Brasenites kansense Wang and Dilcher, 2006b

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 : 8-10

Brasenites kansense Wang and Dilcher, 2006b

Figure 5.3-4

Description. Leaf margin entire; shape suborbiculate ( L / W ratio 1.2:1) to orbiculate ( L / W ratio 1:1); lamina slightly funnel form at the position where the petiole is attached; leaf base peltate central (petiole attached within the boundaries of the leaf margin and near the center of the leaf). Primary venation actinodromous, consisting of 11 primary veins in one leaf lamina; five major primary veins present, with three of them directed oppositely (apically directed) from the other two; three minor primary veins radiate from the leaf center toward each lateral side; central major primary vein of the three extending nearly to the leaf margin, producing pinnate secondary veins; two apically directed and the two basally directed primary veins having strong exmedial branches, which fork repeatedly. Secondary veins produced from forked primary veins join adjacent branches to form polygonal (five- to six-sided) meshes both variable in shape and size, intergrading with higher-order (tertiary or quaternary) veins at a fourth to a third of the distance of the radius near the margin. Numerous small rounded protuberances present on the entire lamina.

Number of specimens examined. 4.

Specimens illustrated. UF 15706-14806 ( Figure 5.3-4 ).

Occurrences. Hoisington III locality, Kansas.

Remarks. One specimen ( Figure 5.3 ) and its line drawing ( Figure 5.4 ) are presented in this report. Figures 5.3 and 5.4 show the typically suborbiculate leaf shape, entire leaf margin, centrally peltate base, and major primary veins of this species. Similar leaves have also been reported from the early Campanian Grünbach flora from the Grünbach Formation of the Grünbach-Neue Welt Basin, Austria (Herman and Kvaček, 2007a, 2007b), and the Late Cretaceous Arman Formation Northeastern Russia (Herman et al., 2016). Brasenites kansense differs from Exnelumbites callejasiae , a fossil taxon described from the Late Cretaceous McRae Formation, Mexico, in having much stronger bilateral symmetry to the venation, an entire margin, and suborbicular lamina (Estrada-Ruiz et al., 2011). For differences among Brasenites , Exnelumbites and other fossil members of the Nelumbonaceae , and other aquatic plants, see Estrada-Ruiz et al. (2011, table 1).

A phylogenetic analysis that includes three Early Cretaceous fossil species (including Brasenites kansense ) with peltate leaves (Taylor et al., 2008) indicates their affinities to Cabombaceae . However, in a recent analysis by Taylor and Gee (2014), adding the fossil leaves of Brasenites kansense (Wang and Dilcher, 2006b) , Pluricarpellatia peltata (Mohr et al., 2008) and Scutifolium jordanicum (Taylor et al., 2008) results in the loss of many of the monophyletic groups found in the living-taxa analysis.

Figures

FIGURE 5. 1-2, Aquatifolia fluitans Wang and Dilcher 2006b, UF15706-8263′, leaf showing the spherical float on the petiole (1) and UF15706-24120, leaf showing cordate base and thin high order venation (2). Scale bars equal 5 mm. 3-4, Brasenites kansense Wang and Dilcher, 2006b, UF15706-14806, specimen (3) and line drawing (4) to show suborbiculate leaf shape, entire leaf margin, peltate central base, major primary veins. Scale bars equal 1 cm.