An emended and amplified description of Pecopteris apicalis Knight, a fern morphospecies of mid-Stephanian age from NW Spain

Resumen

Extensive adpression material of the fern morphospecies Pectopteris apicalis Knight has been collected from overburden from opencast mining in the Paragido-Vallejo area oh the Barruelo Coalfield, close to the collection site of the holotype of the species. This has permitted a more detailed description of the key characteristics than was previously possible and an emended diagnosis. The large frond fragments demonstrate large pinnae of antepenultimate order, length in excess of 0.4 m, with apparent attachment to a very robust petiole in a tripinnate frond structure. Other diagnostic features of the species confirmed in this wide range of material cover the dimensions, acuminate shape, and terminal of last order pinnae, the range of dimensions and shape of pinnules and the characteristic consistently bifurcate venation. Fertile organs have been identified only on one specimen collected from another opencast working in the Barruelo Coalfield, at a lower level in the same stratigraphic unit. Although indistinct, the fertile organs comprise two rows of small circular sori on either side of the mid-vein, reminiscent of the genus Asterotheca, although the material does not permit reliable identification. Discussion of the possible systematic relationship of this species suggests the closet affiliation is with the cyatheoid group of pecopterid marattialean species. The Peragido-Vallejo material occurs within a low diversity flora which has undergone minimal transport from its site of growth, interpreted as in an interdistributary back-swamp area on a near-coastal alluvial plain