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Abstract

This study documents for the first time the occurrence of Shanbeipollenites proxireticulatus Schrank in levels of the Vaca Muerta Formation, Neuquén Basin, Argentina. It represents the first record of this species in high latitudes of the Southern Hemisphere. The Argentinian specimens are associated with useful palynostratigraphical indicators which suggest an early Valanginian age for the palynoflora yielding S. proxireticulatus. Therefore, this finding constitutes the first record from the Cretaceous. This taxon is related to the orders Cycadales/Bennettitales/Ginkgoales. During the Cretaceous in Patagonia cycads and bennettitaleans groups show marked adaptations to warm and strongly seasonal dry climate periodically influenced by volcanic activity. The paleogeographic distribution of the records of S. proxireticulatus, symmetrically located on both sides of the equator, together with its relationship with the climate zones or Biomes, suggest that the parental plants of this pollen grain thrived under warm climate and probably stressed paleoenvironmental conditions. Since the studied sample is located near 1000 m below the Intravalanginian unconformity, and older age (i.e. late Berriasian) cannot be discarded.

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... The type species S. quadrangulatus Qian Lijun and Wu Jingyun (in Qian et al. 1987) was reported from the Jurassic of China. Two other species S. quadratus (Kumar) Schrank and S. proxireticulatus Schrank mainly occur in the Southern Hemisphere (Africa and Argentina: Schrank 1999Schrank , 2004Schrank , 2010Olivera et al. 2018). Schrank (2004) considered Shanbeipollenites similar to some species of Cycadopites which are proximally sculptured, but the former genus can be distinguished by its typically rhombic/quadrangular outline. ...
... The three informal dinoflagellate cyst assemblages recognized by Schrank (2005), for the same interval with Shanbeipollenites were the Rigaudella aemula-Chlamydophorella wallala assemblage from the Nerinea Bed (Oxfordian to Kimmeridgian age); the Endoscrinium attadalense-Ctenidodinium sellwoodii group assemblage from the Middle Saurian Bed (late Kimmeridgian age for this unit); the Dingodinium jurassicum-Kilwacysta assemblage from the Trigonia smeei Bed (Tithonian age). In Argentina, the only record of the genus Shanbeipollenites (S. proxireticulatus) corresponds to an early Valanginian palynoflora from the Vaca Muerta Formation, Neuqu en Basin, Argentina (Olivera et al. 2018). Related to the age of this palynoflora, Olivera et al. (2018) discussed that since the studied sample is located near 1000 m below the Intravalanginian unconformity, dated at the boundary between the early and late Valanginian Qian et al. (1987), based on the translation of Jansonius et al. (2002), S. quadratus Kumar (1987) Schrank, comb. ...
... In Argentina, the only record of the genus Shanbeipollenites (S. proxireticulatus) corresponds to an early Valanginian palynoflora from the Vaca Muerta Formation, Neuqu en Basin, Argentina (Olivera et al. 2018). Related to the age of this palynoflora, Olivera et al. (2018) discussed that since the studied sample is located near 1000 m below the Intravalanginian unconformity, dated at the boundary between the early and late Valanginian Qian et al. (1987), based on the translation of Jansonius et al. (2002), S. quadratus Kumar (1987) Schrank, comb. nov. ...
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A new monosulcate species, Shanbeipollenites lagarcitensis sp. nov. is described from the Lower Cretaceous Lagarcito Formation, Sierras de Guayaguas (north-western San Luis Basin), Argentina. Shanbeipollenites lagarcitensis shares with other species of this genus a broadly ellipsoidal outline and a diagonally disposed distal sulcus. However, the new species differs from the psilate type species Shanbeipollenites quadrangulatus and from S. quadratus by the presence of sculptural elements distributed at the equatorial region, close to the opposite ends of the sulcus. The thicker wall, exine separation, much more strongly diagonal offset of the sulcus and the rugulate-verrucate sculpture with an equatorial distribution close to the opposite ends of the sulcus, distinguish this new species and expands the concept of the genus Shanbeipollenites. The presence of two separate exine layers supports its gymnosperm affinity. Furthermore, the occurrence of Shanbeipollenites lagarcitensis in the Albian Lagarcito Formation from mid–latitudes, central–western Argentina constitutes the youngest record of the genus worldwide. This new record expands the biostratigraphical range of the taxon into the Albian.
... Its record in this assemblage is the first register in our country. Interulobites lajensis mainly registered in Argentina, is another interesting taxon with a narrow biochron ranging from Late Bathonian to Hautterivian (Martínez, 2000b(Martínez, , 2002Olivera et al., 2010Olivera et al., , 2018Olivo et al., 2019). By other hand, Striatella seebergensis was previously recorded in Argentina only till Toarcian, so this mention would constitute the youngest record of this species, coincident with its latest worldwide occurrence (e.g. ...
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A palynological investigation, based on 32 samples from an Upper Jurassic outcrop in the Mto Panga near Mombasa, Kenya, yielded well preserved palynomorphs, including over 70 species of dinoflagellates. Five new species are proposed: Carnarvonodinium granulatum Jiangsp. nov., Ellipsoidinium densireticulatum Jiang sp. nov., Indodinium? parvelatum Jiang sp. nov., Meiourogonyaulax mombasaensis Mungai sp. nov., and Peridictyocysta? bamburiensis Mungai sp. nov. The investigation also revealed three distinct zones. These zones are described and shown to have features in common with Late Jurassic dinoflagellate zones of both Europe and Australia.
