Revision of Fedekurtzia (pteridosperm) and allied fronds from the Carboniferous of Gondwana

Abstract

AbstractCarboniferous foliage ofFedekurtzia argentina(Kurtz) Archangelsky from Gondwana is systematically described and revised. The frond is reconstructed based on specimens of the late Serpukhovian–BashkirianNothorhacopteris/Botrychiopsis/Ginkgophyllumflora of western Argentina, especially from the Jejenes, Tupe and Volcán formations. The whole-frond reconstruction emphasizes the variation in pinnule shape throughout the basal, medial and distal sections of the frond. The basalmost rachis possesses cyclopteroid pinnules grading to pinnae with obovate to wedge-shaped pinnules at the medial section of the frond. Distal pinnae are shorter, bearing imbricate and more dissected pinnules. Specimens from the same type locality from whichF. argentinacomes, previously assigned toTriphyllopteris cuyanaLeguizamón & Vega, are reassigned toF. argentina, as well as ovuliferous and microsporangiate structures in organic connection. Two decades ago a revision of the GermanTriphyllopterisgenus rejectedT. cuyanaas representative of the taxon, and the Argentinian specimens remained as indeterminate “triphyllopteroid” fronds. The ovulate organPolycalyxVega & Archangelsky is considered to be in organic connection with vegetative fragments ofF. argentina, and its cupulate character is discussed. Pollen organs represented by multi-forked axes bearing fusiform sporangia ofRinconadiaVega are also in organic attachment and included in theFedekurtzia argentinareconstruction. The pollen or prepollen grains are trilete and with granulate sculpture. The paper presents a comparison withBotrychiopsis weissianaKurtz emend. Archangelsky & Arrondo, which differs in its rounded and entire-margin pinnules. Similar specimens from Australia formerly described asRhacopteris,SphenopteridiumandArchaeopterisand currently included inFedekurtzia intermediaRigby share morphological characters with the Argentinian species. A revision of the Australian material is necessary to confirm synonymy.Fedekurtziabelongs to the pteridosperms based on the reproductive organs and is here assigned to Austrocalyxaceae. Its reconstruction now constitutes one of the most complete seed-ferns known from the Carboniferous of Gondwana.