Hexagonokaryon

Name

Hexagonokaryon

Rank

Genus

Authors (Name)

Manchester S. R. Judd W. S. Tiffney B. H.  

Authors (Pub.)

Manchester S. R. Correa Narváez J. E. Krinsky K. Judd W. S. Tiffney B. H.  

Publication

Extinct Fagaceae from the Paleocene of Wyoming, USA: cupulate nuts of Hexagonokaryon gen. nov. [2025/12]

Journal

International Journal of Plant Sciences

Annee/Jahrgang

2026

Volume

187

Issue

1 [10.1086/738560]

Page number

3

Year

2025

Parent Taxon

[Family] Fagaceae

Fossil Status

infructescences

Type

Hexagonokaryon nixonii

Diagnosis

Elongate raceme-like infructescence with terminal cupule and long-peduncled lateral cupules. Peduncles 7–10 mm long, 1.2–1.5 mm wide. Cupules widely ovoid, open apically, wide-elliptical in cross section, 5.6–16.3 mm wide, 4.8–6.9 mm deep, and 5.4–6.9 mm high (measured from top of peduncle). Each cupule four-valved, bearing three nuts, of which two or sometimes just one nut may be present (variable). Each of the two lateral nuts associated with two of the cupule valves, and the central nut (when present) associated with an extension of all four cupule valves. Nuts mostly hidden within the cupule (not protruding). Cupule ornamentation often eroded but formed of longitudinal ridges bearing scattered laminar to spiny protrusions that appear to be reduced toward the base and more pronounced/elongated toward the apex of each valve. Nuts ovate in lateral view and trigonal in transverse section near the apex but six-ridged in the lower two-thirds, with three prominent angles (corners) giving an equilateral triangular appearance, augmented by three less prominent ridges placed midway between each of the three main ridges. Nuts 4.6–5.8 mm high, 3.3– 3.5 mm wide, attached basally to the cupule and bearing an epigynous perianth with two whorls of three tepals. Tepals terete, 0.18–0.31 mm wide, 1.3–1.6 mm long; tepals of the lower whorl arising from the intermediate ridges and those of the upper whorl arising from the major ridges. Continuous horizontal rim above the upper cycle of tepals but below the nut apex (interpreted as nectary). Styles not preserved.