Orontiophyllum, a new genus for foliage of fossil Orontioideae (Araceae) from the Cretaceous of central Europe

Abstract

Reinvestigations of fossil taxa are important to ensure that their affinities are well defined, providing important data bearing on biogeography and evolution. Here, we studied fossil leaves previously assigned to Araceae and Zingiberaceae, and found that the vein architecture is most similar to Araceae subfamily Orontioideae. The genus OrontiophyllumJ.Kvaček & S.Y.Smith is proposed for leaves with orontioid venation, but lacking associated reproductive structures, which precludes us from knowing whether they represent an extant genus or an extinct taxon with a mosaic of features. Leaves are ovate and simple. Venation is parallel-pinnate, eucamptodromous, with at least three orders of primary lateral veins that leave the costa at acute angles. Higher order transverse veins are perpendicular to slightly oblique between the primary lateral veins, somewhat irregular, and the finest venation is generally reticulate. Two species are recognized, O.austriacum from the Campanian of Austria and O.riggauense from the Turonian of Germany. The vein architecture shows a mixture of features similar to both Orontium and Lysichiton. The two species differ from each other in the angle of departure of the primary lateral veins from the costa and details of the finer transverse veins. Both fossil taxa are found in sediments, suggesting a wetland environment, a habitat similar to that in which members of Orontioideae are found today. Combined with previous fossils for the subfamily, they show that members of Orontioideae were diverse and widespread across Laurasia in the Cretaceous.