A new vesselless angiosperm stem with a cambial variant from the Upper Cretaceous of Antarctica

We sectioned a permineralized stem preserved in marine calcareous concretions from the Campanian (Upper Cretaceous) of James Ross Island, Antarctic Peninsula using the cellulose-acetate peel technique. The material is a slender stem displaying a combination of characters such as: (i) absence of vessels and axial parenchyma, (ii) presence of a cambial variant which produces axial vascular elements in segments (AVES pattern), and (iii) elongated upright ray cells. This character combination allows us to assign this fossil to family Chloranthaceae and to relate it to an extant genus Sarcandra. Consequently we describe Sarcandraxylon sanjosense gen. et sp. nov., representing the first vegetative fossil of Chloranthaceae—a basal angiosperm family with a fossil record extending back into the Early Cretaceous and dominated by pollen grains and a limited number of reproductive mesofossils. Besides doubtfully assigned leaves, there are no reported Cretaceous macrofossils of Chloranthaceae, which hinders our understanding of the overall pattern of morphological evolution for the family. The new fossil constitutes the first fossil occurrence of the Sarcandra clade in high latitudes of Western Gondwana. The particular wood anatomy and small diameter suggest a new plant habit (sub-shrub) for the physiognomy of the Cretaceous Antarctic floras.Fil: Pipo, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Iglesias, Ari. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Bodnar, Josefina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Área Paleobotánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin

Patagonia’s diverse but homogeneous early paleocene forests: Angiosperm leaves from the Danian Salamanca and Peñas Coloradas formations, San Jorge Basin, Chubut, Argentina

Early Paleocene macrofloras from the Southern Hemisphere are little known, despite their significance for understanding plant evolution, biogeography, and global variation in recovery after the end-Cretaceous extinction. As a foundation for systematic and paleoecological work, we describe 51 angiosperm leaf morphotypes from three distinct, precisely dated early to late Danian time intervals, using collections from the Salamanca and Peñas Coloradas formations in the San Jorge Basin, Chubut Province, Patagonia, Argentina. These rich floras were previously analyzed but with minimal descriptions. The assemblages comprise the first stratigraphically controlled and quantitatively collected floras for the early Paleocene of the Southern Hemisphere. Botanical affinities of the angiosperm morphotypes are not formally assigned here, but we informally associate some of them with families including Arecaceae, Fabaceae, Cunoniaceae, Lauraceae, Nothofagaceae, Rhamnaceae, and Rosaceae; in addition, leaves of Menispermaceae and other Rhamnaceae were formally described in previous work. Other families potentially present in these assemblages include Akaniaceae, Anacardiaceae, Apiaceae, Araceae, Bixaceae, Juglandaceae, Malvaceae, Sapindaceae, and Urticaceae. Remarkably, there is little floral turnover or change in dominance through the Danian floral sequence spanned by the studied localities, even among estuarine vs. continental depositional environments. This finding indicates a homogeneous, generalist, long-lived floral association following the K-Pg extinction, similar in these respects to many North American Danian floras. However, the richness of the Danian Patagonian floras, from paleolatitudes >50 degrees South, along with other lines of evidence from the region, suggests differences in the response of terrestrial ecosystems in southern South America to the terminal Cretaceous event from those of the Northern Hemisphere. The flora appears to be largely paleo-endemic in nature and shows several compositional links to the Eocene floras of Patagonia, emphasizing the importance of diversification within Patagonia after the end-Cretaceous event as a factor leading to the hyperdiverse Eocene regional floras.Fil: Iglesias, Ari. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Wilf, Peter. State University of Pennsylvania; Estados UnidosFil: Stiles, Elena. State University of Pennsylvania; Estados Unidos. University of Washington; Estados UnidosFil: Wilf, Rebecca. State University of Pennsylvania; Estados Unido

The evolution of Patagonian climate and vegetation from the Mesozoic to the present

