[ref. ID; 1663]
Dorsal surface of lorica with a pattern polygonal facets. With one, two or no posterior spine and with six short to medium anterior spine. Highly variable plankton and limnetic species. Cyclomorphic. Very common species. (ref. ID; 1663)

[ref. ID; 2891]
The genus contains, to date, approximately 16 known species which are placed in recognized, defined morphological groups principally on the basis of the variable lorica form. There are three broad Formenkreis recognized: quadrata, valga-tropica and cochlearis, however there are as well several species groups which, although they show a certain morphological stability, are not, without further study, able to be ranked, e.g. reducta, lenzi, serrulata, americana, mixta-javana. The taxonomy of most polymorphic species at present, is based on morphological lorica markings, particularly the foundation pattern (facettation), the dorsal lorica, relative length of lorica spines and the surface structure. (ref. ID; 2891)

[ref. ID; 3073]
Mode of Egg-carrying (ref. ID; 3073 , )

[ref. ID; 3114]
This genus is divided into several species based upon the following characters (Ahlstrom 1943, Gillard 1948): 1. The presence or absence of posterior spines, their number and position. 2. The pattern of dorsal sculpture on the lorica. 3. The proportions of the body, especially as regards size, shape, width and depth. 4. The number of anterior spines. 5. The ornamentation of the ventral plate. 6. The ornamentation of the dorsal plate (rather than the fundamental pattern of the dorsum). According to the Sudzuki's opinion the following characters are available for classification of the species. 1. Position of the posterior spines (terminal for cochlearis group, lateral for quadrata-valga group). 2. Features of the dorsal sculpture on the lorica (as the difference between americana and cochlearis, cochlearis and irregularis, serrulata and cochlearis, or testudo and quadrata). 3. General shape (or proportions) of the lorica (as the difference between K. valga and K. quadrata, cochlearis and faluta, or pyriformis and valga). 4. Features of the occipital spines (as the difference between taurophala and cochlearis). Such characters as presence or absence of the posterior spines, the ornamentation (except for sculpture) of the dorsal plate, however, have no taxonomic value. The number of anterior spines is so constant in this genus contrary to Brachionus, that it might serve for generic separation when it is different (cf. K. reducta). On the contrary, certain dorsal sculpture seems to be a good character for 'subspecific' distinction (as the difference between K. valga valga and K. valga tropica or between edmondsoni and quadrata or irregularis and earlinae). (ref. ID; 3114)

[ref. ID; 4593]
Brachionid rotifers with loricate body, separated into a dorsal and ventral plate. Dorsoventrally ore or less compressed. Anterior margin usually with six spines. Posterior spines often present, one or two in number, single posterior spine usually median. Dorsal plate with sculptural pattern, with or without areolate network, postulation, or fine spines. Many species in fresh water, only a few in brackish water. Keratella cruciformis cruciformis, cr. eichwaldi, quadraa platei, and cochlearis recurvispina are typical brackish-water forms. (ref. ID; 4593)

• Keratella aculeata valga Rodewald, 1935
  See; Keratella valga (ref. ID; 3688)
• Keratella ahlstromi Russell, 1951 (ref. ID; 1709, 1923, 3126 original paper)
• Keratella americana Carlin, 1943 (ref. ID; 1345, 1835, 2198, 2265, 2545, 2806, 2817, 2894, 3022, 3125) reported year? (ref. ID; 3089)
  See; Keratella lenzi
  Syn; Anuraea stipitata Zelinka, 1907 (ref. ID; 1345, 3022); Keratella gracilenta Ahlstrom, 1943 (ref. ID; 3022); Keratella stipitata Harring, 1915 (ref. ID; 1345, 3022)
• Keratella americana nhamundiensis Koste, 1982 (ref. ID; 2806) or Brandorff, Koste & Smirnov, 1982 (ref. ID; 2834 original paper)
  See; Keratella nhamunda
• Keratella australis (Berzins), 1963 (ref. ID; 1709, 2261 , 2757, 2891)
  Syn; Keratella quadrata australis Berzins, 1963 (ref. ID; 2757)
• Keratella bostoniensis Rousselet (ref. ID; 1345)
• Keratella canadensis Berzins, 1954 (ref. ID; 1345, 1923, 2598)
  See; Keratella quadrata
• Keratella carinata Russell, 1950 (ref. ID; 1923, 3181 original paper) or 1952 (ref. ID; 2280)
  See; Keratella javana Hauer (ref. ID; 1923, 2757, 3258)

