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A Paleogene trans-Antarctic distribution for Ripogonum (Ripogonaceae: Liliales)?

Raymond J. Carpenter, Peter Wilf, John G. Conran, and N. Rubén Cúneo

Plain Language Abstract

There is great interest in Southern Hemisphere organisms that have close relatives distributed on lands now separated by vast distances of ocean. For many of these taxa, these distributions could have been established millions of years ago when land connections and suitably ice-free climates existed across the Antarctic region, and in many cases there is strong fossil evidence to support this idea. Here we present fossil leaves of the Australasian monocotyledonous angiosperm Ripogonum, a woody understory plant, from the early Eocene of Patagonia, Argentina. Similar fossils have been described from early Eocene sediments of Tasmania, Australia, and have been discovered recently in early Eocene New Zealand deposits, and the closest relatives of Ripogonum still occur in wet forests of southern South America. These facts support estimates from molecular evidence that Ripogonum and its close relatives diverged in or before the early Eocene and, because Antarctica lay between and was still adjacent to Australia and South America during the early Eocene, suggest that Ripogonum was part of the Antarctic vegetation at this time.

Resumen en Español

¿Una distribución trans-antártica durante el Paleógeno para Ripogonum (Ripogonaceae: Liliales)?

En rocas sedimentarias del Paleógeno de las zonas meridionales de Australia y Sudamérica se está encontrando una impresionante y creciente lista de taxones de plantas y animales interesantes desde un punto de vista biogeográfico, indicando distribuciones trans-antárticas durante el pasado cálido. Se aporta la primera evidencia de que las monocotiledóneas lechosas de Australasia del género existente Ripogonum, estuvieron presentes durante el Eoceno temprano en la Patagonia, Argentina. Dos ejemplares fósiles de hojas están lo suficientemente bien conservados en su forma general, su tamaño original y en los detalles más finos de su venación como para ser asignados al género, de forma que pueden ser estrechamente comparados con las hojas de las especies actuales R. album y R. scandens y de la especie recientemente descrita del Eoceno temprano de Tasmania, Australia, R. tasmanicum. Se describe la nueva especie R. americanum. En general, esta evidencia sugiere que Ripogonum tenía un pasado más amplio, incluyendo la Antártida, durante el Paleógeno temprano, cuando la Antártida estaba mucho más estrechamente conectada tanto a Tasmania como a Sudamérica, y los climas de latitudes altas eran cálidos y húmedos. Ecológicamente, el Ripogonum sudamericano fue probablemente una vid trepadora en un bosque mésico que creció en asociación con una rica flora de sotobosque de helechos y angiospermas.

Palabras clave: Argentina; Australasia; Eoceno; Liliales; nueva especie; Ripogonum

Traducción: Enrique Peñalver

Résumé en Français

Une distribution transantarctique au Paléogène pour Ripogonum (Ripogonaceae: Liliales)?

Une liste impressionnante et croissante de taxons de plantes et d'animaux biogéographiquement intéressants se produit dans des sédiments du Paléogène à la fois au sud de l'Australie et au sud de l'Amérique du Sud, indiquant une distribution transantarctique pendant un passé chaud. Ici, nous fournissons la première évidence que le monocotylédone Australo-Asiatique boisé vivant, Ripogonum était présent lors de l'Éocène inférieur de la Patagonie, en Argentine. Deux feuilles fossiles sont suffisamment bien conservés, en tant que forme générale, taille et détails de nervures fines, afin d'être assigné au genre, étant étroitement comparable aux feuilles des espèces existantes R. album et R. scandens et l'espèce de l'Éocène inférieur récemment décrites R. tasmanicum, provenant de la Tasmanie, en Australie. La nouvelle espèce, R. americanum, est décrite. Dans l'ensemble, cette évidence suggère que Ripogonum avait une étendue beaucoup plus importante dans le passé, y compris en Antarctique, au début du Paléogène, quand l'Antarctique était beaucoup plus étroitement connectée à la fois à la Tasmanie et l'Amérique du Sud et les climats des latitudes élevées étaient chaud et humide. Écologiquement, Ripogonum de l'American du Sud était probablement une vigne de grimpeuse dans une forêt mésique et a grandi en association avec une flore riche de sous-étage de fougères et d'angiospermes.

Mots-clés: Argentine; Australasie; Eocène; Liliales; nouvelles espèces; Ripogonum

Translator: Kenny J. Travouillon

Deutsche Zusammenfassung

Eine paläogene trans-antarktische Verbreitung von Ripogonum (Ripogonaceae: Liliales)?

