Echiniscus

Class : Heterotardigrada

Order : Echiniscoidae

Family : Echiniscidae

Genus : Echiniscus

From Schultze 1840: “The body ovate-elongated, with armor plates, in nine distinct segments, eight feet affixed to alternate segments from the third to the ninth. The head with four thorn-like antennae, eyes simple and two.”

Untranslated: “Corpus ovato-elongatum, scutatum, spinosum, in novem segmenta distinctum, pedes octo alternis segmentis a tertio ad nonum affixi. Caput antennis quatuor spinisque duabus instructum, ocumli simplices duo.”

From Kristensen 1987: “Diagnosis: Echiniscidae with red-granulae eyes, unflexible buccal tube, without pseudosegmental plates IV’. Median plates undivided, caudal plate notched; ventral plates absent. Primary and secondary clavae papillate. Stylet supports absent or not visible by light microscopy. Emended description: The dorsal plates consist of a strongly sculptured head plate, indistinct neck plate, unpaired scapular plate (I), paired segmental plates II and III, unpaired notched caudal plate (IV), undivided plate 1 and 2; if present, me- dian plate 3 also undivided. Lateral intersegmental plates absent, segmental plates II and III may be divided into several pieces, as may the scapular plate (I). The leg plates are strongly developed only on the fourth pair of legs where the edge of the plate forms a serrated collar or a spine fringe. The cephalic sense organs consist of papillate primary and secondary clavae, long cirri A, short internal and slightly longer external cirri. The cirri A have small cirrophores separated from the primary clavae, cirrophores are present also on internal and external cirri. The leg I and 1V sense organs are present although they are not always illustrated in older descriptions. The leg I sense organ is located distally and it may vary from a short to a long spine; the leg IV sense organ is always in the form of a papilla located proximally on the leg. The arctomys and viridis groups lack the trunk appendages, but in other species, the location of spines or cirri have a high taxonomic value, and together with the sculpture of the dorsal plates, these constitute two of the best key characters in the determination of the species in the genus Echiniscus. The claw morphology is highly variable in the genus, accessory hooks, spurs or cusps may be absent as in the type species B. testudo, and the internal claws often have secondary spurs. In the more advanced species secondary and tertiary spurs can be present on the external claws, too. The location (proximal at the base of claw or more distal) also have a high taxonomic value. Colour varies widely e.g. grey, black, green, oliven, brown, red or yellow. The buccal apparatus has a relatively short, rigid buccal tube with stylets longer than the tube. The furcae of the stylets insert on the large, trilobed pharyngeal bulb. The stylet supports were not observed in any of the investigated species. The placoids and outer cuticular linings are well developed.”

From Gąsiorek et al. 2017: “Echiniscids with red eyes composed of pigment granules. Rigid buccal tube lacking stylet supports or with fine, fibrillar stylet supports. Two pairs of segmental plates. Two or three median plates, sometimes transversally subdivided. Incisions (notches) on caudal (terminal) plate. No pseudosegmental plates. Ventral subcephalic and/or genital plates may be present.

Differential diagnosis […phenotypic…] Echiniscus differs from the Pseudechiniscus– like genera (Acanthechiniscus Vecchi et al., 2016; Antechiniscus Kristensen, 1987; Cornechiniscus Maucci and Ramazzotti, 1981; Mopsechiniscus du Bois-Reymond Marcus, 1944; Multipseudechiniscus Schulte and Miller, 2011; Proechiniscus Kristensen, 1987; Pseudechiniscus Thulin, 1911) in having red eyes and lacking pseudosegmental plates (eyes are always crystalline and black, and at least one pseudosegmental plate occurs in these genera). The rigid buccal tube of Echiniscus differentiates the genus from Cornechiniscus, Mopsechiniscus, Multipseudechiniscus, Novechiniscus Kristensen, 1987, and Proechiniscus, in which the posterior portion of buccal tube is flexible (Miller et al., 2012). Moreover, Echiniscus differs from Novechiniscus and Parechiniscus Cuénot, 1926 in having paired segmental plates (whereas Novechiniscus and Parechiniscus have only single plates). Echiniscus can be separated from Bryodelphax Thulin, 1928 and Bryochoerus Marcus, 1936 by the presence of incisions on the caudal plate. Moreover, Bryodelphax and Bryochoerus are generally very small, with adults rarely exceeding 150 μm, whereas typical dimensions of Echiniscus adults are well above 200 μm. Echiniscus typically lacks ventral plates, which are present in Diploechiniscus Vicente et al., 2013 and Testechiniscus Kristensen, 1987. Finally, red granular eyes differentiate the genus from Diploechiniscus, Testechiniscus and Hypechiniscus Thulin, 1928, all of which have black crystalline eyes.”


Alberta:
spitsbergensis (now moved to Testechiniscus)

Canada:
bisetosus (Heinis, 1908)(declared invalid by Maucci 1985, mostly likely aberrent trisetosus or canadensis)
canadensis Murray, 1910 [Echiniscus punctulatus Mihelcic, 1955; bellus Mihelcic, 1967]
horningi Schuster & Grigarick, 1971
mauccii Ramazzotti, 1956
merokensis
oihonnae Richters, 1903 (now diploechiniscus ala Vicente et al, 2013)
quadrispinosus
reymondi Marcus, 1928
spiniger Richters, 1904
sylvanus Murray, 1910
wendti Richters, 1903

North America / Nearctic:
perviridis Ramazzotti, 1959
virginicus Riggin, 1962
viridis group n species