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Two informal sporomorph assemblage zones can be distinguished in the dinosaur-bearing Tendaguru Beds of southeast Tanzanian. The first zone, the Classopollis–Araucariacites–Shanbeipollenites Assemblage Zone, ranges from the Lower to the Upper Saurian Bed, and a mid-Oxfordian to Tithonian age is suggested based on the presence of Shanbeipollenites quadratus. The second zone, the Classopollis–Cicatricosisporites–Ruffordiaspora Assemblage Zone, is restricted in the Trigonia schwarzi Bed, which overlies the Upper Saurian Bed. The combined ranges of Cicatricosisporites hughesii, Ruffordiaspora australiensis and Trilobosporites obsitus would be consistent with a late Berriasian to Hauterivian age of this zone. This is refined further to late Valanginian to Hauterivian on the basis of already existing evidence from fauna and dinoflagellate cysts. From a phytogeographic point of view the Tendaguru locality belongs to the southern Gondwana Trisaccates Province because of the presence of trisaccate podocarpaceous pollen. The quantitative composition of the palynofloras is characterized by the dominance or abundance of pollen produced by the two conifer families Cheirolepidiaceae (Classopollis) and Araucariaceae (mainly Araucariacites). Pollen of Cheirolepidiaceae, typically xerophytic, drought-resistant, thermophilic plants, is dominant throughout the Tendaguru Beds except in parts of the Middle Saurian Bed where pollen of Araucariaceae, a presumably mesic group, becomes most abundant. Classopollis attains the highest degree of dominance in the shallow marine deposits associated with the saurian beds. This may be related to paleoecological and taphonomic factors, namely abundance of Classopollis-producing plants in low-lying coastal environments close to the lagoon-like depositional sites and transportational sorting of sporomorphs leading to a relative enrichment of small and/or anemophilous pollen. The abundance of Araucariacites in the Middle Saurian Bed suggests that araucarians existed in coastal plain environments that were stable enough to allow the growth of large trees. This open araucarian forest, which may have been a source of food for high-browsing dinosaurs, was situated landward of the cheirolepidiacean belt not far from the depositional sites. Pteridophytes and bryophytes were concentrated at moist places and around water bodies. Podocarpaceous conifers producing bisaccate and trisaccate pollen grew in local uplands, while gnetaleans related to Ephedra and Welwitschia may have been present in dry places. The palynological evidence is consistent with a seasonally dry, tropical to sub-tropical paleoclimate. Three new combinations, Equisetosporites certus (Bolkhovitina), Jugella caichigüensis (Volkheimer and Quattrocchio) and Trichotomosulcites microsaccatus (Couper), are proposed, and Jugella semistriata is described as a new species.
Article
A diverse biota including vertebrates, invertebrates, and plants is known from the Early Cretaceous of southeastern Australia. It is preserved in sediments that accumulated in the rift valley formed as Australia began to separate from Antarctica. As there was no significant terrestrial barrier between the two continents at the time, it is likely that the Early Cretaceous biota of the nearest region of East Antarctica may have been quite similar to that of southeastern Australia. Dominant among the vertebrates are turtles and at least four hypsilophodontid dinosaur species. Three species of theropods, including Allosaurus sp., are the only other dinosaurs represented. Other tetrapods include a few scant traces of plesiosaurs, pterosaurs, a lizard, and a labyrinthodont amphibian. Southeastern Australia was located well inside the Antarctic Circle of the day. Oxygen isotope studies suggest mean annual temperatures for the area between -5 and 8°C. These low temperatures are concordant with the character of both the flora and invertebrate fauna. The presence of juvenile hypsilophodontids implies that these animals were breeding in the area. The large eyes and optic lobes of the brain of these dinosaurs relative to other ornithopods suggests they may have been adapted for active behaviour under low light conditions.
Article
Dinocyst assemblages from the Cura Niyeu Formation (Bajocian), the Lotena Formation (middle to late Callovian), the lower Vaca Muerta Formation (early to middle Tithonian), the Picún Leufú Formation (late middle to late Tithonian), the upper Vaca Muerta Formation (Berriasian) and the Agrio Formation (Hauterivian to Barremian) of the Neuqéun Basin, central western Argentina, are recorded. The Bajocian assemblage is characterized by an improvished flora including Batiacasphaera sp., Nannoceratopsis sp. and Rhaetogonyaulax sp.; the Callovian assemblages by Lithodinia jurassica, Nannoceratopsis pellucida and Scriniodinium galleritum subsp. reticulatum; the lower and middle Tithonian by the endemic Hystrichospherina neuquina; the Picún Leufú Formation marked by the first appearance of Dichadogonyaulax culmula; the Berriasian by Cribroperidinium reticulatum and Millioudodinium ambiguum and the first appearance of Pseudoceratium cf. gochtii and Cribroperidinium orthoceras are noted in the Hauterivian.All suites show restrcted diversity and are dominated by acavate, proximate species. Higher dinocyst diversity in the Late Jurassic and Early Cretaceous may reflect a warming trend.
Article
We present nannofossil analyses from five new sections of the Neuquén Basin, which together provide a relatively continuous stratigraphic succession ranging from Tithonian to Hauterivian (Vaca Muerta to Agrio Formations). The sections provide an opportunity to study nannofossils from a relatively little-studied area, which nevertheless represents an important marginal basin and a relict of the single, largest Mesozoic marine habitat, the Pacific Ocean. Our aims were, firstly, to generate biostratigraphic data in order to test existing ammonite-based age-models and, ultimately, to improve stratigraphic correlations between the Argentinian sections and global chronostratigraphic standards; and, secondly, to collect palaeogeographic information in order to improve our understanding of Mesozoic nannoplankton distributions and ecology.
Article
The araucarian pollen grain Cyclusphaera radiata Archangelsky is emended based on newly discovered mate-rial from the Piedra Clavada Formation of Albian age in Santa Cruz province, Argentina. The general morphol-ogy 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 harmo-megthy, 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.