Aus paläogenen Sedimenten des südlichen Australien sowie des südlichen Südamerika tritt eine beeindruckende und wachsende Liste von biogeografisch interessanten Pflanzen-und Tiertaxa auf, die auf eine trans-antarktische Verbreitung in der warmen erdgeschichtlichen Vergangenheit hindeutet. Hier liefern wir den ersten Nachweis, dass das lebende verholzende australasiatische einkeimblättrige Ripogonum während des frühen Eozäns in Patagonien, Argentinien, vorkam. Zwei fossile Blätter sind ausreichend in ihrer Gesamtform, Größe und den feinen Aderdetails erhalten, so dass sie dieser Gattung zugeteilt werden können. Sie sind vergleichbar mit den Blättern der heutigen Arten R. album und R. scandens und mit der erst kürzlich beschriebenen früheozänen Art R. tasmanicum aus Tasmanien, Australien. Die neue Art, R. americanum wird beschrieben. Insgesamt legt dieser Beleg nahe, dass Ripogonum während des frühen Paläogen, als Antarktika noch viel enger mit Tasmanien und Südamerika verbunden war und das Klima in den hohen Breiten warm und feucht war, eine erheblich größere Verbreitung hatte, inklusive Antarktika. Ökologisch gesehen war das südamerikanische Ripogonum wahrscheinlich eine Kletterpflanze in einem mesischen Wald, die in Verbindung mit einer reichen Unterholz-Flora aus Farnen und Angiospermen wuchs.

Schlüsselwörter: Argentinien; Australasien; Eozän; Liliales; neue Arten; Ripogonum

Translator: Eva Gebauer

Arabic

460 arab

Translator: Ashraf M.T. Elewa

 

 

carpenterRaymond J. Carpenter
School of Earth and Environmental Sciences
Benham Bldg DX 650 312
University of Adelaide
South Australia 5005
Australia and School of Plant Science
University of Tasmania
Private Bag 55
Hobart, Tasmania 7001
Australia
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I am interested in all aspects of ecosystem evolution in the Southern Hemisphere, and especially the importance of the leaf fossil record of the latest Cretaceous and Cenozoic. I have worked on fossil assemblages from across Australia, and also in New Zealand and Patagonia, with a focus on the iconic family Proteaceae. My favourite places to visit for inspiration are New Caledonia and Tasmania, as well as the remnant rainforest pockets of eastern mainland Australia. 

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wilfPeter Wilf
Department of Geosciences
Pennsylvania State University
University Park, Pennsylvania 16802
United States of America
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After an eclectic and non-geological undergrad career (B.A. Penn 1985), I spent three years teaching junior high school in New Jersey and then four years freelancing with my guitars in West Philly. I discovered geology and then paleobotany at the early age of 29 and have never looked back. I somehow moved from the street, almost literally, onto the doctoral track in Penn Geology and defended in 1998. Most of my thesis research was done in residence at the Smithsonian, on megafloral and paleoclimatic change across the Paleocene-Eocene boundary in southern Wyoming. During this time and in an ensuing Smithsonian postdoc, I began developing two major subsequent themes of my research: the fossil history of plant-insect associations and the unbelievable riches of Patagonian fossil floras. I spent three terrific years at Michigan, 1999-2002, as a Michigan Fellow and happily joined the Penn State Geosciences faculty in 2002, where I have been developing these and several other wonderful research projects with my students and colleagues all over the world.

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conranJohn G. Conran
Australian Centre for Evolutionary Biology and Biodiversity
School of Earth and Environmental Sciences
Benham Bldg DX 650 312
University of Adelaide
South Australia 5005
Australia
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My major research interests are in exploring the evolution and ecology of major Australasian plant groups such as petaloid monocots, carnivorous plants, Podocarpaceae and Lauraceae. I am particularly interested in the fossil record for monocots and their biogeography, but also study Late Cretaceous and Cenozoic palaeofloras in southern Australia and New Zealand, applying techniques such as total evidence and parsimony analysis to fossil identification and phylogenetic placement, as well as palaeoecology and past climate reconstruction.

 

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cuneoN. Rubén Cúneo
Museo Paleontológico Egidio Feruglio
Consejo Nacional de Investigaciones Científicas y Técnicas
Trelew 9100, Chubut
Argentina
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My research interests are directed to expanding the knowledge of fossil plant groups found in the Patagonia Territory of southern Argentina, from the late Paleozoic through the Eocene, with special focus on the Permian, Jurassic, late Cretaceous and early Eocene. Of particular interest are the systematic, phylogeny and biogeography of early and modern conifers, ferns and ginkgophytes, as well as their paleoecological significance and paleoclimatic importance.

 

FIGURE 1. Ripogonum americanum sp. nov. from Laguna del Hunco and extant R. album, 1, holotype MPEF-Pb 6438a. Note that although the petiolar region is not preserved, a decurrent pair of suprabasal secondary veins and basal pair of submarginal veins are clearly visible. Note also the tertiary veins, higher order reticulate venation, vein loops between the secondary vein pairs, and looped ultimate veins at the margins (arrowed); 2, BRI specimen AQ845060 from Queensland, Australia. Note virtually identical details to those visible in the fossils (Figure 1.1, Figure 2). Scale bars equal 10 mm.

figure 1

FIGURE 2. Ripogonum americanum sp. nov. from Laguna del Hunco, 1, holotype MPEF-Pb 6438b; 2, paratype MPEF-Pb 6439. Note details as described for Figure 1.1. Examples of clearly preserved looped ultimate veins near the leaf margins are arrowed. Scale bars equal 10 mm.

figure 2

FIGURE 3. Geographic configuration (Mollweide projection) at 52 Ma showing early Eocene records (*) of Ripogonum. AUS = Australia, NZ = New Zealand, ANT = Antarctica, SAM = South America. Reconstruction made using the ODSN Plate Reconstruction Service (www.odsn.de/odsn/services/paleomap/paleomap.html).

figure 3