Other:
africanus Murray, 1907
aliquantillus Grigarick, Schuster & Nelson, 1983
angolensis da Cunha & do Nascimento Ribeiro, 1964
apuanus M. Bertolani, 1946
arcangelii Maucci, 1973-74
arctomys Ehrenberg, 1853
arthuri Pilato, Binda & Lisi, 2005
azoricus Fontoura, Pilato & Lisi, 2008 Has spines
baius Marcus, 1928
baloghi Iharos, 1973
barbarae Kaczmarek & Michalczyk, 2002
batramiae Iharos, 1936
becki Schuster & Grigarick, 1966
bigranulatus Richters, 1907
bisculptus Maucci, 1983 Has 3rd median plate, scapular pattern different than other plates
blumi blumi Richters, 1903 [Echiniscus ramazzottii Binda & Pilato, 1969]
blumi schizofilus Bartoš, 1941
calcaratus Richters, 1908
calvus Marcus, 1931
canedoi da Cunha & do Nascimento Ribeiro, 1962
capillatus Ramazzotti, 1956
carsicus Mihelcic, 1966
carusoi Pilato, 1972
cavagnaroi Schuster & Grigarick, 1966
cervicornis Murray, 1906
charrua Claps & Rossi, 1997 No clawspurs
cheonyoungi Moon & Kim, 1994 Spines
cirinoi Binda & Pilato, 1993 Polygonal granules not touching
clavispinosus Fontura, Pilato & Lisi, 2011
clevelandi Beasley, 1999 Lateral appendages
columinis Murray, 1911
corrugicaudatus McInnes, 2009
crassispinosus crassispinosus Murray, 1907
crassispinosus fasciatus Marcus, 1928
curiosus Claxton, 1996
darienae Miller, Horning & Dastych, 1995 Additional cirri, spurs at internal claw tips
dearmatus Bartoš, 1935 [Echiniscus szaboi Iharos, 1973]
dikenli Maucci, 1973
diploglyptus Durante Pasa & Maucci, 1975
divergens Marcus, 1936
dreyfusi de Barros, 1942
duboisi Richters, 1902
egnatiae Durante Pasa & Maucci, 1979
ehrenbergi Dastych & Kristensen, 1995 Resembles testudo
elaeinae Pilato, Binda & Lisi, 2005
elegans Richters, 1906
evelinae de Barros, 1942
filamentosus Plate, 1888
ganczareki Michalczyk & Kaczmarek, 2007
glaber Bartoš, 1937
granulatus (Doyère, 1840) [Echiniscus crassus Richters, 1904; Echiniscus fortis Bartoš, 1935; Echiniscus abanti Maucci, 1973]
heterospinosus Maucci, 1954
hexacanthus Maucci, 1973 Former subspecies of militaris
hoonsooi Moon & Kim, 1990 Lateral spines, polygonal granules
inocelatus Mihelcic, 1938 [Echiniscus inocellatus Mihelcic, 1964]
insuetus Mihelcic, 1967
jagodici Mihelcic, 1951
jamesi Claxton, 1996 Lateral C, D, E
japonicus Morikawa, 1951
jenningsi Dastych, 1984 Very long cirri A
kerguelensis Richters, 1904
knowltoni Schuster & Grigarick, 1971
kofordi Schuster & Grigarick, 1966
lapponicus Thulin, 1911
laterosetosus Ito, 1993 M3, lateral cirri
laterospinosus Rudescu, 1964
latifasciatus Dudichev & Biserov, 2000
lichenorum Maucci, 1983 Dorsal spines, lateral cirri
limai da Cunha & do Nascimento Ribeiro, 1964
lineatus Pilato, Fontoura, Lisi & Beasley, 2008
longispinosus Murray, 1907
loxophthalmus Richters, 1911
madonnae Michalczyk & Kaczmarek, 2006 “Pseudopores” in dorsal plates (can’t focus on edges with LM)
maesi Séméria, 1985 Very small cirri A, lateral spines
malpighii Biserov, 1994 Small cirri A
manuelae da Cunha & do Nascimento Ribeiro, 1962
marcusi Pilato, Claxton & Binda, 1989 Short spines
marginatus Binda & Pilato, 1994 Spines
marginoporus Grigarick, Schuster & Nelson, 1983
markezi Mihelcic, 1971/72
marleyi X. Li, 2007
mediantus Marcus, 1930
merokensis merokensis Richters, 1904 [Echiniscus iharosi Rudescu, 1964]
merokensis suecicus Thulin, 1911
migiurtinus Franceschi, 1957
mihelcici Iharos, 1973
militaris Murray, 1911
molluscorum Fox & Garcia-Moll, 1962
moniliatus Iharos, 1967
montanus Iharos, 1982
mosaicus Grigarick, Schuster & Nelson, 1983 Lateral appendages
multispinosus da Cunha, 1944
murrayi Iharos, 1969
nelsonae X. Li, L. Wang & Yu, 2007
nepalensis Dastych, 1975
nigripustulus Horning, Schuster & Grigarick, 1978
nobilis Mihelcic, 1967
ollantaytamboensis Nickel, Miller & Marley, 2001
osellai Maucci, 1975
pajstunensis Bartoš,1941
palmai Dastych, 1997 Granulation “knobs”
perarmatus Murray, 1907
peruvianus Binda & Pilato, 1994 Lateral & dorsal spines, no spurs
phocae du Bois-Reymond Marcus, 1944
polygonalis Ito, 1993 Lateral cirri
pooensis Rodriguez-Roda, 1948
porabrus Horning, Schuster & Grigarick, 1978
postojnensis Mihelcic, 1967 [Echiniscus loxophtalmus Mihelcic, 1939]
pseudelegans Séméria, 1994 elegans-like pattern
pseudowendti Dastych, 1984 Very long cirri A
punctus McInnes, 1995 Shorter buccal cirri, lateral & dorsal appendages
pusae Marcus, 1928
quadrispinosus quadrispinosus Richters, 1902 [Echiniscus scrofa Richters, 1902]
quadrispinosus brachyspinosus Bartoš, 1934
quadrispinosus cribrosus Murray, 1907
quadrispinosus fissispinosus Murray, 1907
quitensis Pilato, 2007 Short cirrus A
rackae Dastych, 1986 Reticulation
ranzii Ramazzotti, 1964
reticulatus Murray, 1905
robertsi Schuster & Grigarick, 1965
rodnae Claxton, 1996 Spines
rufoviridis du Bois-Reymond Marcus, 1944
rugospinosus Marcus, 1928
scabrospinosus Fontoura, 1982 Slender spurs
semifoveolatus Ito, 1993 Spines
shaanxiensis X. Li, L. Wang & Yu, 2007 Spines
siegristi Heinis, 1911
simba Marcus, 1928
speciosus Mihelcic, 1967 [Echiniscus roseus Mihelcic, 1967]
spiculifer Schaudinn, 1901
spinulosus (Doyère, 1840)
storkani Bartoš, 1940
taibaiensis L. Wang & X. Li, 2005 Many cirri
tamus Mehlen, 1969 4 teeth on dentate collar
tardus Mihelcic, 1951
tenuis Marcus, 1928
tessellatus Murray, 1910
testudo (Doyère, 1840) [Echiniscus bellermanni C.A.S. Schultze, 1840; Echiniscus inermis Richters, 1902; Echiniscus trifilis Rahm, 1921; Echiniscus filamentosus mongoliensis Iharos, 1973]
trisetosus Cuénot, 1932
trojanus Maucci, 1973
tropicalis Binda & Pilato, 1995 Very small cirri, small spines
tympanista Murray, 1911
velaminis Murray, 1910
vinculus Horning, Schuster & Grigarick, 1978
viridianus Pilato, Fontoura & Lisi, 2007
viridis Murray, 1910
viridissimus Péterfi, 1956
walteri Pilato & Lisi, 2003
weisseri Maucci, 1978
zetotrymus Horning, Schuster & Grigarick, 1978

