidea from Pilato 1969 in Marley et al.

Armoured

Parechiniscus

Genus Parechiniscus From Ramazzotti & Maucci: “The plates are not

Armoured

Bryochoerus

From Ramazzotti & Maucci 1983 (tr. Beasley 1995): Median plates

Armoured

Cornechiniscus

Genus Cornechiniscus From Ramazzotti & Maucci 1983 (tr. Beasley 1995):

Lateral Cirri A Absent

Halobiotus

Genus Halobiotus Isohypsibioidea from Marley et al. 2011: “Parachela. Claws asymmetrical (2121); Isohypsibius-type

Lateral Cirri A Absent

Macrobiotus

Genus Macrobiotus Macrobiotoidea from Marley et al. 2011: “Parachela; claw pairs symmetrical

Lateral Cirri A Absent

Eremobiotus

Genus Eremobiotus Isohypsibioidea from Marley et al. 2011: “Parachela. Claws asymmetrical (2121); Isohypsibius-type

Lateral Cirri A Absent

Mesobiotus

Genus Mesobiotus Macrobiotoidea from Marley et al. 2011: “Parachela; claw pairs symmetrical

Lateral Cirri A Absent

Minibiotus

Genus Minibiotus Macrobiotoidea from Marley et al. 2011: “Parachela; claw pairs symmetrical

Lateral Cirri A Absent

Calcarobiotus

Genus Calcarobiotus Macrobiotoidea from Marley et al. 2011: “Parachela; claw pairs symmetrical

Lateral Cirri A Absent

Microhypsibius

Genus Microhypsibius Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Lateral Cirri A Absent

Thulinius

Genus Thulinius Isohypsibioidea from Marley et al. 2011: “Parachela. Claws asymmetrical (2121); Isohypsibius-type

Cephalic Filaments

Bergtrollus

Genus Bergtrollus Bergtrollus, from Dastych 2011: “Semiterrestrial, medium- to large-sized

Lateral Cirri A Absent

Hebesuncus

Genus Hebesuncus Hypsibioidea from Pilato 1969 in Marley et al. 2011: “Parachela; claws asymmetrical

Lateral Cirri A Absent

Haplohexapodibius

Isohypsibioidea from Marley et al. 2011: “Parachela. Claws asymmetrical (2121); Isohypsibius-type claw pairs;

Lateral Cirri A Absent

Insuetifurca

Genus Insuetifurca Macrobiotoidea from Marley et al. 2011: “Parachela; claw pairs symmetrical

Claw Symmetry Relative To Median Plane Of Leg?

Image from Bingemer J, Hohberg K. 2017. An illustrated identification key to the eutardigrade species (Tardigrada, Eutardigrada) presently known from European soils. Soil Organisms. 89 (3): 127-149.

Stylet Support Insertion Point As Percentage Of Buccal Tube Length

Stylet support insertion point = ss divided by Buccal tube length, as %. Note anterior measurements begin at anterior margin of stylet sheaths, ss is centred where stylet supports reach buccal tube (this requires a good dorsal or lateral view for proper measurement)


Image from Tumanov DV. 2006. Five new species of the genus Milnesium (Tardigrada, Eutardigrada, Milnesiidae). Zootaxa. 1122: 1-23.

Buccal Tube Long, Mouth At Anterior Of A Protrusible Snout

Images from Pilato G, Binda MG. 2010. Definition of families, subfamilies, genera, and subgenera of the Eutardigrada, and keys to their identification. Zootaxa. 2404: 1-54.

Pharyngeal Tube With Spiral Reinforcement

Images from Pilato G, Binda MG. 2010. Definition of families, subfamilies, genera, and subgenera of the Eutardigrada, and keys to their identification. Zootaxa. 2404: 1-54.

Peribuccal papillae?

Note: in a tardigrade with snout extended, the flex of the pharyngeal tube may not be obvious.


Images from Pilato G, Binda MG. 2010. Definition of families, subfamilies, genera, and subgenera of the Eutardigrada, and keys to their identification. Zootaxa. 2404: 1-54.

(Lateral) cephalic papillae, peribuccal papillae, Milnesiidae - type claws, exceptionally wide (and usually short) buccal tube?

