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Paleobotanical Section

Axsmith, Brian [1], Creen, Elizabeth [1].

Seed cones associated with Pseudofrenelopsis parceramosa (Cheirolepidiaceae) from the Lower Cretaceous of Arkansas.

Vegetative shoots and pollen cones are known for many members of the Mesozoic conifer family Cheirolepidiaceae; however, seed cones are exceedingly rare. Seed cones associated with Pseudofrenelopsis parceramosa shoots in the Cretaceous Holly Creek Formation of Arkansas were preliminarily described by Stanley in an unpublished thesis (University of Texas, Austin) in 1988. We have reexamined the surviving components of this collection in addition to collecting new material, which includes complete and partial seed cones, isolated cone scales, and bracts. The cones consist of a narrow axis with helically arranged bract-scale complexes. The scales possess at least seven distal lobes oriented in three planes. The adaxial surface contains one large seed mostly covered by an epimatium with fused lateral edges. The subtending bracts are wedge-shaped, and possess lobes along the expanded distal edge. No specialized pollen reception areas could be discerned, but many scale and bract surfaces bear prominent epidermal papillae that might have been involved in pollen capture. The fusion of the epimatium lateral margins is probably a derived feature shared with Alvinia bohemica cones, which are associated with Frenelopsis alata shoots and pollen cones in central Europe. However, the morphology and arrangement of the distal lobes of the Arkansas cone scales is primitive and more similar to that of the non-frenelopsid genera Hirmeriella and Tomaxellia. In fact, the disposition of the lobes in more than two planes is reminiscent of Permian majonicaceous conifers like Dolomitia. Clearly, more seed cone taxa and characters are needed to resolve the phylogeny of the Cheirolepidiaceae. In any event, the Arkansas P. parceramosa plant is now known from seed cones, attached pollen cones (Classostrobus arkansensis) with in situ Classopollis-type pollen, shoots of several orders, and anatomically preserved wood. It is, therefore, one of the most thoroughly and confidently reconstructed members of the Cheirolepidiaceae.


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1 - University of South Alabama, Biological Sciences, Life Sciences Building #124, 307 University Blvd. North, Mobile, Alabama, 36688, USA

Keywords:
conifers
Cheirolepidiaceae
Mesozoic
Cretaceous
Pseudofrenelopsis.

Presentation Type: Oral Paper
Session: 17-5
Location: 404/Hilton
Date: Monday, August 15th, 2005
Time: 2:30 PM
Abstract ID:2


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