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Abstract Detail



Paleobotany

Stockey, Ruth [1], Rothwell, Gar [2].

A new Upper Cretaceous araucarian seed cone from the Brannen Lake locality (Campanian) of Vancouver Island, British Columbia.

One permineralized seed cone embedded in a calcium carbonate concretion was recovered from the Upper Cretaceous (Campanian) Brannen Lake locality, Vancouver Island. The cone, nearly spherical, 6 X 6 cm in diameter, was studied using cellulose acetate peels. Helically arranged cone-scale complexes, up to 3 cm wide, consist of a large bract with an upturned tip and a small, fleshy ovuliferous scale that separates from the bract near the seed chalaza. The cone peduncle bears fleshy rhomboidal leaves and modified cone-scale complexes. Pith of the peduncle and cone axis is parenchymatous with scattered sclereids and resin canals. Secondary xylem of the peduncle, 7-10 cells thick and relatively complete, separates into bundles in the cone axis, where the pith expands. Cortex of the cone axis is parenchymatous with scattered sclereids. Vascularization of the cone-scale complex is single at its origin, dividing in the cortex into bract and ovuliferous scale traces. Winged bracts, with a bulging base, contain numerous small vascular bundles with accompanying small diameter resin canals. Abaxially, bract hypodermis contains numerous distinct, regularly spaced fiber bundles interspersed with rows of crowded stomata. Ovuliferous scales, free from the bract distally, are comprised of parenchymatous cells, a band of sclereids near the seed chalaza, and scattered sclereids. The ovuliferous scale closely adheres to the bract surface bending upward along with the bract tip. Stomata occur on adaxial surfaces of ovuliferous scales and abaxial surfaces of bracts. Seeds are large, ovoid, 1.2 cm long, 1.2 cm in diameter, tapering to a mouth-shaped micropyle. Seeds are vascularized by two bundles entering from the ovuliferous scale. Sclerotesta is thick, composed of branched, interlocking sclereids, and endotesta contains thin-walled elongate cells. Nucellus is free from the integument, except at its base, with a highly convoluted cellular apex, containing possible pollen tubes. Megagametophyte and mature cellular embryos occur in several seeds. The structure of this cone most closely resembles those of Araucaria Section Eutacta, with embedded seeds, small free ovuliferous scale tips that follow the course of the upturned bract tip, and a single trace to the cone-scale complex. While the cone is small, the imbricate bracts are very wide, and seeds that are unusually large for fossil cones of this type. Width and continuity of secondary xylem in the cone axis, and intact cone-scale complexes, indicate that unlike extant Araucaria Section Eutacta, this cone probably did not easily lose its scales at maturity.


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1 - Oregon State University, Department of Botany and Plant Pathology, 2082 Cordley Hall, Corvallis, OR, 97331, USA
2 - Ohio University/Oregon State University, Department of Environmental and Plant Biology/Department of Botany and Plant Pathology, 2082 Cordley Hall, Oregon State University, Corvallis, OR, 97331, USA

Keywords:
Araucaria
Cretaceous
fossil
seed cone
conifer.

Presentation Type: Oral Paper
Number: 25003
Abstract ID:416
Candidate for Awards:None


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