Arborescent lycopsid periderm production was limited
Michael P D'Antonio1, C Kevin Boyce1
1Department of Geological Sciences, Stanford University, 450 Jane Stanford Way, Building 320, Stanford, CA, 94305-2115, USA.
The New Phytologist
|June 8, 2020
Summary
Late Paleozoic lycopsid trees likely had thinner bark than previously assumed. Physiological limits restricted periderm growth, challenging old ideas about their structure and support. This impacts understanding of ancient forest ecosystems.
Area of Science:
- Paleobotany
- Plant Anatomy
- Paleoecology
Background:
- Late Paleozoic arborescent lycopsids are key components of ancient coal-forming forests.
- Previous hypotheses suggested massive periderm (bark) provided structural support for these trees.
- This study re-evaluates the role and extent of periderm in lycopsid tree biology.
Purpose of the Study:
- To test the hypothesis that physiological limitations restricted periderm production in arborescent lycopsids.
- To determine the actual radial thickness of periderm in various lycopsid genera.
- To reassess the contribution of periderm to lycopsid structural support and ontogeny.
Main Methods:
- Analysis of anatomical permineralization fossils for direct periderm thickness measurement.
- Examination of surface impression fossils for indirect periderm thickness estimation.
- Comparative study across six genera of Pennsylvanian arborescent lycopsids.
Main Results:
- Evidence consistently indicates limited periderm production, typically less than 5 cm and always under 15 cm.
- This was observed even in lycopsid trunks estimated to be over 1 meter in diameter.
- Periderm thickness did not significantly increase proximally as previously proposed.
Conclusions:
- Physiological limitations likely prevented the extensive periderm development once attributed to lycopsid trees.
- The abundance of periderm in coal deposits is likely due to taphonomic processes (fossilization bias), not biological reality.
- Reinterpretation of lycopsid biomechanics, growth, and paleoecology is necessary based on limited periderm.
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