Key excerpted & modified from Dastych (1988):
8. Only cirrus A (arctomys gr): 9
— Dorsal & lateral appendages besides A: 11
9. Outer claws of legs IV with small spines at their bases: Echiniscus capillatus
— No small spines on outer IV: 10
10. Diameter of dorsal granulation 0.8-1.5µm: Echiniscus wendti
— Dorsal plates covered with round thickenings 4-7µm in diamter: Echiniscus reticulatus
11. Lateral appendages shorter than dorsal ones: Echiniscus spinulosus
— Lateral appendages longer than dorsal ones: 12
12. Black eyes, ventral plates: Echiniscus spitsbergensis INVALID, now Testechiniscus!
— No eyes, or red eyes. No ventral plates: 13
13. Dorsal appendages C3 & D3 present: E lapponicus
— C3 & D3 never occur: 14
14. Dorsal granulation polygonal or roundish dots with light/dark ring inside each: 15
— Dorsal granulation different: 18
15: C2 & D2 almost equal in length, outer claws of IV without small spines: E granulatus
— C2 several times longer than D2, outer claws of IV with small spines: 16
16: Of lateral appendages, only A developed: E canadensis
— Other lateral appendages occur: 17
17: Lateral B, but no E: E blumi
— No B, E as small spines: E trisetosus
18: Dorsum covered with dots, irregular in shape & distribution, but without very tiny, dense, regularly arranged granulation between them (immersion!), D2 usually distinctly shorter than C2: E merokensis
— On dorsum, between irregularly distributed dots are very tiny, dense and regularly arranged granulation (immersion!), C2 & D2 usually equal in length: E quadrispinosus

Key modified from Ramazzotti & Maucci (1983):
Definitions: Granular sculpture: with proper focusing, looks like granules (which are in reality pores), rounded, with irregular size and distribution, clearly darker at the base (example: E. testudo); b). Polygonal sculpture; with proper focusing the sculpture appears composed of polygons more or less narrowly in contact between them (example: E. granulatus). c). Double sculpture; two sculptures superimposed, one composed of larger granules and one of smaller granules; when focused on one sculpture it appears light, while the other appears dark.

