Acer cf. rubrum

Stults, DZ & Axsmith, BJ, 2015, New plant fossil records and paleoclimate analyses of the late Pliocene Citronelle Formation flora, U. S. Gulf Coast, Palaeontologia Electronica (New York, N. Y.: 1991) 2 (6), pp. 1-35 : 20

Acer cf. rubrum L.

Figure 7.6–7.7

Description. Four partial specimens and one mostly complete specimen are similar to Acer rubrum . Leaves are simple, ovate, petioles slightly eccentric. Widths range from 3.0–5.0 cm. The most complete leaf is 5.8 cm long and 3.0 cm wide; L:W ratio of 2:1. Margins appear somewhat lobed, although the incision is less than 25% of the distance to the midvein. Margins are toothed. Bases are obtuse and rounded in some specimens, but somewhat cordate in others. Apices are acute and straight. Primary venation is basal actinodromous. Agrophic compound veins are evident. Major secondaries are craspedodromous/semicraspedodromous; a few intersecondaries are present. Tertiaries and quaternary veins are irregular reticulate, while quinternary veins are regular reticulate. Two orders of teeth are unequally distributed on the leaf margin. First order tooth sinuses are angular, teeth convex/straight proximally, convex/concave/straight distally. Secondary teeth when present have angular sinuses, teeth straight proximally, straight/concave distally. First order tooth apices are somewhat cassidate, as in the modern species ( Figure 7.8 ).

Site occurrence. Perdido Park.

Remarks. Acer rubrum is common in floodplain forests from Canada to peninsular Florida, and occurring westward to east Texas. The ancestral species of A. rubrum and A. saccharinum apparently split from Asian clades during the late Oligocene to early Miocene, whereas these North American sister species apparently diverged from each other in the earlier Pliocene ( Renner et al., 2008; Saeki et al., 2011).

Figures

FIGURE 7. Representatives Rosaceae (continued), Salicaceae, Rutaceae, and Sapindaceae from the Citronelle Formation. 1. Extant Crataegus floridana from USAM herbarium for comparison with Figure 6. 7, scale bar equals 5 mm. 2. Rubus sp. leaf (UF 19413–062083), scale bar equals 5 mm. 3. Ptelea cf. trifoliata leaf (UF 19210– 062084), scale bar equals 5 mm. 4. Salix sp. leaf (UF 19210–062085), scale bar equals 1 cm. 5. Close-up of Figure 7.4 Salix leaf margin showing salicoid teeth, scale bar equals 2.5 mm. 6. Acer cf. rubrum basal portion of leaf (UF 19210–062087), scale bar equals 1 cm. 7. Acer cf. rubrum leaf (UF 19210–062086), scale bar equals 1 cm. 8. Extant Acer rubrum USAM herbarium for comparison with Figure 7.6–7, scale bar equals 1 cm.