Publications
Osteohistological insight into the growth dynamics of early dinosaurs and their contemporaries
Early dinosaurs from the Ischigualasto Formation exhibited elevated growth rates, comparable to or exceeding those of later Mesozoic sauropodomorphs and theropods. Unlike later dinosaurs, these early species grew more continuously rather than in rapid bursts. This suggests that high growth rates were an ancestral trait for Dinosauria and played a key role in their ecological success, though they did not uniquely set them apart from contemporaries like crocodylomorphs and pseudosuchians.
Primer registro de Oxyrhopus rhombifer bachmanni (Squamata: Dipsadidae) en el Parque Provincial Ischigualasto, San Juan, Argentina
Researchers report the first recorded presence of Oxyrhopus rhombifer bachmanni, a snake species from the Dipsadidae family, within Ischigualasto Provincial Park (PPI), Argentina. This discovery increases the known reptile diversity in the PPI to six snake species and 26 total herpetofauna species. The study builds on prior surveys of mammals, birds, amphibians, and reptiles in this UNESCO-listed site, contributing critical data for conservation and management decisions. By mapping herpetofauna distribution, the research provides actionable insights to protect biodiversity in one of Argentina's most significant natural heritage areas.
Rhexoxylon piatnitzkyi and its ancient adversaries: deciphering plant-beetle interactions and its palaeoecological significance in the Ischigualasto Formation (Upper Triassic, Argentina)
Fossilized evidence from the Ischigualasto Formation reveals ancient interactions between the corystosperm plant Rhexoxylon piatnitzkyi and wood-boring beetles, likely early cerambycids. CT scans and thin sections exposed abundant galleries in branches, targeting secondary phloem and pith, while trunks showed fewer borings. The presence of fungal decay and tracheid fragments in frass suggests the beetle fed on both living and decayed wood. Anatomical features indicate the plant may have deployed defenses against both fungi and insects. This is the first record of insect galleries in corystosperm axes, offering insights into Triassic Gondwanan ecosystems.
Paleoneurology and neuroanatomical notes on the South American “rauisuchian” Saurosuchus galilei from the Ischigualasto formation, San Juan, Argentina
A groundbreaking paleoneurological study of Saurosuchus galilei, a large Triassic predator from Argentina's Ischigualasto Formation, reveals that this 'rauisuchian' possessed an exceptionally acute sense of smell, surpassing expectations for its body size. This enhanced olfactory ability, akin to modern crocodilians and tyrannosaurid dinosaurs, suggests it relied on scent to track prey over long distances, compensating for weaker vision and balance. Researchers identified unique pharyngotympanic pneumaticity in the braincase and detailed structures like cranial nerves (V-XII), olfactory bulbs, blood vessels, and inner ear using natural casts and digital endocasts. The study challenges traditional views of rauisuchian sensory capabilities and provides insights into their ecological role before the rise of theropod dinosaurs.
Araucariaceous fossil woods from the Upper Triassic Ischigualasto Formation (San Juan Province, Argentina): paleofloristic and paleoclimatic implications
A new species of fossil wood, Agathoxylon argentinum, has been identified from the Upper Triassic Ischigualasto Formation in Argentina. This discovery, preserved as silica permineralization, reveals unique anatomical features distinct from other Mesozoic Gondwanan species, linking it to the conifer family Araucariaceae. The study also documents fungal-mediated wood decay and spherical structures interpreted as holocarpic chytrid fungi, providing insights into paleoecological processes. Analysis of growth rings suggests that A. argentinum was an evergreen gymnosperm, thriving in humid conditions. Additionally, the research highlights a significant floristic change in the Ischigualasto Formation, marked by the decline of corystosperm genera and increased humidity, offering new paleoclimatic implications for this UNESCO-listed site.
