Millerocaulis tekelili sp. nov., a new species of osmundalean fern from the Aptian Cerro Negro Formation (Antarctica)

Abstract

Vera, E.I. iFirstarticle. Millerocaulis tekelili sp. nov., a new species of osmundalean fern from the Aptian Cerro Negro Formation (Antarctica). Alcheringa, 1–10. ISSN 0311-5518. Ezequiel Ignacio Vera [evera@macn.gov.ar] División Paleobotánica, Museo Argentino de Ciencias Naturales 'Bernardino Rivadavia', Av. Angel Gallardo 470, C1524DJR, Buenos Aires, Argentina. Also affiliated with Área de Paleontología, Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón II, Ciudad Universitaria, C1428EGA, Buenos Aires, Argentina. Received 29.10.2010, revised 14.3.2011; accepted 24.3.2011. A new species of the osmundalean fossil morphogenus Millerocaulis Tidwell emend. Vera, Millerocaulis tekelili sp. nov. is defined, based on several permineralized stems recovered from exposures of the Lower Cretaceous Cerro Negro Formation on Livingston Island, South Shetland Islands, Antarctica. This new species is characterized by the presence of an ectophloic–dictyoxylic siphonostele, inner parenchymatic and outer sclerotic cortices, heterogeneous sclerotic ring in the petiole bases, absence of sclerenchyma associated with the petiolar xylem trace, petiolar inner cortex with sclerenchyma strands and stipular wings having a large sclerenchyma bundle and several smaller ones. The presence of non-homogeneous sclerotic rings in the petiole bases allows this new species to be clearly distinguished from other Antarctic Millerocaulis, and suggests that it may represent an intermediate form in the evolutionary lineage leading from Millerocaulis to subgenus Claytosmunda of Osmunda.