Triassic species ofDictyophyllumfrom eastern Australia

Abstract

Three species of dipteridacean ferns occur in the Triassic of eastern Australia: Dictyophyllum davidii Walkom 1917, D. bremerense Shirley 1898 and D. shirleyi (Herbst) comb. nov.; the descriptions of the first two are expanded in the light of new material collected. D. bremerense and D. davidii, together with D. tenuifolium Stipanicic & Menendez 1949 from the Late Triassic of Argentina, form a well-defined group restricted to the Middle-Late Triassic of Gondwana. They are characterized by a distinctive soral arrangement, considerably different from that of other species of Dictyophyllum. D. davidii, which occurs in Middle Triassic sediments in Australia and South Africa, is the oldest species of the genus. D. shirleyi is a rare and little known species similar in many respects to D. bremerense. A detailed study of the morphological differences between Dictyophyllum and Thaumatopteris has shown that the latter genus is a junior synonym of Dictyophyllum.