Selaginella ciliifera A. R. Schmidt & L. Regalado, 2022

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 : 202-206

Selaginella ciliifera A. R. Schmidt & L. Regalado , sp. nov.

Holotype: GZG. BST.21997 [ Fig. 15], Geoscientific Collection of the University of Göttingen. – Fig. 1I; 15, 16 (two specimens available).

Diagnosis — Axes compressed. Trophophylls dimorphic. Axillary trophophylls symmetric, ovate, non-carinate, base short-truncate, apex acute to obtuse, margins ciliate to long-ciliate. Dorsal trophophylls distant, adpressed, symmetric to somewhat asymmetric, ovate, non-carinate, base decurrent, apex acute to obtuse, margins sparsely ciliate. Ventral trophophylls distant, ascending, symmetric, oblong to ovate, non-carinate, ligulate, base truncate, apex obtuse to acute, sometimes rounded, margins dentate on basiscopic and distal acroscopic sides, sparsely long-ciliate on medial and proximal acroscopic side. Ligule situated on proximal acroscopic side, close to leaf insertion to branch, ovate. Strobili terminal, compact, bilateral, dorsiventrally complanate, resupinate. Sporophylls dimorphic. Dorsal sporophylls close to distant, spreading, ascending, asymmetric, lanceolate, slightly carinate, base inequilateral, basiscopic side straight, acroscopic side rounded, apex obtuse to acute, sometimes rounded, margins mostly ciliate, occasionally dentate; sporophyll-pteryx incomplete, narrow at base, with ciliate margins. Ventral sporophylls close, adpressed, ovate to broadly ovate, carinate, apex acute to obtuse, margins long-ciliate. Sporangia nearly orbicular. Microspores distally and proximally rugulate.

Description — Rhizophores not preserved. Axes compressed. Trophophylls dimorphic ( Fig. 15A, B; 16A). Axillary trophophylls symmetric, 0.9–1.3 × 0.4–0.5 mm, ovate, non-carinate, base short-truncate, apex acute to obtuse, margins ciliate to long-ciliate, cilia 60–220 µm long. Dorsal trophophylls distant, adpressed, symmetric to somewhat asymmetric, 0.9–1.3 × 0.4–0.6 mm, ovate, non-carinate, base decurrent, apex acute to obtuse, margins sparsely ciliate, cilia 40–140 µm long. Ventral trophophylls distant, spreading, ascending, symmetric, 1.2–2.7 × 0.7–1.0 mm, oblong to ovate, non-carinate, ligulate, base truncate, apex obtuse to acute, sometimes rounded, margins dentate on basiscopic and distal acroscopic sides, sparsely long-ciliate on medial and proximal acroscopic side, teeth 20–50 µm long, cilia 70–150 µm long ( Fig. 15A, B, F). Ligule situated on proximal acroscopic side, close to leaf insertion to branch, 120 × 60 µm, ovate ( Fig. 15G). Strobili terminal, compact, bilateral, dorsiventrally complanate, resupinate, 3.4–5.4 × 2.6–3.2 mm ( Fig. 15A, B; 16A). Sporophylls dimorphic. Dorsal sporophylls close to distant, spreading, ascending, asymmetric, conduplicate, 10 or 11 per strobilus (– 14 in JZC-Bu-004), 1.5–2.4 × 0.4–0.8 mm, lanceolate, slightly carinate, base inequilateral, basiscopic side straight, acroscopic side rounded, apex obtuse to acute, sometimes rounded, margins mostly ciliate, occasionally dentate, teeth or cilia 40–340 µm long ( Fig. 1I; 15C; 16B); sporophyll-pteryx incomplete, narrow at base, with ciliate margins, cilia similar in size to those on sporophyll margins ( Fig. 1I; 15C). Epidermis of dorsal sporophylls composed of uniform isodiametric cells. Ventral sporophylls close, adpressed, conduplicate, 9 or 10 per strobilus, 0.7–1.7 × 0.4–0.8 mm, ovate to broadly ovate, carinate, base not seen, apex acute to obtuse, margins long-ciliate, cilia 90–520 µm long ( Fig. 1I; 15D; 16C). Epidermis of ventral sporophylls composed of elongate cells, with long axes orientated at angles of 15–30° to carina. Sporangia nearly orbicular, 300–480 × 340–500 µm, composed of uniform isodiametric cells with thick anticlinal walls ( Fig. 15E). Microspores 25–35 µm in diam., distally and proximally rugulate ( Fig. 15H, I).

Remarks — The specimen selected here as the holotype ( GZG. BST.21997) shows the presence of a basal ligule on the adaxial leaf surface ( Fig. 15F, G) that is considered a synapomorphy of the heterosporous lycophytes (i.e. Selaginellaceae and Isoetaceae and extinct relatives).

This fossil-taxon closely resembles the general morphology of Selaginella villosa in possessing conspicuously ciliate trophophylls and sporophylls. Despite these similarities, the two taxa differ in the shape of the sporophyll-pteryx of the dorsal sporophylls and the apex of the ventral sporophylls. Selaginella ciliifera has dorsal sporophylls with a sporophyll-pteryx that is narrow at the base and ventral sporophylls that are acute to obtuse at the apex ( Fig. 1I; 15C, D), whereas S. villosa possesses dorsal sporophylls with a sporophyll-pteryx that is broadly enlarged at the base, forming an auricle, and ventral sporophylls that are acuminate at the apex ( Fig. 1J; Fig. 17C–E).

Four present-day taxa share with Selaginella ciliifera the strobili with ciliate dorsal and ventral sporophylls, including S. albociliata P. S. Wang, endemic to China ( Zhang & al. 2013), S. apoensis Hieron. from the Philippines (Mindanao), Sulawesi and Maluku (Seram) ( Van Alderwerelt van Rosenburgh 1915), S. longiciliata Hieron. , from New Guinea to Australia ( N Queensland) ( Van Alderwerelt van Rosenburgh 1915; Jermy & Holmes 1998) and S. macroblepharis Warb. , endemic to New Guinea ( Van Alderwerelt van Rosenburgh 1915). Selaginella apoensis , S. longiciliata and S. macroblepharis differ from S. ciliifera by having ventral sporophylls that are acuminate to aristate at the apex and microspores with smooth surfaces ( Van Alderwerelt van Rosenburgh 1915). The fossil has ventral sporophylls that are acute to obtuse at the apex and rugulate microspores ( Fig. 1I; 15H, I). Selaginella apoensis differs from the fossil in several other structural aspects, namely dorsal and ventral sporophylls that are similar in size and shape (distinctly different in S. ciliifera ) and longer strobili (c. 20 mm long). Strobili of the fossil-taxon are hardly more than 5.5 mm long. Selaginella albociliata differs from the fossil by having longer strobili (6–10 mm long), dorsal sporophylls that are acuminate at the apex and verrucate microspores ( Wang 1990). In contrast, S. ciliifera has shorter strobili, dorsal sporophylls that are obtuse to acute at the apex and rugulate microspores ( Fig. 15B, C, H, I; 16B).

Etymology — The specific epithet is derived from the Latin words cilium: hair-like process, and ferre: to bear, carry. It refers to the numerous and long ciliae which occur especially at the margins of the sporophylls.

Additional specimens studied — JZC-Bu-004, American Museum of Natural History ( Fig. 16), PB25339, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences.