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Abstract The Berriasian–early Valanginian time interval is well represented in the Rio Mayer Formation in the Río Guanaco area (Austral Basin, Argentina). From this locality, well preserved belemnite shells of the genus Belemnopsis sp. and black shales are used to unravel the main palaeoenvironmental conditions of the seas at these high palaeo-latitudes (60°) of southern South America during the Early Cretaceous. Rare earth elements plus yttrium (REY) analyses performed in belemnites rostra reveal Ce anomalies and Y/Ho values that together suggest high oxidizing superficial seawater conditions. On the other hand, sedimentological, ichnological and geochemical (TOC, Ce anomaly and MnO) data, analyzed from the black shale matrix of belemnites, show that they may have been deposited on the bottom of the basin under oxygen deficiency. Cathodoluminescence, scanning electron microscopy, major and trace element geochemistry allowed determining the best preserved microtextures of the belemnites in order to obtain reliable δ18O and δ13C results. Palaeotemperatures calculated from the δ18O results, characterized the studied marine interval from Austral Basin as warm. The belemnites from this Lower Cretaceous succession may have lived under well oxygenated and warm seawater conditions, which were markedly different from those recorded in seafloor sediments (black shales) deposited under suboxic to anoxic conditions. The integration of global palaeotemperature data for the Berriasian–early Valanginian interval, allows suggesting a different gradient for the austral Patagonia at the Southern Hemisphere in relation to those recorded in the Northern Hemisphere. Highlights • C-O isotopes reflect a primary signal in Belemnopsis sp. from the Río Mayer Fm. • Belemnites reveal oxic conditions while black shales indicate anoxic conditions. • The palaeotemperature estimations indicate a warm seawater for the studied interval. • The Early Cretaceous temperature gradients should have been different in both hemispheres. [ABSTRACT FROM AUTHOR]

The Maastrichtian dinosaur-bearing Chorrillo Formation in southern Patagonia (⁓50° S, Austral-Magallanes Basin, Argentina) is a pedogenically modified fluvial succession, which records sediment deposition at mid–high paleolatitudes in the Southern Hemisphere. In order to reconstruct the paleoenvironment and paleoclimates for the Chorrillo Formation, we performed a paleopedological study (abiotic components) of the unit within a well-defined sedimentological–paleontological context, and considering new paleobotanical data of the unit. Using detailed macro and micromorphological features and clay mineralogy of the paleosols, we show that the Chorrillo Formation paleosols are overall smectite-rich soils with vertic and redoximorphic features (i.e., moderately developed hydromorphic Vertisol-, calcic Vertisol-, poorly developed hydromorphic Vertisol-, Histosol-, and argillic Vertisol-like paleosols). The small-scale or high-frequency stacking of such paleosols indicates that they developed under different hydrologic conditions, and subtle differences in grain-size (parent material) and topographic relief on a distal floodplain. Conversely, the large-scale or small-frequency vertical stacking of different paleosols is linked to avulsion processes. Paleobotanical remains through the Chorrillo succession demonstrates different ecological requirements for the inhabited part of the fluvial floodplain. Abiotic and biotic climate proxies suggest that these paleosols formed under a broadly temperate–warm and seasonally humid climate. Overall, these combined data record environmental and climatic conditions during the uppermost Cretaceous, and preserve a record of Maastrichtian terrestrial conditions in the Southern Hemisphere. • Fluvial sediments in southern Patagonia preserve Maastrichtian paleosols. • Stacked hydromorphic, calcic and argillic Vertisols, and Histosols. • Paleosols spatial distribution within the floodplain linked to different location. • Vertical stacking of paleosols linked to avulsion processes. • Maastrichtian paleosols show temperate–warm and seasonally humid climate for mid–high south paleolatitudes. [ABSTRACT FROM AUTHOR]

The discovery of the southernmost world record (49.5°S) of a Late Cretaceous insect fauna and plant-insect interactions is reported herein. The new locality is from the middle Cenomanian lacustrine deposits of the Mata Amarilla Formation belonging to the Austral foreland Basin, southwest Patagonia, Argentina. A first trip to the locality yielded few specimens of Coleoptera, among them an Archostemata: Cupedidae, and also a tiny specimen of Fulgoroidea: Perforissidae represented by Aonikenkissus zamunerae gen. et sp. nov. The Perforissidae were previously recorded from the Berriasian (?)-Barremian, Aptian, Albian, Turonian and Santonian in the Northern Hemisphere. The new species represents the first record of Perforissidae for South America and for the whole Southern Hemisphere. The new record suggests that the Perforissidae had a broader biogeographical distribution, and seem to have been cosmopolitan in the mid-Cretaceous. The Cupedidae reported herein is the first record for the Cenomanian and the first record of the genus Zygadenia in South America. Insect traces found in the same strata are made in an angiosperm palmatilobed leaf and correspond to a piercing and sucking type of damage. This type of damage is compared to recent stipples and to isolated piercings. [ABSTRACT FROM AUTHOR]

Maichnus wetkaroae igen. isp. nov., from the Albian of Patagonia, is composed of two or three ellipsoidal oblate chambers connected to shafts that show swellings and concentrically laminated linings. Such laminated linings are also present in chambers, and probably originated by radial backfilling and/or the successive discharges of liquid organic excretions. This unique morphology occurs in paleosols showing evidence of waterlogging. Trace fossil morphology and the occurrence of traces in clusters in waterlogged soils indicate that M. wetkaroae igen. isp. nov. represents larval burrows of fossorial petalurids. This is the first record of Odonatan trace fossils from paleosols and also the oldest one. M. wetkaroae igen. isp. nov. is one of the oldest insect trace fossils recorded from paleosols. It represents the first and unique paleontological evidence of the ancient origin of the burrowing behavior of petalurids postulated only theoretically until now in evolutionary scenarios of Odonata. • Maichnus wetkaroae igen. isp. nov. is a new trace fossil from the Albian of Patagonia. • It is the first trace fossil attributable to Odonata recorded from paleosols. • It is one of the oldest insect trace fossils recorded from paleosols. • It provides the first and unique evidence of ancestral burrowing behavior of petalurids. • This evidence supports some previous theoretical evolutionary scenarios for Odonata. [ABSTRACT FROM AUTHOR]