| Abstract Detail
Paleobotany De Benedetti, Facundo [1], Zamaloa, Maria Del Carmen [2], Gandolfo, Maria [3], Cuneo, Nestor [4]. Late Cretaceous heterosporous water ferns from Patagonia: assessing monomegaspory. Marsileaceae and Salviniaceae form a monophyletic group of heterosporous water ferns. Extant Marsileaceae comprises three genera (Marsilea, Regnellidium, and Pilularia) while Salviniaceae includes two genera (Azolla and Salvinia). Although the fossil record of water ferns starts at the Late Jurassic, they diversified during the late Cretaceous at the same time that the flowering plants, nevertheless after the K/pg boundary they rapidly declined in diversity. Their fossil record is mostly based on dispersed megaspores and microspores or microspore massulae encompassing many genera and species. Among these species, it is the Late Cretaceous Paleoazolla patagonica from Patagonia, Argentina, which was placed within Salviniaceae. The original diagnosis of Paleoazolla denotes that the megaspore apparatus has a single megaspore and a complex of three to four floats covered by multibarbed hairs, the microspore massulae contain numerous rounded microspores and have multibarbed glochidia. However, recently collected specimens and additional observations of the original material allow a new interpretation of Paleoazolla’s morphological and ultrastructural features. Our interpretation suggests that the heterosporangiate sorus is composed of one ellipsoidal megasporangium surrounded by three to four oval microsporangia; the megasporangium bears a single hairy massula that encloses two megaspores (rarely one or three) whereas the microsporangia contain numerous microspore massulae with non-septate multibarbed glochidia, and one microspore per massula. Based on this evidence, we propose that the homosporangiate sori of Azolla could have evolved from an early lineage of water ferns with heterosporangiate sori. Furthermore, the presence of two megaspores in Paleoazolla’s megasporangium definitely reveals critical gaps in our current knowledge on the evolution of monomegaspory in heterosporous water ferns and emphasizes the need for phylogenies including fossils for elucidating patterns of character acquisition. Log in to add this item to your schedule
1 - Museo Paleontológico Egidio Feruglio, Avenida Fontana 140, Trelew, U, 9100, Argentina 2 - Universidad De Buenos Aires, Ecologia, Genética Y Evolucion, Ciudad Universitaria. Pab 2. Piso 4, Buenos Aires, 1428, Argentina 3 - Cornell University, L.H. Bailey Hortorium, Section Of Plant Biology, 410 Mann Library Building, Ithaca, NY, 14853.0, United States 4 - MEF, Av. Fontana 140, Trelew-Chubut, U, 9100, Argentina
Keywords: water ferns fossil megaspores microspores Late Cretaceous Patagonia.
Presentation Type: Oral Paper Session: CK2, Cookson Award Session II Location: Tucson G/Starr Pass Date: Monday, July 29th, 2019 Time: 11:00 AM Number: CK2004 Abstract ID:117 Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award |