Selaginella longifimbriata 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 : 198

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

Holotype: GZG. BST.21998 [ Fig. 12], Geoscientific Collection of the University of Göttingen. – Fig. 1F; 12 (only specimen available).

Diagnosis — Strobili terminal, bilateral, dorsiventrally complanate. Dorsal sporophylls imbricate, ovate, apex acute to obtuse, margins slightly denticulate; sporophyll-pteryx incomplete, narrow, margins ciliate. Ventral sporophylls imbricate, adpressed, nearly orbicular, apex rounded, margins long-ciliate. Microspores distally rugulate.

Description — Rhizophores, branches and trophophylls not preserved. Strobili terminal, compact, bilateral, dorsiventrally complanate, 11.0–11.8 × 2.4–2.6 mm ( Fig. 12A, B). Sporophylls dimorphic. Dorsal sporophylls imbricate, ascending, c. 40 per strobilus, 1.7–2.1 × 0.4–0.6 mm, ovate, non-carinate, base not seen, apex acute to obtuse, margins slightly denticulate; sporophyll-pteryx incomplete, narrow, ciliate at margins, cilia 80–160 µm long ( Fig. 1F; 12C). Ventral sporophylls imbricate, adpressed, symmetric, c. 40 per strobilus, 0.7–1.0 × 0.6–0.8 mm, nearly orbicular, non-carinate, base not seen, apex rounded, margins long-ciliate, cilia 100–500 µm long ( Fig. 1F; 12D, E). Epidermis of ventral sporophylls composed of elongate cells, with long axes orientated uniformly parallel to long axis of sporophyll. Sporangia suborbicular, 380–520 × 480–640 µm. Microspores 20–30 µm in diam., distally rugulate ( Fig. 12F, G).

Remarks — Although vegetative leaves are not preserved in Selaginella longifimbriata , we presume that it possessed resupinate strobili (see remarks under S. minutissima ).

Selaginella longifimbriata differs from all other Kachin Selaginella fossils with bilateral strobili in its large-sized strobili with non-carinate dorsal sporophylls and distally rounded ventral sporophylls with long-ciliate margins ( Fig. 1F; 12C–E). Co-occurring with this species in the same amber piece is the holotype specimen of the fern Cystodium sorbifolioides L. Regalado & al. described previously by Regalado & al. (2017a).

Selaginella burbidgei Baker , a present-day species endemic to Borneo, resembles S. longifimbriata in several structural features, including strobili more than 13 mm long, acute, nearly entire dorsal sporophylls and strongly ciliate ventral sporophylls ( Baker 1885; Van Alderwerelt van Rosenburgh 1915). However, S. longifimbriata is clearly distinguished from S. burbidgei by having nearly orbicular, distally rounded, non-carinate ventral sporophylls ( Fig. 1F; 12D, E), in contrast to longcuspidate and prominently carinate ventral sporophylls in S. burbidgei .

Etymology — The specific epithet is derived from the Latin words longus: long, and fimbriatus: fringed. It refers to the margin of the ventral sporophylls from which long, slender processes extend.