An enigmatic new archosauriform from the Carnian-Norian Ischigualasto Formation of Northwestern Argentina
Researchers have uncovered Incertovenator longicollum, an enigmatic new archosauriform from the Carnian-Norian Ischigualasto Formation in northwestern Argentina. This discovery sheds light on the evolutionary diversity of Late Triassic archosaurs, with its elongated cervical vertebrae presenting a unique combination of traits found in early avemetatarsalian and pseudosuchian clades. Phylogenetic analyses place Incertovenator within Archosauria, either as an early diverging avemetatarsalian or loricatan, closely related to Aphanosauria, Ornithodira, or Mandasuchus tanyauchen. The study highlights convergent evolution in neck elongation across multiple Triassic archosauriform clades, providing new insights into the morphological and phylogenetic complexity of this pivotal period in vertebrate history.
Anatomical Details of Aetosauria (Archosauria: Pseudosuchia) as Revealed by an Articulated Posterior Skeleton from the Upper Triassic Ischigualasto Formation, San Juan Province, Argentina
Researchers have uncovered significant anatomical details of Aetosauria, a group of early-diverging 'crocodile-line' archosaurs, through the study of an articulated posterior skeleton from the Upper Triassic Ischigualasto Formation in Argentina. The specimen, resembling but not definitively assignable to the genus Aetosauroides, reveals unique features such as robust body structure and a distinct tail morphology. Notably, it displays extensive appendicular armor and a well-preserved caudal ventral carapace, which consists of only two columns of ventral osteoderms and includes a large cloacal vent. The study also identifies a fusion of posterior ventral paramedian osteoderms into a single element, a previously undocumented characteristic in aetosaurs. These findings challenge existing understanding of aetosaur anatomy and paleobiology.
Dicroidium (Zuberia) zuberi (Szajnocha) Archangelsky from exceptional Carnian leaf litters of the Ischigualasto Formation, westernmost Gondwana
Exceptional leaf litters from the Carnian Ischigualasto Formation, Argentina, reveal remarkable phenotypic plasticity in the fern-like plant Dicroidium (Zuberia) zuberi. Unlike previous hypostomatic records, these specimens exhibit thick, amphistomatic cuticles with sunken, randomly distributed stomata and papillae on epidermal cells, suggesting adaptability to environmental conditions. The study leveraged optical and scanning electron microscopy to analyze autochthonous or parauchthonous leaf accumulations preserved in abandoned fluvial channels, which also provided insights into the region's seasonal climate and post-biotic turnover (228.91 Ma). Palynological data further supports a humid environment that fostered this diverse vegetation after significant ecological changes.
Skull osteology of the holotype of the rhynchosaur Hyperodapedon sanjuanensis (Sill, 1970) from the Upper Triassic Ischigualasto Formation of Argentina
A groundbreaking study reveals the first detailed three-dimensional reconstruction of a rhynchosaurid palate, significantly advancing our understanding of these distinctive Triassic herbivores. The research, focusing on the holotype skull of Hyperodapedon sanjuanensis from Argentina's Ischigualasto Formation, utilized repreparation and computed tomography (CT) scanning to uncover novel anatomical features, including the presence of septomaxillae bones—a first for rhynchosaurids. This discovery not only provides critical insights into the complex masticatory apparatus of rhynchosaurs but also sheds light on their evolutionary trajectory, offering a more comprehensive view of their morphological diversity and taxonomic relationships in South America.
A Review of Vertebrate Beak Morphologies in the Triassic; A Framework to Characterize an Enigmatic Beak from the Ischigualasto Formation, San Juan, Argentina
A unique fossil beak (PVSJ 427) from the Late Triassic Ischigualasto Formation, Argentina, provides insight into early beak evolution and ecological convergence. The iron-rich cast fossil, triangular with a concave midline shelf, lacks clear synapomorphies but resembles ornithischian dinosaur predentaries, suggesting an early evolutionary origin of this structure. Researchers analyzed phylogenetic distribution and morphology of Triassic beaks to create a framework for estimating beak similarity, placing PVSJ 427 alongside other vertebrate clades from the period. This study advances understanding of edentulous dietary modifications in early reptiles and their ecological implications, indicating that the animal bearing PVSJ 427 was ecologically convergent with the earliest ornithischian dinosaurs.
