| Description: |
Lejeunea sp. Specimen. Carsten Gröhn Amber Collection (Glinde, Germany) 10410; syninclusion Spruceanthus extinctus (Heinrichs et al.) Gradst. & Sukkharak, with antheridia (Feldberg et al. 2021 a). Age and stratigraphic level. 15‒23 Ma, Langhian – Aquitanian (early to middle Miocene), Simojovel, Chiapas, Mexico. Description. Gametophyte fragment ca. 0.73 mm long, 0.19–0.34 mm wide with leaves [the damaged leaves make the width difficult to assess], light yellowish to nearly transparent (Fig. 3 A, B). Branching Lejeunea - type, leaves and underleaves somewhat smaller than on main shoot, form similar; intact branch 0.43 mm long, ca. 0.2 mm wide with leaves (Fig. 3 C). Stem light yellowish brown, ca. 30 µm wide, surface cells elongated, possibly thick-walled, ventral merophyte ca. 2 cells wide (Fig. 3 A); stem on branch somewhat thinner than main stem [~ 20 µm wide; appears to be shrunken]. Lateral leaves incubous, conduplicate-bilobed, imbricate to (probably) distant, alternate, obliquely spreading on lower part of main axis, on shoot apex and on branch erect (Fig. 3 A – D), insertion line possibly J-shaped [not clearly visible]. Dorsal lobe flat, elliptical to ovate, slightly falcate, on main stem ca. 220 µm long × 150 µm wide in the middle [apex probably damaged], length: width ratio ca. 1.5: 1, margins entire, antical margin regularly arched towards apex, postical margin slightly arched, forming a wide angle with the keel (Fig. 3 A – C); lobes of branch leaves 160–180 µm long × 100–130 µm wide in the middle, length: width ratio 1.4–1.6: 1, apex rounded. Lobe cells isodiametric to oblong, mostly hexagonal (Fig. 3 C – E), up to 1.5 × as long as wide, 15–30 µm long × 10–20 µm wide; cell surfaces smooth; cell walls thin, trigones small, triangular (Fig. 3 E). Ocelli not seen. Ventral lobules Lejeunea - type, vertically inserted, inflated, ovate (Fig. 3 A – C, E), ca. 0.5–0.6 × the length of the dorsal lobe [difficult to assess, because the lobe seems to be damaged at the apex], ca. 150 µm long × 100 µm wide in ... |