According to Mickel & Smith (2004), “this species can be distinguished from congeners in Mexico by its narrower pinnae [1.2-3 cm wide] and occurrence at higher elevations”. It is known only form Mexico, Guatemala, Honduras, and El Salvador.
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- S. underwoodianus – habit
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- S. underwoodianus – lamina base
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- S. underwoodianus – fiddlehead
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- S. underwoodianus – ab side
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- S. underwoodianus – pinna detail
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- S. underwoodianus – sori and indument
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- S. underwoodianus – stem apex
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- S. underwoodianus – stem x-sect
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- S. underwoodianus – petiole x-sect
