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Key to Centropyxis species
1 Test in dorsal view circular or almost circular 2
Test in dorsal view irregular due to various outgrows and invaginations 22
Test in dorsal view elliptical or ovoid or resembling an 8 23
2 Test with spines 3
Test without spines 14
3 Edges of pseudostome with bridges or pilars between edge and dorsal part 4
Bridges absent 7
4 Diameter of the test 140-160 μm, in lateral view hemispherical Centropyxis hemispherica
C. hemisphaerica
Diameter of the test does not exceed 100 μm 5
5 Test in lateral view resembling a cap 6
Test in lateral view in the form of a triangle Centropyxis decloitri
C. decloitri
6 Spines along the entire fundus Centropyxis hirsuta
C. hirsuta
Spines only on the edge of the fundus Centropyxis cassis spinifera
C. cassis spinifera
 
7 Pseudostome slightly eccentric 8
Pseudostome strongly eccentric 9
8 Test 130 – 320 μm Centropyxis discoides
C. discoides
Test < 60 μm Centropyxis delicatula
C. delicatula
9 Pseudostome lobed Centropyxis spinosa
C. spinosa
Pseudostome not lobed, sometimes irregular in shape 10
10 Aperture lobed or crenate Centropyxis aculeata dentistoma
C. aculeata dentistoma
Aperture not lobed or crenate 11
11 Spines very long, located not only on the fundus, but also on the visor Centropyxis discoides solari
C. discoides solari
Spines only located on the fundus 12
12 Spines very long (40-60 μm) Centropyxis tropica
C. aculeata tropica
Spines shorter 13
13 Diameter of the test 110-160 μm Centropyxis aculeata
C. aculeata
Diameter of the test 170-200 μm Centropyxis aculeata grandis
C. aculeata grandis
Diameter of the test 80-90 μm Centropyxis aculeata minima
C. aculeata minima
 
14 Test in lateral view flattened, rarely hemispherical 15
Test in lateral view semi circular or slightly smaller or larger than hemispherical 16
15 Test > 150 μm Centropyxis ecornis
C. ecornis
Test < 60 μm Centropyxis delicatula
C. delicatula
16 Pseudostome very large (about half the diameter of the test), jagged Centropyxis latior
C. latior
Pseudostome not so big, its edge is not jagged 17
17 Test with internal bridges Centropyxis laevigata
C. laevigata
Bridges absent 18
18 Pseudostome slightly eccentric 19
Pseudostome strongly eccentric 20
19 Diameter of the test 140-170 μm Centropyxis austriaca
C. austriaca
Diameter of test < 80 μm Centropyxis minuta
C. minuta
20 Pseudostome small, close to the edge of the anterior part of the test C. plagiostoma
Pseudostome larger, halfway between center and edge 21
21 Diameter of test 100-140 μm Centropyxis orbicularis
C. orbicularis
Diameter of test < 70 μm Centropyxis aerophila sphagnicola
C. aerophila sphagnicola
22 Test in lateral view broad, pseudostome circular or elliptical, small, located on the ventral side of the test Centropyxis aurita
C. aurita
Test elongated elliptical in dorsal view, pseudostome crenate, subterminal, located at an angle of 45° to the longitudinal axis of the test Centropyxis chardeziella
C. chardeziella
23 Test in lateral view similar in shape to the figure-eight by narrowing between the pseudostome and fundus 24
Test in dorsal view elliptical or ovate 30
24 Pseudostome subterminal, located at an angle of 30° with respect to the longitudinal axis of the test Centropyxis loffleri
C. loffleri
Pseudostome located on the ventral side of the test3 25
25 Test without spines 26
Test with spines 27
26 Main part of the test a perfect sphere with an aperture, forming a kind of diaphragm between pseudostome and test body Conicocassis pontigulasiformis
Conicocassis pontigulasiformis
Main part of the test without diaphragma Centropyxis platystoma
C. platystoma
27 Test in lateral view flattened, pseudostome located near the center of the ventral side; length of test 160-170 μm Centropyxis mirabilis
C. mirabilis
Test in lateral view high, at least in the fundus, pseudostome very eccentric, length of test < 120 μm 28
28 Many spines, arranged randomly; visor turned outwards 29
One spine, long; visor not turned outwards Centropyxis platystoma armata
C. platystoma armata
29 Length of test 70-80 μm Centropyxis grelli
C. grelli
Length of test 140-200 μm Centropyxis adami
C. adami
30 Posterior part in lateral view strongly curved inwards, forming a perforated diaphragm, separating the visor from the fundus 31
Test without a perforated diaphragm 32
31 Length of test 65-100 μm Centropyxis sylvatica
C. sylvatica
Length of test 35-45 μm C. sylvatica minor
32 Pseudostome narrow sickle-shaped, test in dorsal view ovoid
= Heleopera???
Centropyxis declivistoma
C. declivistoma
Pseudostome circular or elliptical 33
33 Test in lateral view high, height of the test is equal, slightly less or exceeds the width 34
Test in lateral view more flattened, height less than width 43
34 Height of the test considerably exceeds the width and length Centropyxis deflandrei
C. deflandrei
Height of the test approximately equal to the width of the test. 35
35 Test with spines 36
Test without spines 38
36 One spine, thick, hollow, located on the extension of the longitudinal axis of the test Centropyxis chardezi
C. chardezi
Spines a lot, are located throughout the fundus 37
37 Length of test 90-120 μm Centropyxis gibba
C. gibba
Length of test 60-75 μm Centropyxis notonyx
C. notonyx
 
