María del Carmen Zamaloa

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.

Casuarinaceae from the Eocene of Patagonia, Argentina

Casuarinaceae, today restricted to the Australasian region, has an extensive fossil record. In this article, we evaluate previous records and recent findings from Patagonia, where Casuarinaceae are known from the Tufolitas Laguna del Hunco (early Eocene) in northwestern Chubut, Argentina. Based on characters found in numerous branchlets, infructescences, and male inflorescences with pollen of the Haloragacidites harrisii type, the presence of three fossil species within the genus Gymnostoma is confirmed: G. patagonicum comb. nov., G. archangelskyi sp. nov., and G. argentinum sp. nov. This is the oldest worldwide report of male inflorescences and the first record of vegetative branchlets and male inflorescences for South America. These fossils are of particular interest because Casuarinaceae is now extinct in South America, and they support the view that the family was diverse and had widespread distribution during the early Eocene climatic optimum. The diverse Gymnostoma described here further strengthens biogeographic links between Paleogene floras of Patagonia and Australasia.

The fossil record of Eucalyptus in Patagonia.

PREMISE OF THE STUDY Herein, we name, describe, and illustrate new macrofossil material representing Eucalyptus (Myrtaceae: Myrtoideae, Eucalypteae) from the diverse early Eocene Laguna del Hunco (LH) flora of Chubut Province, Patagonia, Argentina. We explore the significance of these fossils in light of understanding the fossil record of eucalypts and the biogeography of the Eucalypteae. METHODS Fossils representing vegetative and reproductive organs were collected from multiple LH localities over several field seasons. These specimens were prepared, photographed, and compared to extant Eucalyptus. Additional historical collections of Patagonian fossil Eucalyptus were also examined. KEY RESULTS Vegetative and reproductive organs representing five different Eucalyptus taxa were identified in the LH paleoflora. One new taxon each representing leaves, flower buds, and infructescences with co-occurring, isolated capsules are described and named as new Eucalyptus species. Additionally, two flower types cf. Eucalyptus, represented by one specimen each, are illustrated and briefly described. The fossil species have unique characteristics that independently suggest each belongs within the Eucalypteae. The reproductive material is most similar morphologically to extant Eucalyptus, although it also shares many similarities to the closely related genus Corymbia. CONCLUSIONS The LH fossil Eucalyptus material is among the few eucalypt macrofossils that have recently been named and described and are the oldest macrofossils that can presently be definitively ascribed to the Eucalypteae. They also represent the only credible description of Eucalyptus fossils occurring outside of Australasia and suggest a once broader geographic distribution for this group.

