Earliest record of semi-aquatic fern leaves (Family Marsileaceae) in the Mesozoic of Eurasia (Lower Cretaceous, Spain)

Abstract In this paper we present new macrofossils of semi-aquatic fern Family Marsileaceae consisting of leaves and leaflets from the upper Hauterivian- lower Barremian Pinilla de los Moros Formation, Salas de los Infantes village, Burgos province, north of Spain. The leaves show two elliptic to flabellate-shaped leaflets that are joined to a petiole. Leaflets present entire margins and dichotomous anastomosed vein pattern. Comparison between the studied leaves and other marsileaceous leaves indicates close similarities with Regnellites nagashimae species. These leaves were deposited in a related fluvial environment near to the place where semi-aquatic plants grew. The studied macrofossils constitute at present the earliest record of leaves of Family Marsileaceae in the Mesozoic of Eurasia at the moment.