Dicotylophyllum skogii, Wang & Dilcher, 2018

Wang, Hongshan & Dilcher, David L., 2018, Early Cretaceous angiosperm leaves from the Dakota Formation, Hoisington III locality, Kansas, USA, Palaeontologia Electronica (34 A) 21 (3), pp. 1-49 : 38-40

Dicotylophyllum skogii sp. nov.

Figure 25

Specific diagnosis. Lamina thin. Base cordate. Margin entire. Petiole thin, multi-stranded. Primary venation pinnate; primary vein multi-stranded. Secondary vein thin, decurrent on primary vein, subopposite; angle of divergence moderate acute, uniform. Intersecondary veins common, simple. Tertiary veins thin, originating from secondary or intersecondary veins at right angles, forming rectangular or square meshes that are oriented with long axis parallel to secondary veins.

Description. Observed lamina 11 cm long and 5 cm wide; lamina very thin. Base cordate. Observed margin entire. Petiole thin, multi-stranded, 6 cm long and 1.5 mm wide. Primary venation pinnate; observed primary vein 1.5 mm wide, multi-stranded, slightly curved. Secondary venation not observed; secondary vein thin relative to primary vein, 8 pairs observed, decurrent on primary vein, subopposite; angle of divergence moderate acute (ca. 45º), uniform. Intersecondary veins common, simple, 1 to 2 pairs between two adjacent secondary veins. Tertiary veins thin, originating from secondary or intersecondary veins at right angles, forming meshes rectangular or square in shape and oriented with long axis parallel to secondary veins. Veins of higher order not observed.

Number of specimens examined. 1.

Holotype. UF15706-24573 ( Figure 25 ).

Derivation of epithet. In honor of Judith Skog in recognition of her contribution to Dakota paleobotany.

Remarks. The observed lamina is 11 cm long and estimated leaf length may be up to at least 15 cm. Although secondary venation pattern is not observed because of the fragmented nature of the specimen, the combined features of this leaf type, including thin lamina structure, thin primary and higher order veins, large spacing of secondary veins (eight pairs observed on 11 cm lamina), the presence of intersecondary veins, and tertiary venation patterns is distinctive from any other Dakota Formation angiosperm leaves. The multi-stranded primary vein and the presence of intersecondary veins indicate its possible affinity within the Magnoliidae. The thin lamina texture, tertiary and quaternary veins forming rectangular meshes with long axes parallel to secondary veins are observed in some extant herbaceous angiosperms, indicating that Dicotylophyllum skogii may be an herbaceous plant which grows near water.

Figures

FIGURE 25. Dicotylophyllum skogii sp. nov. 1, UF15706-24573, fragment of leaf to show the petiole and strong primary vein. Scale bar equals 1 cm. 2, Enlargement of Figure 25.1 (area indicated by the upper arrow) to show secondary and intersecondary veins. Scale bar equals 2 mm. 3, Enlargement of the base of the leaf in Figure 25.1 (are indicated by the lower arrow) to show venation. Scale bar equals 2 mm.