Confirmación de la presencia de pecarí de collar (Pecari tajacu) en el Parque Provincial Ischigualasto (San Juan, República Argentina)
Research confirms the presence of the collared peccary (Pecari tajacu) in Ischigualasto Provincial Park, Argentina. This finding extends the known distribution of the species, contributing to understanding its ecological range within UNESCO-listed sites. The study employed field observations and ecological data analysis to document the species' occurrence, behavior, and habitat use. Published in Notas Sobre Mamíferos Sudamericanos, this work highlights the importance of monitoring mammal populations in protected areas.
El impacto económico del turismo en localidades pequeñas. Análisis insumo-producto aplicado a los parques Ischigualasto y Talampaya
A study on the UNESCO World Heritage Sites of Ischigualasto and Talampaya Natural Parks in Argentina reveals that increased tourist demand correlates positively with local economic growth, particularly in small communities like Valle Fértil-Villa Unión. Researchers used a hybrid insumo-producto interregional model to overcome data scarcity at the subnational level, combining location coefficients with local surveys from 2015-2016. Simulations showed that while tourism boosts local products, this impact could be amplified by developing regional value chains. The findings underscore the potential for sustainable economic development in small, tourism-dependent regions through strategic investments.
Fluvial architecture and paleoenvironmental evolution of the Los Colorados Formation (Norian): Postrift stage of the Ischigualasto–Villa Unión Basin, NW Argentina
A shift from axial to transverse drainage systems played a central role in the postrift basin filling of the Ischigualasto–Villa Unión Basin during the Norian stage. This finding challenges the traditional view that axial systems are the primary sediment feeders in such basins. Researchers analyzed fluvial architecture and paleoenvironmental evolution using facies analysis, architectural-element evaluation, and vertical stacking patterns across 11 stratigraphic intervals of the Los Colorados Formation. The study revealed changes in channel facies concentration, paleocurrents, and sediment provenance, indicating a transition from an axial to a transverse drainage system. This radial pattern in paleocurrent data suggests that transverse systems can significantly influence postrift basin evolution, as evidenced by modern examples.
Los Baldecitos (San Juan, Argentina) como portal del Parque Provincial Ischigualasto (Patrimonio de la Humanidad) : puesta en valor del patrimonio cultural tangible e intangible
Los Baldecitos, a locality adjacent to the UNESCO-listed Ischigualasto / Talampaya Natural Parks in Argentina, holds significant untapped potential for sustainable tourism development. The study identifies key tangible and intangible cultural heritage assets that could attract visitors, while highlighting critical challenges such as inadequate maintenance of sites, lack of institutional support, and the lingering effects of the COVID-19 pandemic. Despite being part of one of Argentina's most visited protected areas, Los Baldecitos fails to benefit from its proximity due to limited local initiatives and infrastructure. The research underscores the need for community-driven projects, supported by subsidies and technical assistance, to capitalize on the region's heritage and align with global trends toward sustainable tourism.
The Late Triassic Ischigualasto Formation at Cerro Las Lajas (La Rioja, Argentina): fossil tetrapods, high-resolution chronostratigraphy, and faunal correlations
A new high-resolution chronostratigraphic framework for the Late Triassic Ischigualasto Formation at Cerro Las Lajas, Argentina, reveals that rhynchosaur-dominated faunas persisted into the earliest Norian. The study, combining detailed lithostratigraphy and U-Pb geochronology from three intercalated tuffs, constrains the formation's deposition between 230.2 ± 1.9 Ma and 221.4 ± 1.2 Ma, with its fossil-bearing interval dated to 229.20 + 0.11/- 0.15-226.85 + 1.45/- 2.01 Ma. This precise dating allows for biostratigraphic correlations across South American basins and provides a ca. 229 Ma age assignment to the ornithischian Pisanosaurus mertii, partially filling a ghost lineage in early dinosaur evolution. The research also introduces two new biozones, the Hyperodapedon and Teyumbaita, based on rhynchosaur ranges.
