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Updated: Jun 27, 2026

Reconstructing Terrestrial Paleoclimate and Paleoecology with Fossil Leaves Using Digital Leaf Physiognomy and Leaf Mass Per Area
Published on: October 25, 2024
Megaphylls, microphylls and the evolution of leaf development.
1Department of Biological Sciences, Humboldt State University, Arcata, CA 95521, USA. mihai@humboldt.edu
The terms microphyll and megaphyll, used to describe vascular plant leaves, should be abandoned. Current evidence suggests leaf structures evolved independently, not from a shared ancestor, challenging the idea of megaphyll homology.
Area of Science:
- Plant Biology
- Evolutionary Biology
- Developmental Biology
Background:
- The terms 'microphyll' and 'megaphyll' were initially used to denote morphological differences in vascular plant leaves.
- These terms became linked to the concept that vascular plant leaves are not homologous structures.
- 'Megaphyll' has evolved to imply homology of precursor structures in euphyllophyte lineages.
Purpose of the Study:
- To critically evaluate the continued use of the term 'megaphyll' in plant biology.
- To argue for the abandonment of 'megaphyll' due to a lack of supporting evidence for homology.
- To advocate for new definitions of leaf types based on independent evolution.
Main Methods:
- Review of fossil record evidence related to early vascular plant leaf evolution.
- Analysis of developmental pathways in different plant lineages.
- Examination of phylogenetic studies concerning leaf evolution.
Main Results:
- Fossil and developmental evidence does not support homology of euphyllophyte leaf precursor structures.
- Evidence suggests homoplasy (independent evolution) rather than homology for these precursor structures.
- The term 'megaphyll' perpetuates misconceptions about leaf homology.
Conclusions:
- The term 'megaphyll' should be abandoned as it is based on an unsupported hypothesis of homology.
- Continued use of 'megaphyll' can lead to flawed reasoning in developmental and phylogenetic research.
- Alternative definitions for independently evolved leaf types, grounded in development and phylogeny, are necessary.
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