1. Other than cirrus A, there are no other appendages, dorsal or lateral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Besides cirrus A there are other appendages . . . . . . . . . . . . . . , . . . . . . . . 7
2 (1). Red, reddish-brown, or orange color ……………………….. 3
Green color, at least partially ……………………………. 4
3 (2). In the positions C or D there are hemispherical or slightly conical projections . . . . . . . . . . . . . . . . . . . . . E. maucci
There are no lateral hemispherical projections . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . arctomys group
4 (2) Green color only in the caudal part; cavity globules red . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. rufoviridis
The color is entirely green . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5(4). CirrusAisverylong(l50-170µm) . . . . . . . . . . . . . . . . . . . . . . . . E.perviridis
Cirrus A is short, or of medium length (from 30 to 80µm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6 (5). The plates exhibit whitish or black spots; internal claws without spurs . . . . . . . . . . . . . . . . . . 6 (5). The plates exhibit whitish or black spots; internal claws without spurs: E. viridissimus
Color olive green, with dark green spots; internal claws with little spurs . . . . . . . . . . . . . . . . . . . . . . E. viridis
7 (1). There are no dorsal appendages ………………………….. 8
There are dorsal appendages …………………………….. 12
8 (7). The lateral appendages are all filaments . . . . . . . . . . . , . . . . . . . . . . . . . . 9
Other than cirrus A, the lateral appendages are spines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9 (8). The sculpture is of the polygonal type; there are spurs on all the claws of the 4thpair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. becki
The sculpture is “double”; internal claws with spurs, externals with a small spine . . . . . . . . . . . E. postojnensis
10 (8). There is a spine at E ………………………………… 11
There is not any appendage at E ……………………. E. robertsi
11 (10). There is a lateral spine C, “double” sculpture . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . E. cavagnaroi
There is not a lateral spine C; granular sculpture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . E. baius
12 (7). Besides cirrus A, there are no other lateral appendages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Besides cirrus A, there are other lateral appendages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
13 (12). Dorsal appendages are present at C and D . . . . . . . . . . . . . . . . . . . . . . . 14
Dorsal appendages are present in a single position (at B or D) . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . 16
14 (13). Dorsal appendages at C and D are bothspines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E.murrayi
Dorsal appendages C are filaments, D are spines . . . . . . . . . . . . . . . . . . . 15
15 (14).The sculpture is a fine granulation ………………. E.punctulatus
The sculpture is of the polygonal type ……………… E.canadensis
16 (13). There are very small spines at dorsal B and dorsolateral C, spurs are present on all the claws of the 4th pair . . . . . . . . . . . . . . . . . . . E.molluscorum
There are dorsal spines D; spurs are present .only.on.theinternalclaws . . . . . . . . . . . . . . . . . . . . . . E.migiurtinus
17 (12). Appendage E is present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Appendage E is not present (attention! The small spines that are sometimes found at E are not considered appendages) . . . . . . . . . . . . . . . . . . . . . . 74
18 (17). All the lateral and dorsal appendages, including E, are distally enlarged, like a drumstick . . . . . . . . . . . . . . . . . ………. E. tympanista
The appendages, dorsal and lateral, are small teeth, spines, or filaments . . . . . . . . . . . . . . . . . . . . . . . . . 19
19 (18). The appendage E is a spine …………………………….. 20
The appendage E is a filament ………………………….. 48
20 (19). Lateral appendages are present only at A and E, “double” sculpture . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Lateral appendages are present also inotherpositions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
21 (20). Dorsally there are only filaments in position C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. carusoi
Dorsallytherearespines C and D . . . . . . . . . . . . . . . . . . . . . . E.angolensis
22 (20). Except for cirrus A, all the lateral appendages are spines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
There are also lateral filaments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
23 (22). Besides cirrus A, there are lateral spines in all the positions (B, C, D, E) . . . . . . . . . . . . . . . . . . . . . . . . . 24
There are not lateral appendages in all the positions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
24 (23). Dorsally there is only filament C; “double” sculpture . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . E. carusoi
The dorsal appendages are spines . . . . . . . . . ..*……………… 25
25 (24). Dorsal spines are present on the scapular plates, that is at B . . . . . . . . . . ..*……………. 26
Dorsal spines do not exist at B . . . . . . . . . . . . . . . . ..*…………. 27
26 (25). Dorsal spines exist at B, C, and D . . . . . . . . . . . . . . . . . . . . . . . E. arcangelii (sp?)
Dorsally there are 6 spines on the scapular plate, that is at B, 2 spines at C, and 2 spines at D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. africanus
27(25).Dorsallythereareonlyspines D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Dorsally therearespinesCandD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
28 (27). Lateral B, C, and D, and dorsal D spines are very short and difficult to observe; thesculptureis”double” . . . . . . . . . . . . . . . . . . . . . . . E.peramatus
Lateral and dorsal spines D are normally developed and evident; sculpture is granular . . . . . . . . . . . . . . . . 29
29 (28). The internal and external claws of the 4thpairarewithoutspurs . . . . . . . . . . . . . . . . . . . . . . . . E.dreyfusi
The internal claws of the 4th pair bear large and robust spurs . . . . . . . . . . . . . . . . . . . . . . . . . E. virginicus
30 (27). The dorsal and lateral spines are dentate; “double” sculpture . , , , . , . . . . . . . . . . . . . . . . . . . . . . . . E. duboisi
Spines not dentate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
31(M). Green color ………………………………… E.pooensis
Red or orange color …………… – …………………… 32
32 (31). The lateral spines are very short ………………….. E.spinulosus
The lateral spines are normally developed, or else long …………. 33
33 (32). The sculpture is polygonal …………………………. E. pusae
The sculpture is different ……………………………… 34
34 (33). There are dorsal spines C and dorsal teeth D; the sculpture is a fine granulation asastringofpearls . . . . . . . . . . . . . . . . . . . . . . . E. laterospinosus
Different . . . . . . . . . . . . . .._………………………….. 35