  ---

  Keratella cochlearis-group
  Keratella cochlearis and related species have very important problem of their morphological variability and possible transitions between different forms. Lauterborn (1900, 1904) has put forward his theory explaining different forms of the Keratella cochlearis group by step-by-step changes in morphology and splitting of a uniform winter Keratella into a number of successively separating strains of forms during summer, all of then ending up in the winter form again at the end of the season. Apart from minor objections and corrections the theory is still generally accepted in Europe, although it has never been proven experimentally. According to Lauterborn, the three main strains deriving from the winter form, Keratella cochlearis fa. typica are: a) the "macracantha-micracantha-tecta" strain with all cochlearis characters, but a successive reduction of body dimensions and an accelerated reduction of the posterior spine, b) the "hispida" strain, with an increasing pustulation of the lorica along with a successive disappearance of the plaque pattern, and c) the "irregularis" strain with the development of an additional "irregular" plaque, interrupting the median ridge of the lorica. Even in the "hispida" and the "irregularis" strains, the posterior spine is successively reduced. Besides the variable strains, a non-variable, "robusta" group may be found throughout the year, with basically the typical cochelaris characters. Ahlstrom, on the basis of many thousands of careful measurements on material from all over the continent, from Mexico to Alaska, and comparison also with material from Europe and other places, calls into question the direct connection between K. cochlearis and the hispida and irregularis strains respectively. While he accepts, the definition of the robusta as a varieties and does not call into question the same rank for the hispida, he raises the irregularis to the level of an independent species. Further he describes a new species, Keratella earlinae, obviously the North American equivalent to the European K. irregularis, which has not been found n North America so far. K. earlinae as well as K. crassa Ahlstrom seem to be true new world species. They occur widely spread over the continent but have been mistaken without doubt, for K. cochlearis by many authors. (ref. ID; 1402)
  Keratella cochlearis is probably the commonest planktonic rotifer. Carlin (1943) proposed to throw the familiar name K. cochlearis into synonymy with K. stipitata Ehrenberg on the basis of a presumed error by Ehrenberg in drawing a K. quadrata dorsal pattern in a K. cochlearis outline. Some authors have accepted Carlin's suggestion, but there has also been vigorous objection (Berzins, 1954), and it may be hoped that K. cochlearis will not be replaced. These animals may be assignable to K. americana Carlin (= gracilenta Ahlstrom), but there are differences in the dorsal sculpture from Ehrenberg's figure. (ref. ID; 1923)
  According to Ahlstrom (1943), Lauterborn's five series mentioned above are to be as follows:
  1. The macracantha series belongs to the typical K. cochlearis. In the specimens of the United Sates, the median line on the dorsum has a slight jog on the right-side at a point between the first and the second plaques, while the median line is straight in most cases of European specimens. Both types are also found in Japan.
  2. A new combination of names was proposed by Ahlstrom to the typical form of the irregulars series which should be a species separate from the present species. This is seldom seen in Japan.
  3. The robusta series is a large-sized group, in which the median line does not jog. This type is rare in Japan.
  4. The variety hispida, too, is larger size; the whole surface of lorica is hispid, and sometimes the fundamental patterns of dorsum are indistinct. This is rarely met with in Japan.
  5. The forma leptacantha Lauterborn was considered by Ahlstrom to be a local variant of the typical K. cochlearis.
  Keratella cochlearis is one of the commonest rotifers in Japan. The size of body proper varies considerably, the length of hind spine deviating from nothing to as long as or more than the body proper. It will be realized that variation seem to be caused not only by the conditions of localities but also by the seasonal factors. Generally speaking longspined individuals occur in early season and the progress of generations through repeated parthenogenesis makes the reduction of the length of hind spine. The cyclomorphosis may, however, not occur due to the conditions of habitat water; an acyclic generation is resulted. A good samples of such as acycly due to a large body of water is seen in K. cochlearis in the southern basin of Lake Biwa-ko. The length of hind spines and the hind spine indices do not vary in accordance with the climates. In North America, a small-sized K. cochlearis is said to occur in weakly acid water. On the contrary, a remarkably large type of K. cochlearis is found in the waters of similar condition in Japan, e.g., ponds among the Sphagnum-moors on the Shiga Heights and on Mt. Hakkoda. The size of individuals from the Shiga Heights exceeds that of var. robusta, but they belong without doubt morphologically to the macracantha series. Moreover, it is a particular interest that the length of the hind spine is considerably longer than the body proper. It would, therefore, be called as the megacantha type in the macracantha series. The measurements made on more than one thousand individuals of this series revealed us the following facts worthy to be described. A gap is clearly observed between the megacantha type and the macracantha type, and also between the macracantha type and the tecta type, in the latter of which the hind spine is entirely lacking. On the other hand, individuals of intermediate types are continuous in regard to the features which are measured, either the length of body proper and hind spine or the hind spine indices. Anyhow, there can be seen a tendency that the larger the body size, the longer the hind spine. (ref. ID; 2393)
  For reasons of priority Carlin (1943, p. 55) is of the opinion that this species ought to be called Keratella stipitata Ehrenberg. Berzins (1954) does, however, not approve Carlin's motivation, and the present author agrees in this respect with Berzins. In view of the different opinions expressed the author has referred the question, in accordance with the decision of the Zoological Congress in Paris of 1948, to the International Commission on Zoological Nomenclature (See Bull. Zool. Nomencl. 4, p. 76, 1950). Pending the decision of the Committee the author uses the, up to now, most current name, viz. Keratella cochlearis. (ref. ID; 2553)
  The Keratella species with one posterior spine and size anterior spines, and a marked median keel was, without doubt, Keratella cochlearis (Gosse). It is difficult, however, to classify the form within the 8 varieties and 6 forms described (Voigt 1967: 177-180). The identification of varieties and forms is based on the following characteristics: total length of posterior spine, macro- and micro-sculpture dorsally on lorica, thickness and colour of lorica and the angle between posterior spine and ventral list of the lorica. Different varieties may show cyclomorphosis. [Lake Blankvatn specimens] The lorica was thick and yellowish brown. The angle between the posterior spine and the ventral list of lorica varied. The total length and the length of the posterior spine were measured on 40 individuals at different seasons. The individuals tended to be larger in spring that in summer and winter. The proportion between total length and length of posterior spine nearly always seemed to be a constant 10:3. Individuals without posterior spine were not observed. The ornamentation of the lorica was not quite uniform. The lorica had two or three lateral plaques. Post-carinal plaques were more less fully developed. The median keel was either straight or slightly curved into the first left carinal plaque. It was difficult to decide whether the micro-sculpture was large or small. Judging from drawings by Latuerborn (1900 taffel 1), it would be median sized. Dorsally there were no spines on the lorica. After careful study of the works of Ahlstrom (1943), Voigt (1957: 177-180), Pejler (1962) and Sudzuki (1964), the form in Blankvatn was found to bear closest resembles to Keratella cochlearis var. robusta (Lauterborn). In lakes with low production, however, Pejler (1962) found that K. cochlearis had only a very slight cyclomorphosis and the macro sculpture of many individuals from Blankvatn was much like Lauterborn's drawings of K. cochlearis cochlearis. Pejler (1962) fond great morphological differences with the group robusta and suggested that several sibling species might be contained into this group. (ref. ID; 3226)

