Head bearing a wide, circular shield. Lorica cylindrical or pyriform, often with one or two median dorsal spines, or several spine on posterior margin of lorica. Sometimes with a spine at the base of the toes. Mastax malleate. (ref. ID; 1663)
Apparently very rare, the animal does not seem to be mentioned in the literature since 1935, by Hauer. Lorica ovate with rounded distal corners. Head and shield wide, lateral ears very large. Foot stout with three joints (Voigt, 1957 mentions two only), the first one hidden by the tail-like appendage and visible only from the side. Main dorsal spine strong with a wide base, second spine more delicate. One small ventral thorn. Toes sharp, clawlike, slightly bent ventrally. (ref. ID; 2894)
Measurements
Total length 140-150; leg 21; toes 13; dorsal spine 112-115 and 29-31 µm. (ref. ID; 2894)
The anterior hood is large and robust, and the plate at the posterior of the dorsal section is set at about 45 degrees to the longitudinal axis of the animal. (ref. ID; 2285)
Measurements
Length of body 120; length of foot 22; length of toes 10 µm. (ref. ID; 2285)
The extremely variable species Pejler are concerned with here has been classified in the most diverse ways in the literature on the subject. However, there seems little reason in the present connection to enlarge upon the various points of view in the older literature, and Pejler shall limit himself to an account of the most recent published opinions. Here, too, there is great confusion. The array of forms is divided sometimes into two, sometimes three species, which the different authors call by different names: Wulfert (1939 and 1956) uses three names- "S. lamellaris var. mutica (Ehrbg.) 1832", "S. rostrum (Schmarda) 1846" and "S. tridentata (Fresenius)", but does not explicitly define his attitude to the taxonomy of the forms. Wiszniewski (1955) uses the three names "S. lamellaris (Muller 1786)", "S. mutica (Ehrenberg 1832)" and "S. rostrum Wulfert 1939". This altogether original classification appears only in the form of a register of species (together with lists of synonyms). Carlin expresses different opinions in different essays (Carlin-Nilsson 1934 and Carlin 1939). In the latter work he assigns the different forms to two species, S. mutica (Ehrbg.) and S. lamellaris (Mull). Voigt (1956-57) appears to employ the same taxonomy as Carlin, although he uses different names, S. tridentata (= Carlin's S. mutica) and S. rostrum (= Carlin's S. lamellaris). According to him these two "species" are distinguished by the fact that in the former the three posterior lorica spines (where present!) grow from a broad base and in the latter from a narrow base. According to Carlin, the latter "species" has in addition an unpaired spine between the toes, which is missing in the former. As regards the first distinguishing characteristics, all the transitional stages between the typical appearance of the respective "species" occur. Under the name S. tridentata Wulfert (1956, p.485 and Fig.40) depicts a form completely identical with "S. rostrum" except that it has no spine between the toes. Since Wulfert apparently regards this spine as the only distinguishing feature of the species, a grouping together of "S. tridentata" and "S. rostrum" would have seemed a logical step to take, especially as the same author attaches no taxonomic significance to this spine in the closely related species S. aurita, where is may or may not be present (see Wulfert 1950, pp.464-465). Moreover Pejler Lapland material has now shown that the length of the spine in question can vary very considerably (cf. Figs.71 and 74). It may be extremely small (Fig.71) or missing altogether. What is therefore required is a combination into one species of all the various forms. Since the first described form of this variable species is "Brachionus lamellaris Mull.", its name should be "Squatinella lamellaris (Mull.)". (ref. ID; 1450)
A majority of authors, including Voigt (1957) and Koste (1978, 1988) distinguish only two species, diagnosed by the presence or absence of a dorsal spine on the third foot segment. The additional diagnostic characteristic used by Kutikova (1970), Pontin (1978) and Braioni and Gelmini (1983) is the presence or absence of three caudal extensions of the dorsal lorica. The diagnostic value of this characteristic is, however, low: a large number of intermediate forms have been recorded (Carlin, 1939; Koste, 1978). It is therefore not maintained as a diagnostic characteristic for specific diagnosis. Pejler (1962, see ref. ID; 1450) also rejects the validity of the first diagnostic characteristic, based on his observation of a specimen that seemed to be intermediate, and on Wulfert's description of S. aurita, in which a << spine >> (dixit Pejler, << Fortsatz >> (= extension) by Wulfert, 1950) over the basis of the toes is reported to be occasionally present. The structure of the joint between the last foot segment and the toes reveals that such an extension can indeed by represent or absent, but its presence seems to result from a more pronounced retraction of the toes into the last foot segment and does therefore not represent intermediates