Longstrethia aspera (Lesquereux) 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 : 10

Longstrethia aspera (Lesquereux) comb. nov.

Figure 6

*1892 “ Myrica” aspera Lesquereux , p. 66, pl. 2, fig. 11.

Emended specific diagnosis. Lamina margin toothed; serrate axes inclined to the tangent of margin, serration type straight or convex-straight or convex; tooth simple, spacing irregular; sinus rounded; three veins entering each tooth with one medial secondary vein or branch from secondary vein, two accompanying veins from basal and apical side, these two veins joining superadjacent veins of the same order to form loops before entering tooth. Primary venation pinnate; primary vein stout, multi-stranded, course curved. Secondary venation mixed craspedodromous (most of the secondary veins terminating at the margin and the rest brochidodromous); secondary veins thin relative to primary vein, subopposite; originating from primary vein at moderate acute angles, uniformly apically curved before entering the tooth or running along the basal side of tooth before terminating on the tooth with superadjacent secondary veins. Intersecondary veins present, composite. Tertiary veins thin, orthogonal reticulate, forming irregular meshes. Quaternary vein orthogonal reticulate, forming imperfect areoles. Veinlets simple, linear or curved.

Description. Observed lamina 9 cm to 15 cm long and 1.5 cm to 2.5 cm wide. Margin toothed; serrate axes inclined to the tangent of margin, serration type straight or convex-straight or convex; tooth simple, spacing irregular, one per cm; extending on all margin observed; sinus rounded, up to 1.5 mm deep (vertical distance from adjacent tooth apex to bottom of sinus); three veins entering each tooth with one medial secondary vein or branch from secondary vein, two accompanying veins from basal and apical side, these two veins joining superadjacent veins of same order to form loops before entering tooth. Primary venation pinnate; primary vein stout, multi-stranded, course curved. Secondary venation mixed craspedodromous (most of the secondary veins terminating at the margin and the rest brochidodromous); secondary veins thin relative to primary vein, one pair per cm, subopposite; originating from primary vein at moderate acute angles, uniformly apically curved before entering the tooth or running along the basal side of tooth before terminating on the tooth with superadjacent secondary veins. Intersecondary veins present, composite. Tertiary veins thin, orthogonal reticulate, forming meshes irregular in shape and size. Quaternary vein orthogonal reticulate, forming imperfect areoles. Veinlets simple, linear or curved.

Number of specimens examined. 2.

Lectotype. Longstrethia aspera Lesquereux (1892, p. 66, plate 2, figure 11; designated here).

Paratypes. UF15706-24578 ( Figure 6.1, 6.3 ); 24650 ( Figure 6.2 ) .

Occurrences. Hoisington III locality, Kansas.

Remarks. Two specimens with middle portion of lamina are examined. Lesquereux (1892, p. 66, plate 2, figure 11) reported two specimens from the Pipe Creek locality, Cloud County, Kansas and assigned them to the extant genus Myrica . However, leaf architecture and cuticular characters of these leaves show a possible relationship to Illiciales or Trimerniaceae but differ from all extant members of the Magnoliidae in at least several characters (Upchurch and Dilcher, 1990, p. 33-34). We assign these specimens to the fossil genus Longstrethia established by Upchurch and Dilcher (1990) and set up a new combination for the specimens from the Hoisington III locality, Kansas. Longstrethia aspera is similar to Longstrethia varidentata Upchurch and Dilcher in that both have linear leaf shape and toothed margin, but they differ in that (1) leaf margin of Longstrethia varidentata varies from entire to coarsely toothed, (2) secondary venation varies from brochidodromous with strongly flattened brochidodromous loops, to pinnate with an intramarginal vein, and (3) relatively thin and numerous secondary veins. Future collection of specimens with well-preserved cuticle from the Hoisington III locality may provide information to clarify the relationship between the specimens from the Hoisington III locality, Kansas and those from the Rose Creek locality, Nebraska described by Upchurch and Dilcher (1990).

Figures

FIGURE 6. Longstrethia aspera (Lesquereux) comb. nov. 1, UF15706-24578, middle and lower portion of lamina. Scale bar equals 1 cm. 2, UF15706-24560, specimen showing secondary veins and toothed margin. Scale bar equals 5 mm. 3, Enlargement of Figure 6.1 (left middle portion of lamina; indicated by arrow) to show fine venation. Scale bar equals 2 mm.