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Floodplain deposits of the Anfiteatro de Ticó Formation (Baqueró Group, Aptian), in Patagonia (Argentina), are rich in plant remains and contain some of the oldest angiosperm records of southern Gondwana. Many gymnosperm and pteridophyte species, as well as three morphotypes of medium sized angiosperm leaves, have already been described from this unit at different fossiliferous outcrops. We report two new angiosperm morphotypes from the Bajo Tigre locality. Both morphotypes (AT1 and AT2) consist of nano- to microphyllous leaves, nearly elliptic, with untoothed margins and pinnate brochidodromous venation. These leaves mostly exhibit characteristics of a high first or low second rank vein system. This combination of characters is associated with early angiosperm evolution. Morphotype AT1 is similar to one of the brochidodromous morphotypes from the La Cantera Formation (uppermost Aptian), which could be possibly conspecific. Morphotype AT2 has gross features already observed in leaf records from the younger Kachaike Formation (Albian ̶ lower Cenomanian) though they differ in lamina shape and secondary venation features. The angiosperm leaves of the Anfiteatro de Ticó Formation suggest that the early stages of angiosperm evolution in Patagonia had included forms with more than one type of growth habit. [ABSTRACT FROM AUTHOR]

Abstract: Dichotomous rachises bearing Eremopteris golondrinensis Archangelsky foliage in organic connection with probable microsporangiate structures were collected in the mid to late Permian La Golondrina Formation at Laguna Castellanos locality in southern Patagonia. The fertile bodies are receptacles slightly curved distally that bear 4–5 sessile, erect and oblong to elliptic sporangia-like bodies parallel to each other. They are fused laterally and apparently are enveloped by a delicate layer of conjunctive tissue that holds them together and have no visible dehiscence marks. These structures are here interpreted as putative microsporangiate organs. The novel information allows the emendation of the diagnosis of E. golondrinensis by adding new data on the morphology of the frond and its reproductive organs. As the genus Eremopteris has recently been emended excluding this species, a new genus, Kladistamuos with a new combination, K. golondrinensis is proposed here. Kladistamuos is therefore considered to be another SW Gondwana plant fossil of a putative ‘pteridospermous’ affinity, having distally attached fertile organs that differentiate it from the Euramerican species of Eremopteris. [Copyright &y& Elsevier]

Abstract: A scanning and transmission electron microscopy-based ultrastructural study of Arcellites humilisVillar de Seoane and Archangelsky, 2008, from the Kachaike Formation and Piedra Clavada Formation (Albian-Cenomanian) from several localities in Patagonia (Argentina), is presented in this paper. TEM-photographs of thin-sectioned specimens show a thick spore body wall composed of three layers: a thin and dense exine, an inner granular perine sublayer with irregularly disposed small channels and lacunae, and an outer alveolate perine sublayer with channels perpendicular to the external surface. Transverse sections of the A. humilis wall are compared with fossil and extant species of Marsileaceae. We show that the wall ultrastructure is similar in A. humilis, A. santacrucensis, A. disciformis, A. stellatus and Regnellidium upatoiensis. However, the body wall and acrolamella of A. humilis are more similar to those of R. diphyllum Lindman than to those of the Marsilea L. or Pilularia L. species. Water ferns such as members of the Marsileaceae played an important role in aquatic or semi-aquatic niches in Patagonian Cretaceous floras, suggesting that high humidity and temperature prevailed during the Albian-Cenomanian in this region of Argentina. [Copyright &y& Elsevier]

Abstract: The araucarian pollen grain Cyclusphaera radiata Archangelsky is emended based on newly discovered material from the Piedra Clavada Formation of Albian age in Santa Cruz province, Argentina. The general morphology and ultrastructure of the pollen were studied by means of transmitted light, scanning, and transmission electron microscopy. C. radiata is discoid with an equatorial thickening and two large opposite apertures, with radial thickenings in one of them and two central apertural occlusive opercula-like structures. Beneath there is a thick amorphous electron-dense nexine. The combination of characters seen in this pollen type is very unusual, and no parallels are known in fossil or extant gymnosperm grains. Functional interpretation of the apertural exine suggests that the radial thickenings and apertural membranes were involved in harmomegthy, the opercula-like structures in germination, and the apertural nexine perhaps as a strengthening layer. A hypothetical pollination mechanism is also presented for C. radiata. The paleobiogeography of this taxon shows that during the Mesozoic, the plants that produced these grains inhabited an extensive area of Gondwana that included South America, Africa, India and Antarctica. [Copyright &y& Elsevier]

