Anisodromum wolfei Upchurch and Dilcher 1990

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 : 28-30

Anisodromum wolfei Upchurch and Dilcher 1990

Figure 18

Description. Leaflet lamina and base symmetrical. Shape narrow ovate or elliptic, L / W 2 to 2.6, lamina 3 to 4.7 cm wide and 8 to 9 cm long. Apex missing. Base obtuse. Margin entire. Observed petiolule with a 0.2 to 0.3 mm wide decurrent lamina tissue; petiole 0.5 mm wide and 2 mm long. Primary venation of leaflets pinnate; primary vein stout, multi-stranded, course straight. Secondary venation predominately eucamptodromous; secondary veins moderate relative to primary vein, multi-stranded, ca. nine pairs per lamina, opposite or slightly subopposite, decurrent; angle of divergence moderate acute (45º to 65º), with basal pairs at slightly more obtuse angles; basal secondary veins joining superadjacent secondary veins or their exmedial branches to form loops very close to margin; other secondary veins uniformly curved and diminishing near margin; adjacent secondary veins connected by percurrent tertiary veins. Tertiary veins percurrent, moderate relative to secondary veins; angle of origin AO (acute on exmedial side of secondary vein and obtuse on admedial side of secondary veins) or RO (right on primary vein and obtuse on admedial side of secondary vein); course predominately straight, oriented almost at right angle with primary vein; arrangement close (interval between veins less than 0.5 cm). Quaternary vein orthogonal reticulate. Veins of higher order not observed.

Number of specimens examined. 3.

Specimens illustrated. UF 15706-14818 ( Figure 18.1-2 ); 24566 ( Figure 18.3-4 ).

Remarks. Upchurch and Dilcher (1990) described six specimens from the Rose Creek locality, Nebraska and they proposed that the compound leaves most closely resemble Sapindopsis but they differ in that Anisodromum wolfei has secondary venation that shows asymmetric behavior and much less brochidodromous looping, more percurrent and closely spaced tertiary venation, and a structurally reinforced margin. These characters were interpreted as significant at generic level by analogy to extant pinnately compound Rosidae, where genera are distinguished on the basis of secondary, tertiary, and marginal venation (Upchurch and Dilcher, 1990).

Figures

FIGURE 18. Anisodromum wolfei Upchurch and Dilcher, 1990. 1, UF15706-14818, general leaflet shape. Note long petiolule. Scale bar equals 1 cm. 2, Enlargement of Figure 18.1 to show strong secondary veins and percurrent tertiary veins oriented perpendicular to the primary vein. Scale bar equals 2 mm. 3, UF15706-24566, general leaflet shape. Scale bar equals 5 mm. 4, Enlargement of Figure 18.3 to show percurrent tertiary veins oriented almost perpendicular to the primary vein. Scale bar equals 2 mm.