Vikulin, S.V. , Upchurch, Garland , LePage, B.A. .
Cuticle micromorphology of Glyptostrobus from the Early Cenozoic of the Canadian Arctic.
Glyptostrobus Endlicher is a monotypic genus of Cupressaceae that today occurs in Southeast Asia. During the Late Cretaceous and Cenozoic, Glyptostrobus lived at various times on all the northern continents and is considered a “living fossil” because of close morphological resemblance between the fossil shoots, cones, and seeds and those of the living species G. pensilis. Fossil shoots of Glyptostrobus from the Late Paleocene Iceberg Bay Formation of Ellesmere Island and the middle Eocene Buchanan Lake Formation of Axel Heiberg Island provide the oldest record of anatomically preserved Glyptostrobus in North America and insights into past diversity and adaptation. At a qualitative level, cuticular micromorphology is similar to that of living Glyptostrobus. The leaf epidermis is divided into regions with sparse stomata that have isodiametric to slightly elongate cells, and regions with abundant stomata that have predominantly isodiametric cells. The stomata are irregularly oriented, with monocyclic to amphicyclic subsidiary cells that have thickened outer walls and an irregular pattern of specialization. Guard cells bear lignified lamellae that are club-shaped at the stomatal poles, like those of living Glyptostrobus. At a qualitative level, however, the Arctic fossils are distinct. Epidermal cells in fossils often have undulate anticlinal walls, with stomata that are more widely spaced and have a more irregular pattern of subsidiary specialization than those in living Glyptostrobus. Most conspicuously, the Arctic fossils possess crystal-bearing micropapillae that are larger and more abundant than those in living Glyptostrobus. This difference in crystal size and abundance is mirrored by shoots of fossil Metasequoia from the same beds, which have distinctly larger and more abundant crystals than those in living Metasequoia. We suggest that the large and abundant crystals of Arctic Glyptostrobus may represent an adaptation of conifers to the unique polar environments that existed in the Northern Hemisphere during the early Tertiary.
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1 - V.L. Komarov Botanical Institute, Laboratory of Paleobotany, Russian Academy of Sciences, 2 Prof. Popov St., St. Petersburg, 197376, Russia
2 - Texas State University, Department of Biology, 601 University Drive, San Marcos, Texas, 78666, USA
3 - URS Corporation, 335 Commerce Drive, Suite 300, Fort Washington, PA, 19034-2623, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Williford A/Hilton
Date: Wednesday, July 11th, 2007
Time: 8:45 AM