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Abstract Detail



Paleobotany

DAntonio, Michael [1], Boyce, Charles [1].

Arborescent lycopsid periderm production was limited.

Arborescent lycopsids are perhaps the most charismatic group of fossil plants, but despite their abundant fossil record, recent research has shown that significant gaps exist in our understanding of their biology. The most widely accepted hypotheses regarding their growth have been that they developed a massive periderm cylinder and that this tissue would have provided their structural support, given their paucity of wood production. Here, we argue that arborescent lycopsid periderm production would have been limited by geometric constraints on their growth. Depending on specifics of growth, periderm production would have been limited either by longitudinal fissuring in the phellem or by the isolation of the phellogen from nutrients provided by the phloem. We then test this argument by direct interrogation of the fossil record along three independent lines of evidence. We analyzed arborescent lycopsid surface impressions for evidence of separation caused by periderm production, and anatomical permineralizations both for direct measurements of periderm dimensions preserved in coal balls and for the geometry of periderm fragments for analysis of planes of weakness in the periderm. In all, the data strongly support the argument that arborescent lycopsid periderm production was limited. This agrees with a published datum on the thickest arborescent lycopsid periderm ever observed (15 cm). The ubiquitous presence of arborescent lycopsid periderm in Middle Pennsylvanian coals of Euramerica is interpreted to result from taphonomic enrichment in the peat swamps prior to the formation of coal ball concretions. The revised expectations for arborescent lycopsid anatomy have implications for their growth and developmental dynamics, and more broadly, their role in the Late Paleozoic carbon cycle via their burial dynamics.


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1 - Stanford University, Geological Sciences, 450 Serra Mall, Bldg. 320, Stanford, CA, 94305, United States

Keywords:
Arborescent lycopsid
anatomy
Periderm
Developmental biology
Structure.

Presentation Type: Oral Paper
Session: CK1, Cookson Award Session I
Location: Tucson G/Starr Pass
Date: Monday, July 29th, 2019
Time: 9:30 AM
Number: CK1007
Abstract ID:255
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award


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