Menispermites temlyanensis, Zolina & Golovneva & Abstract, 2024

Menispermites temlyanensis

Zolina, Golovneva et Grabovskiy, sp. nov.

Figure 6A–E View FIGURE 6 , Figure 7A–E View FIGURE 7 , Figure 8A–F View FIGURE 8

Plant Fossil Registration number PFN003476

Etymology. After Temlyan Mountain.

Holotype (designated here). Specimen BIN 1588/263, North-East of Russia, Anadyr district of Chukotka, Tanyurer Formation , MaastrichtianDanian ; figure 6 A, 8 B.

Material. Collection BIN 1588, specimens 218, 221, 241, 250–266, 410, 411.

Diagnosis. Leaves trilobate or unlobate, broadly ovate with rounded, peltate base with high pelta; lobes (if presents) small, broadly triangular with rounded apices; central lobe bigger than lateral ones; apex of unlobate leaves attenuate; margin entire; venation palmate, with 3–5 basal veins; midvein producing 3–5 pairs of secondary veins; inner lateral veins straight, terminated in the lobes apices; outer lateral basal veins curved, connected with inner lateral veins; pelta innervated by 2–4 pairs of thin veins.

Description. Leaves are simple, 3–12 cm in length and 3–9 cm in wide. The leaf lamina is broadly ovate in outlines, trilobate, more rarely unlobate. Lobes (if presents) are small, broadly triangular with rounded apices and strait or slightly convex sides ( Figure 6A, D View FIGURE 6 , Figure 7C View FIGURE 7 , Figure 8B, C, E View FIGURE 8 ). Central lobe is significantly bigger than lateral ones. Unlobate leaves have attenuate apex with rounded tip ( Figure 7A, B View FIGURE 7 ). The leaf base is rounded, peltate. The height of the pelta ranges

ZOLINA, GOLOVNEVA, & GRABOVSKIY: MENISPERMITES IN NORTHERN ASIA from one quarter to one third of the leaf length. The margin is entire ( Figure 6C View FIGURE 6 ).

Venation is palmate, with 3–5 basal veins. The midvein is straight or slightly curved. It is thicker and longer that other veins, running to the leaf apex, producing 3–5 pairs of alternate or subopposite secondary veins in the upper one-quarter of the lamina. These secondary veins are connected to each other and form series of loops near leaf apex. Inner basal lateral veins are thick, straight, diverging from the midvein at an angle 35– 45°, running to the lobe’s apices. They produce 1–3 pairs of short curved brochidodromous secondary veins in upper part, which innervate lobes. The lowest acroscopic secondary veins are connected with the lowest secondary veins extending from the midvein. Outer lateral basal veins are curved, thinner and shorter than inner lateral basal veins. They diverge from the midvein at an angle about 75–85° and join with inner lateral veins near the leaf margin. They provide 3–5 thin basiscopic brochidodromous branches. Pelta is innervated by 2–4 pairs of thin, radiating, dichotomously branching veins ( Figure 6A, B, E View FIGURE 6 , Figure 7D, B, E View FIGURE 7 , Figure 8B, D, F View FIGURE 8 ). Tertiary veins form an alternating series of meshes ( Figure 6C View FIGURE 6 , Figure 8B View FIGURE 8 ).

Remarks. The type species of the genus Menispermites , M. obtusilobus ( Figure 4A View FIGURE 4 ) from the Dakota Formation has broadly ovate, trilobate peltate leaves with obtuse apex, low pelta ( 3–4 mm), truncate base and crenate or undulate margin ( Lesquereux, 1874). M. temlyanensis is similar to the type species in its trilobate shape and in the presence of a pelta. The new species differs from M. obtusilobus by its small lobes, high pelta ( 2–4 cm) and entire margin. Two species M. salinensis Lesquereux and M. acerifolius Lesquereux were described from the Dakota Formation together with the type species ( Lesquereux, 1874). Both species are characterized by nonpeltate leaves.

Most species of Menispermites have entire leaves. Since the leaves of the new species are trilobate, they have the greatest resemblance to M. sibiricus . TThis species has broadly ovate 3–5 lobate leaves, with rounded, cordate or truncate base, broadly triangular obtuse lobes and dentate margin ( Figure 4 View FIGURE 4 ). Both species are characterized by well-developed pelta. However, M. temlyanensis is distinguished from M. sibiricus by less developed lobes and by entire margin

Range and occurrence. North-East of Russia, Tanyurer Formation, Maastrichtian–Danian.