Givetian (Middle Devonian) cladoxylopsid ‘ferns’ from Orkney, northern Scotland

Abstract

Two large fossil plants are described from the Givetian (Middle Devonian) Eday Flags, South Ronaldsay, Orkney Isles, northern Scotland. Fossils with branches joined to stems of this age are rare. Each specimen comprises a robust and tapering main trunk from which numerous closely spaced branches arise distally. Although poorly preserved such that generic identifications are not possible, both specimens display the characteristic architecture of the plant order Pseudosporochnales (Cladoxylopsida). The newly discovered specimens demonstrate a variation in size and form that adds further data to the understanding of the ontogeny of these enigmatic plants, complementing recent morphological and anatomical findings. These specimens, in combination with many more fragmentary fossils of the same kind from the Orcadian sedimentary basin, add to our knowledge of the Givetian floras of Britain, and show that large plants with upright stems were present in the Middle Devonian landscape of Scotland.

Global diversification of the common moonwort ferns (Botrychium lunariagroup, Ophioglossaceae) was mainly driven by Pleistocene climatic shifts

“…Ferns are an ancient group of vascular plants, with a fossil records dating back to the middle Devonian (387.7 -382.7 million years) (Berry and Hilton, 2006;Taylor et al, 2009) and divergence from the seed plants estimated to have taken place about 360-430 million years (Des Marais et al, 2003;Lehtonen et al, 2017;Magallón et al, 2013;Pryer et al, 2004;Qi et al, 2018;Rothfels et al, 2015;Testo and Sundue, 2016;Wikström and Kenrick, 2001;Zhong et al, 2014). Devonian fern lineages such as Cladoxylopsida or Rhacophytales (Taylor et al, 2009) have long gone extinct, while most of the about 11,000 extant fern species arose from a Cenozoic radiation (Schneider et al, 2004;Schuettpelz and Pryer, 2009;Testo and Sundue, 2016).…”