In this review, Patagonian phytogeographical patterns are analysed from a global and evolutionary perspective that takes into account aspects from the geology, climatology and plant evolution. The biomes contained within the different climatic belts are inferred through time for the southwestern Gondwana supercontinent on the basis of palaeogeographical reconstructions, climate-sensitive rocks and plant distribution. Some current plant components of Patagonia can be traced back to early Mesozoic times, to the Triassic and Jurassic mesophytic floras. The main features of the Cretaceous and Palaeogene Patagonian floras are described and compared with other Gondwanic areas that shared, at the time, more plant components than they do today. The Neogene floras are analysed in relation to the rise of the Andes and the global climatic cooling, which differentiated the Andean and the Extra-Andean regions, and ended in the modern cool-temperate Andean forest and the arid steppe.En esta revisión se analizan, desde una perspectiva evolutiva y a una escala global, los patrones fitogeográficos de Patagonia tomando en cuenta la evolución vegetal y aspectos geológicos y climáticos. Se infieren los biomas del pasado en relación con las franjas climáticas para el sector sudoccidental de Gondwana, basados en la distribución de plantas, rocas climato-sensitivas y reconstrucciones palaeogeográficas. Algunos componentes de la vegetación actual de Patagonia pueden retrotraerse hasta el Mesozoico Temprano, en las floras mesofíticas del Triásico y Jurásico. Se describen los caracteres generales de las floras del Cretácico y Paleógeno, se comparan con las de otras áreas de Gondwana y se verifica que compartían mayor cantidad de componentes vegetales que las actuales. Las floras del Neógeno son analizadas en relación con el levantamiento de los Andes y el enfriamiento climático global, que diferenciaron la región andina de la extra-andina y que culminó en la formación del Bosque Andino templado-frío y la Estepa árida.Facultad de Ciencias Naturales y Muse

The evolution of Patagonian climate and vegetation from the Mesozoic to the present

In this review, Patagonian phytogeographical patterns are analysed from a global and evolutionary perspective that takes into account aspects from the geology, climatology and plant evolution. The biomes contained within the different climatic belts are inferred through time for the southwestern Gondwana supercontinent on the basis of palaeogeographical reconstructions, climate-sensitive rocks and plant distribution. Some current plant components of Patagonia can be traced back to early Mesozoic times, to the Triassic and Jurassic mesophytic floras. The main features of the Cretaceous and Palaeogene Patagonian floras are described and compared with other Gondwanic areas that shared, at the time, more plant components than they do today. The Neogene floras are analysed in relation to the rise of the Andes and the global climatic cooling, which differentiated the Andean and the Extra-Andean regions, and ended in the modern cool-temperate Andean forest and the arid steppe.En esta revisión se analizan, desde una perspectiva evolutiva y a una escala global, los patrones fitogeográficos de Patagonia tomando en cuenta la evolución vegetal y aspectos geológicos y climáticos. Se infieren los biomas del pasado en relación con las franjas climáticas para el sector sudoccidental de Gondwana, basados en la distribución de plantas, rocas climato-sensitivas y reconstrucciones palaeogeográficas. Algunos componentes de la vegetación actual de Patagonia pueden retrotraerse hasta el Mesozoico Temprano, en las floras mesofíticas del Triásico y Jurásico. Se describen los caracteres generales de las floras del Cretácico y Paleógeno, se comparan con las de otras áreas de Gondwana y se verifica que compartían mayor cantidad de componentes vegetales que las actuales. Las floras del Neógeno son analizadas en relación con el levantamiento de los Andes y el enfriamiento climático global, que diferenciaron la región andina de la extra-andina y que culminó en la formación del Bosque Andino templado-frío y la Estepa árida.Facultad de Ciencias Naturales y Muse

Fossil flowers from the early Palaeocene of Patagonia, Argentina, with affinity to Schizomerieae (Cunoniaceae)

