Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

This article addresses linked topics which have been debated intensely in the specialized literature: it proposes to identify the rulers of Teotihuacán, and their palace, through iconographic analysis of images worked in different materials. I present new arguments in favor of my proposal that the figures wearing the Great Tasseled Headdress fulfilled the role of rulers of the city. I also analyze a set of images on ceramics which indicate that their palace, with martial attributes, was a triad of pyramids, probably also including a monumental ceremonial platform. I propose that a possible candidate for the seat of government of Teotihuacan is the archaeological triad of the Plaza of the Columns.

The coastal region of northeastern Brazil holds one of the most important records of mosasaurids from the Late Cretaceous of South America. Analysis of these discoveries allowed us to create a picture of the composition of the fauna, as well as the diversity and paleobiogeography of these clades. In the region, the mosasaurid fossils are contained in Cenomanian to Maastrichtian geological units of epicontinental marine origin, in the Cotinguiba (Sergipe-Alagoas Basin), Alcântara (São Luís Basin), Itamaracá (Paraíba Basin), Calumbi (Sergipe-Alagoas Basin), and Gramame (Paraíba Basin) formations. Paleogeographic data corroborate that these deposits represent low-latitude equatorial environments. The Brazilian fauna is represented by fourteen taxa from one family (Mosasauridae), two subfamilies (Mosasaurinae: Prognathodontini, Globidensini and Mosasaurini; Plioplatecarpinae: Plioplatecarpini), and some indeterminate mosasaurid specimens. Mosasaurids from the northeastern region of Brazil resemble Late Cretaceous marine reptiles from western Africa (Angola, Congo, and Morocco), suggesting faunal continuity in the seaway that bridged these areas. The study of this marine fauna is crucial to understanding the evolutionary and paleobiogeographic history of the group during the opening of the South Atlantic Ocean.

This contribution presents the Isomass method, aimed at verifying the conserved behaviour of elements in geochemically open systems even when the parent rock composition is lacking. The method estimates system size changes for a specific element that is assumed to be conserved by calculating the amount of material transfer for each of the other elements, thus verifying (or rejecting) the initial assumption. By analysing the calculated amount of material transfer (or daughter system size ratios), additional conserved elements (if any) can be identified. The Isomass method is used here to evaluate a set of numerically generated samples whose element concentrations derived after mass additions and losses are assigned to daughter rocks. In addition, it is also applied to three real datasets that examine soil formation, magmatic fractionation in a komatiitic lava, and hydrothermal metasomatism. The method is capable of: (1) determining which elements confirm their conserved behaviour for a variety of geological environments; (2) identifying which other elements are conserved, added or lost; (3) calculating the amount of material transfer; and (4) providing a measure of the extent of the conserved character of elements. The method illustrates that the whole-rock compositions of parent and daughter samples do not represent the actual material transfer that occurred during geochemically open geological processes, as conserved elements may appear enriched or depleted, and non-conserved elements may have concentrations that do not reflect the actual material transfers that took place. The Isomass method is therefore a proper and valuable tool for the verification of conserved elements and the investigation of material transfer in rocks.

Understanding crystal growth in high-grade metamorphic rocks provides unique insights into metamorphic processes and geological evolution. This study investigates the petrographic characteristics, crystal growth mechanisms, and chemical composition of garnets from the Santander Massif of Colombia, a region known for its high-grade metamorphic rocks. Petrographic analysis reveals a discrepancy between anhedral to subhedral garnet forms on an outcrop scale and euhedral forms in hand samples, which may be due to limited or heterogeneous pressure and temperature conditions or spatial constraints at the outcrop scale, and more homogeneous conditions at the hand sample scale. Advanced techniques, including scanning electron microscopy (SEM) and atomic force microscopy (AFM), show that garnet crystals predominantly exhibit trapezohedral {211} and dodecahedral {110} faces, indicating different growth mechanisms. Electron probe microanalysis (EPMA) reveals a homogeneous chemical composition in the garnets, predominantly almandine with minor pyrope, grossular, and spessartine components. The application of cathodoluminescence (CL) and differential interference contrast (DIC) microscopy provides additional insights into mineral characteristics and growth features, contributing to a comprehensive understanding of garnet formation. These findings offer new valuable perspectives on the metamorphic conditions and processes of the rocks that form the Santander Massif.

