The anatomy and seed plant affinities ofRhacopterisandSpathulopterisfoliage from the Dinantian (Lower Carboniferous) of Scotland

Abstract

AbstractPermineralised material ofRhacopteris lindseaeformis(Bunbury) Kidston andSpathulopteris obovata(Lindley & Hutton) Kidston, showing both external morphology and excellent anatomical preservation, is described from the Lower Carboniferous (?Asbian, Upper Viséan) tuffs and dolomitic ashes outcropping at Weaklaw–Gullane, East Lothian, Scotland. These specimens provide the first anatomical information on these two well-known plant compression genera. The rachises haveLyginorachis-type anatomy with distinctive characters in the two species.Spathulopterisrachises correspond toLyginorachis kingswoodenseMeyer-Berthaud, previously described from the localities of Kingswood and East Kirkton, whereasRhacopterisshows similarities with the petiole attributed toBiligneafrom Oxroad Bay. Both foliage types conform to seed-fern frond organisation. This new evidence contradicts previous interpretations ofRhacopterisas a fern or a progymnosperm. We suggest thatRhacopteris lindseaeformisandSpathulopteris obovatarepresent the foliage of some of the arborescent gymnosperms which are found associated in several contemporaneous localities.