Aquatic ferns from the Upper Cretaceous Loncoche Formation, Mendoza, central-western, Argentina

Abstract

Herein, we report new fossil remains with marsileaceous affinity associated with dispersed microspores corresponding to Crybelosporites, different types of massulae of Salvianiaceae (Paleoazolla patagonica and Azolla circinata), and a single megaspore assigned to the fossil genus Grapnelispora. These fossils were recovered from the Late Cretaceous Loncoche Formation, at the Calmu-Co section, Malargu ¨e Group, Northern Neuque ´n Basin, Mendoza, Argentina. The macrofossils include scattered leaflets, rhizomes, roots, and a sporocarp-like structure. They share characters with members of the aquatic fern family Marsileaceae; however, based on the characters preserved, they could not be placed within any extant or fossil species; therefore, the fossils are better included within a new fossil-taxon, Mendozaphyllum loncochense. Dispersed spores of Crybelosporites pannuceus, also belonging to Marsileaceae, were recovered from the entire section. Additionally, abundant isolated massulae with affinity to the aquatic fern family Salviniaceae, and a single megaspore assigned to Grapnelispora loncochensis, were identified from the plant bearing layer. The presence of Marsileaceae fossils in the Campanian-Maastrichtian Loncoche Formation, Mendoza, extends towards the north the paleogeographical distribution of the family Marsileaceae in Argentina, since previous records are from Patagonia. A fluvial to deltaic environment with lacustrine episodes is suggested by the sedimentology of the lower and middle parts of the Calmu-Co section and supported by the abundant fresh water algae recovered from the palynological association. This was probably the optimum habitat for the growth of aquatic ferns related to Marsileaceae and Salviniaceae and explains its abundance in the studied sediments.

Salviniales from the Late Cretaceous of the Golfo San Jorge Basin

“…(Rhizosperma) sp., Azollopsis polyancyra (Stough) Sweet andHills, 1974, A. circinata Oltz andHall, in Hall (1968) and A. spp. reported from the Loncoche, Allen and Paso del Sapo formations in Mendoza, Neuqu en and Chubut provinces (Papú, 1988(Papú, , 2002Vallati, 2010;Puebla et al, 2014). Massulae of Azollopsis polyancyra have been also reported from the Upper Cretaceous deposits of the Austral Basin (Stough, 1968;Marenssi et al, 2004).…”

“…The Upper Cretaceous megafossil record of Marsileaceae in Argentina includes leaves, leaflets, rhizomes and associated sporocarps from the La Colonia Formation of the Chubut province (Cúneo et al, 2013;Cúneo et al, 2014;Hermsen et al, 2014) and leaflets, rhizomes, roots, and a sporocarp-like structure from the Loncoche Formation of the Mendoza Province (Puebla et al, 2014).…”

Cretaceous climatic reconstruction from Argentina based on palynological data

“…From the Albian to the end of the Cretaceous, the aquatic ferns became important components of the microfloras from South America (Prámparo, 2012). The family Osmundaceae, together with Salvinaceae, are well represented in different basins in Argentina (Papú, 1997;Puebla et al, 2015;Narváez et al, 2016).…”

Catálogo de ejemplares tipo de las Colecciones Paleontológicas del Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA), Mendoza, Argentina

“…División Monilophyta Orden Salviniales Bartling Familia Marsileaceae Mirbel Género Mendozaphyllum Puebla, Prámparo & Gandolfo, 2014Diagnosis (Puebla et al, 2014): Planta con rizoma, raíces y hojas compuestas. El rizoma posee raíces en su región ventral y hojas en la dorsal con dos o cuatro foliolos glabros en forma de cuña o aovados, peciolo presente, ápice entero a crenado, base recta a convexa y venación dicotómica abierta, carece de anastomosis y vena marginal.…”

“…Mendozaphyllum loncochense Puebla, Prámparo & Gandolfo, 2014 (Figura 2) Descripción (Puebla et al, 2014: P. 280): La planta está compuesta por rizomas que poseen raíces y hojas. La planta más grande y completa consiste en un fragmento de rizoma (2,5 cm de largo y 4 cm de ancho) que posee numerosas raíces en su parte ventral y folíolos en la dorsal.…”