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Abstract Detail



Paleobotanical Section

Hermsen, Elizabeth J. [1], Gandolfo, Maria A, [2], Zamaloa, Maria [3], Cuneo, Nestor [4].

Morphology of Azolla-like sporophytes and associated spores from the Late Cretaceous of Patagonia, Argentina.

Macrofossil vegetative and reproductive remains of an Azolla-like sporophyte have recently been identified from the Cañadón del Irupé locality of the Campanian to Maastrichtian middle facies assemblage of the La Colonia Formation, north-central Chubut Province, Argentina. This locality is known to yield a variety of other terrestrial and aquatic plants, the latter including marsileaceous fern remains (compound leaves and sporocarps) and the angiosperm Nelumbo puertae with associated nelumbonaceous reproductive structures. The Azolla-like plant consists of stems bearing roots, alternately arranged lateral branches, and alternately arranged simple leaves. Sori (sensu N. Nagalingum, H. Schneider, and K.M. Pryer, 2006; sporocarps of many other authors) are attached to some specimens, although, given the preservation of the associated vegetative organs, it is difficult to determine their precise position of attachment to the sporophyte. Megasporangiate sori occur individually or in groups of two to three; each is stalked and ovate in shape, with an indusium coming to a point at its apex. The microsporangiate sori are circular in shape and larger than the megasporangiate sori; each microsporangiate sorus has a a number of microsporangia, each presumbaly cotaining a massula of microspores. The ornamentation of the in situ microspore massulae could not be observed. Megaspores with morphology similar to that of Palaeoazolla patagonica A. Archangelsky, C.J. Phipps, T.N. Taylor & E.L. Taylor, described from the Cerro Buitre locality of the La Colonia Formation in 1999, were found dispersed in the same matrix as the sporophytes. SEM’s of megaspores macerated from the matrix show that, like P. patagonica, they have no collar, no column, and a fibrous surface. No evidence of multibarbed glochidia was seen. Microspore massulae macerated from sediments sampled from Cañadón del Irupé and the nearby Cerro Bosta locality have attached glochidia with anchor-shaped tips but no additional barbs. Thus, these spores are different from those of P. patagonica. The lack of a column and collar on the associated megaspores suggests that they do not belong within the clade formed by extant Azolla, and, therefore, that the sporophytes probably do not, either. The Azolla-like sporophytes from Cañadón del Irupé are among the oldest macrofossil evidence of Salviniaceae. Maastrichtian Azolla-like organs are also known as petrifactions from India.

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1 - Ohio University, Department of Environmental and Plant Biology, Porter Hall, Athens, OH, 45701, USA
2 - Cornell University, L. H. BAILEY HORTORIUM, 410 Mann Library Building, ITHACA, NY, 14853-4301, USA, 607/255-3273
3 - Universidad De Buenos Aires, Laboratorio De Paleobotanica, Intendente Guiraldes 2620 Pabellon 2, FCEN, Buenos Aires, 1248, Argentina
4 - MEF AV. FONTANA 140, TRELEW-CHUBUT, N/A, 9100, Argentina

Keywords:
Salviniaceae
Azolla
Palaeoazolla
spores
Cretaceous
fossil
fern
aquatic.

Presentation Type: Oral Paper:Papers for Sections
Session: 44
Location: Prince of Wales/Riverside Hilton
Date: Wednesday, July 31st, 2013
Time: 1:30 PM
Number: 44001
Abstract ID:201
Candidate for Awards:None


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