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Abstract Detail


Paleobotanical Section

Bippus, Alexander [1], Friedman , Maria [1], Stockey, Ruth [2], Tomescu, Alexandru [1].

Thalloid fossils comparable to bryophyte and fern gametophytes from the Lower Cretaceous (Valanginian-Hauterivian) of Vancouver Island, British Columbia.

The Early Cretaceous (Valanginian-Hauterivian) fossil assemblages from Apple Bay (Vancouver Island, British Columbia) contain a great diversity of permineralized plant fossils,among which are several thalloid specimens. One of them is a thallus fragment at least 13 mm wide and 310 µm thick, reminiscent of complex liverwort gametophytes. Most of the thallus consists of cells 71-96 µm in diameter that transition to smaller cells (23-29 µm diameter) toward its lower side; cells throughout the thallus are ca. 140 µm long. The outer thallus layers are incompletely preserved. Fragments preserved on one side consist of thin-walled cells of variable size (18-33 µm) and bear structures reminiscent of rhizoid bases. On the opposite side of the thallus, fragments of tissue consisting of thin-walled cells 22-28 µm in diameter could be remnants of a photosynthetic layer and the upper epidermis. A second specimen, 5 mm wide and very thin (up to six cells thick; 144 µm), is reminiscent of hornwort gametophytes. Mixed cells of variable sizes (18 x 23 µm to36 x 49 µm) define several chambers up to 312 x 63 µm, which are interpreted as mucilage cavities. The underside holds long rhizoids 18-27 µm thick, attached to basal cells 25-48 µm wide. A third specimen is an irregular fragment 1.8mm long and 580 µm in maximum thickness. A uni- to bistratose layer of smaller cells (21-26 µm in diameter) encloses larger cells 42-72 µm in diameter. The specimen bears structures interpreted as emergent antheridia. The best preserved of these structures is spherical, 212 µm in diameter, with a unistratose jacket layer comprising ca. 35 cells (each 50-70 µm in size and 19-38 µm thick). Spherical emergent antheridia similar to the structures on this Apple Bay specimen tend to be rare in bryophytes, where they are generally stalked. The structures of the Apple Bay specimen are sessile and similar to the antheridia of many leptosporangiate ferns, of which several families are known at this locality. While thalloid liverworts are not uncommon in the fossil record, instances of cellular preservation are rare; in contrast, the fossil record of hornworts and fern gametophytes is almost non-existent. Anatomical comparisons with extant liverwort, hornwort, and fern gametophytes will provide the criteria for resolving the affinities of these intriguing Apple Bay fossils.

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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

Keywords:
Cretaceous
bryophyte
liverwort
hornwort
fern
gametophyte
fossil
antheridia
thalloid
leptosporangiate.

Presentation Type: Oral Paper:Papers for Sections
Session: 9
Location: Union A/Hyatt
Date: Monday, July 9th, 2012
Time: 10:30 AM
Number: 9001
Abstract ID:875


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