Mexiglossa varia Delevoryas and Person, 1975

León, María Patricia Velasco de, Martínez, Erika Lourdes Ortiz, Barragan, Miguel Angel Flores, Madrid, Diana Silvia Guzmán & Martinez, Pedro Christian Martínez, 2024, New records of Bennettitales and associated flora from the Jurassic of the Cualac Formation, Mexico, Palaeontologia Electronica (a 14) 27 (1), pp. 1-19 : 12-14

Mexiglossa varia Delevoryas and Person, 1975

Figure 5 A-G

Material examined. CFZCr2-1, Cr4-2, 3, 6, 8, 10, Cr5-1, 2, 3, Cr7-1, 2, 5-8, Cr8-1, 2, 5-8, Cr9-1-3, Cr10-2-10, 13-15, Cr11-1, 2, 5-8, Cr12-1, 3, Cr13- 1,2, Cr14-1-3, Cr15-1, 2, Cr17-1, Cr18-2-4, Cr19-3, Cr21-2, 3, 5-9, Cr22-1, 6, 8, Cr24-1, 3, Cr25-1, Cr28-1, 5, 7, 8, 10, 12-14, Cr30-2, 4, 9, 12, Cr38-1, 2, Cr39-1-4, 6, Cr40-1, Cr41-1, Cr42-2-6, 9, 11, 12, Cr43-1-7, Cr48-1-4, Cr49-1, 4, Cr50-2, 4, Cr51-1, 5, 7, 9, 11, 12, 15, 17, Cr52-1, 3, 5, 8, 10, 12, 13, Cr53-2, 5-7, 9, 17, 18, Cr54-1, 2, Cr55-6, Cr56-5, 8, 10,12, Cr55-6, Cr56-5, 8, 10, 11, Cr65-1, Cr66-1, Cr67-1, Cr69-1, Cr70-1, 2, Cr71-1, 2, Cr72-1, Cr73-1, Cr74-1, Cr75-2, 3, Cr76-1, Cr77-1, Cr79-1, Cr80-1, Cr81-1-3, Cr82-1, 2, 9-12, Cr84-1,3, 6, 7, Cr88-1, 2, Cr89-2, 3, Cr90-2, Cr97-3, Cr104-2, Cr105-1, Cr118-1, 2, 4, 6, Cr121-1, 2, Cr123-2, Cr124-2, Cr129-1

Description. Impressions and compressions of oblanceolate to lanceolate, even elliptic, leaflets 7– 26 cm long and 2–8 cm wide, margin entire, thick midvein tapering towards the apex measuring 3– 0.7 mm between eight to 11 anastomosing secondary veins. Mucronate, acuminate, acute, or rounded apices ( Figure 5 A-B). The cuticle has quadrangular to rectangular epidermal cells 3–5 μm wide and 8–15 μm long, the largest are 9–25 μm wide and 23.2–69.4 μm long. Slightly undulate cell walls with a thickness of 0.5–1.5 μm, and the thickest of up to 9 μm ( Figure 5 C-E). Sunken stomata without apparent arrangement, stomatal opening is 0.5–3 μm wide and 2–5 μm long, from paracytic to anisocytic. Rounded to oval stomata 10–13 μm wide and 10–20 μm long in some specimens. Thin, 1–2 μm wide and 1.5–3 μm long, and thickened, 4–7 μm wide and 6–10 μm long, guard cells. Anisocytic subsidiary cells 2.5–4.2 μm wide and 5–8 μm long ( Figure 5F ). Simple trichomes in the midvein 0.4 μm wide and 0.3–0.5 long ( Figure 5G ).

Discussion. When analyzing the morphological characters of this species, differences are mainly observed in the venation patterns, and there are also anatomical variants in specimens Cr4-6, Cr8- 6, Cr11-1, Cr30-13, and Cr70-2 with smaller epidermal cells and very thin cell walls, larger paracytic stomata, and thickened guard cells without trichomes. These data allow the identification two fossil taxa of this genus that probably correspond to independent species. However, this point is beyond the scope of the present work and should be reevaluated in future studies.

Figures

FIGURE 5. Leaves of Mexiglossa and Czekanowskia. A-B - whole leaves of Mexiglossa varia, note that the midvein cells; C-E- F-G light microscopic images, rectangular epidermal cells of Mexiglossa with straight walls; D - electron microscopy image, thick walls of epidermal cells; F - arrows indicate two stomata; G - trichomes present on leaves of Mexigossa varia; H - linear leaves of the genus Czekanowskia, the arrows indicate the middle vein and the fork of the leaf; I - specimen CFZcr105 shows base of bundle of laciniae, the arrow indicates a bifurcation. Scale in A 3 cm; B 3 cm; C 10 μm; D 50 μm; E 15 μm; F 15 μm; G 2.5 μm; H 1 mm; I 5 mm.