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Dioscorea wilkinii
Dioscorea wilkinii A.D. Pan, B.F. Jacobs, Currano Bot. J. Linn. Soc., 175(1): 18. 22 Apr 2014
- Name
- Dioscorea wilkinii
- Rank
- Species
- Generic Name
- [Genus] Dioscorea
- Authors (Pub.)
- Pan A. D.
Jacobs B. F.
Currano E. D.
- Publication
- Dioscoreaceae fossils from the late Oligocene and early Miocene of Ethiopia [2014/4]
- Journal
- Botanical Journal of the Linnean Society
- Volume
- 175
- Issue
- 1
- Page number
- 18
- Year
- 2014
- Fossil Status
- leaves
- Stratigraphy
- Chattian
- Location
- Guang River, Chilga, North Gondar Zone, Amhara Region, north-western Ethiopia; [12° 30′ N, 37° 7′ E]
- Paleoregion
- Africa (East)
Data for Holotypus
- Repository
- National Museum of Ethiopia, Addis Ababa, Ethiopia
- Repository Number
- CH40-110
Data for Paratypus
- Repository
- National Museum of Ethiopia, Addis Ababa, Ethiopia
- Repository Number
- CH40-P19 (Fig. 2), CH54-119A (Figs 2, 3)
- Diagnosis
- Entire margined (untoothed), notophyllous to mesophyllous leaflets. Leaflets are ovate, possess concave to convex bases and are symmetric (terminal leaflets) or asymmetric (lateral leaflets). Fragments range in size from 48 to 89 mm in length and 44.0 to 75.5 mm in maximum width. The estimated leaflet length to width ratio is 1–1.25 : 1. Base angles are obtuse to acute relative to the central primary vein (midvein). Specimens have f ive to seven primary veins arising from the base or suprabasally and become brochidodromous near the margin. The midvein lacks secondary veins arising from it, but other primary veins possess secondaries that arise at acute angles and form brochidodromous loops near the margin. Tertiary veins are generally straight or, less often, sinuous, alternate or opposite percurrent and nearly perpendicular to the midvein. Tertiary veins arising from more distal primary and secondary veins are more obtusely angled than those arising more proximally and form a loose basal concentric vein arrangement. The spacing between proximal tertiary veins and where secondary vein divergence occurs is generally closer, c. 2 mmapart, whereas, distally, the tertiary venation spacing is roughly 5–7 mm. Quaternary veins are polygonal reticulate and are usually four- or fivesided. CUTICLE: Adaxial epidermal cells 23–44 μm long and 18–26 μm wide. Anticlinal cell walls are straight to slightly sinuous in shape. Periclinal cell walls are wrinkled and thin. Abaxial cells are of similar size to those on the adaxial surface, but with anticlinal cell walls that are straight to sinuous and with striated periclinal cell walls. Stomata are confined to one surface of the leaf, assumed to be the abaxial surface. Stomatal complexes anomocytic with five to nine subsidiary cells. Stomata are round to oval in shape, ranging from 23 to 29 μm in length and 23 to 27 μm in width. Thickened hair bases are also present on the abaxial surfaces and are surrounded by five to seven cells.
