Nothofagus and the associated palynoflora from the Late Cretaceous of Vega Island, Antarctic Peninsula

Nothofagaceae fossil leaves and an associated palynoflora from Late Cretaceous sediments of Vega Island, eastern Antarctic Peninsula, are presented. The leaves are described as Nothofagus sp. 1 and Morphotype LDB 1, and come from the Snow Hill Island (late Campanian-early Maastrichtian) and the López de Bertodano (late Maastrichtian) formations, respectively. The palynoflora obtained from levels immediately above and below the Nothofagus sp. 1 and in the same horizon as the Morphotype LDB 1, included terrestrial and marine elements. In the palynoflora associated with Nothofagus sp. 1, conifers are dominant and pollen grains with Nothofagus affinity are represented by four species: Nothofagidites kaitangataensis (Te Punga) Romero 1973 and Nothofagidites senectus Dettmann and Playford 1968 which belong to the ancestral pollen type, as well as Nothofagidites dorotensis Romero 1973 and Nothofagidites sp. of the brassii-type. Cryptogamic spores, marine dinoflagellate cysts and algae, among others, are part of the assemblage. The palynoflora associated with the Morphotype LDB 1 also contains abundant conifer and angiosperm pollen grains with N. dorotensis as the only Nothofagus species recorded. Marine dinoflagellate cysts are scarce while fungi and phytodebris are common elements. The joint presence of marine and non-marine palynomorphs supports a probable nearshore environment at time of deposition for both units. Pollen and spore evidence suggests a mixed conifer and angiosperm forest, with Podocarpaceae and Nothofagus as the main components, and fern, lycopods, and mosses in the understory. This forest developed under temperate and moist conditions during the middle Campanian-Maastrichtian.Fil: Romero, Edgardo Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Rodriguez Amenabar, Cecilia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Cátedra de Paleontología; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Zamaloa, María C.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Concheyro, Graciela. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Cátedra de Paleontología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentin

Oldest Known Eucalyptus Macrofossils Are from South America

The evolutionary history of Eucalyptus and the eucalypts, the larger clade of seven genera including Eucalyptus that today have a natural distribution almost exclusively in Australasia, is poorly documented from the fossil record. Little physical evidence exists bearing on the ancient geographical distributions or morphologies of plants within the clade. Herein, we introduce fossil material of Eucalyptus from the early Eocene (ca. 51.9 Ma) Laguna del Hunco paleoflora of Chubut Province, Argentina; specimens include multiple leaves, infructescences, and dispersed capsules, several flower buds, and a single flower. Morphological similarities that relate the fossils to extant eucalypts include leaf shape, venation, and epidermal oil glands; infructescence structure; valvate capsulate fruits; and operculate flower buds. The presence of a staminophore scar on the fruits links them to Eucalyptus, and the presence of a transverse scar on the flower buds indicates a relationship to Eucalyptus subgenus Symphyomyrtus. Phylogenetic analyses of morphological data alone and combined with aligned sequence data from a prior study including 16 extant eucalypts, one outgroup, and a terminal representing the fossils indicate that the fossils are nested within Eucalyptus. These are the only illustrated Eucalyptus fossils that are definitively Eocene in age, and the only conclusively identified extant or fossil eucalypts naturally occurring outside of Australasia and adjacent Mindanao. Thus, these fossils indicate that the evolution of the eucalypt group is not constrained to a single region. Moreover, they strengthen the taxonomic connections between the Laguna del Hunco paleoflora and extant subtropical and tropical Australasia, one of the three major ecologic-geographic elements of the Laguna del Hunco paleoflora. The age and affinities of the fossils also indicate that Eucalyptus subgenus Symphyomyrtus is older than previously supposed. Paleoecological data indicate that the Patagonian Eucalyptus dominated volcanically disturbed areas adjacent to standing rainforest surrounding an Eocene caldera lake

New age constraints for the Salamanca Formation and lower Río Chico Group in the western San Jorge Basin, Patagonia, Argentina: Implications for Cretaceous-Paleogene extinction recovery and land mammal age correlations

