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What leaf shape and vein pattern did extinct Sphenophyllales plants have?
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Equisetopsida
Giant horsetail of Europe (Equisetum telmateia).
The extinct Sphenophyllales plants were characterized by their distinct leaf morphology, which differed from the reduced, scalelike leaves of modern horsetails.
- Leaf Shape: The leaves of Sphenophyllales were wedge-shaped or triangular.123
- Vein Pattern: These leaves featured a repeatedly forking, or dichotomous, venation system.12
These leaves, often referred to as sphenophylls, were arranged in whorls along the plant's jointed stems. Unlike the single, unbranched midvein found in the leaves of extant Equisetum, the dichotomous branching of the veins in Sphenophyllales represents a more complex vascular arrangement within the group's fossil forms.12