35 (34). There are dorsal spines D, robust, strongly divergent; indistinct sculpture . . . . . . . . . . . . . . . . . . . . E. diveqens
There are dorsal spines C and D of equal length, not divergent; granular sculpture . . . . . . . . . . . . . . . . . . . E. spiniger
36 (23). Other than cirrus A and spine E, there is a spine at C or D ……….. 37
BesidescirrusAandspineE,thereare spinesCandD ………… 39
37 (36). There is a lateral spine at C, dorsally there are short spines C and D, claws without spurs . . . . . . . . . . . . . . . . . . . . . . . . * . . . . . . E. calcaratus
Different; “double” sculpture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
38 (37). There are lateral spines C or D; dorsally there is filament C . . . . . . . , . . . . . . . . . . . . . . . . . . . . . E. carusoi
There is lateral spine C; dorsally spine D, that is often lacking . . . . . . . . . . . . . . . . . . . . . . . . . . E. cavagnaroi
39 (36). Dorsally there are spines C and D, notched, sculpture with, scattered pores . . . . . . . . . . . . . . . . . . . E. manuelae
Thedorsalappendages are onlyatCorD . . . . . . . . . . . . . . . . . . . . . . . . 40
40(39).Dorsally existsonlyspineC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Dorsally exists filament C or spine D, “double” sculpture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
41(40). All the spines are rough; dorsolateral tooth C present; “double” sculpture . . . . . . . . . . . . . . . . E. reymondi
The sculpture is a dense granulation; there are no dorsolateral teeth; spurs arepresentonallclawsofthe4thpairof legs . . . . . . . . E.virginicus
42 (40). Dorsal filament C present ………………………… E. carusoi
Dorsal spine D present ……………………… E. crassispinosus
43 (22). Except for spine E, all the other lateral appendages are filaments; poiygonal sculpture . . . . . . . . . . . . . 44
Besides E there are other lateral spines; granular sculpture . . . . . . . . . . . 46
44 (43).The lateral appendages are filaments A, B, C, and D, and spine E; dorsal appendages are present at B, C, and D . . . . . . . . . . . . . . . . . . . . . . . E. militaris
In the dorsal positions there are appendages at C and D, not B . . . . . . . . 45
45 (44). The lateral appendages are filaments A, C, and D, and spine E, dorsally filament C and spine D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. trojanus
The lateral appendages are filaments A, B, C, and D, and very short spine E; dorsally robust spine C and short divergent spine D . . . . . . . . . . . . . . . . . . . . . . . . . E. heterospinosus
46 (43). The lateral appendages are spines or filaments A, B, C, D, E, dorsally there are long spines C and short triangular teeth D . . . . . . . . . . . . . . . E. laterospinosus
Different . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
47 (46). The lateral appendages are short filaments, flankedbyasmallspineatC,D,andE; dorsally there is a short filament C, and a filament or spine D, near this last, some small teeth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. baloghi
The lateral appendages are filaments A and C, spines D and E, dorsally only spines C . . . . . . . . . . … E. simba
43 (19). Laterally there are only filaments A and E …………………… 49
There are also other lateral appendages …………………….. 51
49.(48). Filament E has a short bifurcation; dorsally there are filaments C and very short teeth D, there are also dorsolateral appendages C’ . . . . . . . . . . . . . . . . . . . ……. E. cervicornis
The filament E is not bifurcated dorsally there are only appendages D . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
50(49).Theplatesaredeprivedofsculpture ………………….. E.glaber
There is “double” sculpture present ………………….. E. evelinae
51(48). All the lateral appendages are filaments …………………….. 52
Laterally spines are also present .. ………………………. 66
52 (51). There are lateral filaments in all the positions (A, B, C, D, E) ……… 53
Lateral filaments are not present in all the positions …………….. 58
53 (52). There are dorsolateral appendages B’, C’, D’, E’; dorsal appendages at B,C,andD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E.multispinosus
There are no dorsolateral appendages . . . . . . . . . . . . . . . . . . , . . . ., . . . . 54
54 (53). “Double” sculpture; dorsal spines C and D …………. E. quadrispinosus
Granular sculpture ………………………………….. 55
55 (54). Dorsally there are filaments C and short teeth or spines D; moreover, at C and D, spines very converged at the median plane, arranged like scissors, which may also be lacking . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . E. lapponicus
Different . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
56 (55). The dorsal spines C and D are rough and coarse; there are no spurs on the claws ofthe4thpairoflegs . . . . . . . . . . . . . . . . . . . . . . . E. rugospinosus
Different . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
57 (56). The dorsal appendages C (spines or filaments) are situated at the posterior angles of plate II, or only slightly displaced toward the median line . . . . . . . . . . . . . . . . E. merokensis
The dorsal appendages C are considerably displaced toward the median line . . . . . . . . . . . . . . . . E. columinis
58 (52). Lacking the lateral appendages D ………………………… 59
Lateral appendages D present …………………………… 61
59 (58). There are lateral filaments A, C, E; dorsal filament C; polygonal sculpture . . , . . . . . . . . . . . . . . . E. nepalensis
Different . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
60 (59). There are lateral filaments A, C, E, sometimes also B; granular sculpture ………… E. testudo
There are lateral filaments A, B, C, E; dorsally two spines C on each side, and spine D . . . . . . . . . . . . . . …….. . . . . . . . E. filamentosus
61 (58). Dorsally there are only spines C, granular sculpture …………….. 62
Dorsally there are filaments or spines C and D ………………. 63
62(61).LaterallytherearefilamentsA,C,D,E ……………….. E.iharosi
Laterallythereare filaments A,D,E …………………. E.jagodici
63 (61). “Double” sculpture; dorsally spines C and D ………… E. quadrispinosus
Granular sculpture; dorsally spine or filament C and D ………….. 64
64 (63). Granular sculpture, dense and fine on all the plates, very coarse and sparse on the terminal; dorsal filaments C and D, laterals A, C, D, E, near D a spine . . . . . . . . . . . . . . . . . . . . . . E. velaminis
Granular sculpture uniform on all the plates . . . . . . . . . . . . . . . . . . . . . . 65
65 (64). Dorsally long “rigid filaments” C andD . . , . . . . . . . . . . . . . E. bartramiae (sp?)
Dorsally filaments C, and spines or teeth D, which may be lacking . . . . . . . . . . . . . . . . . . E. merokensis
66 (51). There are lateral appendages in all the positions (A, B, C, D, E) . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Lateral appendages are not present in all the positions . . . . . . . . . . . . . . . 71
