For updated keys to this group see: A. Aptroot, A. & R. Lücking, 2016, A revisionary synopsis of the Trypetheliaceae (Ascomycota: Trypetheliales). Lichenologist 48(6): 763-982, genera Bogoriella (p. 903) and Novomicrothelia (p. 933).

1a (If no special features, then go to 9) Foliicolous, with hypocuticular, lobed thallus (Perithecia in groups of 1-8, 0.1-0.2 mm wide and 0.1 mm tall; asci 40-50(-55) x 10-12(-15) mu; spores ca. 14 x 4 mu, smooth, dark brown; New Zealand) --- M. striguloides Sérus. & Aptroot
1b On bark or rarely wood --- 2

2a Ascospores muriform, except when juvenile or over-aged (Thallus pale brownish to whitish, with border lines; perithecia single, with wide fringe, 0.7-0.9 mm wide and ca. 0.2 mm tall; asci ca. 100 x 28 mu; spores 4 x 2-4 loculate, 25-35 x 12-15 mu, with rounded ends, smooth, grey; pycnidia absent; Cuba, New Guinea, Guyana, 100-500 m) --- M. decipiens (Müll. Arg.) R.C. Harris
2b Ascospores transversely septate --- 3

4a Spores under 28 mu long; pycnidia absent; lichexanthone absent (Thallus whitish grey, with border lines; perithecia single, with fringe, 0.3-0.5 mm wide and 0.1-0.3 mm tall, wall to 100 mu thick; hamathecium with oil droplets; asci 80-100 x 12-15(-25) mu; spores 24-28 x 8-10.5 mu, with almost equal locules, with rounded ends, verruculose; pycnidia absent; Trinidad, Costa Rica) --- M. oleosa Aptroot
4a Spores mostly over 30 mu long; pycnidia present; lichexanthone usually present --- 5

5a Perithecia ca. 0.5-0.7 mm wide (Thallus whitish to creamy, with border lines, sometimes with lichexanthone; perithecia single, with wide fringe, ca.0.5-0.7(-0.8) mm wide and 0.15-0.2 mm tall; hamathecium with oil droplets, these often restricted to less fertile parts; asci ca. 130-160 x 20-30 mu; spores ca. 30-40 x 10-14 mu, with slightly larger upper locule, with rounded ends, verruculose, olivaceous brown; pycnidia 75-125 mu wide, conidia bacilliform, simple, hyaline, ca. 12-15 x 0.8 mu; Venezuela, smooth bark of large branches.) --- M. xanthonica Komposch, Aptroot & Hafellner
5b Perithecia ca. 0.7-1.0 mm wide (Thallus creamy white, with border lines, with lichexanthone; perithecia single, with wide fringe, ca. 0.7-1.1 mm wide and 0.3-0.4 mu tall; hamathecium with oil droplets, these mainly restricted to centre and margins; asci ca. 140-190 x 20-24 mu; spores ca. 30-45 x 10-15 mu, with slightly larger upper locule, with rounded ends, verruculose, olivaceous brown; pycnidia 75-125 mu wide, conidia bacilliform, simple, hyaline, ca. 15-21(-26) x 0.4 mu; Venezuela, smooth bark of large branches.) --- M. macrocarpa Komposch, Aptroot & Hafellner

6a Excipulum K+ crimson-red, dissolving (Thallus pinkish white, becoming whitish grey, with border lines; perithecia single, with fringe, ca. 0.5-0.7 wide and 0.1.0.2 mu tall; asci 45-80 x 11-14(-16) mu; spores 17-22 x (6-)7-10.5 mu, with upper locule about twice as large as lower locule, with rounded ends, minutely punctate-verruculose, olivaceous brown to red-brown; pycnidia mainly near the border lines, ca. 50 mu wide, conidia bacilliform, simple, hyaline, 2.5-3.5 x 1-1.5 mu; Mauritius, Costa Rica) --- M. leuckertii D. Hawksw. & J.C. David
6b Excipulum K+ olivaceous or K-, not dissolving or with yellow solution --- 7