Abstract: The schizaeaceous extant genus Mohria has a distribution restricted to South Africa and Madagascar area. Its cicatricose spores are characterised by their large size and muri with hollow longitudinal channels unknown in other schizaeaceous genera. Fossil spores that sometimes have been referred to Mohria lack this typical character and therefore the determinations were discarded. Early Cretaceous (Albian) sediments from Patagonia, referred to the Piedra Clavada Formation of the Austral Basin, contain spores that have the characters now found in Mohria. These fossils are hereby assigned to the new genus Palaeomohria that includes several morphological types. The paleogeographical proximity of South Africa and Patagonia in Southwestern Gondwana persisted from the Permian to the Early Cretaceous, during a time when floras of both regions had significant similarities. In this context, the finding of Mohria-like spores in Patagonia suggests that the distribution of this fern was more extended in the past and became restricted while the continents shifted apart during the Cretaceous/Tertiary. The two living Mohria species may then represent relict taxa of a much more varied and rich group that flourished during the Early Cretaceous in SW Gondwana. [Copyright &y& Elsevier]

Three new species of the cycadean pollen cone Androstrobus, viz. A. munku, A. patagonicus, and A. rayen, are described. All specimens are represented by microsprophylls or fragmentary cone pieces, and they have been found in the same fossil bed at the locality Bajo Grande, in Santa Cruz province, Argentina, which is referred to the Anfiteatro de Ticó Formation of Aptian age. This is the first record of the genus in Argentina and South America. The good preservation of the material allowed the study of cuticles and pollen with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is noted that Androstrobus is a poorly defined genus that needs a revision of the type material as well as new specimens from the type locality to certify the presence of pollen. Comparisons with other Androstrobus species are made, especially with those that have been described with cuticular characters and structure of pollen. Attention is paid to the similarity of the alveolate pollen ultrastructure of the Patagonian fossils with some extant cycads, especially with genera of the Zamiaceae and Cycadaceae. The variety of pollen cones found in the same bed agrees with the presence of different vegetative organs, leaves, and fronds found previously at the same place, and that were referred to the cycads on the base of their cuticular structure. The abundance of cycads during the mid-Cretaceous in southern Argentina is a contrasting evidence with the present-day absence of the group in southern South America. [Copyright &y& Elsevier]

Well-preserved and diverse Early Cretaceous palynological assemblages were studied from an outcrop section of the Springhill Formation at the Río Correntoso locality (PRC), close to Ghío Lake, in Santa Cruz Province, Patagonia, Argentina. The studied log corresponds to the northernmost outcrops known for the Springhill Formation in the Austral Basin. Most of the palynomorphs algae (Botryococcus, Sphaeroplea, Lecaniella, Zygnema, Pseudoschizaea, Schizosporis, Ovoidites), and some angiosperm pollen grains (Proxapertites , Longapertites, Arecipites) are distinctive and characterize the palaeoenvironment and palaeoclimate of PRC, which was dominated by estuarine coastal margin sedimentites deposited under warm and humid conditions. These angiosperm pollen grains correspond to the earliest record of these group in Patagonia, represented by diverse monosulcates and one rare tricolpate type. This new record of angiosperm pollen in the Springhill Formation provides further evidence that one of the earliest diversifications of angiosperms started at least during the early Cretaceous in Patagonia. Sergio Archangelsky provided an invaluable expertise in the field of paleobotany in multiple ways. His knowledge transcended not only through his papers but also through his exceptional oratory skills. His talks were always enriching in every aspect, combining an engaging historical account with a vision towards the future. "...La paleobotánica un placer, debe ser algo agradable, es decir uno cuando trabaja en paleobotánica le gusta lo que hace, y cuando uno está describiendo, uno se va, y es lo mismo que componer una pieza musical, te perdés, te perdés en todo y lo hacés con gusto, con pasión..." "...The paleobotany is a pleasure, it should be something enjoyable, meaning that when you work in paleobotany, you love what you do. And when you're describing, you get lost, just like composing a musical piece. You lose yourself, in everything, and you do it with pleasure, with passion...". The file with the voice of Sergio Archangelsky is in Supplementary file under Sergio_Archangelsky.mp3. • The palynoflora of the Springhill Formation includes algae and land plants. • Pollen records show features of early members of some taxa (monocots and eudicots). • Angiosperm pollen grains provides evidence for early radiation of some basal taxa in Patagonia. • Palynoflora studied indicates freshwater palaeoenvironment, warm and humid climate. [ABSTRACT FROM AUTHOR]