Revision of the Proteaceae Macrofossil Record from Patagonia, Argentina

Proteaceae are restricted to the Southern Hemisphere, and of the seven tribes of the subfamily Grevilleoideae, only three (Macadamieae, Oriteae, and Embothrieae) have living members in Argentina. Megafossil genera of Proteaceae recorded from Patagonia includeLomatia, Embothrium, Orites, andRoupala. In this report, we evaluate and revise fossil Argentine Proteaceae on the basis of type material and new specimens. The new collections come from the Tufolitas Laguna del Hunco (early Eocene, Chubut Province), the Ventana (middle Eocene, Río Negro Province), and the Río Ñirihuau (late Oligocene-early Miocene, Río Negro Province) formations, Patagonia, Argentina. We confirm the presence ofLomatia preferruginea Berry,L. occidentalis (Berry) Frenguelli,L. patagonica Frenguelli,Roupala patagonica Durango de Cabrera et Romero, andOrites bivascularis Romero, Dibbern et Gandolfo. Fossils assigned toEmbothrium precoccineum Berry andE. pregrandiflorum Berry are doubtful, and new material is necessary to confirm the presence of this genus in the fossil record of Patagonia. A putative new fossil species of Proteaceae is presented as Proteaceae gen. et sp. indet. Fossil Proteaceae are compared with modern genera, and an identification key for the fossil leaf species is presented. Doubtful historical records of Proteaceae fossils for the Antarctic Peninsula region and Patagonia are also discussed. Based on this revision, the three tribes of Proteaceae found today in Argentina were already present in Patagonia by the early Eocene, where they probably arrived via the Australia-Antarctica-South America connection.ResumenLa familia Proteaceae está restringida al Hemisferio Sur, y en Argentina sólo tres (Macadamieae, Oriteae y Embothrieae) de las siete tribus de la subfamilia Grevilleoideae están representadas. En Patagonia, megafósiles asignados a Proteaceae incluyen los génerosLomatia, Embothrium, Orites yRoupala. En este trabajo, se evalúan y revisan todos los registros fósiles de Proteaceae para Argentina basados en el material tipo y en nuevos especímenes. Las nuevas colecciones fueron realizadas en las formaciones Tufolitas Laguna del Hunco (Eoceno Temprano, Provincia del Chubut), Ventana (Eoceno Medio, Provincia de Río Negro) y Río Ñirihuau (Oligoceno Tardío-Mioceno Temprano, Provincia de Río Negro), Patagonia, Argentina. Se confirma la presencia deLomatia preferruginea Berry,L. occidentalis (Berry) Frenguelli,L. patagonica Frenguelli, Roupala patagonica Durango de Cabrera et Romero, andOrites bivascularis Romero, Dibbern et Gandolfo. Los fósiles asignados aEmbothrium precoccineum Berry andE. pregrandiflorum Berry son dudosos, y nuevo material es necesario para confirmar la presencia de este género en el registro fósil de Patagonia. Una posible nueva especie fósil es presentada como Proteaceae gen. et sp. indet. Los fósiles asignados a Proteaceae son comparados con géneros modernos, y se proporciona una clave para la identification de las especies fósiles. Los registros fósiles históricos dudosos de Proteaceae para la región de la Península Antártica y Patagonia son también discutidos. Basados en esta revisión, las tres tribus de Proteaceae que se hallan hoy en Argentina se encontraban ya presentes en Patagonia durante el Eoceno temprano, donde probablemente arribaron vía la conección Australia-Antártida-Sudamérica.

Early Eocene 40Ar/39Ar age for the Pampa de Jones plant, frog, and insect biota (Huitrera Formation, Neuquén Province, Patagonia, Argentina)

Abstract. The Pampa de Jones fossil site, a stratigraphically isolated roadcut near the northeastern shore of Nahuel Huapi Lake in Neuquén Province, Argentina, holds a rich fossil biota including a macroflora, a microflora, insects, and most famously, an ontogenetic series of pipid frogs. The site exposes tuffaceous mudstone and sandstone beds of probable lacustrine origin, considered to belong to the volcanic Huitrera Formation. However, there have been no reliable age constraints for the fossil assemblage. We undertook laser fusion analyses of sanidine and biotite crystals occurring in a tuff layer found 4.4 m above the main fossil horizon. Twenty-eight sanidine crystals yielded an 40Ar/39Ar age of 54.24 ± 0.45 Ma that is preferred over our biotite age of 53.64 ± 0.35 Ma. Pampa de Jones is thus the oldest well-dated Eocene fossil site in Patagonia, predating two other recently 40Ar/39Ar-dated sites: Laguna del Hunco (51.91 ± 0.22 Ma) and Río Pichileufú (47.46 ± 0.05 Ma). The improved age control makes possible a finer scale of evolutionary hypothesis testing and turnover analysis in the region. The age is concordant with the sites placement in the Huitrera Formation and a depositional origin related to Early Paleogene arc volcanism, and it correlates to an interval of significant climate fluctuations following the Paleocene-Eocene boundary.