7a Ostiole lateral; asci up to ca. 10 mu wide, with uniseriate spores (Thallus whitish, with border lines; perithecia single, usually oval, without fringe, 0.4-0.5 mm wide and ca. 0.15 mm tall, with lateral ostiole; asci ca. 130 x 10 mu; spores 18-22 x 6-7 mu, with equal locules or slightly larger upper locule, with rounded ends, verruculose, grey; pycnidia near the border lines, ca. 0.1 mm wide; conidia bacilliform, simple, hyaline, ca. 3 x 0.5 mu; Norfolk Island) --- M. lateralis Sipman
7a Ostiole apical; asci over 10 mu wide, with (sub-)biseriate spores --- 8

8a Anthraquinone around ostiole (Thallus pinkish grey, without border lines; perithecia single, with fringe, 1.0-1.3 mm wide and 0.2-0.6 mu tall, young ostiole red, K+ (anthraquinone); wall completely carbonized, to 80 mu thick; asci ca. 150 x 20 mu; spores 23-29 x 11-14 mu, with equal locules, with rounded ends, verruculose; pycnidia 60-100 mu wide, conidia bacilliform, simple, hyaline?, 6-8 x 0.3-0.5 mu; Dominica) --- M. rubrostoma Aptroot
8b No anthraquinone present --- 9

11a Thallus with border lines; pycnidia mainly near the border lines (Thallus brownish; perithecia in groups of 1(-3), with fringe, 0.4-0.7 mm wide and 0.1-0.3 mm tall; wall to 100 mu thick; asci 80-90 x 10-15 mu; spores (12-)15-18 x (6-)7-8 mu, with larger, rounded upper locule and often attenuated lower locule, smooth; pycnidia c. 0.1 mm wide, conidia not known; widespread in palaeotropics and neotropics, mostly at ca. 2000-3000 m.) --- M. punctata Aptroot
11b Thallus without border lines; pycnidia between the perithecia --- 12

12a Tropical taxon; thallus whitish (pale grey or pinkish); perithecia in groups of (1-)2-6 (Thallus whitish grey (-pale rose?), without border lines; perithecia with to 100 mu wide fringe, ca. 0.15-0.2 mm wide (groups to ca. 1 mm wide) and 0.08-0.12 mm tall, only ostiole exposed; involucrellum 10-15(-29) mu thick; asci 45-60 x 15-24 mu; spores 15-20 x 6-9 mu, with equal locules, with rounded or somewhat attenuated ends, delicately verruculose, brown; pycnidia between the perithecia, ca. 0.05 mm wide, conidia bacilliform, simple, hyaline, 12-15 x 0.5-1(-1.5) mu; Puerto Rico, Ecuador) --- M. socialis (Zahlbr.) D. Hawksw.
12b Temperate (European) taxa; thallus indistinct; perithecia mostly single --- 13

13a Perithecia (incl. fringe) ellipsoid, ca. 0.5-0.8 x 0.2-0.3 mm (Thallus indistinct; perithecia single, with ellipsoid, 300 mu wide fringe, 0.5-0.8 x 0.2-0.3 mm wide and 0.12-0.16 mm tall, only ostiole exposed; involucrellum 20-30 mu thick; asci 35-60 x 14-16(-20) mu; spores (12-)14-18(-20) x 6-8(-8.5) mu, little constricted, with equal locules, with rounded ends, slightly verruculose, dark brown; pycnidia between the perithecia or on separate thalli, 0.05-0.1 mm wide, conidia ellipsoid, polarilocular, hyaline, (9-)11-12.5(-14) x 4-6.5 mu; Europe, mostly on Betula.) --- M. wallrothii (Hepp) D. Hawksw.
13b Perithecia (incl. fringe) rounded --- 14

14a Pycnoconidia finally brown and 1-septate (Thallus indistinct; perithecia single, with fringe, 0.3-0.5mm wide and 0.1-0.125 mm tall, only ostiole exposed; involucrellum 5-15 mu thick; asci 42-50 x (15-)18-20(-26) mu; spores (12.5-)13.5-15.5(-17) x (6-)6.5-7.5(-8) mu, with equal locules, with rounded ends, verruculose, dark brown; pycnidia between the perithecia, 0.05-0.1 mm wide, conidia elongate-ellipsoid, finally 1-septate and brown, 13-14.5 x 5.5-6.5 mu; Central Europe, on Mespilus.) --- M. melanospora (Hepp) D. Hawksw.
14b Pycnoconidia persistently hyaline and simple --- 15