• Keratella cochlearis (ref. ID; 3064 male , 3073, 3285, 3530)
• Keratella cochlearis (Ehrenberg) (ref. ID; 2889, 2932)
• Keratella cochlearis (Gosse, 1851) (ref. ID; 1132, 1345, 1350, 1474, 1803, 1836, 1929, 1946, 2198, 2225, 2261 , 2265, 2268, 2269, 2276, 2545, 2551, 2715, 2806, 2814, 2823, 2836, 2841, 2891, 3114 , 3125, 3127, 3180, 3271, 3275, 3335, 3514, 3688) reported year? (ref. ID; 1490, 2904, 2977, 3022, 3029, 3046, 3086, 3091, 3141, 3146, 3208, 3232, 3235, 3345, 3484, 3600, 5022), cochlearis cochlearis Gosse (ref. ID; 1473, 2619, 2763, 3083, 4593) or (Gosse) Ahlstorm (ref. ID; 1402, 1909)
  Syn; Anuraea cochlearis Gosse, 1851 (ref. ID; 1345, 1350, 2276, 2551, 2841, 3022, 3271, 3275, 3514, 3688) reported year? (ref. ID; 3141, 3208); Anuraea cochlearis baltica Imhof, 1886 (ref. ID; 3271, 3688); Anuraea cochlearis carinata Levander, 1892 (ref. ID; 3271, 3688); Anuraea cochlearis hispida Lauterborn, 1898 (ref. ID; 3271); Anuraea cochlearis irregularis Lauterborn, 1898 (ref. ID; 3271); Anuraea cochlearis leptacantha Lauterborn, 1900 (ref. ID; 3271); Anuraea cochlearis longispina Lang, 1928 (ref. ID; 3688); Anuraea cochlearis macracantha Lauterborn, 1898 (ref. ID; 3271); Anuraea cochlearis pellucida Imhof, 1892 (ref. ID; 3271, 3688); Anuraea cochlearis recurvispina Jagerskiold, 1894 (ref. ID; 3271); Anuraea cochlearis revoluta Brehm, 1910 (ref. ID; 3271, 3688); Anuraea cochlearis stipitata Weber, 1898 (ref. ID; 3271); Anuraea cochlearis tecta Lauterborn, 1898 (ref. ID; 3271); Anuraea intermedia Imhof, 1883 (ref. ID; 3688) or 1885 (ref. ID; 3271); Anuraea longispina Imhof, 1883 (ref. ID; 3271); Anuraea longistyla Schmarda, 1859 (ref. ID; 3271, 3688); Anuraea stipitata Ehrenberg, 1843 (ref. ID; 3688) non Anuraea stipitata Ehrenberg, 1838 (ref. ID; 3022); Anuraea stipitata wartmanni Asper & Heuscher, 1889 (ref. ID; 3271); Anuraea tecta Gosse, 1851 (ref. ID; 3271); Anuraea tecta cava Zernov, 1901 (ref. ID; 3271); Anuraea tecta recurvispina Zernov, 1901 (ref. ID; 3271); Anuraea tuberosa Imhof, 1885 (ref. ID; 3271, 3688); Keratella americana Carlin (ref. ID; 1132); Keratella cochlearis (Gosse) Berzins, 1954 (ref. ID; 1345); Keratella cochlearis (Gosse) Harring, 1913 (ref. ID; 1345, 3022); Keratella stipitata Carlin, 1943 (ref. ID; 3688); Keratella stipitata Ehrenberg, 1838 (ref. ID; 3514) reported year? (ref. ID; 1132, 2836)
• Keratella cochlearis faluta Ahlstrom, 1943 (ref. ID; 1946), var. faluta Ahlstrom, 1943 (ref. ID; 1345, 1909)
  Syn; Keratella faluta Ahlstrom, 1943 (ref. ID; 1345)
• Keratella cochlearis hispida (Lauterborn) (ref. ID; 1468, 1946, 2269), var. hispida (Lauterborn, 1898) (ref. ID; 1350, 1402, 3688) or (Lauterborn, 1900) (ref. ID; 1345, 2608) reported year? (ref. ID; 1474, 2284, 3086)
  Syn; Anuraea cochlearis hispida Lauterborn, 1898 (ref. ID; 1350); Anuraea cochlearis var. hispida Lauterborn, 1900 (ref. ID; 2284); Anuraea stipitata hispida Bartos, 1946 (ref. ID; 3688)
• Keratella cochlearis var. hispida f. ecaudis (Amman, 1921) (ref. ID; 1345)
• Keratella cochlearis var. hispida f. pustulata Lauterborn, 1900 (ref. ID; 1345, 3688)
• Keratella cochlearis irregularis (Lauterborn, 1898) (ref. ID; 2825) reported year? (ref. ID; 2269), var. irregularis (Lauterborn, 1898) (ref. ID; 1350) or 1900 (ref. ID; 1345, 3335) reported year? (ref. ID; 1474)
  Syn; Anuraea cochlearis irregularis Lauterborn, 1898 (ref. ID; 1350)
• Keratella cochlearis irregularis angulifera (Lauterborn) (ref. ID; 2269), var. irregularis f. angulifera Lauterborn, 1900 (ref. ID; 1345)
• Keratella cochlearis irregularis connectens (Lauterborn) (ref. ID; 2269), var. irregularis connectens Lauterborn (ref. ID; 1474, 2608), var. irregularis f. connectens Lauterborn (ref. ID; 3335)
• Keratella cochlearis var. irregularis f. ecaudata Lauterborn, 1900 (ref. ID; 3335)
• Keratella cochlearis var. irregularis f. pustulata Lauterborn, 1900 (ref. ID; 2891)
• Keratella cochlearis irregularis wartmanni (Asper & Heuscher) (ref. ID; 2269)
• Keratella cochlearis javana Hauer, 1937 (ref. ID; 3083), var. javana Hauer, 1937 (ref. ID; 3523 original paper)
  See; Keratella javana (ref. ID; 1350, 3258, 3274)
• Keratella cochlearis macracantha (Lauterborn, 1898) (ref. ID; 3335) reported year? (ref. ID; 1468, 2269, 5031), f. macracantha (Lauterborn, 1900) (ref. ID; 2702) reported author and year? (ref. ID; 3235), var. macracantha (Lauterborn, 1898) (ref. ID; 1345, 1350, 1474, 3688) reported year? (ref. ID; 3063)
• Keratella cochlearis var. macracantha f. micracantha Lauterborn, 1900 (ref. ID; 1345, 1474, 3688)
• Keratella cochlearis var. macracantha f. tuberculata Lauterborn, 1900 (ref. ID; 1345, 3688)
  Syn; Anuraea cochlearis tuberculata Weber & Montet, 1918 (ref. ID; 3688)
• Keratella cochlearis micracantha (Lauterborn) (ref. ID; 2269)
• Keratella cochlearis pachyacantha Thomasson, 1980 (ref. ID; 2729 original paper, 3514)
• Keratella cochlearis recurvispina (Jagerskiod, 1894) (ref. ID; 1946) reported year? (ref. ID; 4593), var. recurvispina (Jagerskiod, 1894) (ref. ID; 1345) or Jagerskiold, 1894 (ref. ID; 3688)
  Syn; Anuraea cochlearis var. recurvispina (Jagerskiod, 1894) (ref. ID; 1345) or Jagerskiold, 1894 (ref. ID; 3688); Anuraea tecta var. recurvispina Sernov, 1901 (ref. ID; 1345) or Zernov, 1901 (ref. ID; 3688)
• Keratella cochlearis robusta (Lauterborn, 1901) (ref. ID; 3114 ) reported year? (ref. ID; 1468, 2890), var. robusta (Lauterborn, 1900) (ref. ID; 1345, 1402, 2702, 2989, 3688)
  Syn; Anuraea cochlearis robusta Lauterborn, 1900 (ref. ID; 3688), var. robusta Lauterborn, 1900 (ref. ID; 1345); Keratella stipitata var. robusta (Lauterborn) Bartos, 1946 (ref. ID; 1345)
• Keratella cochlearis robsta f. tecta (ref. ID; 3073 )
• Keratella cochlearis tecta (Gosse, 1851) (ref. ID; 3335) reported year? (ref. ID; 2269, 2619, 2934, 5031), f. tecta (Gosse) (ref. ID; 2932), var. tecta (Gosse, 1851) (ref. ID; 1350, 1402, 3688) or 1886 (ref. ID; 1345) reported year? (ref. ID; 1474, 3063)
  Syn; Anuraea tecta Gosse, 1851 (ref. ID; 3688)
• Keratella cochlearis tecta (Lauterborn) (ref. ID; 1468), var. tecta (Lauterborn, 1900) (ref. ID; 1847)
• Keratella cochlearis tecta maior (Lauterborn, 1900) (ref. ID; 3335), var. tecta f. maior Lauterborn, 1900 (ref. ID; 3688)
• Keratella cochlearis var. tecta f. macracantha (Lauterborn, 1898) (ref. ID; 1350)
  Syn; Anuraea cochlearis macracantha Lauterborn, 1898 (ref. ID; 1350)
• Keratella cochlearis var. tecta f. micracantha (Lauterborn, 1898) (ref. ID; 1350)
  Syn; Anuraea cochlearis micracantha Lauterborn, 1898 (ref. ID; 1350)
• Keratella cochlearis var. tecta f. punctata Lauterborn, 1900 (ref. ID; 3688)
  Syn; Anuraea cochlearis tecta punctata Lauterborn, 1900 (ref. ID; 3688)
• Keratella cochlearis tuberculata (Lauterborn) (ref. ID; 2269)
• Keratella cochlearis typica (Gosse) (ref. ID; 2934), f. typica (Gosse) (ref. ID; 3015)
• Keratella cochlearis var. alba (ref. ID; 3114 )
• Keratella cochlearis var. angulifera (Lauterborn) (ref. ID; 1474)
• Keratella cochlearis var. faluta Ahlstrom, 1943 (ref. ID; 1345, 1909, 1946)
  Syn; Keratella faluta Ahlstrom, 1943 (ref. ID; 1345)
• Keratella cochlearis var. javana Hauer, 1938 (ref. ID; 1350)
  See; Keratella javana
• Keratella cochlearis var. leptacantha Lauterborn, 1900 (ref. ID; 1345, 3688) reported year? (ref. ID; 1474)
• Keratella cochlearis leptacantha ecauda (Lauterborn) (ref. ID; 1474, 2269, 2619)
• Keratella cochlearis var. leptacantha f. ecaudis Lauterborn, 1900 (ref. ID; 3688)
  Syn; Anuraea cochlearis leptacantha ecaudata Lauterborn, 1900 (ref. ID; 3688); Anuraea stipitata leptacantha ecaudata Dieffenbach, 1912 (ref. ID; 3688)
• Keratella cochlearis var. regularis f. ecaudata Lauterborn, 1900 (ref. ID; 1345)

