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Abstract Detail



Paleobotanical Section

Petlewski, Alaina [1], Tomescu, Alexandru M.F. [2].

Permineralized pinaceous leaves in the Lower Cretaceous Budden Canyon Formation of northern California.

The Lower Cretaceous (Valanginian-Turonian) Budden Canyon Formation of California has yielded compressed and permineralized fossil bryophytes, fungi, ferns, and seed plants. Some of these fossils are preserved anatomically by calcium carbonate permineralization in near-shore marine deposits of the Lower Chickabally Mudstone Member (Barremian-early Aptian, 120-125 Ma). Conifer leaves of pinaceous affinities are abundant in this fossil assemblage. Although the leaves vary widely in cross-sectional outline (circular-ovoid to polygonal), their anatomy is consistently similar. They are amphistomatic, with conspicuously plicate mesophyll 2-3 cell layers thick, and two external lateral resin canals. The leaf epidermis is often missing due to abrasion during transport. The hypodermis consists of up to four layers of fibers. The endodermis, with circular to elliptical outline, consists of large circular cells. The transfusion tissue, 1-4 cells thick, includes a characteristic outer layer of cells remarkably similar in size and shape to the endodermal cells. The two bundles of the vascular strand are separated by a band of sclerenchyma (1-5 cells thick) that connects patches of abaxial and adaxial sclerenchyma. These Budden Canyon leaves are similar to extant Pinus and Picea, with which they share an endodermis with circular-elliptical outline, external resin canals, and the amphistomatic condition. The conspicuously plicate mesophyll, two vascular bundles, and absence of palisade cells are most similar to Pinus. However, most Picea species have two resin canals, like the Budden Canyon leaves, and some lack palisade cells or have slightly plicate mesophyll. Midoriphyllum piceoides, representing Lower Cretaceous Picea-like leaves from Vancouver Island, is similar to the Budden Canyon leaves in its variable cross-sectional outline, plicate mesophyll, two resin canals, and lack of palisade cells. However, Midoriphyllum has smaller endodermal cells and differently-shaped transfusion tissue cells, as well as a single vascular bundle. The Budden Canyon leaves are more similar anatomically to Upper Cretaceous Pinus hokkaidoensis from Hokkaido; both have two external resin canals and two vascular bundles, large circular endodermal cells, and a similar sclerenchymatous complement of the vascular strand. However, P. hokkaidoensis leaves have a triangular cross section and thinner mesophyll with less conspicuous plication. The Budden Canyon leaves could represent the foliage of the plant producing Pityostrobus californiensis ovulate cones which have been described previously from the unit. These fossils corroborate similar evidence consisting of coniferous seed cones and leaves from other Cretaceous localities, which is thought to indicate that the Pinaceae were undergoing rapid mosaic evolution during the Cretaceous.


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1 - Humboldt State University, Department of Biological Sciences, 1 Harpst St., Arcata, CA, 95521, United States
2 - Humboldt State University, Department Of Biological Sciences, 1 Harpst Street, Arcata, CA, 95521, USA

Keywords:
fossil
Pinaceae
Cretaceous
California.

Presentation Type: Oral Paper:Papers for Sections
Session: 11
Location: Salon 5/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 11:00 AM
Number: 11004
Abstract ID:454
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award


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