15a Pycnoconidia under 4.5 mm long (Thallus indistinct; perithecia single, with 30-50 mu wide fringe, (0.2-)0.3-0.4 mm wide and 0.09-0.12 mm tall; involucrellum 20-35 mu thick; asci 40-55 x 12-17 mu; spores (12.5-)13.5-16(-17.5) x (5.5-)6.5-8(-9) mu, with equal locules or slightly larger upper locule, with rounded ends, verruculose, olivaceous; pycnidia between the perithecia, 45-75 mu wide; conidia bacilliform, simple, hyaline, 3-4 x 0.5-0.7 mu; W Europe, on Corylus.) --- M. atlantica D. Hawksw. & Coppins
15b Pycnoconidia over 4.5 mm long (Thallus indistinct; perithecia single, round to elliptic, with 50 mu wide fringe, ca. 0.3 mm wide and 0.06-0.08 mm tall, only ostiole exposed; involucrellum 9-12 mu thick; asci 45-62 x 12-16 mu; spores (11.5-)12.5-15(-17.5) x (4-)5-6(-7) mu, with equal locules or slightly larger upper locule, with rounded ends, verruculose, golden brown to brown; pycnidia between the perithecia, 30-50 mu wide, conidia bacilliform, simple, hyaline, 5-8 x 0.7-1.5 mu; Central Europe, on twigs and branches.) --- M. macularis (Hampe ex Massal.) Keissler

16a (10) Perithecia (incl. fringe) under 0.3 mm wide --- 17
16b Perithecia (incl. fringe) 0.3-0.5 mm wide --- 19
16c Perithecia (incl. fringe) over 0.5 mm wide (Thallus pinkish grey, without border lines?; perithecia single, with fringe, 0.5-0.9 mm wide and 0.1-0.2 mm tall; wall to 150 mu thick; asci 60-80 x 10-15 mu; spores 14-17 x 4-6.5 mu, with larger upper locule, with rounded ends, verruculose; pycnidia absent; Indonesia 200 m.) --- M. alata Groenhart ex Aptroot

17a Perithecia without fringe (Thallus pale creamy brown, with border lines?; perithecia single, 0.2-0.25 mm wide and 0.08-0.11 mm tall; involucrellum 25-45 mu thick; asci 42-60 x 8.5-12 mu; spores 12.5-14(-15.5) x 4-5.5 mu, with equal locules or larger upper locule, with rounded ends, weakly constricted, weakly verruculose, pale olivaceous brown; pycnidia absent; Cuba, Australia, New Guinea.) --- M. exigua (Müll. Arg.) D. Hawksw.
17b Perithecia with distinct fringe --- 18

18a Thallus with distinct border lines; paraphyses ca. 2.5 mu thick (Thallus indistinct?; perithecia single, with purplish basal fringe, 0.2-0.3 mm wide and 0.07-0.11 mm tall; involucrellum 25-40 mu thick; asci 55-65 x 10-14 mu; spores (11-)12-14(-15) x (5-)5.5-6.5(-7.5) mu, with somewhat larger upper locule, with rounded to weakly attenuated ends, verruculose, pale brown to golden brown; pycnidia absent; China, Japan.) --- M. fumulosa (Zahlbr.) D. Hawksw.
18b Thallus without border lines; paraphyses 1-1.5 mu thick (Thallus indistinct?; perithecia single, ca. 0.3 mm wide and 0.06-0.11 mm wide; involucrellum 14-35 mu thick; paraphyses 1-1.5 mu thick; asci 55-65 x 12-14 mu; spores (12.5-)13.5-15(-16) x (5.5-)6-6.5(-7) mu, with larger upper locule, with rounded ends, verruculose, olivaceous brown; pycnidia absent; China.) --- M. minutula (Zahlbr.) D. Hawksw.