First record of a basal mammaliamorph from the early Late Triassic Ischigualasto Formation of Argentina
Researchers have identified Pseudotherium argentinus, a new basal mammaliamorph cynodont from the early Late Triassic Ischigualasto Formation in Argentina. This discovery provides critical insights into the evolutionary path leading to mammals and Mammaliaformes. The study utilized high-resolution X-ray computed tomography (CT) to analyze the well-preserved skull of Pseudotherium, revealing unique features such as an elongated but uncoiled cochlea and turbinal-like bones in the nasopharyngeal passage. Phylogenetic analysis suggests that Pseudotherium may be closely related to Tritylodontidae or lie within Mammaliamorpha, though relationships remain uncertain due to limited fossil data. The study highlights the need for more complete specimens and broader CT datasets to clarify these evolutionary relationships. The CT dataset of Pseudotherium argentinus is publicly available under a Creative Commons license.
New Specimen Sheds Light on the Anatomy and Taxonomy of the Early Late Triassic Dinosauriforms from the Chañares Formation, NW Argentina
A new partial skeleton from the Chañares Formation, Ischigualasto / Talampaya Natural Parks, provides critical insights into the anatomy and taxonomy of early Late Triassic dinosauriforms. The specimen (CRILAR-Pv 552) includes previously unknown anatomical features such as a premaxilla, inner ear, and anterior zeugopodium, which clarify debates surrounding the synonymy of two species: Lewisuchus admixtus and Pseudolagosuchus major. Analysis confirms that Pseudolagosuchus major is a junior synonym of Lewisuchus admixtus, resolving a 20-year-old controversy. Phylogenetic analysis positions Lewisuchus admixtus at the base of Silesauridae, contributing to our understanding of early dinosaur evolution.
The Validity of Lagosuchus Talampayensis Romer, 1971 (Archosauria, Dinosauriformes), from the Late Triassic of Argentina
A reassessment of the fossil record from the Ischigualasto / Talampaya Natural Parks, Argentina, reveals that Lagosuchus talampayensis, a key 'proto-dinosaur' species, is not distinct but shares critical anatomical traits with Marasuchus lilloensis. This finding, based on new observations of the holotype's femoral head morphology, suggests L. talampayensis is a senior synonym of M. lilloensis. The study challenges previous classifications and sheds light on early dinosauromorph diversity in the Late Triassic Chañares Formation, refining our understanding of dinosaur precursors' evolutionary relationships.
A new rhynchosaur maxillary tooth plate morphotype expands the disparity of the group in the Ischigualasto Formation (Late Triassic) of Northwestern Argentina
A new rhynchosaur maxillary tooth plate morphotype, discovered in the Ischigualasto Formation (Late Triassic) of Northwestern Argentina, significantly expands the known morphological disparity of hyperodapedontine rhynchosaurs. This specimen, PVL 2728, features a unique combination of traits: a single longitudinal groove dividing symmetric lateral and medial tooth-bearing areas with relatively large tooth crowns, which deviates from previously documented South American rhynchosaurs. Quantitative analyses confirm its distinctiveness, suggesting a greater diversity in the group during the Late Triassic period. This finding challenges existing understanding of rhynchosaur evolution and distribution within southwestern Pangaea.
Ant species (Hymenoptera: Formicidae) in the three forests of the Ischigualasto Provincial Park, a protected area of the Monte Desert, Argentina
A survey of ant species in the Ischigualasto Provincial Park, Argentina, revealed 33 distinct ant species, with 17 representing new records for the Monte Desert and Dry Chaco ecoregions. Prosopis forests emerged as hotspots for ant diversity, hosting 24 unique species out of the 32 identified there, surpassing Ramorinoa (11 species) and Bulnesia (4 species) forests. This study significantly advances our understanding of ant biodiversity in hyper-arid desert habitats, particularly within Prosopis forests, which are critical for conserving species richness amid ongoing desertification pressures.