38 Test length >110 μm 39
Test length < 90 μm 40
39 Visor very wide, resembling the edge of a hat Centropyxis cordobensis
C. cordobensis
Visor not so large, formed by very large grains of sand Centropyxis janetscheki
C. janetscheki
40 Pseudostome subterminal, located at an angle of 45 ° to the longitudinal axis of the test Centropyxis sacciformis
C. sacciformis
Pseudostome located on the ventral side of the test 41
41 In lateral view test in pseudostomal area almost not narrowed Centropyxis villiersi
C. villiersi
In lateral view test in pseudostomal area narrowed 42
42 Height of the test slightly exceeds the width C. gibba inermis
Height of the test is slightly smaller than the width Centropyxis aerophila
C. aerophila
43 Width of test exceeds the length 44
The width of test does not exceed the length 45
44 Length of test 50-60 μm Centropyxis aculeata lata
C. aculeata lata
Length of test 150-205 μm Centropyxis compressa
C. compressa
 
45 Pseudostome subterminal, located at an angle of 50-60 ° to the longitudinal axis of the test 46
Pseudostome ventrally located 47
46 Thorns 1-6, elongated test Centropyxis marsupiformis
C. marsupiformis
Spines 4-8, test wider Centropyxis marsupiformis obesa
C. marsupiformis obesa


47 Test with spines 48
Test without spines 53
48 A wide flat keel is located along the perimeter of the test, the outgrowth of which forms spines Centropyxis horrida
C. horrida
Keel is absent 49
49 Spines are located on both the abdomen and on the visor Centropyxis decloitrella
C. decloitrella
Spines only on the abdomen 50
50 Test in dorsal view trapezoidal Centropyxis pyriformis
C. pyriformis
Test dorsal view is oval, elliptical or ovate 51
51 There is a groove between the organic mouth area of the test and the posterior end C. percolahiensis
Furrow absent 52
52 Pseudostome circular Centropyxis aculeata
C. aculeata
Pseudostome oval Centropyxis aculeata oblonga
C. aculeata oblonga
 
53 Length of test < 100 μm 54
Length of test > 100 μm 55
54 Test elongate elliptical in dorsal view; pseudostome circular or semicircular, large, occupies 1/3 part of the length of the test Centropyxis elongata
C. elongata
The test is broad-elliptical in dorsal view, pseudostome convex in the front, straightly cut from the rear; visor is lined with large xenosomes Centropyxis cassis
C. cassis


55 Test with internal bridges 56
Test without internal bridges 57
56 Ventral surface curved, pseudostome located almost at the center Centropyxis kurakchayensis
C. kurakchayensis
Ventral surface flat, pseudostome eccentrically Centropyxis gasparella
C. gasparella
57 Length of test > 200 μm, there is a wide visor in the form of the fields of a hat Centropyxis recurvata
C. recurvata
Test smaller, visor not so wide 58
58 Pseudostome small, roundish, located at the bottom of a deep pre-oriental funnel Centropyxis invaginata
C. invaginata
Pseudostome larger 59
59 There is a groove between the organic aperture of the test and the xenosomes on the posterior end C. percolahiensis inermis
Groove absent, posterior end usually contains large sand grains Centropyxis constricta
C. constricta

This key was published by Mazei and Tsyganov in 2006, Moskou, in Russian. I’ve translated it and modified it by adding some species.

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