  ---

• Keratella crassa Ahlstrom, 1943 (ref. ID; 2281) reported year? (ref. ID; 1402)
  Syn; Anuraea stipitata Kellicott, 1896 (ref. ID; 1402)
• Keratella crenata Harring, 1913 (ref. ID; 3127)
• Keratella cruciformis (Thompson, 1892) (ref. ID; 1345, 1866, 3688) reported year? (ref. ID; 3573), cruciformis cruciformis Thompson (ref. ID; 4593)
  Syn; Anuraea cruciformis Thompson, 1892 (ref. ID; 1345, 1350, 3688); Keratella cruciformis Harring, 1913 (ref. ID; 1345)
• Keratella cruciformis eichwaldi Levander (ref. ID; 4593), var. eichwaldi (Levander, 1894) (ref. ID; 1350, , 2393, 3063, 3688) reported year? (ref. ID; 3170)
  See; Keratella eichwaldi
  Syn; Anuraea cruciformis Thompson, 1892 (ref. ID; 3063); Anuraea eichwaldi Levander, 1894 (ref. ID; 1350, 3063, 3688); Anuraea tecta Plate, 1890 (ref. ID; 3688)
• Keratella earlinae Ahlstrom, 1943 (ref. ID; 2715, 2894) reported year? (ref. ID; 1402, 5946)
• Keratella earlinae var. nesiotica (Ahlstrom, 1943) (ref. ID; 3114)
• Keratella edmondsoni (Ahlstrom) (ref. ID; 1803, 1831, 1898)
• Keratella eichwaldi (Levander, 1894) (ref. ID; 680, 1866, 2261 ) reported year? (ref. ID; 3273)
  Syn; Anuraea eichwaldi Levander (ref. ID; 3273); Keratella cruciformis var. eichwaldi (ref. ID; 3273)
• Keratella falculata (Ehrenberg, 1838) (ref. ID; 1345, 2836, 3688)
  Syn; Anuraea aculeata falculata Schodduyn, 1923 (ref. ID; 3688); Anuraea falculata Ehrenberg, 1838 (ref. ID; 2836, 3688); Anuraea serrulata Ehrenberg, 1838 (ref. ID; 2836); Keratella serrulata var. aspina Edmondson, 1936 (ref. ID; 2836); Keratella serrulata var. ehrenbergi Edmondson, 1936 (ref. ID; 2836)
• Keratella falculata (Gillard, 1948) (ref. ID; 1923)
  Syn; Keratella serrulata (ref. ID; 1923)
• Keratella gracilenta Ahlstrom, 1943
  Syn; Keratella americana Carlin, 1943 (ref. ID; 1345 unstable?, 3022)
• Keratella hiemalis Carlin (1943) (ref. ID; 1345, 1402, 1468, 1705, 1923, 2269, 2551, 2593, 2989, 3147, 3158, 3231, 3264 original paper, 3688) reported year? (ref. ID; 3046, 3086, 3235, 5022) reported author and year? (ref. ID; 5389)
• Keratella irregularis Lauterborn, 1898 (ref. ID; 3275, 3688) reported year? (ref. ID; 1402), irregularis irregularis Lauterborn (ref. ID; 1468)
  Syn; Anuraea cochlearis irregularis Lauterborn, 1898 (ref. ID; 3688), var. irregularis Lauterborn, 1898 (ref. ID; 3275); Keratella cochlearis irregularis Hauer, 1925 (ref. ID; 3688); Keratella stipitata irregularis Bartos, 1946 (ref. ID; 3688)
• Keratella irregularis f. angulifera Lauterborn, 1900 (ref. ID; 3688)
• Keratella irregularis f. connectens Lauterborn, 1900 (ref. ID; 3688)
• Keratella irregularis f. wartmanni Asper & Heuscher, 1889 (ref. ID; 3688) reported year? (ref. ID; 1345)
  Syn; Anuraea cochlearis var. regularis ecaudata Lauterborn, 1900 (ref. ID; 3688); Anuraea cochlearis ecauda Dieffenbach, 1912 (ref. ID; 3688); Anuraea stipitata var. wartmanni Asper & Heuscher, 1889 (ref. ID; 3688)
• Keratella javana Ahlstrom, 1943
  See; Keratella cochlearis var. javana (ref. ID; 1352), Keratella javana Hauer (ref. ID; 3258)
• Keratella javana Hauer, 1932 (ref. ID; 1847), 1937 (ref. ID; 2757, 3127, 3258, 3274), 1938 (ref. ID; 2393, 3514) or Hauer (Russell), 1952 (ref. ID; 1923)
  Syn; Keratella carinata Russell, 1950 (ref. ID; 1923) or 1952 (ref. ID; 2757, 3258); Keratella cochelaris var. javana Hauer, 1937 (ref. ID; 3258, 3274); Keratella javana Ahlstrom, 1943 (ref. ID; 3258)
• Keratella kamtchatica Kutikova, 1970 (ref. ID; 1866)
• Keratella kostei Paggi, 1981 (ref. ID; 1836)
• Keratella lenzi Hauer, 1953 (ref. ID; 2265, 2545, 2715, 2806, 2899 original paper, 3037, 3040), lenzi lenzi Hauer, 1953 (ref. ID; 1309, 1923)
  Syn; Keratella valga f. brehmi Ahlstrom, 1943 (ref. ID; 3031); Keratella valga f. aspina Edmondson & Hutchinson, 1934 (ref. ID; 3031)
• Keratella lenzi (f. ayui) (ref. ID; 1309)
  Syn; Keratella americana (ref. ID; 1309)
• Keratella lenzi caudata Koste, 1972 (ref. ID; 2545 original paper), (f. caudata) (ref. ID; 1309)
  Syn; Keratella americana (ref. ID; 1309)
• Keratella lenzi heliaca Berzins, 1955 (ref. ID; 3031 original paper) (f. heliaca) (ref. ID; 1309)
• Keratella maliensis (ref. ID; 1835)
• Keratella nhamunda Koste & Robertson, 1983 (ref. ID; 2806, 2808 original paper)
  Syn; Keratella americana nhamundaiensis Koste, 1982 (ref. ID; 2808); Keratella americana nhamundiensis Koste, 1982 (ref. ID; 2806)
• Keratella ona Boltovskoy & Urrejola, 1977 (ref. ID; 2214)
• Keratella paludosa (Lucks, 1912) (ref. ID; 1345, 1856, 2642, 2994, 3688)
  Syn; Anuraea aculeata var. cochlearis Voigt, 1902 (ref. ID; 1345, 3688); Anuraea paludosa (Voigt) Lucks, 1912 (ref. ID; 1345, 3688); Keratella paludosa (Lucks) Harring, 1913 (ref. ID; 1345); Keratella quadrata cochlearis Emeljanov, 1927 (ref. ID; 3688)
• Keratella paludosa var. obtusa Hauer, 1935 (ref. ID; 3688)
• Keratella paludosa var. typica Wulfert, 1956 (ref. ID; 3688) reported year? (ref. ID; 2932)
  Syn; Keratella paludosa var. aspina Wulfert, 1950 (ref. ID; 3688)
• Keratella procurva (Thorpe, 1891) (ref. ID; 1309, 1448, 1803, 1805, 1847, 2210, 2261 , 2704, 2758, 2812, 2891, 3031, 3180, 3258, 3514) reported year? (ref. ID; 3023), procurva procurva Thorpe (ref. ID; 4606)
  Syn; Anuraea procurva Thorpe, 1891 (ref. ID; 3031, 3258, 3514); Keratella procurva Berzins, 1953 (ref. ID; 3031); Keratella valga f. valga Edmondson & Hutchinson, 1934 (ref. ID; 3031, 3258); Keratella valga var. procurva Ahlstrom, 1943 (ref. ID; 3031, 3258) or (Thorpe, 1891) (ref. ID; 3514)
• Keratella procurva haterumensis (ref. ID; 2261 , 2874 original paper)
• Keratella procurva robusta Koste & Shiel, 1980 (ref. ID; 2758 original paper)
• Keratella pyriformis Ahlstorm, 1943 (ref. ID; 1345)
  Syn; Keratella quadrata var. pyriformis Ahlstorm, 1943 (ref. ID; 1345)

