Microaltingia

Name

Microaltingia

Rank

Genus

Authors (Pub.)

Zhou Z.-K. Crepet W. L. Nixon K. C.  

Publication

The earliest fossil evidence of the Hamamelidaceae: Late Cretaceous (Turonian) inflorescences and fruits of Altingioideae [2001/5]

Journal

American Journal of Botany

Volume

88

Issue

5

Page number

754

Year

2001

Parent Taxon

[Family] Hamamelidaceae

Fossil Status

inflorescences (pistillate with fruits)

Type

Microaltingia apocarpela

Diagnosis

Pistillate inflorescences globose to subglobose, with about ten tightly packed florets. Capitula pedunculate. Vessel members in the peduncle have oblique end walls with scalariform perforation plates and intervascular pitting that is scalariform to opposite/alternate. Individual florets unisexual (pistillate only), actinomorphic, small (;1.2 mm). Two to three whorls of glabrous phyllomes inserted on the rim of the hypanthium. Phyllomes bearing stomata. In immature flowers, there are apparently at least 13 lobes in the first cycle of phyllomes. The lobes are fleshy, sterile, and usually concentrically fused. Two to three cycles of phyllomes can be observed in fruits. No evidence of stamens or staminodia is found in the pistillate florets. The gynoecium consists of two carpels composing a semi-inferior ovary that is distally free from the hypanthium and forms a perigynous flower. There are no trichomes on the surface of the gynoecium. The carpels are distally apocarpous. The ovary is bilocular with each locule having its own carpellary wall in the region of contiguity. The styles and stigmas are completely free and are lost in the mature fruits. The stigmas are apical, capitate, and have multicellular shallow papillae. Each carpel contains about ten marginal seeds arranged in two rows. All seeds look to be of the same size and shape (elliptic to polygonal, slightly impressed, saddle-shaped) with an apical hilum. There are ridges on the seed surface and seeds lack wings. At maturity, the carpels undergo apical dehiscence both septicidally and loculicidally. The pollen grains, found on the stigmas and the surface of the peduncle, are relatively small, 9–10 mm in polar (P) diameter, only 3.1–3.5 mm in equatorial (E) diameter, perprolate (P/E 2.86), and consistently tricolpate. Colpi extend almost the entire polar length of the grains. There is no indication of an endoaperture in any of the grains examined with scanning electron microscopy (SEM). Exine sculpturing is reticulate with relatively large lumina that show some variation in size.