Paleogene fossil mammals marks the initial steps towards the assembly of the highly autochthonous Cenozoic South American faunas, and the rise of evolutionary and ecological novelties within lineages that spread across the continent. Although common to many areas, their greatest diversity and knowledge undoubtedly comes from central Patagonia, where superb exposures in Argentina’s extra-Andean and Atlantic coastal zones have been profusely studied since the second half of the 19th century. In harsh contrast, Paleogene mammals from Chilean Patagonia have only recently begun to be known, based on novel discoveries mostly conducted in the Aysén Region. Here we present the first detailed description of a Paleogene mammal from the austral, Magallanes Region, composed of an isolated lower molar identified as a left m1 or m2. The tooth was exhumed from estuarine deposits of the Upper Member of the Río Turbio Formation in Sierra Baguales, along with thousands of chondrichthyan teeth, and other fossil remains belonging to bony fishes, aquatic mammals, and diverse sauropterygians. The particular morphology and dimension of the tooth allow its recognition as Albertogaudrya unica Ameghino 1901, a large, middle to early late Eocene member of the order Astrapotheria, previously recorded in central Patagonia of the Chubut Province, Argentina, and the Aysén Region, in Chile. The occurrence of A. unica in Sierra Baguales extends by more than 400 kilometers to the south the presence of this iconic Casamayoran through Mustersan? age species, also providing a new element to the biogeographic discussions about the cohesive character of the austral faunas, and the early conformation of the regional provincialism that has characterized Patagonia during much of the Cenozoic. It also helps to constrain a 40-37 Ma age for the fossiliferous levels of the Upper Member of the Río Turbio Formation at Sierra Baguales, consistent with previous biochronologic and geochronologic results. Along with the detailed morphological description of the new specimen, we also comment on taphonomic aspects of the depositional context, its regional chronological and zoogeographic importance, and some particularities of the occlusal morphology of the molar, which shows an interesting and unusual pattern of enamel wear whose development and functionality are also discussed.

El trabajo de Cáceres (2025) tiene el gran mérito de poner en discusión una estrategia geofísica indirecta para la estimación de la isoterma de Curie y al mismo tiempo proveer de una aproximación al gradiente geotérmico en la zona central de Chile, en continente y extensión costa afuera. El gradiente termal es muy relevante para una serie de problemas en geociencias. Por una parte, como recurso energético la geotermia aún tiene la opción de constituirse en una componente complementaria para la estrategia de descarbonización a escala local y planetaria. Adicionalmente, el estimar el flujo de calor es clave para la comprensión de los procesos geodinámicos que condicionan principalmente los ambientes de convergencia de placas. Por estas razones es muy importante avanzar en estrategias que permitan reconocer este parámetro físico, y este artículo de Cáceres (2025), da la oportunidad de avanzar en esta necesaria discusión.

A biostratigraphic reevaluation of the conodont faunas of the Acoite Formation at the La Ciénaga de Purmamarca, northwestern Argentina, is presented here to constrain its depositional age and improve its regional correlation. The new conodont assemblage, consisting of 636 elements, includes Balognathidae indet., Drepanodus arcuatus, Drepanoistodus pitjanti, D. cf. andinus, D. sp. A, Gothodus andinus, Kallidontus nodosus, Paroistodus sp., and Zentagnathus argentinensis. These species were obtained from the same beds sampled by previous authors, who attributed varying ages to the conodont assemblage. Of special importance is the record of K. nodosus, which allows for precise correlation of the lower levels of the Gothodus andinus Zone with the early Floian Prioniodus elegans Zone (Fl 1). This finding is consistent with the graptolite and trilobite data available at the La Ciénaga de Purmamarca, and it raises caution regarding the taxonomic determination of Baltoniodus triangularis, the index fossil for the Lower-Middle Ordovician Series boundary in other stratigraphic sections of the Acoite Formation along the Eastern Cordillera.

The present study provides a synthesis of the diversity and geographical distribution of Titanosauria (Dinosauria: Sauropoda) from Upper Cretaceous rocks of the Bauru Group in Brazil. There are currently ten valid species of titanosaurs described for the Bauru Group, some of which exhibit similarities to species found in Argentina. Among these species is the well-known clade Aeolosaurini, which is considered as endemic to South America. Members belonging to the Aeolosaurini clade remains have so far been found only in Argentina and Brazil. This faunal similarity helps in the interpretation of the paleogeographic distribution of these organisms, which reflects intense faunal interchange First record of vertebrate.

The insertion of women in Chilean volcanology faces gender barriers that limit their access and professional development. Chile has the fourth lowest percentage of women with a STEM (Sciences, Technology, Engineering, and Mathematics) degree among OECD (Organization for Economic Co-operation and Development) countries, with an 8% compared to an average 16%. Likewise, only one out of three Chilean researchers is a woman. Within this context, the present study aims to investigate gender gaps in the integration of women in Chilean volcanology by following a predominantly qualitative, mixed-method approach, to recognize the stereotypes and gender roles that perpetuate them. By analyzing enrollment statistics, scientific publication data, and surveys and interviews, an underrepresentation of women in research, gender wage gaps, and difficulties in balancing work and caregiving responsibilities are found. Women are also commonly stereotyped in their aptitudes for fieldwork and face a constant need for validation. Nevertheless, they develop collective transformative practices from support networks and making role models visible. Deepening on the implementation of gender equity policies in STEM areas and strengthening female representation from early formative years are strongly recommended.

In Memoriam