A new marattiaceous fern from the Lower Jurassic of Patagonia (Argentina): the renaissance of Marattiopsis

Abstract

We here describe Marattiopsis patagonica sp. nov. (Marattiaceae) based on vegetative and fertile foliage impressions from the Lower Jurassic of Chubut Province, Patagonia, Argentina. The new species exhibits a unique combination of vegetative and reproductive features, including a prominent basal auricle; finely undulate, denticulate, to serrulate pinnule margins; interstitial fibres (venuli recurrentes) alternating with regular veins; submarginal position and distinctive relative<br />length of synangia (about 1220% of the pinnule width); and relatively small number of sporangia pairs per synangium (usually 14 or 16). The new species is assigned to the morphogenus Marattiopsis, since it shows no characters that would allow an unambiguous placement in any of the modern genera, Marattia s.s., Ptisana, or Eupodium. The newly established paraphyly of the Marattia s.l. species has a profound impact on the classification of fossil species. In this context, we provide a brief assessment of the significance of the fossil Marattiopsis for phylogenetic and biogeographical interpretations. It appears that essentially modern marattioid ferns, including Marattiopsis, which are commonly considered to be typical elements of tropical areas of the northern hemisphere during the Mesozoic, may have left an important but largely ignored fossil record in subtropical Gondwana.