  ---

  Keratella quadrata-group
  Keratella quadrata (O. F. Muller, 1786) and K. valga (Ehrenberg, 1834) were placed together with several other varieties under a single species Anuraea aculeata Ehrenberg, 1832. It is because the foundation patterns on the dorsum as well as the position and the length of the posterior spines are quite uniform in them. After examining extensive materials from South Africa and India, Edmondson & Hutchinson (1934) were fully convinced of the correctness of the contention that K. quadrata and K. valga are to be recognized as two distinct species. The correct designation for the species was proposed for the first time by these authors. According to Edmondson & Hutchinson (1934), K. quadrata has the following characters. 1. maximum breadth of lorica slightly greater than the posterior breadth. 2. posterior portion is greater than the anterior breadth. 3. two posterior spines are usually subsequal. According to Edmondson & Hutchinson (1934) this species comprises the following nine formae, f. platei, f. divergens, f. frenzeli, f, quadrata, f. testudo, f. brevispina, f. valgoides, f. irregularis and f. curvicornis. Later Carlin (1943) divided this species precisely into the following four 'groups', viz, frenzeli (with var. platei,) quadrata, dispersa and reticulata, while Ahlstrom (1943) into six 'varieties', viz, adnata, platei, edmondsoni, brevispina, curvicornis and pyriformis besides the typical species quadrata quadrata (with formae, testudo, araneosa). Gillard (1948) treated this species as K. quadrata OE quadrata, K. quadrata OE frenzeli respectively, and Voigt (1957) adopted Carlin's system adding one form klementi. Thus, the treatment of formae, and variety of this species still contains some unresolved problems. (ref. ID; 3114)
  Keratella quadrata (Muller) and Keratella valga (Ehrenberg): In spite of the valuable contributions of Hartmann (1918) and others, there still appears to be considerable uncertainly as to the status and correct designation of the various forms included by Harring (1913) under K. quadrata (Muller). After examining extensive material from South Africa and India we are fully convinced of the correctness of the contention that two species, K. quadrata (= aculeata Ehrenberg) and K. valga, are to be recognized. Moreover, the nomenclature of these two species in their typical forms raises no difficulties. Anuraea aculeata Ehrenberg (1832) is expressly stated by its describer (1832) to be identical with Brachionus quadratus Muller. Ehrenberg's best figure (1838, T. LXII, fig. xiv, 1) may therefore be taken in conjunction with those of Muller (1786, T. XLIX, figs. 12, 13) as defining the typical form of quadrata. The posterior margin of the lorica in Ehrenberg's figure, measured across the outer margins of the bases of the posterior spines, is wider than the anterior margin similarly measured across the bases of the antero-lateral spines. The posterior spines are parallel (Muller) or very slightly divergent, about two-fifths as long (Ehrenberg) or half as long (Muller) as the lorica. Both reticular and punctate sculpture are clearly indicated by Ehrenberg. Muller's figure is so unsatisfactory that in fixing the typical form it is best to abide by the excellent illustration given by Ehrenberg, save that it is convenient to regard typical quadrata as having practically parallel posterior spines, as is indicated by Muller. Anuraea valga Ehrenberg (1834) may be regarded as typically represented by Ehrenberg's best figure (1838, T. LXII, fig. xv, 1), which shows a form in which the posterior width of the lorica is distinctly narrower than the anterior. The right spine is about one-third, the left one-quarter of the length of the lorica. Reticulate and punctate sculpture are both clearly indicated. In examining as much material and as many illustration as are available to us we have rarely had any difficulty in assigning individuals or illustrations to one or the other species. It is true that in a few figures of European specimens (e.g. Virieux 1916, fig. 46, Wesenberg-Lund, 1930, Plate VII, figs. 8, 26, and 46) the anterior and posterior borders are equal or the former very slightly longer than the latter. But such specimens do not appear to show the pronounced narrowing of valga and it must be remembered that a very minute error in drawing on the part of an observer not studying the dimensions in question would produce just such differences as found in some of these figures. Fedeev (1927) used the relation between the anterior and posterior widths of the lorica to separate tropica Apstein from the other forms of K. quadrata (s. lat.), apparently understanding by Apstein's name what we here regard as K. valga. Within these species the use of misapplied varietal terms appears to have led to considerable confusion. Thus in his monumental work on the cyclical phenomena in rotifers Wesenberg-Lund (1930) objects to certain of Hartmann's conclusions as to the production of valga forms from resting eggs. But it is clear from a study of Wesenberg-Lund's figures that what this author calls valga is a form of quadrata (s. s.) while Hartmann's observations on this point referred primarily to the true K. valga (Ehrenberg). Since such confusion is bound to result from the present unsatisfactory state of the varietal nomenclature of these two species we have attempted to standardise as far as possible the names of the various forms, introducing a minimum of new names and adhering to the principle of priority. Though the latter is not binding in such cases, it would appear to provide the best method of determining the relative merits of two synonym, and the neglect of the principle in the past has led authors to create new varietal name without an adequate study of the literature so that the form of valga with a single posterior spine has been provided with at least thee and probably four names. Kratzschmar (1908, 1913), Hartmann (1918) and Wesenberg-Lund (1930) have studied the morphological cycle in this species. Normally the first generations from sexual eggs are composed of forms with long divergent spines (f. divergens Voigt); these later give place to forms with shorter more parallel spines (f. quadrata Muller). Later one (f. valgoides n.) or both spines (f. curvicornis Ehrenberg) are lost and at such periods sexual reproduction is stated to occur. The amount of cyclomorphosis is very variable in different localities but in general this species exhibits a cycle of reduction. In a few cases an initial elongation of the spines has been observed and in a series called by Hartmann "A. aculeata-valga", but consisting of apparently morphologically normal reduced forms of K. quadrata, the cycle begins with curvicornis, to which the addition of one minute papilliform spines produces the form named by Jakubski (1915) irregularis, and two minute spines testudo Ehrenberg. In general the two posterior spines of quadrata are subequal in length, but in certain forms unequal spines apparently indicate a transition from divergens (right spine) to quadrata (left spine). Fadeev has figured as valga a specimen of quadrata with unequal subparallel spines but this may best be regarded as a transition to valgoides, though Wesenberg-Lund's figures and our collection from Tso Nyak indicate that the latter form may probably appear in a quadrata population without intermediate forms with unequal spines. The following names are probably sufficient to describe the chief members of the cycle and to designate the varieties present in single collections. (ref. ID; 3513)