20a Spores mostly below 15 mu long (Thallus indistinct?; perithecia single, ca. 0.3 mm wide and 0.06-0.11 mm tall; involucrellum 14-35 mu thick; paraphyses 1-1.5 mu thick; asci 55-65 x 12-14 mu; spores (12.5-)13.5-15(-16) x (5.5-)6-6.5(-7) mu, with larger upper locule, with rounded ends, verruculose, olivaceous brown; pycnidia absent; China.) --- M. minutula (Zahlbr.) D. Hawksw.
20b Spores mostly over 15.5 mu long (Thallus whitish, without border lines; perithecia single, 0.3-0.4 mm wide and 0.12-0.15 mm tall; involucrellum 30-40 mu thick; asci 50-60 x 8-15 mu; spores (14-)15.5-17.5 x (6-)6.5-7.5 mu, with equal locules or slightly larger upper locule, with rounded ends, smooth to verruculose, olivaceous brown; pycnidia absent; India, Kerala.) --- M. nonensis (Stirt.) D. Hawksw.

21a Spores often under 15 mu long, with slightly unequal loculi; perithecia without fringe usually under 250 mu wide (Thallus whitish to pale rose, with border lines; perithecia single, with ca. 50 mu wide fringe, 0.4-0.5 mm wide and 0.06-0.1 mm tall; involucrellum 25-50 mu thick; asci 50-65 x 12-14 mu; spores 13.5-16 x 6-7 mu, with upper locule almost twice as large as lower locule, with rounded ends, verruculose, golden brown; pycnidia absent; pantropical.) --- M. subfallens (Müll. Arg.) D. Hawksw.
21b Spores rarely under 15 mu long, with strongly unequal loculi; perithecia without fringe usually over 250 mu wide (Thallus whitish to pale brown, with border lines; perithecia single, with fringe, 0.4-0.5 mm wide and ca. 0.1-0.14 mm tall; involucrellum 35-45 mu thick; asci 65-80 x 12-15 mu; spores 14.5-17.5(-19) x 6-7.5 mu, with upper locule around twice as large as lower locule, with rounded ends, verruculose, brown; pycnidia absent; pantropical.) --- M. miculiformis (Nyl. ex Müll. Arg.) D. Hawksw.

23a Perithecia (incl. fringe) strongly ellipsoid, 0.5-0.8 x 0.2-0.3 mm; pycnoconidia ellipsoid, polarilocular (Thallus indistinct; perithecia single, with 300 mu wide, ellipsoid fringe, 0.5-0.8 x 0.2-0.3 mm wide and 0.12-0.16 mm tall, only ostiole exposed; involucrellum 20-30 mu thick.; asci 35-60 x 14-16(-20) mu; spores (12-)14-18(-20) x 6-8(-8.5) mu, weakly constricted, with equal locules, with rounded ends, scarcely verruculose, dark brown; pycnidia between the ascomata or on separate thalli, 50-100(-120) mu wide, conidia ellipsoid, polarilocular, hyaline, (9-)11-12.5(-14) x 4-6.5 mu; Europe, mostly on Betula.) --- M. wallrothii (Hepp) D. Hawksw.
23b Perithecia (incl. fringe) rounded; pycnoconidia bacilliform, simple --- 24

25a Perithecia 0.4-0.5 mm wide, with pore area exposed only; temperate USA (Thallus indistinct, with border lines; perithecia single or in groups of 2-3, with 50-100 mu wide fringe, 0.4-0.5 mm wide and 0.1-0.15 mm tall, only ostiole exposed; involucrellum 40-60 mu thick; asci 50-65 x 10-12 mu; spores 17-20(-21) x 7-8(-9) mu, with equal locules or with slightly larger upper locule, with rounded ends, verruculose, olivaceous brown; pycnidia between the perithecia and more dense near the border lines, 50-75 mu wide, conidia bacilliform, simple, hyaline, 3-4 x 1-1.5 mu; USA, Massachusetts.) --- M. willeyana (Müll. Arg.) D. Hawksw.
25b Perithecia 0.4-0.7 mm wide, completely exposed; tropical (Thallus brownish, with border lines; perithecia single or in groups of 2-3, with fringe, 0.4-0.7 mm wide and 0.1-0.3 mm tall; wall to 100 mu thick; asci 80-90 x 10-15 mu; spores (12-)15-18 x (6-)7-8 mu, with larger, rounded upper locule, and often attenuated lower locule, smooth; pycnidia mainly near the border lines, c. 0.1 mm wide, conidia not known; widespread in palaeotropics and neotropics, mostly at ca. 2000-3000 m.) --- M. punctata Aptroot