Pb isotope geochemistry and reappraisal of Sr-Nd isotopes of the Cerro Morado basic magmatism (Ischigualasto-Villa Union Triassic basin, NW Argentina): Implications for the mantle sources
A new isotopic analysis of alkaline basalts from the Los Baldecitos Formation in Argentina's Ischigualasto-Villa Unión Triassic basin reveals that these rocks originated from a single, uncontaminated mantle source with a PREMA reservoir signature. The study, using Sr-Nd-Pb isotopes, found moderately radiogenic lead compositions and highly radiogenic neodymium values, indicating minimal crustal involvement or ancient crust influence. Contrary to previous suggestions, the data rule out a HIMU component in the mantle source, providing clearer insights into the region's geological history.
A New Early Coelophysoid Neotheropod from the Late Triassic of Northwestern Argentina
Researchers have identified Powellvenator podocitus, a new early coelophysoid neotheropod dinosaur from the Late Triassic of northwestern Argentina. This discovery significantly expands the South American record of predatory dinosaurs, which was previously limited to two species. The study analyzed partial hindlimbs and reclassified an earlier specimen, revealing unique anatomical features that distinguish Powellvenator podocitus from other basal dinosaurs. Phylogenetic analysis placed it within Coelophysoidea, as the sister-taxon of Procompsognathus triassicus and Coelophysinae, marking it as the first coelophysoid from South America alongside Lucianovenator bonoi.
Relaciones tróficas entre mamíferos herbívoros nativos y exóticos del Parque Provincial Ischigualasto (San Juan, Argentina)
Research in Ischigualasto Provincial Park reveals that exotic herbivores exhibit broader and more consistent trophic niche breadth compared to native species, which show narrower niches, particularly during the dry season. Despite low densities of exotic species, diet overlap between natives and exotics remains stable across seasons, suggesting minimal competition for food resources. The study highlights the importance of permanent monitoring to assess potential future impacts of exotic species on native herbivore communities in this hyper-arid Monte region.
Revision of the early crocodylomorph Trialestes romeri (Archosauria, Suchia) from the lower Upper Triassic Ischigualasto Formation of Argentina: one of the oldest‐known crocodylomorphs
A detailed revision of the early crocodylomorph Trialestes romeri from Argentina's Ischigualasto Formation challenges prior classifications, confirming it as one of the oldest known non-crocodyliform crocodylomorphs. The study resolves debates about its phylogenetic placement and rejects earlier interpretations that suggested a mesotarsal ankle joint or dinosaurian affinities. Using comprehensive phylogenetic analysis, researchers positioned Trialestes within Crocodylomorpha, closer to Crocodyliformes than other early archosaurs like Pseudhesperosuchus. This work clarifies the species' taxonomic status and significance, highlighting it as one of the most complete early crocodylomorphs from the late Triassic period.
Pre- dispersal seed loss of Ramorinoa girolae (Fabaceae) in Ischigualasto Provincial Park (San Juan, Argentina
A significant proportion of seeds (58%) of the vulnerable tree Ramorinoa girolae, endemic to Argentina, are lost due to pre-dispersal predation by Anypsipyla univitella. This study quantified seed loss and assessed factors influencing predation, revealing that fruits with more predators, more seeds, and smaller sizes experienced higher predation rates. Seed abortion was a minor factor of loss (6%). The research sampled 17 adult trees across three stands in Ischigualasto Provincial Park, analyzing fruit size, number of seeds, and predator presence using Generalized Linear Mixed Models.
Age constraints on the dispersal of dinosaurs in the Late Triassic from magnetochronology of the Los Colorados Formation (Argentina)
A new magnetochronological study of the Los Colorados Formation in Argentina's Ischigualasto-Talampaya Natural Parks reveals that dinosaur-bearing deposits span from 227 to 213 million years ago, confirming their Norian age and predating the Jurassic by over 11 million years. This finding demonstrates a diachronous rise of dinosaurs across the Americas, with North American records (Chinle Formation) appearing later in the Norian. The research suggests that early dinosaur faunas thrived in a temperate humid belt before broader dispersal, likely driven by climate shifts and reduced atmospheric CO₂ levels. The study employs magnetic polarity correlations to refine age constraints, providing critical insights into Late Triassic vertebrate evolution.