• Keratella quadrata (ref. ID; 3073, 3193, 5389)
• Keratella quadrata Bory de St. Vincent (ref. ID; 3600)
• Keratella quadrata (O. F. Muller, 1786) (ref. ID; 1345, 1350, 1402, 1803, 2225, 2261 , 2268, 2269, 2276, 2551, 2757, 2836, 2841, 2998, 3114, 3271, 3275, 3335, 3514, 3688) reported year? (ref. ID; 1474, 1490, 2393, 2640, 2890, 2934, 3015, 3029, 3046, 3063, 3065, 3086, 3141, 3208, 3222, 3234, 3235, 3264, 3513, 5022, 5031) reported author and year? (ref. ID; 2770, 2904, 3285, 3292), quadrata quadrata (O. F. Muller, 1786) (ref. ID; 2891) reported year? (ref. ID; 4593)
  Syn; Anourella aculeata Dujardin, 1841 (ref. ID; 3271, 3688); Anourella curvicornis Dujardin, 1841 (ref. ID; 3271); Anourella luth Bory de St. Vincent, 1826 (ref. ID; 2836, 3271, 3688); Anourella squamula Bory de St. Vincent, 1822 (ref. ID; 3688); Anourella valga Dujardin, 1841 (ref. ID; 3271); Anuraea aculeata Ehrenberg, 1832 (ref. ID; 1350, 2276, 2757, 2836, 2841, 3114, 3208, 3271, 3688) or 1932 misspelling? (ref. ID; 3514) reported year? (ref. ID; 3141); Anuraea aculeata asymmetrica Daday, 1894 (ref. ID; 3271); Anuraea aculeata brevispina Weber, 1898 (ref. ID; 3271); Anuraea aculeata cochlearis Voigt, 1902 (ref. ID; 3271); Anuraea aculeata curvicornis Weber, 1898 (ref. ID; 3271); Anuraea aculeata divergens Voigt, 1902 (ref. ID; 3271); Anuraea aculeata dumasi Richard, 1894 (ref. ID; 2836, 3271); Anuraea aculeata platei Jagerskiold, 1894 (ref. ID; 2836, 3271); Anuraea aculeata regalis Imhof, 1885 (ref. ID; 2836, 3271, 3688); Anuraea aculeata resupina Imhof, 1892 (ref. ID; 2836, 3271); Anuraea aculeata valga Weber, 1898 (ref. ID; 3271); Anuraea aculeata valgata Morozov, 1915 (ref. ID; 3688); Anuraea brevispina Gosse, 1851 (ref. ID; 3271); Anuraea curvicornis Ehrenberg, 1834 (ref. ID; 2836, 3271) or 1838 (ref. ID; 2757); Anuraea falculata Ehrenberg, 1838 (ref. ID; 3271); Anuraea frenzeli Eckstein, 1895 (ref. ID; 3271); Anuraea longicornis Schmarda, 1850 (ref. ID; 2836, 3271); Anuraea octoceros Ehrenberg, 1834 (ref. ID; 2836, 3271, 3688); Anuraea procurva Thorpe, 1891 (ref. ID; 3271); Anuraea quadridentata Ehrenberg, 1838 (ref. ID; 3271); Anuraea scutata Thorpe, 1891 (ref. ID; 3271); Anuraea squamula Ehrenberg, 1832 (ref. ID; 3688); Anuraea testudo Ehrenberg, 1832 (ref. ID; 3271); Anuraea valga Ehrenberg, 1834 (ref. ID; 3271); Anuraea valga asymmetrica Barrois & Daday, 1894 (ref. ID; 3271); Anuraea valga monstrosa Barrois & Daday, 1894 (ref. ID; 3271); Anuraea valga tropica Apstein, 1907 (ref. ID; 3271); Brachionus quadrata O. F. Muller, 1786 (ref. ID; 1350, 2276); Brachionus quadratus O. F. Muller, 1786 (ref. ID; 2836, 3271, 3275, 3514, 3688); Keratella quadrata Bory de St. Vincent, 1822 (ref. ID; 2836, 3271); Keratella quadrata f. araneosa Ahlstrom, 1943 (ref. ID; 2836); Keratella quadrata f. testudo (Ehrenberg) Ahlstrom, 1943 (ref. ID; 2836); Kerona octoceros Abildgaard, 1793 (ref. ID; 3271, 3688); Vaginaria squamula Schrank, 1803 (ref. ID; 3688)
• Keratella quadrata araneosa Ahlstrom, 1943 (ref. ID; 2135) reported year? (ref. ID; 1474)
  See; Keratella quadrata (ref. ID; 2836)
• Keratella quadrata australis Berzins, 1963 (ref. ID; 2417, 3023 original paper)
  See; Keratella australis (ref. ID; 2757)
• Keratella quadrata dispersa Carlin (ref. ID; 3193, 3444, 4606) reported author? (ref. ID; 1345), f. dispersa Carlin, 1943 (ref. ID; 3688), var. dispersa (Carlin, 1943) (ref. ID; 2702, 3114)
  See; Keratella quadrata tropica
• Keratella quadrata f. brevispina (ref. ID; 1350, 3513), var. brevispina (Gosse) (ref. ID; 1705) reported author and year? (ref. ID; 3114)
  See; Keratella testudo, Keratella quadrata
• Keratella quadrata f. brevispina Pawlowski, 1938 (ref. ID; 3154)
  See; Keratella serrulata Ehrenberg, 1838 (ref. ID; 3688)
• Keratella quadrata var. brevispina f. gossei Ahlstrom, 1943 (ref. ID; 2836) reported author and year? (ref. ID; 1705) See; Keratella testudo
• Keratella quadrata f. curvicornis (Ehrenberg) (ref. ID; 3513) reported author and year? (ref. ID; 3114), var. curvicornis (Ehrenberg) (ref. ID; 1345)
  See; Keratella quadrata
• Keratella quadrata divergens Voigt (ref. ID; 5031), f. divergens (Voigt, 1902) (ref. ID; 1350) reported year? (ref. ID; 3513) reported author and year? (ref. ID; 3114), var. divergens Voigt, 1902 (ref. ID; 3688)
  Syn; Anuraea aculeata Voigt, 1902 (ref. ID; 3688); Anuraea aculeata divergens Voigt, 1902 (ref. ID; 1350)
• Keratella quadrata frenzeli (Eckstein, 1895) (ref. ID; 3158) reported author and year? (ref. ID; 1345), f. frenzeli (Eckstein, 1895) (ref. ID; 3688) reported year? (ref. ID; 1350, 2932, 3513) reported author and year? (ref. ID; 3114)
  See; Keratella quadrata
  Syn; Anuraea frenzeli Eckstein, 1895 (ref. ID; 3688)
• Keratella quadrata f. irregularis (Jakubski) (ref. ID; 1345, 1350, 3513) reported author and year? (ref. ID; 3114)
  See; Keratella testudo, Keratella quadrata
• Keratella quadrata f. klemeti Voigt, 1957 (ref. ID; 1345 original paper, 2890)
  Syn; Anuraea aculeata Ehrenberg, 1832 (ref. ID; 1345); Brachionus quadrata O. F. Muller, 1786 (ref. ID; 1345); Keratella quadrata Bory de St. Vincent, 1822 (ref. ID; 1345)
• Keratella quadrata f. longicornis (Schmarda) (ref. ID; 1345)
• Keratella quadrata f. nova Klement (ref. ID; 2889)
• Keratella quadrata platei (Jagerskiold) (ref. ID; 4593), f. platei Jagerskiold, 1894 (ref. ID; 3688) reported year? (ref. ID; 3513) reported author and year? (ref. ID; 3114), var. platei (Jagerskiold, 1894) (ref. ID; 1345)
  See; Keratella quadrata
  Syn; Anuraea aculeata var. platei (Jagerskiold, 1894) (ref. ID; 1345); Anuraea aculeata var. resupina Imhof, 1892 (ref. ID; 1345, 3688)
• Keratella quadrata f. quadrata Carlin, 1943 (ref. ID; 3688)
• Keratella quadrata hiemalis (ref. ID; 2261 )
• Keratella quadrata reticulata Carlin (ref. ID; 3345), f. reticulata Carlin, 1943 (ref. ID; 3688) reported year? (ref. ID; 1345), var. reticulata Carlin, 1943 (ref. ID; 3114)
• Keratella quadrata f. valgoides Edmondson & Hutchinson, 1934 (ref. ID; 3513 original paper) reported author? (ref. ID; 1345) reported author and year? (ref. ID; 3114)
  See; Keratella quadrata
• Keratella quadrata testudo (Ehrenberg) (ref. ID; 3062), f. testudo (Ehrenberg, 1882) (ref. ID; 1345, 1350) reported year? (ref. ID; 3513) reported author and year? (ref. ID; 3114)
  See; Keratella quadrata (ref. ID; 2836), Keratella testudo (ref. ID; 2836)
  Syn; Anuraea testudo Ehrenberg, 1832 (ref. ID; 1350)
• Keratella quadrata tropica (ref. ID; 2417, 3073, 3114)
• Keratella quadrata var. adnata (ref. ID; 3114)
• Keratella quadrata var. edmondsoni Ahlstrom, 1943 (ref. ID; 3181) reported author and year? (ref. ID; 3114)
• Keratella quadrata var. pyriformis (ref. ID; 3114)