Miocene algae and spores from Tierra del Fuego, Argentina

Continental deposits of the Cullen Formation (early or middle Miocene) exposed on the northeast coast of Isla Grande de Tierra del Fuego (southernmost Patagonia) are analyzed. Twenty-four taxa of algae, and bryophyte and pteridophyte spores are identified, including three new species, which are Anthocerisporis gandolfii sp. nov., Coptospora archangelskyi sp. nov. and Ophioglossisporites cullensis sp. nov. Sedimentologic and palynological data suggest a system of meandering water channels. The diverse and abundant spore assemblage reinforces the proposed paleoenvironment indicated by pollen assemblage and stratigraphy, consisting of humid temperate forests and local occurrences of bog, freshwater and near-shore lake communities.

Potamogetonaceae Fossil Fruits from the Tertiary of Patagonia, Argentina

The subcosmopolitan and aquatic monocot family Potamogetonaceae Berch. and J. Presl 1823 comprises extant and fossil genera. Its known fossil record is composed mainly of fruit remains, and it comes only from Eocene to Pliocene sediments of the Northern Hemisphere (Europe, Saudi Arabia, and China). Recently, several fruits sharing characters with living and fossil Potamogetonaceae genera have been found within the Paleogene Baibián Beds, Chubut, Patagonia, Argentina. Fossils were collected at the Puesto Baibián locality, which outcrops at the eastern sector of the Sierra de La Colonia. Fossils are impressions/compressions of infructescences and isolated fruits and seeds preserved as molds and casts. The infructescences are probably racemes bearing fruits placed most likely in whorls of four each. Isolated fruits are small one‐seeded bisymmetrical endocarps. Palynological studies of the beds show the presence of an assemblage similar to those found in sediments of the Northern Hemisphere where Potamogetonaceae fossil fruits were previously recorded. This report constitutes the first fossil record of Potamogetonaceae for the Southern Hemisphere.

Pollen morphology and fossil record of the feathery mistletoe family Misodendraceae

Abstract Misodendraceae is a small family of mistletoes in the order Santalales. Its distribution is restricted to the southern South American temperate forests. The family comprises the sole genus Misodendrum with eight species of hemiparasitic shrubs, mainly parasitising the southern beech Nothofagus. This contribution presents palynological evidence from seven species, using light microscopy and scanning electron microscopy. Pollen grains are consistently small, periporate and echinate, although differences in the length of echini and number and size of pores were noted. Pollen features can be used to distinguish groups of species and, in some cases, individual species. Cluster analysis of pollen characters differentiates two main groups: one includes M. brachystachyum, M. oblongifolium and M. quadriflorum; and the other includes M. gayanum, M. linearifolium, M. punctulatum and M. angulatum. Palynological results are compared with previous systematic studies of the family. The South American fossil pollen record is summarised and characters of the fossil pollen are analysed using UPGMA to test the relationships between extant and fossil species. Miocene pollen resulted similar to species of subgenus Angelopogon while Eocene pollen is disimilar to extant species of Misodendraceae.

FLORA ANGIOSPÉRMICA DE PICO QUEMADO, FORMACIÓN ÑIRIHUAU (OLIGOCENO TARDÍO), PROVINCIA DE RÍO NEGRO, ARGENTINA

Abstract ANGIOSPERM FLORA OF PICO QUEMADO, ÑIRIHUAU FORMATION (LATE OLIGOCENE), RÍO NEGRO PROVINCE, ARGENTINA. Pico Quemado is located East of San Carlos de Bariloche, and stratigraphically placed in the lower member of the Ñirihuau Formation (late Oligocene — middle early Miocene). Fossil leaves (compressions and / or impressions) of dicotyledonous angiosperms were studied and twenty two morphotypes are described. The families identified were Nothofagaceae, Myrtaceae, Rosaceae, Myricaceae, Malvaceae and Fabaceae and the genus Nothofagus Blume was found to be the dominant. The macroflora is compared with twenty two tertiary paleofloras from Patagonia, and similarity indices obtained by the Jaccard coefficient, yielded values less than 13 %. This low index could be explained as due to the younger age of the Pico Quemado paleoflora compared to most of the other paleofloras and/ or because it thrived at a lower paleolatitude. The paleofloristic analysis suggests a temperate to cold-temperate climate and no analogous vegetation among other known Patagonian fossil floras.