67 (66). Except for filaments A and E, all the lateral appendages are spines; there are no dorsolateral appendages . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Besides A and E, all other lateral appendages are filaments; there are dorsolateral appendages . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
68 (67). Dorsally there are spines B, C, and D; clawsofthe4thpairwithoutspurs . . . . . . . . . . . . . . . . . E.weisseri
Dorsally there are spines C and D; there are spurs on the claws of the 4th pair . . . . . . . . . . E. dikenli
69 (67). Dorsally there are spines B, C, and D, laterally there are appendages A, B, C,D,E,ofwhichBandDhavea curved spine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. multispinosus
There are no appendages B dorsally . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
70 (69). There are lateral filaments A, B, C, E, and a lateral spine D; the dorsal appendages are a filament C and a spine D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. oihonnae
The lateral appendages A, C, E are spines or filaments; B, D are spines; dorsally spines C aud D . . . . . . ………………….. E. horningi
71 (66). Lateral appendages B present …………………………… 72
Lateral appendages B lacking …………………………… 73
72 (71). Lateral appendages D present; dorsally spines C present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. siegristi
Lacking lateral appendages D; dorsally spines D present . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . E. testudo
73 (71). A short lateral spine D is present; dorsally there are filaments C and spines D . . . . . . . . . . . . . . . . .- . . . . . . . . . . . . . . . . E. meridionalis
Lacking lateral appendages D; dorsally there are spines D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. testudo
74 (17). There are present lateral appendages A,B, C,andD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Besides E, lacking any (not all!) other lateral appendages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
75 (74). Al the lateral appendages are filaments; there are dorsolateral appendages; polygonal sculpture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Lacking dorsolateral appendages . . ..*…………………….. 79
76 (75). Dorsolateral appendages B’ present ……………………….. 77
Dorsolateral appendages B’ not present …………………….. 78
77 (76). There are short dorsolateral spines B’,C’,andD’ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E.spinuloides
Only dorsolateral filament B’ . . . . . . . . . . . . . . . . . . . . . . . . . . E. ramazzotti
78 (77). There are dorsolateral appendages C’andD’ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E.melanophtalmus (sp?)
Only dorsolateral appendages D’ i . . . . . . . . . . . . . . . . . . . . E. spitsbergensis NOT VALID, now Testechinscus!
79 (75). The lateral appendages terminate distally in a club; ventral armor present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. clavisetosus
The lateral appendages are not terminated inaclub,lackingventralarmor . . . . . . . . . . . . . . . . . . . . . . . . . . 80
80 (79). All the lateral appendages are filaments; dorsal appendages C and D present . . . . . . . . . . . . . . . . . . . . . . 81
Lateral A, C, and D are filaments; lateral B is a spine; dorsally there is a spine B, filaments C, and teeth D . . . . . . . . . . . . . . . . . . . . . E. apuanus (?)
81 (80). The dorsal appendages C and D are robust spines of almost equal length; internal claws of the 4th pair with spurs, externals smooth . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. granulatus
The dorsal appendages are filaments C and spines D; the internal claws of the 4th pair with spurs, the externals with 1, 2 or 3 spines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. blumi
82 (74). There are lateral appendages A, C, and D …………………… 83
There are less than three lateral appendages …………………. 95
83 (82). All the lateral appendages are filaments …………………….. 84
The lateral appendages C and D are spines ………………….. 92
84 (83). Dorsolateral appendages present; polygonal sculpture …………… 85
Dorsolateral appendages not present ………………………. 87
85 (84). There are dorsolateral appendages C’ and D’; dorsally small teeth C and D . . . . . . . . . . . . . . . . . E. marinellae
There are dorsolateral appendages D’; the dorsal appendages are filaments c and spines or teeth D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
86 (85). Red eyespots; internal claws of the 4th pairwith spurs, externals smooth . . . . . . . . . . . . . . . . . . E.menzeli
Blackeyespots,alltheclawsofthe4thpairwithspurs . . . . . . . . . E.rosaliae
87 (84). Dorsally there are only small teeth C …………….. E. laxophthalmus
Dorsallythereare appendages CandD …………………….. 88
88 (87). The dorsal appendages C are filaments …………………….. 89
Dorsal appendages C and D are both spines …………………. 90
89 (88). The dorsal appendage C is a filament, D is a spine; polygonal sculpture; the internal clawsofthe4th pair have a spur, the externals one or more spines . . . . . . . . E. trisetosus
The dorsal appendages C and D are both filaments; granular sculpture; all the claws without spurs . . . . . . . . . . . . . . . . . . . . . . . . . E. longispinosus
90 (88). The dorsal appendages C and D are both spines; polygonal sculpture; internal claws with spurs, externals smooth . . . . . . . . i . . . . . . . . . . . . . . . . . . . E.granulatus
Granular sculpture; spurs on all four clawsofthe4thpair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
91 (90). Eyes present; dentate collar with 9-12 indistinctly separate teeth . . . . . . . . . . . . . . . . . . . . . . E. knowltoni
Eyes absent; dentate collar with 5-6 teeth, very distinct . . . . . . . . . . . . . . . . . . . . . . . . . . . E. inocellatus
92 (83). The dorsal appendages are spines C and D ………………….. 93
Dorsally there are spines D, and possibly also filaments C ………… 94
93 (92). Polygonal sculpture ……………………………… E. osellai
Granular sculpture …………………………….. E. egnatiae
94 (92). The dorsal appendages are filament C and spine D; laterally there are long spines . . . . . . . . . . . . . . E. storkani
Dorsally there are only spines D; the lateral spines are short . . . . . . . . . . . . . . . . . . . . . . . E. canedoi
95 (82). Lateral appendages A and D are present; polygonal sculpture ……… 96
Lateral appendages A and C are present ……………………. 97
96 (95). The lateral appendages A and D are filaments; dorsal appendages C and D are spines . . . . . . . . . . . E. pajstunensis
The lateral appendage D is a spine; the dorsal appendage C is a filament, D a spine . ………… E. bisetosus
97 (95). Lateral appendage C is a spine; dorsally there is a filament C and spine D, polygonal sculpture . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. bisetosus
Lateral appendages A and C are filaments . . . . . . . . . . . . . . . . . . . . . . . . 98
98 (97). Dorsally there are filaments C and spines D; polygonal sculpture . …………. E. mediantus
Dorsally there are only spines D; sculpture is not polygonal, and has different on the cephalic and terminal plates, compared to the other plates . . . . . . E. diploglyptus

