Anisodromum upchurchii, 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 : 30

Anisodromum upchurchii sp. nov.

Figure 19.1-2

Specific diagnosis. Lamina base acute, decurrent. Margin entire. Primary venation pinnate; primary vein stout, multi-stranded, straight. Secondary venation brochidodromous, secondary veins moderate relative to primary vein, opposite, subopposite or alternate; angle of divergence wide acute, uniformly curved apically; secondary vein spacing distant. Intersecondary veins common, usually opposite to a secondary vein on the other side of lamina. Tertiary veins moderate relative to secondary veins, percurrent, course straight, oriented almost at right angles with primary vein.

Description. Incomplete leaves observed. Apex missing. Base acute, decurrent. Margin entire. Primary venation pinnate; primary vein stout, multi-stranded, straight. Secondary venation brochidodromous, secondary veins moderate relative to primary vein, ca. six pairs per lamina, opposite, subopposite or alternate; angle of divergence wide acute, with lowest pair more acute than pairs above, uniformly curved apically; secondary vein spacing distant (distance between veins 1 to 1.5 cm. Intersecondary veins common, one or two per intercostal region; extending less than one half distance of half lamina, usually opposite to a secondary vein on the other side of lamina. Tertiary veins moderate relative to secondary veins, percurrent, course straight; angle of origin AO (acute on exmedial side and obtuse on admedial side of secondary veins or intersecondary vein) or RO (right on primary vein and obtuse on admedial side of secondary or intersecondary veins), primary vein-tertiary vein angle almost right (90º); tertiary vein interval close (interval between veins less than 0.5 cm). Veins of higher order not observed.

Number of specimens examined. 4.

Holotype. UF15706-24576 ( Figure 19.1-2 ).

Derivation of epithet. In honor of Garland R. Upchurch in recognition of his contributions to Dakota Formation angiosperm paleobotany.

Remarks. Anisodromum upchurchii differs from Anisodromum wolfei in that it has large angles of divergence for secondary veins, large distance between secondary veins, fewer secondary veins, and intersecondary veins arranged opposite to secondary vein on the opposite side of the lamina. Anisodromum upchurchii and A. schimperi are similar in that they both have irregularly spaced secondary veins. They differ in that the secondary venation of A. schimperi is festooned brochidodromous and its tertiary veins are orthogonally reticulate near primary vein.

The wide divergence angle of the secondary veins and the primary-tertiary vein angle of Anisodromum upchurchii are similar to Morphotype CM 05 ( Magnoliaephyllum sp. ) from the mid-Cretaceous Cedar Mountain Formation of Utah, USA (Harris and Arens, 2016, p. 646-648, figure 4.1-3). They differ in that the divergence angle of secondary veins is larger and the percurrent tertiary veins is less dense in Anisodromum upchurchii compared with those of Morphotype CM 05.

It is unknown if the specimens from the Hoisington III locality represent simple or compound leaves. Therefore, we tentatively assign these specimens to the genus Anisodromum . Future collection with better preserved specimens may confirm this assignment or help separate them from this genus.

Figures

FIGURE 19. 1-2, Anisodromum upchurchii sp. nov., UF15706-24576, middle portion of lamina showing strong primary and secondary veins (scale bar equals 1 cm) (1) and enlargement of an area in Figure 19.1 (indicated by arrow) to show percurrent tertiary veins (scale bar equals 2 mm) (2). 3-4, Anisodromum schimperi (Lesquereux) comb. nov., UF15706-24635, leaf showing uneven spacing of secondary veins and reticulate tertiary veins (scale bar equals 5 mm) (3) and; UF15706-24633, leaf showing secondary venation and reticulate tertiary veins (scale bar equals 5 mm) (4).