Stockey, Ruth A. , Wiebe, Nicholas J.P. .
Mosaic evolution of Early Cretaceous Pinaceae and the origins of extant genera.
LARGE numbers of pinaceous leaves have been recovered from the Early Cretaceous (Valanginian- Hauterivian) Apple Bay Locality on Vancouver Island, Canada. Needles are preserved as cellular permineralizations in calcitic marine nodules. Leaves were washed down river and deposited in the ocean before preservation. Five distinct pinaceous leaf types are present at the site with anatomy similar to Picea, Tsuga, Abies, Pseudotsuga, and Pinus. Picea-like leaves have similar vascular bundle structure and resin canal number and placement to those of extant Picea, but have a more plicate mesophyll, extensive hypodermal sclerenchyma and a variable leaf shape. Leaves with a similar leaf shape, resin canal number and placement, palisade and hypodermis to those of Abies differ in the number of vascular bundles and endodermal outline. Tsuga-like leaves show similarities in leaf shape, stomatal location, resin canal position and the presence of a palisade to those of extant species from two sections of the genus, but differ in the presence of spongy mesophyll, hypodermal cell outlines and in having an indistinct endodermis. Leaves similar in all anatomical details to Pseudotsuga and Pinus are present at the Apple Bay site suggesting that these genera may have evolved by the Early Cretaceous, and these remains represent the earliest fossil record for the family. The mosaic of characters of these leaves are reminiscent of a similar situation for Cretaceous pinaceous seed cones, wherein novel combinations of characters define different species of the genus Pityostrobus. These pinaceous leaves support the interpretation that some of the extant genera had not evolved by this time, but that like the angiosperms, the pines were undergoing rapid evolution during the Early Cretaceous.
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1 - University of Alberta, Department of Biological Sciences, Biological Sciences Centre, Cw 405, Edmonton, Alberta, T6G 2E9, Canada
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, August 1st, 2006
Time: 9:15 AM