Abstract: The record of Cycadales in Patagonia begins in the Triassic and extends up to the Oligocene. In this region the group is highly diversified and includes several taxa represented by trunks, leaves and pollen cones. A new cycadalean genus and species, Restrepophyllum chiguoides, form the Aptian Anfiteatro de Ticó Formation, Santa Cruz province, Argentina, is described here. The fossil is a leaf compression with well-preserved cuticle. Its morphology, anatomy and ultrastructure are studied by means of light and electron microscopy. The leaf is lanceolate, serrate, and possesses a prominent midvein and decurrent laterals showing an open, simple or dichotomous venation. The leaf is hypostomatic, and the abaxial cuticle is thinner than the adaxial one. The stomata are irregularly distributed and indistinctly oriented between veins. They are monocyclic to imperfectly dicyclic (haplocheilic); the suprastomatal aperture is raised over the epidermis and the guard cells are sunken. Scattered trichomes and crystalliferous idioblasts are also present. The cuticle is composed of three layers: the outer and inner layers are lamellate, while the middle one is granulate. This new cycad leaf is compared with similar fossil leaves from Gondwana and Europe/North America, and also with similar extant cycad leaves. Based on the general morphology and the main characters of the cuticle, R. chiguoides is assigned to the family Zamiaceae; moreover it is more closely related to the living Zamia (Chigua) restrepoi (D. Stevenson) Lindstrom than to any other member of the Cycadales. Paleophytogeographic evidence suggests a South American origin of Zamia/Chigua and a further migration to northern latitudes. This new type of leaf also suggests the putative existence of a Chigua clade that may be traced back to the Early Cretaceous when two cycadalean families, Zamiaceae and Stangeriaceae, were already well-established in Patagonia. [Copyright &y& Elsevier]

An understanding of paleonvironmental and paleoceanographic evolution of the Southwestern Atlantic Ocean during the Palaeogene is prevented by the lack of precise tools to date and correlate the sedimentary units. Palynological samples collected in the upper portion of the Man Aike Formation, which crops out southern Lago Argentino area, in the southwest of the Austral Basin (50°21′45″S–72°14′30″W), contain well preserved marine organic dinoflagellate cysts, which are potentially important biostratigraphic and paleoenvironmental indicators. Herein we describe the composition of the Man Aike Formation's dinoflagellate cyst assemblages and compare them to similar assemblages collected in the same basin in the upper member of the Río Turbio Formation using Compositional Statistical Analysis. The dinoflagellate cyst assemblages from the upper part of the Man Aike Formation are highly correlated to the assemblages from the upper member of the Río Turbio Formation from outcropping sections (51°31′13″S–72°15′11″W) and with the lower part of sediment cores drilled by Yacimientos Carboníferos Fiscales in the Río Turbio Formation area. These dinoflagellate cyst assemblages show a very low correlation with the assemblages from the upper part of the Yacimientos Carboníferos Fiscales's cores. The comparison of our results with the high-resolution Southern Pacific Ocean dinoflagellate cyst zonation for the late Palaeocene to late Eocene allow us to date some of the dinoflagellate events recorded in formations of southwestern Patagonia. The assemblages from the Man Aike Formation and the lower part of the upper member of the Río Turbio Formation relate to the zones SPDZ11 and SPDZ12 and are assigned to the mid-middle Eocene (late Lutetian to early Bartonian). The biostratigraphy proposed herein constrains the age of the Man Aike Formation and equivalent units based on calcareous microfossil data, mollusks affinities and 87Sr/86Sr isotopic values to an age ranging between ∼42 and 39 Ma. The assemblages from the upper part of the upper member of the Río Turbio Formation relate to the SPDZ13 Zone, which corresponds to the late Eocene (early Priabonian). The dinoflagellate cyst assemblages indicate that they were under the influence of relatively warm, marine open waters in an inner-shelf environment for the lower part of the sections. In the upper part of the sections, the assemblages suggest shallow marine waters associated with coastal areas and high trophic levels, possibly as a result of freshwater inputs. [ABSTRACT FROM AUTHOR]