26a Ascospores with equal locules (Thallus whitish grey (-pale rose?), without border lines; perithecia in groups of (1-)2-6, with to 100 mu wide fringe, ca. 0.15-0.2 mm wide (groups to ca. 1 mm wide) and 0.08-0.12 mm tall, only ostiole exposed; involucrellum 10-15(-29) mu thick; asci 45-60 x 15-24 mu; spores 15-20 x 6-9 mu, with equal locules, with rounded or somewhat attenuated ends, delicately verruculose, brown; pycnidia between the perithecia, 50-75 mu wide, conidia bacilliform, simple, hyaline, 12-15 x 0.5-1(-1.5) mu; Puerto Rico, Ecuador) --- M. socialis (Zahlbr.) D. Hawksw.
26b Ascospores with unequal locules (Thallus brownish, border lines?; perithecia usually in groups of 2-3 confluent, sometimes with fringe, 0.2-0.35 mm wide and to 0.15 mm tall; involucrellum 20-30 mu thick; asci 65-75 x 12-14 mu; spores 17-22(-24) x 5.5-7.5 mu, with larger upper locule, with rounded ends, verruculose, pale olivaceous brown, without halo; pycnidia between the perithecia?, 75-100 mu wide, conidia bacilliform, simple, hyaline, 4-5 x 1-1.5 mu; New Zealand.) --- M. minutissima (Knight) D. Hawksw.

29a Ascospores under 20 mu long, sparsely punctulate (Thallus indistinct?, with border lines; perithecia single, with to 100 mu wide fringe, 0.5-0.6 mm wide and 0.12-0.25 mm tall; involucrellum 20-30 mu thick; asci 80-110 x 14-18 mu; spores 16-19.5 x 7.5-10(-10.5) mu, with upper locule more than twice as large as lower locule, with rounded ends, sparsely punctulated, dark olivaceous brown; pycnidia absent; California, Mimulus.) --- M. dothideaspora (Cooke & Harkn.) D. Hawksw.
29b Ascospores mainly over 20 mu long, (finally) verruculose --- 30

30a Asci under 22 mu wide (Thallus pale brown, with border lines; perithecia single, ca. 0.4 mm wide and 0.2-0.25 mm tall; involucrellum 30-50(-70 below) mu thick; asci 80-100 x 10-20 mu; spores 19-23(-27) x (7.5-)9-11(-12) mu, with larger upper locule, with rounded ends, verruculose, golden brown; pycnidia absent; India.) --- M. conothelena (Nyl.) D. Hawksw.
30b Asci over 22 mu wide (Thallus creamy or whitish or indistinct, with border lines; perithecia single, with or without fringe, ca. 0.5 mm wide and 0.1-0.25 mm tall; involucrellum 30-70 mu thick; asci 80-90(-100) x (23-)26-31 mu; spores (17.5-)21-24(-26) x (7.5-)9-11.5(-13) mu, with larger upper locule, with rounded ends, verruculose, deep golden brown; pycnidia absent; neotropical, Philippines) --- M. thelena (Ach.) D. Hawksw.

31a (28) Ascocarps conical, over 150 mu high, without distinct fringe (Thallus whitish-rose, with border lines; perithecia single, 0.3-0.4 mm wide and 0.15-0.225 mm tall; involucrellum 50-65 mu thick; asci (55-)65-73 x (12-)13-14 mu; spores (13.5-)17-19(-21) x (5.5-)6.5-7.5(-8.5) mu, with equal locules or larger upper locule, with rounded (-attenuate) ends, verruculose. olivaceous brown; pycnidia absent; pantropical.) --- M. captiosa (Krempelh.) D. Hawksw.
31b Ascocarps flattened, under 150 mu high, with distinct fringe --- 32

32a Ascospores mostly under 17.5 mu long; tropical (Thallus whitish to pale brown, with border lines; perithecia single, with fringe, 0.4-0.5 mm wide and (0.08-)0.1-0.14 mm tall; involucrellum 35-45 mu thick; asci 65-80 x 12-15 mu; spores 14.5-17.5(-19) x 6-7.5 mu, with upper locule about twice as large as lower locule, with rounded ends, verruculose, brown; pycnidia absent; pantropical.) --- M. miculiformis (Nyl. ex Müll. Arg.) D. Hawksw.
32b Ascospores mostly over 17.5 mu long; oceanic Europe (Thallus creamy or whitish, with border lines; perithecia single, 0.3-0.5 mm wide and 0.09-0.125 mm tall; involucrellum 25-40 mu thick; asci 55-70 x 12-18 mu; spores (15.5-)17.5-21(-25) x (6-)7-9(-10) mu, with equal locules or larger upper locule, with rounded or somewhat attenuated ends, verruculose, olivaceous brown; pycnidia absent; W. Europe.) --- M. confusa D. Hawksw.