The Salamanca Formation of the San Jorge Basin (Patagonia, Argentina) preserves critical records of Southern Hemisphere Paleocene biotas, but its age remains poorly resolved, with estimates ranging from Late Cretaceous to middle Paleocene. We report a multi-disciplinary geochronologic study of the Salamanca Formation and overlying Rio Chico Group in the western part of the basin. New constraints include (1) an 40Ar/39Ar age determination of 67.31 ± 0.55 Ma from a basalt flow underlying the Salamanca Formation, (2) micropaleontological results indicating an early Danian age for the base of the Salamanca Formation, (3) laser ablation HR-MC-ICP-MS (high resolution-multi collector-inductively coupled plasma-mass spectrometry) U-Pb ages and a high-resolution TIMS (thermal ionization mass spectrometry) age of 61.984 ± 0.041(0.074)[0.100] Ma for zircons from volcanic ash beds in the Penas Coloradas Formation (Rio Chico Group), and (4) paleomagnetic results indicating that the Salamanca Formation in this area is entirely of normal polarity, with reversals occurring in the Rio Chico Group. Placing these new age constraints in the context of a sequence stratigraphic model for the basin, we correlate the Salamanca Formation in the study area to Chrons C29n and C28n, with the Banco Negro Inferior (BNI), a mature widespread fossiliferous paleosol unit at the top of the Salamanca Formation, corresponding to the top of Chron C28n. The diverse paleobotanical assemblages from this area are here assigned to C28n (64.67–63.49 Ma), ∼2–3 million years older than previously thought, adding to growing evidence for rapid Southern Hemisphere floral recovery after the Cretaceous-Paleogene extinction. Important Peligran and “Carodnia” zone vertebrate fossil assemblages from coastal BNI and Penas Coloradas exposures are likely older than previously thought and correlate to the early Torrejonian and early Tiffanian North American Land Mammal Ages, respectively.Centro de Investigaciones Geográfica

Cretaceous-Paleocene Patagonian Spore and Pollen Clumps: New Findings, Alternative Explanations, and Opened Questions

There are few studies focused on spore and pollen clumps in paleopalynological samples, and these are only reports from the Northern Hemisphere. These aggregates may be of animal or floral origin. The goal of this contribution is to provide the first detailed study of spore and pollen clumps from the Southern Hemisphere, and to discuss their possible origin, botanical affinities, and pollination modes, based on their morphological characteristics, preservation and comparison with putative living representatives. Three fern spore clumps and 18 angiosperm pollen clumps were recognized in Maastrichtian-Danian La Colonia Formation sediments that outcrop at Chubut Province, Patagonia, Argentina. Most clumps are monospecific and composed of undamaged elements but some of them have two types of spore/pollen with corroded and/or fragmented exines. These findings represent the most diverse and abundant record of fern and angiosperm clumps from the Late Cretaceous and early Paleocene so far known from South America and the Southern Hemisphere. These results are indicative of the need for comprehensive large-scale studies on pollination of modern taxa and careful processing of palynological samples to lessen the already large bias in paleopalynological interpretations. The paucity of information on clumps in the fossil record has impaired our comprehension of dispersion/pollination in deep time.Fil: de Benedetti, Facundo. Museo Paleontológico Egidio Feruglio; Argentina. Cornell University; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zamaloa, María C.. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Gandolfo, María A.. Cornell University; Estados Unido

Late cretaceous aquatic plant world in Patagonia, Argentina.

