Selaginella

Schmidt, Alexander R., Korall, Petra, Krings, Michael, Weststrand, Stina, Bergschneider, Lena, Sadowski, Eva-Maria, Bechteler, Julia, Rikkinen, Jouko & Regalado, Ledis, 2022, Selaginella in Cretaceous amber from Myanmar, Willdenowia 52 (2), pp. 179-245 : 183-186

Key to fossil Selaginella from Kachin amber

1. Strobili dorsiventrally complanate; sporophylls dimorphic ( Selaginella subg. Stachygynandrum ).. 2

– Strobili quadrangular; sporophylls monomorphic. 11

2. Ventral sporophylls serrulate-denticulate, serrate or dentate at margins.......................... 3

– Ventral sporophylls short- to long-ciliate at margins. 7

3. Sporophyll-pteryx of dorsal sporophylls nearly entire, with only a few teeth at margins..................................... Selaginella minutissima

– Sporophyll-pteryx of dorsal sporophylls conspicuously serrulate, with multiple teeth at margins.... 4

4. Ventral sporophylls conspicuously serrate or dentate at margins, teeth 25–40 µm long; strobili composed of 2 rows of smaller dorsal sporangia and 2 rows of larger ventral sporangia.... Selaginella heterosporangiata

A

B C D E

F

G H I J A

B

E

F

C

D

G

H

I J K

– Ventral sporophylls denticulate to serrulate at margins, teeth 5–21 µm long; strobili with no particular pattern of sporangial arrangement............. 5

5. Ventral trophophylls close to imbricate; axillary and ventral trophophylls broadly ovate...................................... Selaginella grimaldii

– Ventral trophophylls distant from each other; axillary and ventral trophophylls predominantly oblong.. 6

6. Ventral sporophylls broadly ovate; sporangia orbicular.................. Selaginella ohlhoffiorum

– Ventral sporophylls ovate-lanceolate; sporangia ellipsoid..................... Selaginella cretacea

7. Dorsal sporophylls predominantly dentate or denticulate at margins............................ 8

– Dorsal sporophylls predominantly ciliate at margins, but also dentate or serrate at basiscopic margin.. 10

8. Ventral sporophylls nearly orbicular, apex rounded.................... Selaginella longifimbriata

– Ventral sporophylls broadly ovate to ovate-lanceolate, apex attenuate............................. 9

9. Strobili up to 3.5 mm long; dorsal sporophylls with incomplete sporophyll-pteryx; megaspores proximally rugulate-reticulate.. Selaginella patrickmuelleri

– Strobili up to 6.5 mm long; dorsal sporophylls with nearly complete sporophyll-pteryx; megaspores proximally echinate............ Selaginella wangxinii

10. Dorsal sporophylls with sporophyll-pteryx narrow at base; ventral sporophylls acute to obtuse at apex............................ Selaginella ciliifera

– Dorsal sporophylls with sporophyll-pteryx broadly enlarged at base forming an auricle; ventral sporophylls acuminate at apex...... Selaginella villosa

11. Sporophyll-pteryx present..... Selaginella aurita

– Sporophyll-pteryx absent................... 12

12. Sporophylls acuminate at apex, entire to erose at margins................. Selaginella amplexicaulis

– Sporophylls attenuate, sometimes aristate at apex, at least denticulate, minutely serrate or dentate at margins.................................... 13

13. Trophophylls monomorphic ( Selaginella subg. Ericetorum ).................................. 14

– Trophophylls dimorphic.................... 15

14. Trophophylls lanceolate, attenuate at apex, amplexicaul at base, erose at margins.................................... Selaginella wunderlichiana

– Trophophylls ovate, short-acuminate at apex, peltate at base, short-ciliate at basal acroscopic margin, sparsely dentate at medial margins, nearly entire at distal margins............. Selaginella isophylla

15. Basal sporangium (presumably megasporangium) protruding and conspicuously larger than rest of sporangia on strobilus........................ 16

– Sporangia uniform in size throughout strobilus.. 17

16. Dorsal trophophylls ovate, obtuse at apex; sporophylls distant, ovate, attenuate at apex, exauriculate at base................. Selaginella heinrichsii

– Dorsal trophophylls oblong-lanceolate, attenuate to aristate at apex; sporophylls imbricate, broadly ovate, attenuate to aristate at apex, rounded at base........................ Selaginella konijnenburgiae

17. Sporangia ellipsoid or ovoid... Selaginella ovoidea

– Sporangia generally suborbicular............. 18

18. Axillary trophophylls broadly ovate, nearly entire or with a few sparse teeth or cilia; microspores in monads...................... Selaginella wangboi

– Axillary trophophylls elliptic to narrowly elliptic, serrulate-serrate, denticulate-dentate to short-ciliate at margins; microspores in tetrads............ 19

19. Axillary trophophylls short-ciliate or denticulate at margins, cilia or teeth 30–60 µm long................................... Selaginella tomescui

– Axillary trophophylls mostly serrate or dentate, with teeth 15–50 µm long....................... 20

20. Strobili 1–2 mm long; sporophylls ovate, attenuate at apex, slightly denticulate to erose at margins, teeth ≤ 10 µm long............... Selaginella pellucida

– Strobili 4.0– 5.5 mm long; sporophylls lanceolate, long-attenuate to aristate at apex, sparsely dentate at margins, teeth 30–40 µm long.. Selaginella obscura