Notes for identification of arctoyms group
arctomys: sculpture dense, uniform punctation, closer together than their diameter, not resolvable
aliquantillus: colourless, very fine regular granulation plus random distribution of small distinct pores on all plates. Cirrus A 34µm.
barbarae: irregular dark granules, 1-3µm, larger on scapular & terminal plates
bigranulatus: double granulation (dense fine & larger less dense)
bisculptus: pattern on ant portion of pp & M2 (large granules) very different than post portion (pores in pattern), scapular different again (pores in larger pattern)
calvus: fine punctuation, has M3, very long cephalic papillae & short cirri A (only 1.5x clava)
capillatus: cirrus A huge, up to 1.5x length of tardi
carsicus: red. Sculpting complex, and differs on scapular & terminal compared to pp & m.
charrua: similar ornamentation to E quitensis. Short cirrus A (30-47µm)
cirinoi: similar to reticulatus or phocae
corrugicaudatus: distinct ridges on caudal plate (?). Colourless other than granules in cavity. Simple granulation
dearmatus: course, regular granulation. Spurs on external claws
elegans: fancy sculpturing, dense granules joined forming hexagons (wheel with six spokes). No DC?
insuetus: red-brown, uniformly distributed granules & depressions, has M3, no spurs even on internal claws
japonicus: small depressions with circular or hexagonal margins, similar to E reticulatus; internal circular zone finely punctated. Extremely small spur on internal claws
jenningsi (cirrus A >= body & thicker than clava), IV spur near middle of claw, not bent down as much as on I-III. Double granulation: 0.3-0.5µm round spots ~equal on all plates; biggest pores on end plate, mostly star-shaped, 2-3x bigger (1-2µm) than spots
kerguelensis: gran ulation or punctuation, more or less fine and regular; dots always have appearance of pores. Cirrus A 50-80µm. Easily distinguished by sculpture composed of sparse and distant pores (testudo type)
kofordii: no eyes. M3. scapular & terminal plates with protruding bands which intersect (?). Very short Cirrus A (22µm), large granules irregularly arranged, diameter up to 2.5µm
latifasciatus: no eyes. Polygonal granules up to 2µm, connected by strips. Diameter of granules & area bounded by strips decreasing from scapular to terminal. Cirrus A 23-29% of body. inner spurs
limai: maximum length 142µm, red eyes. Very thick plates, more or less regular punctationn. Very short cirrus A (14-15µm). Cephalic scapular & terminal plates carinate & facetted
malpighii: short cirrus A (30-35µm), sculpture tubercules & randomly distributed pores. Head & terminal have mostly pores, other plates have mostly tubercules. No eyes
marginoporus: colourless, granules & pores, pp entirely granulated with no stripe, DC 7-8 large teeth
markezi: dark red, black eyes (!), long cirri A. Complex sculpting: high appears smooth, lower clear granules sparse, orderly arranged; each granule is vided into 3 thickenings of the cuticle in the shape of leaves arranged in rays, totalling a reticular design. On cephalic plate only a light granulation, spurs on internal claws. Dentate collar numerous small teeth, continuous or occasionally interrupted
mihelcici: red-orange, no eyes. Sculpting: dorsally appears to be clear circles with darker interior, in whose centre is a clear dot; lower one sees clear granules, circular, distributed regularly and not in contact. No notches! Dentate collar 7-9 slender teeth. Internal curved spurs
moniliatus: clear yell-orange, eyes. Granules of different size, coarser on cephalic & scapular plates, smaller on pp & M1 & 2. Large granules at posterior margin of M1 & 2 (& corresponding margins of pp). PP both divided by transverse line. Small tubercles at interior margin of IV, dentate collar with 6 teeth (those at lateral ends longer). No spurs
mosaicus: colourless. scapular plates has 4-6 pores (1-2.8µm) surrounding large granules (2-3µm), larger on posterior margin. Cephalic plate small pores & granules rostrally. M1&2 pattern similar to posterior of scapular. Terminal plate has pronounced pores, pore pattern forms triangular or hexagonal pattern. Interpore areas joined, forming reticulate pattern. Cirrus A 33µm. DC 10-12 sharp spines of irregular size. Internal spurs. Prominent buccal papilla,larger than clava
nigripustulus: no eyes. Scapular plate has weak polygonal design, other plates have pores irregular in size & spacing; some large (3µm) opaque granules irregularly distributed. Dentate collar: 10 teeth (looks different in fig). Internal spurs.
nobilis: red-brown, red eyes. short buccal cirri (little longer than cephalic papilla). Very long cirri A (2/3 animal length). pp sculpted on first & last third, smooth in middle. sculpting: high focus, clear granules connected by clear spaces derived from mesh design, interior dark; lower at first clear (round or elongate) forming polygonal pattern. Dentate collar 5-6 teeth (often double, with 2 points), joined. Sharp spur on externals