In this contribution, we describe latest Cretaceous aquatic plant communities from the La Colonia Formation, Patagonia, Argentina, based on their taxonomic components and paleoecological attributes. The La Colonia Formation is a geological unit deposited during a Maastrichtian-Danian transgressive episode of the South Atlantic Ocean. This event resulted in the deposition of a series of fine-grained sediments associated with lagoon systems occurring along irregular coastal plains in northern Patagonia. These deposits preserved a diverse biota, including aquatic and terrestrial plants and animals. The aquatic macrophytes can be broadly divided into two groups: free-floating and rooted, the latter with emergent or floating leaves. Free-floating macrophytes include ferns in Salviniaceae (Azolla and Paleoazolla) and a monocot (Araceae). Floating microphytes include green algae (Botryoccocus, Pediastrum and Zygnemataceae). Among the rooted components, marsileaceous water ferns (including Regnellidium and an extinct form) and the eudicot angiosperm Nelumbo (Nelumbonaceae) are the dominant groups. Terrestrial plants occurring in the vegetation surrounding the lagoons include monocots (palms and Typhaceae), ferns with affinities to Dicksoniaceae, conifers, and dicots. A reconstruction of the aquatic plant paleocommuniy is provided based on the distribution of the fossils along a freshwater horizon within the La Colonia Formation. This contribution constitutes the first reconstruction of a Cretaceous aquatic habitat for southern South America

Pollen from the K–Pg boundary of the La Colonia Formation, Patagonia, Argentina

The La Colonia Formation, outcropping in northern Chubut Province (Patagonia, Argentina), is a Maastrichtian–Danian sequence deposited during a marine transgression of the South Atlantic Ocean. Its fine-grained sediments are associated with lagoon systems that preserved a very rich and diverse biota composed of invertebrates, vertebrates, plants, algae, and fungi. A palynological study was carried out based on 157 samples collected from four representative stratigraphic sections of this geological unit. The plant communities were dominated in terms of richness by ferns and angiosperms, but algae and gymnosperms were also well-represented. About 250 palynomorphs are recognized. The gymnosperms comprise 20 species including representatives of Araucariaceae, Cheirolepidiaceae, Ephedraceae, and Podocarpaceae while the angiosperms include 67 species within the families Araceae, Arecaceae, Aristolochiaceae, Asteraceae, Cannabaceae, Chlorantaceae, Cunoniaceae, Ericaceae, Gunneraceae, Juncaceae, Liliaceae, Malvaceae, Nelumbonaceae, Nothofagaceae, Proteaceae, and Typhaceae and several taxa of uncertain affinities. Here, we present the systematic study of the gymnosperm and angiosperm pollen components of the flora. Two new gymnosperm species and 22 new angiosperm species are erected. Additionally, we introduce the southernmost records of Triprojectacites and Normapolles groups even though their botanical relationships and origin remain unknown. The highly diverse palynoflora of the La Colonia Formation provides critical evidence for understanding the evolution of Southern Hemisphere floras and of certain clades and families and support the hypothesis that the effect of the mass extinction event was less significant at the southernmost portion of South America than in other parts of Earth.Fil: de Benedetti, Facundo. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zamaloa, María C.. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Gandolfo, Maria Alejandra. Cornell University; Estados UnidosFil: Cúneo, Néstor Rubén. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Spores and pollen organs representing free-floating aquatic macrophytes.

<p>A: <i>Azolla</i>-like megaspore (SEM) without floats preserved; MPEF-MEB 5505 (scale = 50 µm). B: <i>Azolla</i> microspore massula (SEM); BAFCB meb 263 (scale = 20 µm). C: <i>Paleoazolla patagonica</i> megaspore with floats preserved (SEM); MPEF-MEB 5506 (scale = 200 µm). D: <i>Paleoazolla patagonica</i> microspore massula (SEM); MPEF-MEB 5507 (scale = 10 µm). E: Araceae pollen grain (<i>Pandaniidites</i> sp.); BAFCB pm 259 (LM) (scale = 10 µm).</p

Map showing the location of the outcrops of the La Colonia Formation examined for this study in the Cerro Buitre and Arroyo Mirasol Chico areas.

<p>Modified after (101).</p

Free-floating microphyte components (chloroccocalean microalgae).

<p>A, B (SEM): <i>Pediastrum</i> spp.; BAFCB meb 262. C: <i>Botryoccocus</i> sp. (SEM); BAFCB meb 262. D, E: Zygnemataceae spores (LM); BAFCB pm 260. Scales A, B, C = 1000 µm; D, E = 10 µm.</p