34a Perithecia rounded, with rounded fringe (Thallus pinkish grey, without border lines?; perithecia single, with fringe, 0.5-0.9 mm wide and 0.1-0.2 mm tall; wall to 150 mu thick; asci 60-80 x 10-15 mu; spores 14-17 x 4-6.5 mu, with slightly larger upper locule, with rounded ends, verruculose; pycnidia absent; Indonesia, 200 m) --- M. alata Groenhart ex Aptroot
34b Perithecia elliptic, with elliptic fringe (Thallus indistinct; perithecia single, with elliptic, to 350 m wide fringe, ca. 0.6-1.0 x 0.3-0.4 mm wide and 0.15-0.2 mm tall; involucrellum 60-100 mu thick; asci (65-)70-100 x 15-20 mu; spores 18-22 x (7.5-)8.5-10.5 mu, with larger upper locule, with rounded ends, smooth, olive-brown to red-brown; pycnidia absent; France, California, Pakistan, on wood and twigs.) --- M. inaequalis (Fabre) D. Hawksw.

35a Perithecia (incl. fringe) under 0.3 mm wide; temperate zone of Europe (Thallus whitish, without border lines; perithecia single, ca. 0.2 mm wide and 0.1-0.12 mm tall, only ostiole exposed; invoucrellum 15-25 mu thick; asci 65-75 x 15-18 mu; spores (15-)16-18 x (6.5-)7-8(-9) mu, with equal locules or slightly larger upper locule, with broadly rounded ends, verruculose, dark brown; pycnidia absent; Europe, on Abies, Quercus.) --- M. pachnea (Körber) D. Hawksw.
35b Perithecia (incl. fringe) over 0.3 mm wide; tropical --- 36

36a Perithecium fringe 50-100 mu wide (Thallus indistinct; perithecia single, 0.4-0.5 mm wide and 0.1-0.17 mm tall, only ostiole exposed; involucrellum 30-50 mu thick; asci ?; spores (15.5-)17-19(-23) x 5-7 mu, with equal locules, with rounded ends, verruculose, olivaceous brown; pycnidia absent; neotropical, Hawaii.) --- M. anonacea (Müll. Arg.) D. Hawksw.
36b Perithecium fringe under 50 mu wide --- 37

37a Ascospores under 18 mu long (Thallus whitish, without border lines; perithecia single, 0.3-0.4 mm wide and 0.12-0.15 mm tall; involucrellum 30-40 mu thick; asci 50-60 x 8-15 mu; spores (14-)15.5-17.5 x (6-)6.5-7.5 mu, with equal locules or somewhat larger upper locule, with rounded ends, smooth to verruculose, olivaceous brown; pycnidia absent; India, Kerala) --- M. nonensis (Stirt.) D. Hawksw.
37b Ascospores mostly over 18 mu long --- 38

38a Perithecia flattened, not over 100 mu tall (Thallus olivaceous, without border lines; perithecia single, 0.2-0.4 mm wide and 0.07-0.09(-0.1) mm tall; involucrellum 20-35 mu thick; asci 63-67 x 17-20 mu; spores (17.5-)19-22(-23) x (8-)8.5-10(-10.5) mu, with equal locules or slightly larger upper locule, with rounded ends, verruculose, olive-brown; pycnidia absent; Mexico: Jalisco.) --- M. modesta (Müll. Arg.) D. Hawksw.
38b Perithecia conical (Thallus indistinct; perithecia single, 0.2-0.4 mm wide, conical; asci ?; spores 21-22 x 8 mu, with rounded upper and attenuated lower end, verruculose; pycnidia absent; Brazil, on Fourcroya (Amaryllidac.).) --- M. pachytheca (Saccardo & Sydow) Aptroot

