Pseudofagus idahoensis C.J.Smiley et Huggins

Plant Fossil Names Registry Number: PFN002956


Authors: C. J. Smiley & L. M. Huggins

Rank: species

Genus: Pseudofagus C.J.Smiley et Huggins

Reference: Smiley, C. J. & Huggins, L. M. (1981): Pseudofagus idahoensis, n. gen. et sp. (Fagaceae) from the Miocene Clarkia flora of Idaho. – American Journal of Botany 68(6): 741–761., link

Page of description: 748

Name is type for

Pseudofagus C.J.Smiley et Huggins 1981


Holotype T-0016, University of Idaho Mines Museum, USA
Figures: figs 6, 12

Note: Paratypes: T-0017 to T-0026, T-0030 to T-0041; slide nos. T-0042 to T-0051 (housed in University of Idaho Mines Museum).

Original diagnosis/description

Leaf architecture – Leaves simple, symmetrical, elliptic; apex acuminate; base acute to obtuse, sometimes cuneate; length usually 10–14 cm, rarely to 24 cm; width usually 5–6 cm, rarely to 10 cm; margin toothed, acutely serrate, teeth regularly spaced, usually simple but may be one or more compound teeth per leaf, basal side straight, apical side concave; occasional compound tooth with small subsidiary tooth on basal side and terminating a weak branch from exmedial side of secondary vein; venation pinnate, craspedodromous, simple; primary vein of moderate size, straight or slightly curved, zigzag in acuminate tip only; secondary veins regularly spaced, subopposite to alternate, of moderate thickness, usually 19–22 in number, diverging at angles of 40–45° except near base where 50–60°, unbranched, straight, basal 2 or 3 secondaries slightly recurved; tertiary veins near right angles to adjacent secondaries, zigzag, randomly reticulate, constant, oblique to midrib at angle of 45°, arrangement irregular, intervals between tertiaries 1–2 mm and irregularly spaced; quaternary veins about medium size, randomly oriented; quinternary veins about medium size, orthogonal; areoles well-developed, oriented, quadrangular and pentagonal, slightly rounded, medium size of 0.3–0.5 mm; veinlets simple, linear and once-or twice-branched; marginal ultimate venation looped; petiole length 12 mm, width 1 mm, normal attachment, with fine pubescence, overlapped by peduncle of associated fruit, petiole and peduncle apparently fused at base; texture chartaceous.

Cuticle, upper epidermis – Cuticle fragile; cells of nonvenous areas irregular, variable, randomly oriented; shape variable, usually tetragonal, pentagonal, or hexagonal; end walls oblique and diamond-shaped; anticlinal walls straight, rarely with slight undulations, corners becoming more rounded near midrib, thickness medium, lacking surface ornamentation; cells usually longer than wide, length 14–35 μm (avg 22 μm), width 8–18 μm (avg 11 μm). Trichome bases confined to midrib, secondary veins and immediately adjacent tissue. Trichome bases on nonvenous tissue composed of central circular ring 11–17 μm diam; ring thickness 4 μm; ring derived from thickened walls of 5 or 6 surrounding basal cells that are otherwise little modified; cells arranged in radial pattern, length 7–24 μm (avg 14 μm), width 4–15 μm (avg 8 μm). Trichome bases on veins usually elliptic, less commonly circular, length 10–17 μm (avg 14 μm), width 6–15 μm (avg 10 μm); ring thickness 2–4 μm; ring derived from thickened walls of 6 or 7 surrounding basal cells; basal cells unmodified, or modified to form a "star" pattern, length 9–67 μm (avg 26 μm), width 3–10 μm (avg 7 μm). Stomata absent on upper epidermis.

