Abstract Detail

Paleobotany

Lalica, Madison [1], Arnett, Victoria [1], Tomescu, Alexandru [2].

Broadening the spectrum of plant-associated fungal remains in the Early Devonian (Emsian) flora of the Battery Point Formation (Gaspe, Quebec, Canada).

The Early Devonian plant fossil assemblages of the Battery Point Formation include both compression fossils and permineralized plants. Some of the permineralized fossils have been shown to host fungal material. This consists of spore-like bodies found in inside plant axes: some are up to 175 µm in diameter, with two distinct wall layers and hyphal attachments, similar to glomeromycete spores, while others are smaller single-walled bodies. Our investigations of the Battery Point Formation have uncovered similar material , as well as new types of putative fungal structures. The most abundant type are the double-walled spores described previously, but with a broader size range (25 and 175 µm) and representing three or four size classes. These spores are restricted to the inner cortex of Psilophyton and other trimerophyte axes. Smaller spore-like bodies of various types and sizes are also found in the inner cortex of Psilophyton axes, including c. 18 µm light-colored spores and chains or clusters up to 110 µm, consisting of 3-15 dark globose spores (11 µm in diameter). Some axes contain minute (<4 µm thick) dark hypha-like structures. The epidermis and sub-epidermal cells of zosterophyll axes host small (7 µm) thin-walled bodies sometimes aggregated in chains; larger, reddish oval bodies (up to 78 µm) with a longitudinal slit; and hypha-like structures (2.5 µm thick; up to 15 µm long) that project inside the cell from the cell walls. The tracheids of a Psilophyton axis contain small (19 µm) dark spores and a dehisced Psilophyton sporangium contains a 23 µm thin-walled spore. Small globose spores (12-14 µm) are also found in the phloem of Psilophyton. A zosterophyll axis hosts a larger (60 µm) spherical spore between the xylem and phloem. These different structures represent at least eight different spore types based on size, shape, and wall structure, and two types of hyphae. The taxonomic affinities of these remains are under scrutiny but they are most likely fungal. For Early Devonian plant-fungal interactions, the rich Rhynie chert assemblages have been the only source of information up until now. The new Gaspe material re-emphasizes the importance of permineralized fossils for uncovering plant-fungal interactions deep in the fossil record. While the details of these interactions (e.g., whether the fungi were infecting tissues of living plants or decomposing dead material) have yet to be clarified, these new findings broaden the spectrum of plant-associated fungal remains known in the Early Devonian.

1 - Humboldt State University, 1 Harpst Street, Arcata, CA, 95521, USA
2 - Humboldt State University, 1 Harpst St., Arcata, CA, 95521, United States

Keywords:
fossil
fungi
fossil plant
Devonian
Canada
plant-fungal interactions.

Presentation Type: Oral Paper
Session: CK1, Cookson Award Session I
Location: Tucson G/Starr Pass
Date: Monday, July 29th, 2019
Time: 8:15 AM
Number: CK1002
Abstract ID:934
Candidate for Awards:Isabel Cookson Award