Persea sp.

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 : 12

Persea sp.

Figure 4.3, 4.6

Description. Persea sp. is represented by one complete leaf from the Scarborough School site, and six complete to mostly complete specimens from the Perdido Park site. All specimens are elliptical. The two most complete specimen laminae measure 9.0 cm long X 2.4 cm wide and 7.2 cm long X 2.4 cm wide, L:W ratios approximate 3– 3.8:1. Widths of incomplete specimens range from 2.8–3.0 cm. Bases are acute. Apices are acute, some are acuminate with drip tips. Primary venation is pinnate. Secondary veins are excurrent, arcuate, and weakly brochidodromous. Tertiary and quaternary veins are irregular reticulate, but the quinternary veins are mostly regular, reticulate. A perimarginal vein is present, but portions of the leaf also seem somewhat curled under as to appear revolute. One specimen presents this feature as a thickened area with the appearance of extraneous cuticle.

Site occurrence. Perdido Park and Scarborough School.

Remarks. Three species of Persea occur in the flora of North America today. Persea humilis is found on the Florida peninsula only, whereas P. borbonia and P. palustris are more widely distributed along areas of the Atlantic coastline of the mid- to southeastern United States and extending to east Texas. Persea palustris occupies swampy areas, whereas the other two species prefer drier settings. Biogeographic investigations of the family Lauraceae indicate that American members of Persea diverged from Asian counterparts with the onset of cooling at the Eocene-Oligocene boundary (~ 32 m. y.a.). Fossils of Persea have been reported from the western Miocene Clarkia and Succor Creek floras ( Smiley and Rember, 1985; Fields, 1996).

Figures

FIGURE 4. Representative Lauraceae from the Citronelle Formation. 1. Lindera sp. leaf (UF 19210–062072), scale bar equals 1 cm. 2. Extant Lindera leaf from USAM herbarium for comparison with Figure 4.1, scale bar equals 1 cm. 3. Persea sp. leaf (UF 19210–062073), scale bar equals 1 cm. 4. Sassafras albidum leaf (UF 19210–062074), scale bar equals 1 cm. 5. Close-up of Figure 4.1 Lindera leaf showing high order venation, scale bar equals 2.5 mm. 6. Close-up of Figure 4.3 Persea leaf showing high order venation, scale bar equals 2.5 mm.