Fossil picrodendroid fruit from the Upper Danian of Nûgssuaq, West Greenland

Abstract

Rosenkrantzia picrodendroides n.gen. et n.sp., based on 4. 7 specimens of fossil fruit in very good preservation, is described. The fruit was a nut (or drupe), with a thick pericarp of primitive anatomy. It is l-locular, containing one fully developed seed; about half of the specimens also contain remnants of a second aborted seed. The seed is pendulous from an apical placenta and has a long longitudinal raphe. Hilum is distal, chalaza basal. The original ovary can be reconstructed: l-locular with min. two ovules, pendulous from the distal placenta, anatropous. The fully developed seed consists mainly of two thick, interfolded cotyledons with no distinct endosperm. The taxonomical investigation includes a study of fruits of two of the recent Picrodendron species. A phylogenetic conclusion is advanced which supports the position of the Picrodendraceae in the order Juglandales. The taxonomic position of Rosenkrantzia appears to lie somewhere between the Cupuliferae ( Quercus group) and Juglandales, or in palaeontological terms, between the Dryophyllum and Dewalquea groups.