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• Keratella quadridentata (Ehrenberg) (ref. ID; 1345)
• Keratella reducta Huber-Pestalozzi, 1929 (ref. ID; 1345)
• Keratella sancta Russell, 1944 (ref. ID; 680, 1923, 3224 original paper, 3521) or 1945 (ref. ID; 2277)
• Keratella serrulata (Ehrenberg, 1838) (ref. ID; 1345, 1350, 2207, 2214, 2266, 2276, 2757, 2823, 2891, 2993, 3063, 3154, 3275, 3506, 3688) or 1858 (ref. ID; 2771) reported year? (ref. ID; 2932, 3029, 3208, 5022)
  See; Keratella faculata (ref. ID; 1923)
  Syn; Anourella pala Bory de St. Vincent, 1822 (ref. ID; 3688); Anourella cithara Bory de St. Vincent, 1827 (ref. ID; 3688); Anuraea aculeata serrulata Hudson & Gosse, 1886 (ref. ID; 3688); Anuraea aculeata var. serrulata Wermel, 1930 (ref. ID; 1345, 3688); Anuraea serrulata Ehrenberg, 1838 (ref. ID; 1350, 2276, 2757, 3063, 3275, 3688) or 1858 (ref. ID; 2771) reported year? (ref. ID; 3208); Anuraea falculata Ehrenberg, 1838 (ref. ID; 3688); Brachionus pala O. F. Muller, 1786 (ref. ID; 3688); Keratella quadrata f. brevispina Pawlowski, 1938 (ref. ID; 3154, 3688); Keratella serrulata Harring, 1913 (ref. ID; 1345); Keratella serrulata var. ehrenbergi Edmondson, 1936 (ref. ID; 1345)
• Keratella serrulata f. curvicornis (Rylov) (ref. ID; 1472), var. curvicornis Rylow, 1926 (ref. ID; 2593, 3688)
  Syn; Keratella serrulata var. aspina Edmondson, 1936 (ref. ID; 3688)
• Keratella serrulata var. aspina Edmondson, 1936 (ref. ID; 2771 original paper, 2836)
  See; Keratella falculata (ref. ID; 2836), Keratella serrulata, Keratella serrulata f. curvicornis (ref. ID; 3688)
• Keratella serrulata var. ehrenbergi Edmondson, 1936 (ref. ID; 2771 original paper, 2836) reported year? (ref. ID; 3688)
  See; Keratella falculata (ref. ID; 2836), Keratella serrulata
• Keratella shieli Koste, 1979 (ref. ID; 2757, 2891 original paper)
• Keratella sinensis Segers & Wang, 1997 (ref. ID; 1898)
  Syn; Keratella cochlearis var. after Sudzuki (1964) (p.112, plate 18, Figure 9) (ref. ID; 1898); Keratella cochlearis f. tecta after Turner (1986) (p.6, Figure 2a) (ref. ID; 1898)
• Keratella slacki (Berzins, 1963) (ref. ID; 665, 1025, 1709, 1834, 2757, 2891)
  Syn; Keratella valga slacki Berzins, 1963 (ref. ID; 1834, 2757)
• Keratella stipitata (ref. ID; 5389)
• Keratella stipitata Carlin, 1943
  See; Keratella cochlearis Gosse, 1851 (ref. ID; 3688)
• Keratella stipitata (Ehrenberg, 1838) (ref. ID; 2836, 3022, 3158) reported year? (ref. ID; 2328, 2640, 3065, 3264)
  See; Keratella cochlearis (ref. ID; 1132, 2836, 3514)
  Syn; Anuraea cochlearis Gosse, 1851 (ref. ID; 2836); Anuraea cochlearis hispida Lauterborn, 1898 (ref. ID; 2836); Anuraea cochlearis irregularis Lauterborn, 1898 (ref. ID; 2836); Anuraea cochlearis leptacantha Lauterborn, 1900 (ref. ID; 2836); Anuraea cochlearis macracantha Lauterborn, 1898 (ref. ID; 2836); Anuraea cochlearis pellucida Imhof, 1892 (ref. ID; 2836); Anuraea cochlearis revoluta Brehm, 1910 (ref. ID; 2836); Anuraea cochlearis stipitata Weber, 1898 (ref. ID; 2836); Anuraea cochlearis tecta Lauterborn, 1898 (ref. ID; 2836); Anuraea cochlearis var. baltica Imhof, 1886 (ref. ID; 2836); Anuraea cochlearis var. carinata Levander, 1892 (ref. ID; 2836); Anuraea cochlearis var. recurvispina Jagerskiold, 1894 (ref. ID; 2836); Anurae intermedia Imhof, 1885 (ref. ID; 2836); Anuraea longispina Imhof, 1883 (ref. ID; 2836); Anuraea stipitata Ehrenberg, 1838 (ref. ID; 2836); Anuraea tecta Gosse, 1851 (ref. ID; 2836); Anuraea tuberosa Imhof, 1885 (ref. ID; 2836)
• Keratella stipitata var. irregularis Lauterborn (ref. ID; 2640)
• Keratella taurocephala Myers, 1938 (ref. ID; 2593, 2715) reported year? (ref. ID; 1909, 3086)
• Keratella testudo (Ehrenberg, 1832) (ref. ID; 2836, 2998, 3146, 3264, 3506, 3688) reported year? (ref. ID; 1490, 2889, 3193, 4593, 5022) or (Ehrenberg, 1832) Carlin, 1943 (ref. ID; 1345, 1472, 1474, 1923, 1948, 2269, 2597, 2640) reported author and year? (ref. ID; 5389)
  Syn; Anuraea aculeata brevispina Weber, 1898 (ref. ID; 3688); Anuraea aculeata var. testudo (Ehrenberg) (ref. ID; 1345, 2836); Anuraea brevispina Gosse, 1851 (ref. ID; 1345, 2836, 3688); Anuraea testudo Ehrenberg, 1832 (ref. ID; 1345, 2836, 3688); Keratella quadrata brevispina (Ehrenberg) (ref. ID; 2998); Keratella quadrata f. brevispina (Gosse) Edmondson & Hutchinson, 1934 (ref. ID; 2836); Keratella quadrata f. curvicornis Weber, Edmondson & Hutchinson, 1934 (ref. ID; 2836); Keratella quadrata f. irregularis Jakubski, Edmondson & Hutchinson, 1934 (ref. ID; 2836); Keratella quadrata testudo Ahlstrom, 1943 (ref. ID; 3688); Keratella quadrata f. testudo (Ehrenberg, 1882) (ref. ID; 1345, 1350); Keratella quadrata f. testudo (Ehrenberg) Edmondson & Hutchinson, 1934 (ref. ID; 2836); Keratella quadrata var. brevispina (Gosse) Ahlstrom, 1943 (ref. ID; 2836); Keratella quadrata var. brevispina f. gossei Ahlstrom, 1943 (ref. ID; 2836)
• Keratella testudo gossei Ahlstrom (ref. ID; 3146)
• Keratella testudo irregularis (Jakubski) (ref. ID; 3146), f. irregularis Iakubski, 1915 (ref. ID; 3688)
  Syn; Anuraea aculeata curvicornis var. irregularis Iakubski, 1915 (ref. ID; 3688)
• Keratella thomassoni Hauer, 1958 (ref. ID; 3006 original paper) (ref. ID; 2198)
• Keratella ticinensis (Callerio, 1920) (ref. ID; 2994, 2998, 3158, 3335, 3506, 3688) reported year? (ref. ID; 3264), (Callerio, 1920) Carlin, 1943 (ref. ID; 1345, 1923) or Carlin (ref. ID; 1806, 1909) reported author and year? (ref. ID; 5389)
  Syn; Anourella curvicornis Dujardin, 1841 (ref. ID; 3688); Anuraea aculeata curvicornis Weber, 1898 (ref. ID; 3688); Anuraea aculeata var. tincinensis Callerio, 1920 (ref. ID; 1345, 2998); Anuraea curvicornis Ehrenberg, 1834 (ref. ID; 3688); Anuraea quadridentata Ehrenberg, 1838 (ref. ID; 3688); Keratella aculeata curvicornis Rodewald, 1935 (ref. ID; 3688); Keratella aculeata ticinensis Callerio, 1920 (ref. ID; 3688); Keratella curvicornis Lucks, 1937 (ref. ID; 3688); Keratella quadrata curvicornis Jakubski, 1921 (ref. ID; 3688); Keratella quadrata var. curvicornis (Ehrenberg, 1834) (ref. ID; 1345, 2998)
• Keratella tropica Apstein, 1907 (ref. ID; 670, 1805, 2265, 2339, 2704, 2715, 2812, 2837, 2867, 3031, 3512, 3514, 3688) reported year? (ref. ID; 663, 1803, 1929, 2619, 3020) reported author and year? (ref. ID; 2871), tropica tropica (ref. ID; 2757)
  Syn; Anuraea aculeata var. tropica Tschugunov, 1921 (ref. ID; 3031) or Tschungunoff, 1921 (ref. ID; 3688); Anuraea valga f. tropica Apstein, 1907 (ref. ID; 3031, 3688), var. tropica Apstein, 1907 (ref. ID; 3514); Keratella quadrata Spandl, 1926 (ref. ID; 3031, 3688); Keratella quadrata valga f. asymmetrica Ueno, 1938 (ref. ID; 3031, 3688); Keratella valga f. asymmetrica Hauer, 1937-1938 (ref. ID; 3688); Keratella valga f. brehmi Ahlstrom, 1943 (ref. ID; 3031); Keratella valga f. tropica Edmondson & Hutchinson, 1934 (ref. ID; 3031), Hauer, 1937-1938 (ref. ID; 3688) or Ueno, 1938 (ref. ID; 3688)
• Keratella tropica f. asymmetrica (Barrois & Daday) (ref. ID; 2619, 2628, 3688) reported author and year? (ref. ID; 663)
  Syn; Anuraea valga f. asymmetrica Barrois & Daday, 1894 (ref. ID; 2628); Keratella valga f. asymmetrica Hauer, 1938 (ref. ID; 2628)
• Keratella tropica f. heterospina (ref. ID; 663)
• Keratella tropica f. monstrosa (Barrois & Daday) (ref. ID; 2619, 2704)
• Keratella tropica f. reducta Fadeew, 1927 (ref. ID; 3688) reported author and year? (ref. ID; 663)
  Syn; Keratella quadrata var. tropica f. reducta Fadeew, 1927 (ref. ID; 3688)
• Keratella tropica f. tropicamonstrose Edmondson & Hutchinson, (1934) (ref. ID; 1929)
• Keratella tropica var. aspina Fadeew, 1927 (ref. ID; 3688)
  Syn; Keratella quadrata var. tropica f. aspina Fadeew, 1927 (ref. ID; 3688)