Background and Aims: Early Palaeocene (Danian) plant fossils from Patagonia provide information on the recovery from the end-Cretaceous extinction and Cenozoic floristic change in South America. Actinomorphic flowers with eight to ten perianth parts are described and evaluated in a phylogenetic framework. The goal of this study is to determine the identity of these fossil flowers and to discuss their evolutionary, palaeoecological and biogeographical significance. Methods: More than 100 fossilized flowers were collected from three localities in the Danian Salamanca and Peñas Coloradas Formations in southern Chubut. They were prepared, photographed and compared with similar extant and fossil flowers using published literature and herbarium specimens. Phylogenetic analysis was performed using morphological and molecular data. Key results: The fossil flowers share some but not all the synapomorphies that characterize the Schizomerieae, a tribe within Cunoniaceae. These features include the shallow floral cup, variable number of perianth parts arranged in two whorls, laciniate petals, anthers with a connective extension, and a superior ovary with free styles. The number of perianth parts is doubled and the in situ pollen is tricolporate, with a surface more like that of other Cunoniaceae outside Schizomerieae, such as Davidsonia or Weinmannia. Conclusions: An extinct genus of crown-group Cunoniaceae is recognized and placed along the stem lineage leading to Schizomerieae. Extant relatives are typical of tropical to southern-temperate rainforests, and these fossils likely indicate a similarly warm and wet temperate palaeoclimate. The oldest reliable occurrences of the family are fossil pollen and wood from the Upper Cretaceous of the Antarctica and Argentina, whereas in Australia the family first occurs in upper Palaeocene deposits. This discovery demonstrates that the family survived the Cretaceous-Palaeogene boundary event in Patagonia and that diversification of extant lineages in the family was under way by the earliest Cenozoic.Fil: Jud, Nathan A.. Cornell University; Estados UnidosFil: Gandolfo, Maria Alejandra. Cornell University; Estados UnidosFil: Iglesias, Ari. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Wilf, Peter. State University of Pennsylvania; Estados Unido

Caracterización estratigráfica, sedimentológica y paleoflorística del Grupo Sorocayense (Triásico) en el área de Barreal, provincia de San Juan, Argentina

The northern area of Cuyo Basin (west‐central Argentina) corresponds to the Rincón Blanco half-graben, whose filling is arranged into the Rincón Blanco and Sorocayense groups. In the present study, we propose a new stratigraphic scheme for the Sorocayense Group in the Barreal depocenter (San Juan Province), revise the palaeoenvironmental interpretations, and organize and analyse the plant assemblages of previous and new fossiliferous levels. We defined three tectosedimentary sequences. The basal sequence represents the initial graben filling with pyroclastic flows, alluvial fan, and ephemeral fluvial systems, and is arranged in a new unit, the Cerro Colorado del Cementerio Formation. The middle sequence, including Barreal and Cortaderita formations, is characterized by sediment gravity flow deposits and different fluvial systems, with development of floodplains with vertisols and calcisols, and temporal ponds/lakes. In turn, the Cortaderita Formation was divided into the following lithostratigraphic members: Don Raúl and La Emilia. The upper sequence, represented by Cepeda Formation, was deposited by distributary fluvial and ephemeral fluvial systems. Twelve fossiliferous strata (EF) were recognized, which were all identified in the middle sequence: EF1 to EF3 in the Barreal Formation, EF4 to EF8 in the Don Raúl Member, and EF9 to EF12 in the La Emilia Member, both of Cortaderita Formation. The taphocoenosis found in the Barreal and Cortaderita formations were dominated by corystosperms, with conifers, cycadales, and peltasperms as subordinate forms. The available evidence from the taphofloras, palaeosols and palaeonvironments indicate the development of seasonal subtropical climates, which vary from arid or semi-arid in the basal sequence, sub-humid to semi-arid in the middle sequence, and arid or semi-arid in the upper sequence. On the basis of the new information, geological correlation and age of the lithostratigraphic units were accurately re-evaluated. Based on the palaeofloristic content and the correlation with the Rincón Blanco Group, it is possible to infer that the basal sequence was accumulated during late Early Triassic-early Middle Triassic, the middle sequence during the Middle Triassic, while the upper sequence was deposited in the early Late Triassic.El área norte de la cuenca Cuyana (centro-oeste de la Argentina) corresponde al hemigraben de Rincón Blanco, cuyo relleno comprende los grupos Rincón Blanco y Sorocayense. En este estudio, se propone un nuevo esquema estratigráfico para el Grupo Sorocayense en el depocentro de Barreal, se reinterpretan los paleoambientes, y se organizan y analizan las asociaciones plantíferas de niveles fosilíferos nuevos y previamente estudiados. Se definieron tres secuencias tecto-sedimentarias. La secuencia basal representa el relleno inicial del hemigraben con depósitos de flujos piroclásticos, abanicos aluviales y sistemas fluviales efímeros, y es incluida en una nueva unidad: Formación Cerro Colorado del Cementerio. La secuencia media, que comprende a las formaciones Barreal y Cortaderita, se caracteriza por depósitos de flujos gravitacionales de sedimentos, y diferentes sistemas fluviales, con planicies de inundación en las que se desarrollaron vertisoles y calcisoles, y estanques o lagunas temporales. La Formación Cortaderita fue dividida en los siguientes miembros litoestratigráficos: Don Raúl y La Emilia. La secuencia superior, representada por la Formación Cepeda, fue depositada por sistemas fluviales distributarios y efímeros. Se reconocieron doce estratos fosilíferos (EF), todos identificados en la secuencia media: EF1 al EF3 en la Formación Barreal; EF4 al EF8 en el Miembro Don Raúl; y EF9 al EF12 en el Miembro La Emilia, ambos de la Formación Cortaderita. Las tafocenosis halladas están dominadas por corystospermas, con las coníferas, cycadales y peltaspermas como formas subordinadas. La evidencia disponible acerca de las tafofloras, paleosuelos y paleoambientes indican el desarrollo de climas subtropicales estacionales, que varían de áridos a semiáridos en la secuencia basal, subhúmedos a semiáridos en la secuencia media, y áridos o semiáridos en la secuencia superior. Con la nueva información, se reevaluaron las correlaciones y la edad de las unidades en forma más precisa. Sobre la base del contenido paleoflorístico y la correlación con el Grupo Rincón Blanco, se infiere que la secuencia basal se depositó durante el Triásico Temprano tardío–Triásico Medio temprano, la secuencia media durante el Triásico Medio y la secuencia superior durante el Triásico Tardío temprano.Fil: Bodnar, Josefina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Área Paleobotánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Iglesias, Ari. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Colombi, Carina Ester. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Drovandi, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentin

Fossil moonseeds from the Paleogene of West Gondwana (Patagonia, Argentina)

Premise of the Study: The fossil record is critical for testing biogeographic hypotheses. Menispermaceae (moonseeds) are a widespread family with a rich fossil record and alternative hypotheses related to their origin and diversification. The family is well-represented in Cenozoic deposits of the northern hemisphere, but the record in the southern hemisphere is sparse. Filling in the southern record of moonseeds will improve our ability to evaluate alternative biogeographic hypotheses. Methods: Fossils were collected from the Salamanca (early Paleocene, Danian) and the Huitrera (early Eocene, Ypresian) formations in Chubut Province, Argentina. We photographed them using light microscopy, epifluorescence, and scanning electron microscopy and compared the fossils with similar extant and fossil Menispermaceae using herbarium specimens and published literature. Key Results: We describe fossil leaves and endocarps attributed to Menispermaceae from Argentinean Patagonia. The leaves are identified to the family, and the endocarps are further identified to the tribe Cissampelideae. The Salamancan endocarp is assigned to the extant genus Stephania. These fossils significantly expand the known range of Menispermaceae in South America, and they include the oldest (ca. 64 Ma) unequivocal evidence of the family worldwide. Conclusions: Our findings highlight the importance of West Gondwana in the evolution of Menispermaceae during the Paleogene. Currently, the fossil record does not discern between a Laurasian or Gondwanan origin; however, it does demonstrate that Menispermaceae grew well outside the tropics by the early Paleocene. The endocarps’ affinity with Cissampelideae suggests that diversification of the family was well underway by the earliest Paleocene.Fil: Jud, Nathan A.. Cornell University; Estados UnidosFil: Iglesias, Ari. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Wilf, Peter. State University of Pennsylvania; Estados UnidosFil: Gandolfo, Maria Alejandra. Cornell University; Estados Unido