A new labidostomid from Australia 
327 
Morphology of the palp as for family, with four 
articles and usual chaetotaxy: 1;1;3;4+ w; solenidion 
co tiny and dorsal. 
Podosoma and Ventral Shield (Figure IB) 
Epimeral plates alveolated, except in the 
posterior zone where ornamentation is produced 
by slightly striated alveolae; strong apodemes. 
Epimeral plate III strongly reduced, epimera I and 
II developed. Epimeral plate I with the usual pore. 
Epimeral chaetotaxy: 15-18; 10; 6-7; 6. Ventral 
shield with 7-9 cuticular pores arranged in a 
transverse row situated behind epimera IV. 
Male genital valves strongly setose, setae 
disposed in 4 irregular longitudinal rows. Female 
genital valves with only about 20 setae. When 
genital valves of both males and females are 
closed, the sagittal edges are closely appressed. 
Females with a narrow furrow into which anterior 
edge of paraprocts fit ensuring solidarity of 
movements of paraprocts and genital valves. 
Progenital chamber with two pairs of genital 
papillae in both sexes. Anal shields each with 3 
setae. Fundamental ornamentation pattern of anal 
and genital valves is alveolated but pentagonal or 
hexagonal walls tending to disapear leaving only 
costules visible and giving a stellate secondary 
pattern. 
Legs and Claws 
Legs divided into trochanter, basifemur, 
mesofemur, telofemur, genu, tibia, tarsus and 
apotele. Claws of legs I-IV with only two, large 
ungues (10 pm), middle unguis absent. Tarsi I—III 
with eupathidia. Tarsal extremities present 
dorsally (Figure 3C), tarsal recess visible where 
claws can be partially retracted (very similar to 
that of Sphaerolichus barbarns Grandjean, 1939). 
Remarks 
As noted above, this species is very similar to S. 
fS.) womersleyi from South Australia, but can be 
distinguished by features of the tarsi, dorsal shield, 
and fixed cheliceral digit. The principal diagnostic 
feature of this species is the bidactylous tarsi II—IV: 
it is an important character state which can be 
considered as autapomorphic. 
Despite the unique occurence of bidactylous legs, 
this species seems to form a natural group with S. 
(S.) womersleyi, S. (S.) adelaideae from Australia and 
S. (S.) circinus from New Zealand. This suggests 
that they might share a common ancestor, and that 
apomorphic character states of S. (S.) biungniculata 
can be only interpretated as elements of species- 
level differentiation. 
The claws of labidostomids, as in the 
Sphaerolichidae, show distinct heteronychy on legs 
II, III and IV, with the median unguis being the 
weakest and lost from leg I (Grandjean 1941). 
Sellnickiella biungniculata is unique amongst known 
labidostomids and shows only two claws on all 
legs. Of particular interest would be the nature of 
the tarsal claws in the immature instars: 
protonymphs of labidostomids present a 
symetrical, tridactylous claw on leg IV. It is on this 
argument that Grandjean proposed that the 
tridactylous condition reperesented the primitive 
state, with bidactylous and monodactylous claws 
representing advanced states. 
Also of interest is the presence of tarsal 
eupathidia on legs 1—III: it is an usual character 
amongst Labidostomidae and is rare among 
Actinedida which usually have the eupathidia 
restricted to tarsi I—II. This character is also shared 
with Sphaerolichidae. Grandjean (1941) underlined 
the possible relationships between Labidostomidae 
and Sphaerolichidae on the basis of common 
primitive morphological characters. Unfortunately, 
the genus Sphaerolichus is only known from a few 
rare northern hemisphere species. Since 
Grandjean's publications (1941, 1942), new data on 
the lack of gland-like organs in labidostomids 
(notably Sellnickiella) clearly demonstrate that 
affinities between these families are strong enough 
to consider those Endeostigmata which lack rutella 
(Sphaerolichidae and Lordalycidae) are closer to 
the primitive Actinedida (Eupodina, 
Labidostomina) than to other families of this 
heterogeneous group. 
ACKNOWLEDGEMENT 
I wish to warmly thank Mark Harvey (Western 
Australian Museum) for providing the specimens 
listed above and for assistance with the 
preparation of the manuscript. 
REFERENCES 
Atyeo, W.T. and Crossley, D.A. (1961a). Labidostomidae 
from Australia (Acarina, Prostigmata) with 
description of a new species. Transactions of the Royal 
Society of South Australia 84: 83-86. 
Atyeo, W.T. and Crossley, D.A. (1961b). The 
Labidostomidae of New Zealand. (Acarina) Records 
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Bertrand, M. (1990a). La famille des Labidostomidae 
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Bertrand, M. (1990b). Nouvelles esp&ces de 
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Bertrand, M. and Theron, P.D. (1992). Nouveaux 
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