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Abstract Detail

Paleobotanical Section

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

Marsileaceaephyllum leaflets and associated sporocarps and spores from the Cañadón del Irupé locality, Upper Cretaceous La Colonia Formation, Chubut Province, Argentina.

Marsileaceae Mirbel is a family of heterosporous, aquatic ferns that includes three genera: the large genus Marsilea L. is currently thought to form a clade sister to the clade formed by the small genus Pilularia L. and the monotypic genus Regnellidium Lindman. Here, we present new material representing fossil Marsileaceae from the Cañadón del Irupé locality of the La Colonia Formation, Upper Cretaceous (Campanian-Maastrichtian), Chubut Province, Argentina. This material includes leaflets, associated sporocarps, and dispersed megaspores and a microspore massula with affinities to Marsileaceae. The leaflets are Marsilea-like and conform to the form genus Marsileaceaephyllum Nagalingum. The leaflets are sometimes found paired; they are reniform and have reticulate venation. Associated sporocarps are found isolated or attached to stalks; the sporocarp wall has a prominent sclerenchymatous region, as is typical of Marsileaceae. Each sporocarp has its own stalk, and these are arranged linearly on either side of a common stalk. Notably, the sporocarps have a raphe, a feature found only in some species of extant Marsilea.The megaspores associated with the fossils conform to the dispersed spore taxon Molaspora Schemel, a widespread, primarily Upper Cretaceous taxon which is morphologically highly similar to the megaspores of extant Regnellidium. Given differences between the Cañadón del Irupé sporocarps and other fossil sporocarps, we interpret the Patagonian sporocarps as representing a new, extinct taxon. The material found in the Cañadón del Irupé locality is important because, together with fossils assigned to Regnellidium presented at this meeting (see abstract by Cúneo et al.), they represent the first report of Molaspora from South America and only the second report of marsileaceous macrofossil remains (the other report is from Brazil). Interestingly, the Cañadón del Irupé material is consistent with a previously recognized pattern whereby various non-Regnellidium-type marsileaceous vegetative and reproductive structures are associated with Molaspora (Regnellidium-like) megaspores in the Cretaceous.

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1 - Cornell University, Department of Plant Biology, 412 Mann Library Building , Ithaca, NY, 14853, USA
2 - Cornell University, L. H. BAILEY HORTORIUM, 410 Mann Library Building, ITHACA, NY, 14853-4301, USA
3 - MEF AV. FONTANA 140, TRELEW-CHUBUT, N/A, 9100, Argentina


Presentation Type: Oral Paper:Papers for Sections
Session: 46
Location: Union A/Hyatt
Date: Wednesday, July 11th, 2012
Time: 9:00 AM
Number: 46004
Abstract ID:549

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