Herein, we described three types of fossil fungi associated with permineralized legume wood from Upper Miocene deposits in the Río de Agua Verde locality (Chiquimil Formation, Catamarca Province, Argentina). These are represented by diverse fungal remains, including septate hyphae bearing unicellular and multicellular conidia, distributed inside the vessel elements. Vegetative and asexual reproductive structures preserved were compared to extant mitosporic fungi and related to three different genera. The fossils are particularly similar to extant Gilmaniella Barron, Brachysporium Saccardo, and Ramichloridium Stahel ex de Hoog, but display some differences that preclude unequivocal assignment. Due to the absence of host reactions signs in the infected wood, we suggest that the fungi were probably saprotroph and invaded the fossil wood after its death.

In the Argentinian Cordillera Oriental, the Iturbe River area represents an intermediate territory between Sierra de Santa Victoria to the north and the Quebrada de Humahuaca to the south. Lower Ordovician outcrops of this region were cited in the literature as highly fossiliferous, although they are still imperfectly known. A Tremadocian succession of the Santa Rosita Formation near the village of Iturbe, Jujuy Province, is described herein. It displays different marine paleoenvironments and a relatively high-diversity trilobite assemblage. The sedimentary features of the lower and middle parts of the succession denote deposition in upper offshore and offshore transition environments, whereas those of the upper part are characteristic of a deeper, lower offshore setting. Taxa recognized include Gymnagnostus sp., Micragnostus iturbensis sp. nov., Geragnostus callaveiformis Harrington and Leanza, Geragnostus sp., Conophrys cf. salopiensis (Callaway), Leptoplastides granulosus (Harrington), Bienvillia tetragonalis (Harrington), B. rectifrons (Harrington), Parabolinella boliviana Juarez Huarachi, Asaphellus stenorhachis (Harrington), Apatokephalus tibicen Přibyl and Vaněk, and Pyrimetopus sp. This association indicates correspondence with the Bienvillia tetragonalis Zone (lower upper Tremadocian); a unit that to date is recorded with confidence only in a few localities of the Cordillera Oriental, in diverse facies. This study provides information on the morphology of several key taxa of the biozone, as well as new evidence in favour of a correlation with the Conophrys salopiensis Zone of England. The assemblage studied is assignable to the middle Tremadocian Olenid-Asaphellus biofacies, which occurs typically in upper offshore to offshore transition deposits.

Environmental change, such as variation in upwelling and the consequent fluctuation in marine primary productivity, may have profound effects on organisms. Trophon geversianus shells from Caleta de Los Loros (San Matías Gulf, Northern Patagonia, Argentina) were analyzed in order to compare morphological variability at different spatio-temporal scales. To do so, we performed morphometric analyses at three sites, two fossil deposits of different age from the late Holocene and one modern assemblage. In general, modern shells were thicker than fossil ones. A slight trend of size reduction is also observed over the time considered, since modern shells were, on average, smaller than fossil ones. Size variations of T. geversianus shells are explained on the basis of phenotypic plasticity as a response to the environmental changes recorded in the San Matías Gulf during the Holocene. These changes include variations in paleo-productivity, such as sea surface temperatures, salinities and water circulation changes, which would have modified nutrient availability. Furthermore, Caleta de Los Loros was validated as an outlier site along a latitudinal gradient. Shells from this peculiar place bear a closer resemblance to shells found in sites further south in the Magellan Province. Environmental conditions and oceanographic features related to the presence of upwelling events that were probably responsible for this pattern are discussed.

The non-marine Triassic displays distinct regional differences in tetrapod fossil assemblages even in adjacent regions, and these patterns have been hypothesized to reflect provincialism. For example, in the “Middle Triassic” of Gondwana, the Río Seco de la Quebrada Formation (Puesto Viejo Group) in western Argentina shares a number of taxa with the Cynognathus AZ of the Burgersdorp Formation (Karoo Basin) in South Africa. In contrast, the nearby Chañares Formation of northwestern Argentina is compositionally distinct and shows more affinities with the Dinodontosaurus AZ of the lower Santa Maria Formation in southern Brazil and the top of the upper Omingonde Formation of Namibia. These problems are exacerbated by recent radioisotopic dates from the Chañares Formation and the Puesto Viejo Group that suggest these units are actually Carnian in age. We provide new data for the biostratigraphy and biogeography of these units in the form of the first record of a stahleckeriine dicynodont from the Chañares Formation, an ulna referable to Stahleckeria. This new occurrence strengthens the correlation between Chañares, Santa Maria, and the top of Omingonde units but reinforces the differences with the Río Seco de la Quebrada and Burgersdorp units. Hypotheses for this provincialism include assemblages of different ages, distinct environments controlled by paleolatitude or paleotopography between basins that formed a barrier to faunal interchange.