A new species of Ashicaulis Tidwell (Osmundaceae) from Aptian strata of Livingston Island, Antarctica

A new species of Ashicaulis, A. australis sp. nov., is described in detail. The specimen, collected from the Cerro Negro Formation (Aptian) at Byers Peninsula, Livingston Island (Antarctica), increases the number of fossil representatives of the Osmundaceae in the southernmost continent. The specimen shows a differential state of preservation across the stem, but is good enough to show details of most of the tissues, enabling a study of the anatomy, allowing its comparison with other Ashicaulis species, and justifying its assignment to a new species. Ashicaulis australis is characterized by the presence of parenchymatous pith, sub-exarch protoxylem clusters in the vascular ring, delayed leaf gaps and petiole bases with small patches of sclerenchyma scattered in the cortex, two groups of the same tissue lateral to the trace, and a large patch followed by 6–9 smaller aligned sclerenchymatous groups in the stipular wings.