40a Perithecia 0.8-1.0 mm wide, with 200-400 mu wide fringe (Thallus indistinct; perithecia in groups of 2-8 with common fringe, 0.8-1.0 mm wide and 0.12-0.17 mm tall; involucrellum 60-100 mu thick; asci ?; spores (21-)22-25 x 7.5-9(-10.5) mu, with equal locules or larger upper locule, with rounded ends, verruculose, golden brown; pycnidia absent; S. Africa, Fiji Islands) --- M. confluens (Müll. Arg.) D. Hawksw.
40b Perithecia 0.4-0.5 mm wide, without distinct fringe (Thallus whitish, without border lines; perithecia single, 0.4-0.5 mm wide and 0.15-0.18 mm tall; involucrellum 35-60 mu thick; asci 75-90 x 12-18 mu; spores (21-)24-28(-30) x 5-9(-11) mu, with equal locules or slightly larger upper locule, with rounded ends, verruculose, sometimes with 2 pseudosepta, olivaceous brown; pycnidia absent; pantropical.) --- M. hemisphaerica (Müll. Arg.) D. Hawksw.

42a Most ascospores under 23 mu long, with rounded ends (Thallus pale brown, with border lines; perithecia single, ca. 0.4 mm wide and 0.2-0.25 mm tall; involucrellum 30-50(-70 below) mu thick; asci 80-100 x 10-20 mu; spores 19-23(-27) x (7.5-)9-11(-12) mu, with larger upper locule, verruculose, golden brown; pycnidia absent; India.) --- M. conothelena (Nyl.) D. Hawksw.
42b Most ascospores over 24 mu long, with attenuated ends (Thallus whitish, without border lines; perithecia single, ca. 0.4 mm wide and 0.15-0.2 mm tall; involucrellum 40-80 mu thick; asci 90-120 x 14-16 mu; spores (22-)24-28(-29.5) x (8.5-)9-11.5(-12.5) mu, with larger upper locule, verruculose, reddish brown; pycnidia absent; Colombia) --- M. apposita (Nyl.) D. Hawksw.

43a Thallus with border lines (Thallus creamy or whitish or indistinct; perithecia single, with or without fringe, ca. 0.5 mm wide and 0.1-0.25 mm tall; involucrellum 30-70 mu thick; asci 80-90(-100) x (23-)26-31 mu; spores (17.5-)21-24(-26) x (7.5-)9-11.5(-13) mu, with larger upper locule, with rounded ends, verruculose, deep golden brown; pycnidia absent; neotropical and Philippines.) --- M. thelena (Ach.) D. Hawksw.
43b Thallus without border lines (Thallus pinkish white, border lines?; perithecia single, 0.5-0.6 mm wide and 0.2-0.3 mm tall; involucrellum 45-60 mu thick; asci (65-)75-90 x 20-30 mu; spores (21-)22-28(-30) x (8.5-)9-11(-12) mu, with slightly larger upper locule, with rounded ends, often with 2 pseudosepta, verruculose, brown; pycnidia absent; palaeotropical and Dominica) --- M. obovata (Stirt.) D. Hawksw.

44a (9) Endospore layer thin and short-lived --- 45
44b Endospore layer thick and long-lasting (Thallus whitish, with border lines; perithecia single, 0.8-1.1 mm wide and ca. 0.2-0.3 mm tall; asci 110-130 x 30 mu; spores 35-45 x 13-15 mu, with equal locules or slightly larger upper locule, with rounded ends, often with 2 pseudosepta, verruculose, grey; pycnidia between the perithecia and near the border lines; conidia not seen; Costa Rica, Colombia, New Guinea, Australia, on bark, 1300-1900 m) --- Ornatopyrenis queenslandica (Müll. Arg.) Aptroot

45a Hymenium partially inspersed --- 3a
45b Hymenium completely clear (Thallus whitish?, without border lines; perithecia single, ca. 0.4 mm wide; asci 150-180 x 30-44 mu; spores 32-38 x 14-18 mu, with larger upper locule with rounded end and smaller lower locule with somewhat conical end, without pseudosepta, verruculose, grey; pycnidia and conidia not seen; Vienna (Austria)) --- Mycomicrothelia lojkae (Rehm) Y.Z. Wang, Aptroot & K.D. Hyde