Stockey, Ruth A. , Rothwell, Gar W. , Klymiuk, Ashley A. .
Is Doylea a cupulate seed fern, a conifer, or neither?
Anatomically preserved Lower Cretaceous cupules assignable to Doylea tetrahedrasperma have been discovered within a compact cone. The cone measures 1.2 cm in diameter, consisting of a stout eustelic axis from which appendages diverge in a helical arrangement. Each appendage is constructed of a bract and axillary complex that are fused basally and separate distally. The axillary complex (shoot) produces two leaves at about the level of separation from the bract, with each terminating in a single tetrahedral ovule that is recurved and more or less enclosed by the leaf that forms a cupule-like structure. Ovules are distinctively triangular in cross section, with prominent integumentary lobes distally. The nucellus separates from the integument at the chalaza and produces a large pollen chamber. Bisaccate pollen grains are preserved both between the integumentary lobes and within the pollen chamber of several ovules. Both external morphology and internal vascular architecture are consistent with the cones having a compound organization. Although the uni-ovulate cupules of Doylea are superficially similar to angiosperm carpels, the compound cone is reminiscent of conifers, and the morphology of individual bract/axillary complexes is similar to that of ovulate stalks of Ginkgo. The occurrence of Doylea cupules within a compound cone shows an unexpected combination of characters, revealing seed plant diversity was even greater than previously expected immediately before the first occurrence of angiosperm megafossils.
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1 - University of Alberta, Department of Biological Sciences, Biological Sciences Centre, Cw 405, Edmonton, Alberta, T6G 2E9, Canada
2 - Ohio University, Department of Environmental & Plant Biology, Porter Hall, Richland Avenue, Athens, Ohio, 45701-2979, USA
3 - University of Alberta, Department of Biological Sciences, Biological Sciences Centre, CW, 405, Edmonton, AB, T6G 2E9, Canada
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Superior A/Cliff Lodge - Level C
Date: Wednesday, July 29th, 2009
Time: 10:45 AM