Cephalic image modified from Nelson DR, Guidetti R, Rebecchi L. 2009. Tardigrada. Ch. 14 in Ecology and Classification of North American Freshwater Invertebrates, Thorp JH, Covich AP (eds.), 3rd ed.

Claw image modified from Pilato G, Binda MG. 2010. Definition of families, subfamilies, genera, and subgenera of the Eutardigrada, and keys to their identification. Zootaxa. 2404: 1-54.

Pharyngeal tube flexible?

Note: in a tardigrade with snout extended, the flex of the pharyngeal tube may not be obvious.


Images from Pilato G, Binda MG. 2010. Definition of families, subfamilies, genera, and subgenera of the Eutardigrada, and keys to their identification. Zootaxa. 2404: 1-54.

Serrated / dentate cuff / collar on legs IV

Left image from Kristensen RM. 1987. Generic revision of the Echiniscidae (Heterotardigrada), with a discussion of the origin of the family. pp. 261-335 in Bertolani R (ed). Biology of Tardigrades: Selected symposia and monographs.

Right Image from Richters F. 1926. Tardigrada. in Krumbach T. 1927. Handbuch der Zoologie, 3rd band, Walter de Gruyter & Co.

Leg sensory structures

Typically papilla on leg IV (se4 in image) and variable shape on leg I


Image from Kristensen RM. 1987. Generic revision of the Echiniscidae (Heterotardigrada), with a discussion of the origin of the family. pp. 261-335 in Bertolani R (ed). Biology of Tardigrades: Selected symposia and monographs.

Trunk appendages

Appendages (after Cirrus A) labeled according to plate … B (Scapular plate), C (First segmental plate), D (Second segmental plate), E (terminal plate). “B” is lateral, “Bd” is dorsal

Be careful! There can be great variability within a population, with individuals (especially juveniles) lacking some appendages. When in doubt, choose “Unclear” to ignore this character!


Left image from Ramazzotti G, Maucci W. 1983. Il phylum Tardigrada(III edizione riveduta e aggiornata). English translation by C. W. Beasley, 1995. Memorie dell’ Istituto Italiano di Idrobiologia 41: 1-1012.

Right image cropped from Kristensen RM. 1987. Generic revision of the Echiniscidae (Heterotardigrada), with a discussion of the origin of the family. pp. 261-335 in Bertolani R (ed). Biology of Tardigrades: Selected symposia and monographs.

Cirrus A form

Images modified from Kristensen RM. 1987. Generic revision of the Echiniscidae (Heterotardigrada), with a discussion of the origin of the family. pp. 261-335 in Bertolani R (ed). Biology of Tardigrades: Selected symposia and monographs.

Lower image (Mopsechiniscus) modified from du Bois-Reymond Marcus E. 1944. Sobre tardigrados brasileiros. Communicaciones Zoologicas del Museo de Historia Natural de Montevideo. 1(13): 1-19 plus plates.

Terminal / caudal plate with two notches?

Images modified from Kristensen RM. 1987. Generic revision of the Echiniscidae (Heterotardigrada), with a discussion of the origin of the family. pp. 261-335 in Bertolani R (ed). Biology of Tardigrades: Selected symposia and monographs.

First image (Echiniscus) modified from Richters F. 1926. Tardigrada. in Krumbach T. 1927. Handbuch der Zoologie, 3rd band, Walter de Gruyter & Co.

Inner & outer buccal cirri present

Image modified from Nelson DR, Guidetti R, Rebecchi L. 2009. Tardigrada. Ch. 14 in Ecology and Classification of North American Freshwater Invertebrates, Thorp JH, Covich AP (eds.), 3rd ed.

Pseudosegmental plate between last medial plate & terminal plate?

Note on 2nd image, what you see before the terminal plate is either no plate, or a full-width medial plate; don’t confuse the latter with a pseudosegmental plate!
Also, sometimes the pseudosegmental plate is paired, like segmental plates II & III. It’s still pseudosegmental!

Images from Clifford HF. 1991. Aquatic invertebrates of Alberta. University of Alberta Press, Alberta, Canada.

Segmental plates larger than intersegmental?

Image modified from Lindahl & Balser (1999), http://www.iwu.edu/~tardisdp/Keypage35.html

Any Paired Plates?

Images from Kristensen RM. 1987. Generic revision of the Echiniscidae (Heterotardigrada), with a discussion of the origin of the family. pp. 261-335