Cuticle, lower epidermis – Cuticle very fragile; cells randomly oriented, irregular, length 11–30 μm (avg 21 μm), width 6–14 μm (avg 12 μm); anticlinal walls commonly straight, some slightly undulate; wall thickness medium to thin; surface ornamentation of cells lacking. Stomata isolated, randomly oriented; stomatal complex having two guard cells surrounded by a heavily cutinized ring of 5 or 6 subsidiary cells; ring 30–40 μm diam (avg 33 μm); guard cells usually lost, 21–24 μm (avg 23 μm) in length, 7–10 μm (avg 8.4 μm) in width, guard cell surfaces smooth, polar dots and cuticular rim present; outer stomatal ledge conspicuous, thick, plain; subsidiary cells polycystic, anticlinal walls slightly thickened lacking undulations, shape irregular, length 13–24 μm (avg 18 μm), width 6–12 μm (avg 9 μm).

Leaf phytoliths – Phytoliths abundant, evenly distributed, over nonvenous tissue; shape discoid, 10–28 μm diam (avg 19 μm); soluble in 10% HCl.

Reproductive structures – Complete fruit a single nut with a basal cupule; fruit length 3.5–4 cm, width 1.2–3 cm, exclusive of peduncle; peduncle departing from axil of leaf, length 4–4.5 cm, width 0.6–1 mm, distal 5 mm expanding to become acute base of cupule, proximal end converging with and overlapping petiole of leaf, base of peduncle attached to base of leaf petiole.
Nut trigonous, distinctly keeled, surfaces concave, elliptic in lateral view; base round, enclosed by cupule; nut apex rounding, abruptly accuminate; nut exposed for most of length; length 2–4 cm (avg 3 cm), width 1.2–3 cm (avg 1.5 cm); surface pubescent, hairs less than 1 mm long, profuse near nut apex; nut separating from cupule when mature.
Cupule diminutive, ligneous when mature, enclosing nut base, surface usually smooth, rarely with weak papillae, pubescent especially near apical rim; apical rim irregularly toothed, teeth terminating in leaflike appendages usually 12 or 13 in number, petiolate with expanded apical lamina, 7–15 mm long, 1–2.5 mm wide, expanded laminae elliptic in shape, margins entire or with one or two simple teeth, venation composed of a midrib and two secondary veins terminating in a marginal tooth, may be one or two additional weaker secondaries terminating at margin; apical appendages of cupule apparently flexible when young, firm when mature, free of nut, having appearance of a whorl of small leaves encircling basal half of nut; cupule with no evidence of distinct valvation.
Nut pericarp thin; cells irregular, variable, randomly oriented; cell shapes variable, usually pentagonal or hexagonal; end walls oblique or rounded, anticlinal walls straight or arcuate, thin, lacking surface ornamentation; cells isometric to elongate, length 9–20 μm (avg 12.2 μm), width 4–11 μm (avg 7.2 μm). Trichome bases of pericarp numerous, randomly distributed over surface of nut; bases of trichomes composed of central circular or elliptic ring derived from thickened walls of 6–8 surrounding basal cells; base length 8–11 μm (avg 9.4 μm), width 5–11 μm (avg 7 μm); shape of basal cells a modified wedge, arranged with long axes perpendicular to central ring, resulting in a "star" pattern. Trichomes rarely preserved, unicellular, length in excess of 20 μm, width 6 μm. Pericarp stomata rare, randomly oriented; stomatal complex having two guard cells surrounded by a ring of 5–8 subsidiary cells, cyclosystic; subsidiary cells 20–30 μm long (avg 25 μm), 5–11 μm wide (avg 9 μm); guard cells rarely preserved, 24–30 μm long, 8–11 μm wide, lacking a polar thickening of cutin; guard cells surrounded by a circular rampart 2 μm thick, formed by walls of subsidiary cells; outer stomatal ledge conspicuous, medium, plain.


Neogene, Miocene


United States
UIMM P-33, 2 mi south of Clarkia, Shoshone County, Idaho

Plant fossil remain

macro- and meso-fossils-embryophytes except wood


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