phocae: red, red eyes. Miniscule dots assembled in areola of circular outline (discs, not hollow circles!). Internal spurs
pseudelegans: similar pattern to E elegans, but only on plates, not over whole dorsal cuticle. Also has DC, unlike E elegans
pseudowendti (cirra A 1/3-2/3 of length), inner spurs similar on I-IV. Double granulation, 0.5-1.5µm round or polygonal spots biggest on M3; 0.5µm pores ~ equal on all plates
quitensis: terminal plate unfaceted, plates have small dots joined by very thin stripes difficult to see, and light points; ant portion of pp & M2, and where M3 would be have only large polygonal dots. Internal spurs. Short (36µm) cirrus A
rackae: network pattern. DC: 5-9 teeth. Inner spurs. Cirrus A 35-50% of body (90-120µm)
ranzii: reddish, red eyes (small & often barely visible). External buccal cirri much longer than internal (2 or 3x). Long cirri A (0.5 to 0.9 of body length, average 0.66). M3 present & always very visible in adults. Double sculpture – fine background punctation, coarse puncatation as in E bigranulatus (but denser & more regular). Spurs on external IV. DC: 4-9 teeth.
reticulatus: polygonal sculpture, hexagons. Cirrus A 2/3 of length. Very long spine on I. Internal spur. Has M3.
robertsi: Sculpture well defined & separate polygons. M3. Has spines D! Internal spurs.
rufoviridis: Has M3. No spurs
speciosus: rosy-red, eyes dark red (almost black). Complex sculpture (dimples): highest: small dark circular elements surrounded by clear polygonal perimeter forming a reticular design; lower, no polygonal mesh, rather a dark bkg scattered with miniscule brilliant clear dots; lower: in place of bright granules see dark dots of equal size circumscribed by slender irregular polygons in contact with each other; lowest: larger clear granules, distant and dispersed. Cirrus A almost full length or 3/4, strongly facetted terminal plate, somewhat facetted cephalic. DC: ribbon-like thickened band, small conical teeth near each other, equal shape & size, very short, 12-15. Internal robust spur.
sylvanus: yellow, 275µm. Sculpture: dots of different size, positioned at different distances, with appearance of pores or small depressions. PP have, near rostral margin & parallel to it, slender projecting band, extended to the sides. M1 widely separated from scapular. M2 subdivided, with a smooth transverse band, in two distinct sculptured parts. No M3. Terminal 3 facets, median caudal indistinctly subdivided in 2. Cephalic papillae well developed, internal & external buccal cirri short, cirri A ~50µm and much larger and wider than in other Echiniscus, and not sharp at ends but truncate, scarcely rounded. Clava large & triangular. DC: 8-10 sharp teeth very close but not in contact. Claws large (~25µm). Internal small curved spurs.
tamus: DC: 4 large separate teeth, hexagonal sculpting, cirrus A 32µm
tardus: dark red, instead of eyes has small cuticular projection. Internal spurs. Miniscule clava. Dense uniform granulation which can appear as hexagons with slender sides at correct focal plane.
tenuis: 140-190µm, colorless or yellowish, black eyes (!). All smooth, not sculptured. Only when completely dried is regular & extremely fine punctation visible. No DC! No spurs.
tesselatus: Yellow, very long cirri A. Sculpture: very large papillae, with granular appearance, or of hemispherical knobs. Plates subdivided by smooth bands in characteristic manner. No spurs.
vinculus: 150-260µm, average 200. Internal buccal cirri 10µm, outer 14µm. No eyes. Sculpture: pores or irregular granules, interposed wide smooth areas on the scapular & terminal plates. DC: 11-15 teeth. Internal small spurs. Pilato Binda Lisi (2005) more info & images, looks quite like my slide 2. Each granule surrounded by 5-8 pores, so joined to one another by small lines. sculpture less regular on head plate, on the anterior portion of scapular plate and on terminal plate. Smooth transverse band is present on the paired plates II and III and on the median plate 2, and along the posterior margins of all plates
walteri: similar to tesselatus but not as pronounced
wendti: red to lemon-yellow, up to 300µm. Granules round patches of points with phase; in higher focus small round punctated areas, circumference subdivided into dashes, appears connected by small lines; in lower focus, groups of circular dots, similar to sculpture of E phocae, circles max diameter 3µm Elements often larger on M1&2. No M3. Cirrus A may be 55-70% of body length.

Key to bigranulatus group in michalczyk kaczmarek 2006, add this!


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

Other images modified from Gąsiorek P, Stec D, Morek W, Michalczyk Ł. 2017. An integrative redescription of Echiniscus testudo (Doyère, 1840), the nominal taxon for the class Heterotardigrada (Ecdysozoa: Panarthropoda: Tardigrada). Zoologischer Anzeiger. 270: 107-122.

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.

Schultze CAS. 1840. Echiniscus bellermanni, animal crustaceium, macrobioto hufelandi affine. Berolini, Berlin.

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