Thalerius

Class : Eutardigrada

Order : Isohypsibioidea

Family : Incerta

Genus : Thalerious

Genus Thalerius

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

Isohypsibioidea from Bertolani et al. 2014: “Double claws asymmetrical with respect to the median plane of the leg (2121), normally with similar shape and size on each leg; double claws of the Isohypsibius type (secondary branch of the external claw inserted perpendicularly on the claw basal tract), or reduced from it: Hexapodibius type (very short, without common basal tract, with a base as large as the sum of the primary and secondary branch widths, and with an evident suture between primary and secondary branch); Haplomacrobiotus type (one branch only); completely absent (Apodibius). Buccal tube completely rigid (apart Paradiphascon; see below) and often relatively large, without (Dastychius, Eremobiotus, Halobiotus, Isohypsibius, Paradiphascon, Pseudobiotus, Thulinius) or with (Apodibius, Doryphoribius, Haplomacrobiotus, Haplohexapodibius, Hexapodibius, Parhexapodibius) ventral lamina. Eggs with smooth shell laid within the exuvium.”

Isohypsibiidae from Marley et al. 2011: “Isohypsibioidea. Claw pairs of similar size and shape. External and internal claws exhibiting articulation (the basal section and secondary branch form a solid unit while the primary branch and secondary branch articulate). Claws Isohypsibius-type, forming a right-angle between basal section and secondary branch. AISM ridge-like.”

Genus description from Dastych 2009: “Semiterrestrial, medium sized hypsibiids. Claw system of Hypsibius-type. The bases of external claws expanded posteriorly, each with a roundish, deep incision, the sides of the incision with a well formed tooth. Main branches of external claws thin and markedly long. At the base of each internal claw on legs I to III a distinct cuticular bar. Each bar with two unique, small and half-rounded plates close to each other. Buccopharyngeal apparatus similar to that of species of the Isohypsibius prosostomus-group. Mouth tube without strengthening bar. Pharynx with three macropiacoids and one microplacoid. […] The new genus can be distinguished from all other eutardigrade genera by the presence of peculiarly incised and oriented bases of ail external ciaws and the presence of unique small plates at each cuticular bar on legs I to III.
The claw system of Thalerius gen. nov. resembles most closely that of Ramajendas Pilato & Binda, 1990, a taxon reported from the (Sub-) Antarctic region. However, although the external claws in Ramajendas are quite similar to those of the new genus (see Pilato & Binda 1990) as far as the long flexible and thin main branch and the similar shape of the remaining part of the claw are concerned, they differ in having distinct lunules (particularly large on legs IV) and no incision at the claw base. The structures are differently formed in Thalerius gen. nov. Furthermore, Ramajendas has no plates at the cuticular bars on legs I-III and no external incision between the base and secondary branch of external claws as in the new genus. Further, the internal ciaws in Ramajendas are of the Isohypsibius-type (Pilato & Binda, I. c.), those in Thalerius gen. nov. resemble more the Hypsibius-type.”


Citations :

Thalerius images and captions from Dastych H. 2009. Thalerius konradi gen. nov., sp. nov., a new tardigrade from the periglacial area of the Ötztal Alps, Austria (Tardigrada). Contributions to Natural History. 12: 391-402.

Bertolani R, Guidetti R, Marchioro T, Altiero T, Rebecchi L, Cesari M. 2014. Phylogeny of Eutardigrada: New molecular data and their morphological support lead to the identification of new evolutionary lineages. Molecular Phylogenetics and Evolution. 76: 110-126.

Marley NJ, McInnes SJ, Sands CJ. 2011. Phylum Tardigrada: A re-evaluation of the Parachela. Zootaxa. 2819: 51-64.

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