between forms with or without a spine. Pejler's (1962) observation must probably be interpreted in the same way. As a result, only two taxa of specific rank are here recognised (apart from the insufficiently described S. cirrata (Muller, 1773): see Koste, 1978). In Koste (1978, 1988) the species provided with a spine is called S. rostrum (Schmarda, 1846) with a synonyms S. lamellaris (Muller, 1786) (!) and S. aurita Wulfert, 1950. Evidently, this is erroneous as the name S. lamellaris is the senior synonym. On the original figure of S. lamellaris by Muller (1786, reproduced in Voigt, 1957), no spine on the third foot segment is shown. Recognising this, Carlin-Nilsson (1934) used the name to denote the taxon deprived of a dorsal spine on the third foot segment. Hauer (1936), however, argumented that it is possible that Muller had overlooked this spine in his description, because of an observation by Ehrenberg (1838, in Hauer, 1936) who mentions by does not depict << eine Borste...dicht uber den Fuszfingern >> in his redescription of S. lamellaris. Hauer's (1936) assumption can not be verified, but it has served as a basis for the synonymisation of S. lamellaris with S. rostrum by Carlin (1939). The alternative hypothesis that Ehrenberg's (1838) and Muller's (1786) specimens, identified by these two authors as S. lamellaris, were not conspecific, is based on the observations provided by both authors and is favored by us. Carlin's (1939) synonymisation of S. lamellaris with S. rostrum, based on Ehrenberg's observations, is therefore rejected. The synonymy of S. aurita with S. rostrum by Koste (1978) is also considered erroneous. We conclude that the names S. rostrum and S. lamellaris (new synonymy: S. aurita), until proof of the contrary, are the valid names for the species with and without a spine on the last foot segment, respectively. In the highly variable species S. lamellaris, specimens with a differently formed caudal edge of the dorsal lorica occur. The nominate form has strongly developed caudal extensions of the dorsal lorica (as depicted by Braioni and Gelmini (1983) and Wulfert (1956)), but these extensions can be weakly developed (corresponding with S. tridentata Fresenius, 1858; Fig.5, in the combination S. lamellaris var. tridentata) or, be absent (corresponding with S. mutica Ehrenberg, 1832: Fig.6; in the combination S. lamellais var. mutica). (ref. ID; 2915)
Pejler encountered a form that can be distinguished from S. longispinata by, among other things, its larger size, more robust shape of the body and lack of spines at the base of the toes. In all these respects it is identical with S. leydigi (see Zacharias 1886, pp.255-256, and Myers 1942, p.270). The toes, however, are grown together at the root, and moreover Pejler observed a pattern on the lorica, a feature which would seem to be entirely new for the whole genus Squatinella. Nevertheless Pejler do not consider these grounds sufficient to justify the setting up of a new species. (ref. ID; 1450)
In dorsal view it is quite slender with a constricted neck and somewhat pointed head-lamella. There is a slight tail, the foot has two joints (not three as shown by Voigt) and two toes. The long dorsal spine is not normally observed in the swimming animal, as it is held vertically except when it is suddenly flipped down. In the side view the animal is quite sturdy. The corona is oblique, with auricles. The whole ventral area is coffee-brown. There is a large ventral suction cup which can attach the animal so strongly toe the substrate that it can not be removed by pipetting. This suction cup might be the structure Voigt (1967, p.194) mentions under S. longipsinata as 'winglike appendages' and as ventral hooklets under S. bifurca. The dorsal spine, originating at approximately the middle of the trunk, is at least twice the length of the animal. Its base is very broad and seems to be empty in the fully extended animal, but can be filled by internal organs. (ref. ID; 2593)
Measurements
Body length 147-165; width 70; height (dorsoventrally at the distal base of spine) 80-100; dorsal spine 320-390; foot 26; toe 30-32 µm. (ref. ID; 2593)
In the group of Squatinella's with smooth dorsal lorica, S. lunata is easily diagnosed by the following characteristics: 1) absence of a dorsal spine of the last foot pseudosegment; 2) presence of backward postero-lateral projections of the rostrum and 3) presence of two lobes on the caudal edge of the dorsal lorica. Characters (1), (2) and (3) distinguish the species from S. rostrum (Schmarda); (2) and (3) distinguish it from S. lamellaris (O.F. Muller). Characters (2) and (3) are unique to the species. (ref. ID; 2844)
Descriptions
Rostrum rounded anteriorly, with two conspicuous backward postero-lateral projections, asymmetrical in some specimens. Short neck present. Spineless dorsal lorica strongly domed, ovoid in dorsal view. Caudal edge with two projections. Foot with three pseudosegments, basal short, bearing a pair of equal toes. (ref. ID; 2844)
Male: Male unknown. (ref. ID; 2844)
Etymology
The name-lunata is derived from the Latin lunatum, referring to the shape of the species' rostrum. (ref. ID; 2844)
