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Abstract Detail



Paleobotany

Savoretti, Adolfina [1], Bippus, Alexander [2], Stockey, Ruth [3], Rothwell, Gar [4], Tomescu, Alexandru [5].

Additional bryophyte diversity in the Lower Cretaceous of Vancouver Island (British Columbia, Canada): an anatomically-preserved tristichous moss.

The Early Cretaceous Apple Bay flora of Vancouver Island (Valanginian, 136 Ma) comprises permineralized plant assemblages preserved in carbonate concretions. This flora has yielded representatives of most major vascular plants groups, a lichen, and several fungi. A wide variety of bryophytes is present, making this one of the most diverse fossil bryophyte floras worldwide. Notable within the assemblage are polytrichaceous and leucobryaceous mosses, as well as hypnanaean tricostate mosses. A new bryophyte type identified at Apple Bay is characterized by very small gametophytes. The stem, 500 µm in diameter (including leaf bases), is triquetrous and branches three-dimensionally at close intervals. This branching architecture indicates an upright growth habit consistent with acrocarpy. The stem epidermis consists of flat cells with thicker walls than the cortical cells. The cortex comprises 3-4 layers of larger parenchyma and shows a sharp transition, at the center of the stem, to an area that lacks cellular preservation, which suggests the missing cells were delicate or small and could have formed a conducting strand. Leaves are densely imbricate, with helical tristichous phyllotaxis, and diverge at a sharp angle. Leaves are keeled, with recurved margins. The lamina is bistratose at the leaf base, becoming partially bistratose distally along the costa, and eventually unistratose in the upper leaf half. The strong costa is attenuate and exhibits some differentiation between thicker-walled epidermal cells and thinner-walled internal cells. This new Apple Bay moss has a distinctive combination of features: tristichous helical phyllotaxis and a bistratose leaf lamina. However, given their broad but infrequent taxonomic distribution, both of these features are probably homoplasic. Each occurs in several extant families: tristichous phyllotaxis in at least 10 extant families and bistratose leaf lamina in at least 15 extant families. Of these, four families (Meesiaceae, Polytrichaceae, Grimmiaceae, Pottiaceae) include species that have tristichous phyllotaxis or bistratose lamina, but not both. Additionally, no extant moss shows bistratose lamina organization similar to that of the Apple Bay moss (bistratose basally, transitioning to unistratose apically): in living mosses, leaves are completely bistratose or they are bistratose either apically, marginally, in patches, or in streaks. Together, these suggest that the Apple Bay fossil represents a distinct moss type with no extant counterpart. This is the fifth moss described from Apple Bay and the third acrocarp type in this bryoflora, adding another element to the rich diversity of this Early Cretaceous flora and to the sparse bryophyte fossil record.


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1 - Instituto de Botanica Darwinion, Labarden 200, San Isidro, Buenos Aires, 1642, Argentina
2 - Humboldt State University, Department of Biological Sciences, 1 Harpst Street, Arcata, CA, 95521, United States
3 - Oregon State University, Department of Botany and Plant Pathology, Corvallis, Oregon, 97331, USA
4 - Oregon State University, Department Of Enviromnental & Plant Biology, 2082 Cordley Hall, Corvallis, OR, 97331, USA
5 - Humboldt State University, Department Of Biological Sciences, 1 Harpst Street, Arcata, CA, 95521, USA

Keywords:
anatomy
bryophyte
Canada
Cretaceous
fossil
moss
Paleobotany
permineralized.

Presentation Type: Oral Paper
Number: 12001
Abstract ID:219
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award


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