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  Keratella valga-group
  Keratella quadrata (O. F. Muller, 1786) and K. valga (Ehrenberg, 1834) were placed together with several other varieties under a single species Anuraea aculeata Ehrenberg, 1832. It is because the foundation patterns on the dorsum as well as the position and the length of the posterior spines are quite uniform in them. After examining extensive materials from South Africa and India, Edmondson & Hutchinson (1934) were fully convinced of the correctness of the contention that K. quadrata and K. valga are to be recognized as two distinct species. The correct designation for the species was proposed for the first time by these authors. Under this species Edmondson & Hutchinson (1934, p. 170-171) distinguished eight formae based upon the condition of the posterior spines. They are: f. valga, f. asymmetrica, f. monstrosa, f. longicornis, f. tropica, f. reducta, f. brehmi and f. aspina. Carlin divided these formae into three, namely valga, tropica and procurva. And Ahlstrom (1943, pp. 448-453), var. procurva, f. typica, f. brehmi respectively. Recently, Berzins (1955) reviewed thoroughly this valga complex, and distinguished four species and one subspecies, namely K. valga, K. tropica, K. procurva (f. valga after Edmondson & Hutchinson), K. lenzi and K. lenzi var. heliaca, all based upon the posterior area of the dorsum. However, the question still remains unanswered, since Edmondson & Hutchinson simply divided the specimens on the basis of the length of the posterior spine, while, Berzins did it on the basis of the dorsal pattern of the lorica. (ref. ID; 3114)

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• Keratella valga (Ehrenberg, 1834) (ref. ID; 1345, 1350, 1803, 2277, 2393, 2757, 2816, 2836, 3031, 3114, 3264, 3688) reported year? (ref. ID; 3029, 3065, 3126, 3208, 3484, 3513, 5022, 5031) reported author and year? (ref. ID; 2871, 5389), valga valga (Ehrenberg, 1834) (ref. ID; 1345, 2860, 3073 , 3083), valga f. valga Ehrenberg (ref. ID; 3523)
  Syn; Anourella valga Dujardin, 1841 (ref. ID; 3688); Anuraea aculeata valga Skorikov, 1896 (ref. ID; 3031) or Skorikow, 1896 (ref. ID; 3688); Anuraea aculeata valga Weber, 1898 (ref. ID; 3688), var. valga Weber, 1898 (ref. ID; 1345, 3031); Anuraea procurva Thorpe, 1891 (ref. ID; 1345, 2836); Anuraea scutata Thorpe, 1891 (ref. ID; 1345, 2836); Anuraea valga Ehrenberg, 1834 (ref. ID; 1350, 2277, 2757, 2836, 3031, 3126, 3208, 3688); Anuraea valga assymetrica Barrois & Daday, 1894 (ref. ID; 3688); Keratella aculeata valga Rodewald, 1935 (ref. ID; 3688); Keratella quadrata Edmondson & Hutchinson, 1934 (ref. ID; 3031); Keratella quadrata Harring, 1913 (ref. ID; 3688); Keratella quadrata valga Fadeev, 1927 (ref. ID; 3031) or Jakubski, 1921 (ref. ID; 3688); Keratella valga Carlin, 1943 (ref. ID; 3031)
• Keratella valga f. aspina Fadeew (ref. ID; 1345) or Fadeev (ref. ID; 3513) reported author and year? (ref. ID; 3114)
• Keratella valga f. asymmetrica Barrois & Daday, 1894 (ref. ID; 1350) reported year? (ref. ID; 3513) reported author and year? (ref. ID; 3114), var. asymmetrica (Barrois & Daday) (ref. ID; 1345, 3523)
• Keratella valga f. brehmi Klausener, 1908 (ref. ID; 3688) reported year? (ref. ID; 1345, 3031, 3513) reported author and year? (ref. ID; 3114)
  Syn; Anuraea curvicornis Klausener, 1908 (ref. ID; 3688); Anuraea curvicornis f. brehmi Klausener, 1908 (ref. ID; 3031)
• Keratella valga f. heterospina Klausener, 1908 (ref. ID; 3688)
• Keratella valga f. longicornis Schmarda (ref. ID; 3513) reported author and year? (ref. ID; 3114)
• Keratella valga f. monospina Klausener, 1908 (ref. ID; 3688)
• Keratella valga f. monstrosa Barrois & Daday, 1894 (ref. ID; 1350) reported year? (ref. ID; 3063, 3513) reported author and year? (ref. ID; 3114), var. monstrosa (Barrois & Daday) (ref. ID; 1345)
• Keratella valga f. reducta (Fadeew) (ref. ID; 1345) or Fadeev (ref. ID; 3513) reported author and year? (ref. ID; 3114)
• Keratella valga tropica (Apstein, 1907) (ref. ID; 2891, 3083) reported year? (ref. ID; 3062) reported author and year? (ref. ID; 3073), f. tropica (Apstein, 1907) (ref. ID; 1345, 1350, 2064, 2261 ) reported year? (ref. ID; 3063, 3513, 3523) reported author and year? (ref. ID; 3114, 3292), var. tropica Apstein (ref. ID; 3262)
• Keratella valga f. tropica-asymmetrica Apstein-Barrios & Daday (ref. ID; 3484), var. tropica-asymmetrica (ref. ID; 1350)
• Keratella valga f. tropica-monstrosa (Barrois & Daday) (ref. ID; 3484)
• Keratella valga tropica f. daitojimensis Sudzuki, 1992 (ref. ID; 2874 original paper)
• Keratella valga slacki Berzins, 1963 (ref. ID; 2261 , 3023 original paper)
  See; Keratella slacki (ref. ID; 1834, 2757)
• Keratella valga var. procurva (Thorpe, 1891) (ref. ID; 1345, 2278)
  See; Keratella procurva (Thorpe, 1891) (ref. ID; 3514)
  Syn; Anuraea procurva Thorpe, 1891 (ref. ID; 2278); Keratella procurva (Thorpe, 1891) (ref. ID; 1345)
• Keratella valga var. tropica-asymmetrica (ref. ID; 1350)
• Keratella yamana Boltovskoy & Urrejola, 1977 (ref. ID; 2214)