Tomescu, Alexandru , Steenbock, Christopher , Friedman , Maria , Stockey, Ruth .
The Early Cretaceous Apple Bay flora of Vancouver Island: a hotspot of fossil bryophyte diversity.
The Apple Bay flora hosts one of the most diverse and best characterized plant fossil assemblages of the Early Cretaceous. Dated at the Valanginian-Hauterivian boundary, ca. 136 million years old, this flora that is broadly coeval with the oldest angiosperms consists of anatomically preserved plants that are studied using the cellulose acetate peel technique. The Apple Bay flora has yielded representatives of most major groups of tracheophytes - lycopodialean and selaginellalean lycopsids, equisetopsids, ten fern families, and several types of gymnosperms -, as well as a basidiomycete. While a few bryophyte fossils had been recognized early at Apple Bay, the most inconspicuous constituents of this flora remained unnoticed until recently. We conducted a careful survey of 0.162 m2 of acetate peels from 39 different carbonate concretions, which revealed an unexpectedly rich bryophyte flora. Of the total 223 bryophyte specimens found (ca. 1 specimen/7.25 cm2), 124 are leafy gametophytes and 7 are thalloid gametophytes. The leafy gametophytes represent a minimum of 9 different taxa, mostly mosses. These include a typical leucobryacean; one type with three-ranked phyllotaxis; several types of smaller or larger gametophytes with uni- and mutistratose, strongly costate leaves, with or without a conducting strand; one type with tricostate unistratose leaves, complete with a rich and diverse association of bryophilic organsisms; at least two of the types include specimens bearing antheridia. The thalloid gametophytes include specimens reminiscent of liverworts and hornworts, as well as fern gametophytes; one of these also bears antheridia. In addition to the gametophytes, 72 specimens recognizable as bryophyte axes by their diminutive size and the absence of tracheids, show no evidence of leafy appendages and are tentatively interpreted (pending complete sectioning) as sporophyte setae. These show an impressive amount of diversity in structure, with a minimum of 10 morphotypes distinguished based on presence or absence of a conducting strand and radial differentiation of tissues. In the case of 20 additional specimens, the plane of sectioning or the state of preservation precludes identification beyond the bryophyte axis category. The Apple Bay flora now stands as the most diverse fossil bryophyte flora worldwide. Aside from the numerous bryophyte fossils, our survey revealed a significant fungal presence - fossils including perithecial and cleistothecial ascomycetes, wood rotting fungi, and fungal sclerotia, as well as a lichen. Addition of these bryophytic and fungal components makes the Apple Bay flora the most botanically diverse pre-angiospermous fossil flora known to date.
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1 - Humboldt State University, Department of Biological Sciences, 1 Harpst Street, Arcata, CA, 95521, USA
2 - Oregon State University, Department of Botany and Plant Pathology, 2082 Cordley Hall, Corvallis, OR, 97331, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Union A/Hyatt
Date: Tuesday, July 10th, 2012
Time: 3:45 PM