Crataegus sp. 2

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 : 18

Crataegus sp. 2 .

Figure 6.7–6.8

Description. A second simple leaf is also attributed to Crataegus , but appears to represent a separate species. The leaf is ~ 1.5 cm long and 1.2 cm at its widest distally, obovate, L:W ratio 1:1. Margin unlobed, serrate. The base is missing, but was probably very narrow basally. Apex is obtuse. Primary framework is pinnate. Secondary venation is craspedodromous, veins departing the mid-rib at 20° to 30°. Tertiary through quintinary venation is irregular reticulate. Two orders of somewhat rounded teeth, sinuses angular, both orders of teeth convex proximally and distally.

Site occurrence. Perdido Park.

Remarks. This specimen appears similar to extant Crataegus floridana , which is sometimes considered a form of C. flava ( Figure 7.1 ). Specific identification, even of extant species, can be challenging. Crataegus is well represented in North America with ~ 214 species, 41 of which occur today in the southeastern United States. Fossil genera similar to Crataegus occur in the early and middle Eocene Okanogan Highlands of eastern Washington, USA, and British Columbia, Canada. Some of the earliest records of the modern genus occur in the late Eocene Florissant flora of Colorado ( Devore and Pigg, 2007); fruit records have been reported from European Miocene deposits ( Kvacék and Walther, 2004). Leaves of Crataegus have been identified from the western Miocene floras of Clarkia and Succor Creek ( Smiley and Rember, 1985; Fields, 1996). Europe or eastern North America is most probably the ancestral range of modern Crataegus species, with the modern species having an estimated divergence in the late Miocene (~ 14.3 Ma) ( Lo et al., 2009).

Figures

FIGURE 6. Representative Oleaceae (continued), Platanaceae, and Roseaceae from the Citronelle Formation. 1. Fraxinus leaflet (UF 19210–062078), scale bar equals 1 cm. 2. Close-up of Figure 6.1 Fraxinus leaflet showing higher order venation, scale bar equals 5 mm. 3. Platanus occidentalis leaf (UF 19210–062079), scale bar equals 1 cm. 4. Platanus occidentalis fruit (UF 19211–062080), showing persistent style at arrow, scale bar equals 1 cm. 5. Crataegus leaf species 1 (UF19315–062081) similar to C. spatulatha, scale bar equals 5 mm. 6. Close-up of Figure 6.5 Crataegus leaf showing higher order venation, scale bar equals 2.5 mm. 7. Crataegus species #2 leaf (UF 19210–062082), wedge-shaped lamina similar to C. floridana, compare with Figure 7.1, scale bar equals 5 mm. 8. Close-up of Figure 6.7 Crataegus leaf showing higher order venation, scale bar equals 2.5 mm.

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.