Evolutionary and ecological perspectives of Late Paleozoic ferns. Part III. Anachoropterid ferns (including Anachoropteris, Tubicaulis, the Sermayaceae, Kaplanopteridaceae and Psalixochlaenaceae)

International audienceThe anachoropterid ferns, previously assigned to the family Anachoropteridaceae, are a group of anatomically preserved late Paleozoic filicalean ferns characterized by a C-shaped foliar xylem with abaxially recurved arms (inversicatenalean anatomy) and two main protoxylem strands. The variously curved to strongly inrolled foliar xylem certainly reflects different evolutionary trends within the morphogenus Anachoropteris. The occurrence of two groups of Tubicaulis is supported by differences in cauline and foliar anatomy and the presence vs. absence of precocious pinnae. Tubicaulis with solid protostele bears petioles which are not of the Anachoropteris type. Protostelic, rarely siphonostelic, cauline structures corresponding to several types of epiphyllous shoots are well documented on rachides of several Anachoropteris species and in the genus Kaplanopteris. These shoots, borne on dominant scrambling fronds, are a common means of vegetative propagation, similar to those known in the contemporaneous botryopterid ferns. This contrasts with the highly branched rhizomatous cauline system of Psalixochlaena (a whole plant reconstruction is provided) and the erect stems, of tree-ferns type, known in some Tubicaulis and the probably related Grammatopteris. A hemi-epiphytic habit characterized some Anachoropteris and Tubicaulis. This group of ferns therefore exhibited an important diversity of habits. Information on the distal regions of fronds, i.e. on pinnule morphology and fertile parts, is unfortunately missing in the majority of taxa. Where known, the pinnules are small and dissected, and sporangia, grouped in sori, have a lateral annulus. However, differences in soral and sporangial morphology support the recognition of the families Sermayaceae, Kaplanopteridaceae and Psalixochlaenaceae. The discovery of new fertile anachoropterid pinnae with adaxially borne branched soral receptacles will justify the distinction of a new family. Finally, there is no well supported anatomical evidence of fertile frond compressions belonging to anachoropterid fern