Rogersia dakotensis Wang and Dilcher, 2009

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 : 12-16

Rogersia dakotensis Wang and Dilcher, 2009

Figures 9.1, 9.3 , 10.1

Description. Leaf simple; whole lamina and base symmetrical; form linear oblong, L / W >9, 7.5 cm to 9 cm long and 0.5 cm to 1 cm wide. Apex attenuate. Base acute, decurrent. Margin entire. Petiole short, stout. Primary venation pinnate; primary vein stout, multi-stranded; course straight or slightly curved. Secondary venation brochidodromous; secondary veins thin relative to primary vein; subopposite, decurrent on primary vein; angle of divergence narrow acute (ca. 30º), spacing irregular; secondary veins uniformly curved to join exmedial branches of superadjacent secondary veins or superadjacent secondary veins at a distance of one fifth to one fourth of half lamina to form an intercostal region with its long axis oblique primary vein (ca. 30º), then continuing to join exmedial branches of adjacent secondary veins to form two series of loops; these loops enclosing elongate areas with long axis almost parallel to leaf margin; secondary veins running along the margin appearing to be intramarginal veins. Intersecondary veins present, one per intercostal region, simple, extending about one half of the distance from primary vein to leaf margin and then intersect with superadjacent secondary veins. Tertiary veins thin, irregular, percurrent with retroflexed or straight course. Veins of higher order not observed.

Number of specimens examined. 200.

Occurrences. Hoisington III locality, Kansas and Courtland I locality, Minnesota .

Specimens illustrated. UF 15706-24798 ( Figure 9.1, 9.3 ); UF 15706-24620 ( Figure 10.1 ).

Remarks. Rogersia dakotensis is similar in leaf shape and angle of divergence of secondary veins to Wolfiophyllum heigii from the Braun’s Ranch locality of Kansas, but they differ in that W. heigii has eucamptodromous secondary venation, forking secondary veins near margin, and percurrent or exmedially ramified tertiary veins ( Table 2 ).

Figures

FIGURE 9. 1 and 3, Rogersia dakotensis Wang and Dilcher, 2009, UF15706-24798, general leaf shape, note thin secondary veins forming intramarginal veins (scale bar equals 5 mm) (1) and enlargement to show intramarginal veins formed by looping secondary veins (scale bar equals 1 mm) (3). 2 and 4, Rogersia parlatorii Dilcher and Wang, 2006, UF15706-7529, specimen showing leaf shape (scale bar equals 5 mm) (2) and enlargement to show secondary venation (scale bar equals 5 mm) (4).

FIGURE 10. 1, Rogersia dakotensis Wang and Dilcher, 2009, UF15706-24620, general leaf shape. Note short petiole. Scale bar equals 5 mm. 2-3, Wolfiophyllum pfaffianum (Heer) Wang and Dilcher, 2009, UF15706-14815, basal and middle portion of leaf, note strong primary vein and entire margin (scale bar equals 1 cm) (2) and enlargement of Figure 10.2 (area indicated by arrow) to show eucamptodromous venation, note intersecondary veins (Scale bar equals 1 mm) (3).