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The new genus Cruciaetheca (Equisetales, Sphenopsida) is described from the Río Genoa Formation, Lower Permian of Chubut Province, Argentina. Ramified, whorled vegetative axes terminally bearing leaf whorls of the Phyllotheca type characterize this genus; some last‐order axes bear fertile internodes with whorls of cruciate sporangiophores between unmodified leaf whorls. We describe three species, Cruciaetheca patagonica (Feruglio) Cúneo et Escapa nov. comb., Cruciaetheca feruglioi Cúneo et Escapa nov. sp., and Cruciaetheca genoensis Cúneo et Escapa nov. sp., that are diagnosed from vegetative and reproductive features. The new material is compared with other Paleozoic equisetaleans from different geographical regions. We reevaluate the use of the genus Phyllotheca in light of finding Phyllotheca foliar whorls associated with completely distinct reproductive characters. The systematic position of Cruciaetheca is discussed as well as the significance of its cruciate sporangiophores and other characters.
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Cúneo et al. (2006) studied this question.
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