Ulmus cf. alata Michaux, 1803

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 : 21

Ulmus cf. alata Michaux, 1803

Figure 8.4–8.5

Description. Five simple, ovate leaves are similar to specimens of modern Ulmus alata . Lamina lengths range from 2.5–4.2 cm and widths from 1.2–2.3 cm, L:W ratio 2:1. Margins are serrate. Bases are acute, some displaying an asymmetrical basal petiole insertion. Apices are acute and straight. Primary vein framework is pinnate. Secondary venation is craspedodromous, excurrent. Occasionally, second order veins branch just before reaching the margin. Spacing of secondaries is fairly uniform, but decreases somewhat basally. Angles of most secondary veins are ~ 45º, but angles increase proximally. Tertiary veins are difficult to discern, but appear to be irregular reticulate as are the fourth order veins. Teeth are of two orders with secondary teeth appearing on the basal side of the primary tooth. There are 3–5 first order teeth per cm. Tooth sinuses are angular, teeth usually convex/straight proximally, convex/ straight distally. The first order teeth are about as wide as long, giving them a broad appearance. There are no extenuating tips on teeth apices ( Figure 8.5 ).

Site occurrence. Lambert Station.

Remarks. Ten species of Ulmus occur in North America. Of these, U. alata , U. americana , U. crassifolia , and U. rubra occur in the southeastern United States. Fossil Ulmus leaves have been recorded from the western Miocene Succor Creek Flora, and possibly from the Miocene Clarkia site of Idaho ( Smiley and Rember, 1985; Fields, 1996).

Figures

FIGURE 8. Representative Sapindaceae (continued), Smilicaceae, and Ulmaceae from the Citronelle Formation. 1. Acer cf. saccharinum partial leaf (UF 19315–062088), scale bar equals 1 cm. 2. Smilax sp. partial leaf (UF 19413– 062089), scale bar equals 5 mm. 3. Close-up of Figure 8.2 Smilax leaf showing higher order venation details, scale bar equals 2.5 mm. 4. Ulmus sp. leaf (UF 19413–062090), scale bar equals 5 mm. 5. Close-up of Figure 8.4 Ulmus leaf showing margin details and multiple orders of teeth, scale bar equals 2.5 mm.