PALAEOMOHRIA SPORES FROM THE CENOMANIAN IN PATAGONIA, ARGENTINA

PATRICIO E. SANTAMARINA; VIVIANA D. BARREDA; ARI IGLESIAS; AUGUSTO NICOLÁS VARELA

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2021 vol. 58 p. 289 - 296

0002-7014

THE ANEMIACEAE, a fern family represented by the sole extant genus Anemia Swartz, include c.a. 115 species widely distributed in the tropical America, Africa, Madagascar, and India (Labiak, et al., 2015; Mickel, 2016). Anemia is developed primarily in open habitats with well-drained soils, and uncommonly, in savannahs and open forests. It grows under warm and dry climates, from sea level to 3200 m of altitude, and shows a terrestrial or epilithic growth habit (Tryon & Tryon, 1982; Ramos-Giacosa, 2016). The spores of this family are easily distinguishable due to their distinctive cicatricose ornamentation conformed by parallel ridges (Tryon & Lugardon, 1990). The fossil record of Anemiaceae is comprised largely of dispersed spores. Although there are macrofossils assigned to the family, these are quite scattered (see Hernandez-Castillo et al., 2006 and Mohr et al., 2015). Seven spore genera were recorded worldwide from the Late Jurassic to the Neogene: Appendicisporites Weyland & Krieger, Cicatricosisporites Potonié & Gelletich emend. Dettmann & Clifford; Costatoperforites Déak emend. Mendes et al., Nodosisporites Déak emend. Dettmann & Clifford, Palaeomohria Archangelsky, Plicatella Maljavkina emend. Burden & Hills, and Ruffordiaspora Dettmann & Clifford (Dettman & Clifford, 1992; Collinson, 2001; Archangelsky, 2009 Mendes et al., 2017). In Argentina, the oldest record of these spores is from the Late Jurassic of the Neuquén Basin, achieving their highest diversity during the Aptian?Albian interval. Later on, the diversity of Anemiaceae dropped, with their last records in the Miocene (Volkheimer & Quattrocchio, 1975; Prámparo, 1989; Archangelsky & Archangelsky, 2010a, b; Narváez et al., 2013; Anzótegui et al., 2019). Up to now, Palaeomohria was known only for the early?middle Albian Piedra Clavada Formation, Santa Cruz Province (Archangelsky, 2009). This genus is characterized for having channeled muri instead of the common solid structure in most cicatricose spore taxa. When originally described by Archangelsky (2009), Palaeomohria was related to the genus Mohria Swartz (no longer valid, see discussion and conclusion), extant ferns restricted to southern and western Africa and Madagascar. Here we report new records of Palaeomohria from the Cenomanian of southern Patagonia (Mata Amarilla Formation), describe the new specimens in detail, and discuss their botanical affinity in the light of the latest phylogenetic studies. We also explore the biogeographic importance of this finding.