Abstract Detail

Paleobotany

Tomescu, Alexandru [1], Gensel, Patricia [2].

The Early Devonian Battery Point Formation of Quebec – a remarkable window on the rise of plant anatomical complexity.

First documented in the mid-1800s, the Emsian fossil assemblages of the Battery Point Formation have yielded a wealth of information on Early Devonian plants. Throughout the 19^th and 20^th centuries, most of this information came from compression fossils. Only five taxa where documented anatomically by the 2010s, when renewed focus on permineralized fossils of the Battery Point Formation – many of them collected by Francis Hueber – opened a window on the anatomy of Early Devonian plants that reveals previously unrecognized levels of diversity and complexity. As a result, the Battery Point Formation currently counts 12 anatomically-characterized taxa and at least 12 additional types with distinctive anatomy not yet described formally. Five other taxa recognized in the stratigraphically-equivalent Campbellton Formation bring the total to at least 29 anatomically-preserved plant types recognized in the broader tectono-stratigraphic area of the Gaspé Belt. These plants encompass a broad taxonomic range – rhyniopsids, zosterophylls, and euphyllophytes including some with complex actinosteles and different types of secondary growth. Compared to the two other prominent Early Devonian floras – in the slightly older Rhynie chert (Scotland; 11 anatomically-preserved taxa) and Posongchong Formation (China; four taxa with anatomical preservation) –, the Battery Point Formation stands out as the most anatomically-diverse Early Devonian flora worldwide. The Early Devonian plants of the Gaspé Belt inform multiple aspects of plant evolution. The diversity of euhyllophytes demonstrates diversification was well underway in this clade as early as 400 Ma ago, including the oldest anatomically-preserved representatives of some lineages. Early members of the radiatopsids and moniliformopsids inform phylogenetic relationships within their groups. Data on spore wall development in Psilophyton provide empirical support for hypotheses on the evolution of spore wall development in euphyllophytes. A Psilophyton-type plant offers an early glimpse of the evolution of plant-herbivore interactions, suggesting a previously unrecognized level of specialization by Emsian time. Another euphyllophyte exhibits anatomy relevant to discussions on the evolution of pith. The varied plant types demonstrate diverse lineages exploring multiple dimensions of anatomical morphospace and inform evo-devo approaches to morphological evolution. The diversity of actinosteles fits an ‘early high disparity’ macroevolutionary pattern and suggests a biphasic rise in disparity among euphyllophytes (first anatomy, later morphology). Periderm-type development as wound response is present in two types of tissue. Plants exhibiting distinct modes of secondary growth illustrate a mosaic pattern of deployment of discrete developmental processes, consistent with modular assembly of the regulatory toolkit for secondary growth.

1 - Humboldt State University, Department Of Biological Sciences, 1 Harpst Street, Arcata, CA, 95521, United States
2 - University Of North Carolina, Department Of Biology, CB# 3280, Coker Hall, Chapel Hill, NC, 27599, United States

Keywords:
Fossil
anatomy
Paleobotany
complexity
Devonian
Euphyllophyte
evolution
evo-devo
plant anatomy
Canada.

Presentation Type: Oral Paper
Session: PL5, Paleobotany: Honoring Fran Hueber - Session III
Location: /
Date: Tuesday, July 20th, 2021
Time: 3:45 PM(EDT)
Number: PL5004
Abstract ID:981
Candidate for Awards:None