Anatomy and phylogenetic position ofVenaticosuchus rusconiiBonaparte, 1970 (Archosauria, Pseudosuchia), from the Ischigualasto Formation (Late Triassic), La Rioja, Argentina
A new phylogenetic analysis confirms that Venaticosuchus rusconii, a Late Triassic pseudosuchian archosaur from the Ischigualasto Formation in Argentina, is a valid ornithosuchid with unique morphological traits. The study, based on a rediscription of its incomplete skull and postcranial elements, identifies distinctive features such as ventrally directed basipterygoid processes, an expanded dentary margin, and the absence of specific foramina that distinguish it from other ornithosuchids like Riojasuchus tenuisceps and Ornithosuchus longidens. Phylogenetic placement shows V. rusconii is more closely related to R. tenuisceps, supported by shared traits in the antorbital fenestra and jugal structure. This research clarifies the evolutionary relationships within Ornithosuchidae, contributing to our understanding of Late Triassic archosaur diversity.
Osteology of Pseudochampsa ischigualastensis gen. et comb. nov. (Archosauriformes: Proterochampsidae) from the Early Late Triassic Ischigualasto Formation of Northwestern Argentina
A new genus, Pseudochampsa ischigualastensis, is proposed for the previously described 'Chanaresuchus ischiguaastensis', a proterochampsid archosauriform from the Early Late Triassic Ischigualasto Formation in northwestern Argentina. Detailed osteological analysis and phylogenetic reassessment reveal that 'Chanaresuchus ischiguaastensis' does not belong to the genus Chanaresuchus, as previously thought. Instead, it forms part of a trichotomy with Gualosuchus reigi and Rhadinosuchus gracilis, challenging the monophyly of Chanaresuchus. This discovery provides critical insights into the taxonomy and evolutionary relationships of proterochampsids, a group of crocodile-like, semi-aquatic archosauriforms endemic to South America during the Middle-Late Triassic period.
Redescription of the Skull ofColoradisaurus brevis(Dinosauria, Sauropodomorpha) from the Late Triassic Los Colorados Formation of the Ischigualasto-Villa Union Basin, northwestern Argentina
A comprehensive redescription of the skull of Coloradisaurus brevis, a basal sauropodomorph from the Late Triassic Los Colorados Formation in Argentina's Ischigualasto-Villa Union Basin, reveals new autapomorphies and supports its placement within Massospondylidae. The study identifies unique cranial features, such as circular upper temporal fenestrae and distinct laminae on the basisphenoid and parasphenoid, while also noting convergent traits shared with plateosaurids, like a low mandibular articulation and broad maxillary wall. This dual characterization highlights the complex evolutionary relationships among basal sauropodomorphs, blending massospondylid characteristics with plateosaurid-like features, suggesting a more nuanced phylogenetic pattern than previously recognized.
Trophic interactions between the native guanaco (Lama guanicoe) and the exotic donkey (Equus asinus) in the hyper-arid Monte desert (Ischigualasto Park, Argentina)
A high overlap in diets between the native guanaco and exotic feral donkey during the dry season suggests potential competition, which could intensify with increasing donkey populations. The study quantified food availability, analyzed diet composition through microhistological fecal analysis, and assessed seasonal dietary shifts. While donkeys consistently relied on grasses, guanacos primarily consumed shrubs, especially during the wet season when grass cover was minimal or absent. This research highlights the ecological impact of invasive species on native fauna in hyper-arid ecosystems like Ischigualasto Provincial Park.
A new non-mammaliaform eucynodont from the Carnian-Norian Ischigualasto Formation, Northwestern Argentina
A new small eucynodont, a non-mammaliaform cynodont, has been identified from the Carnian-Norian Ischigualasto Formation in northwestern Argentina. This discovery enriches the diverse fossil record of the region and provides insights into the evolutionary history of cynodonts during this period. The new taxon is characterized by distinct morphological features, including an extended palatal process of the premaxilla and a unique postorbital bar angle. Phylogenetic analysis places this genus within Probainognathia, more derived than Probainognathus but closely related to Ecteninion and Trucidocynodon. The study proposes a new clade, Ecteniniidae, which represents the sister-group of Prozostrodontia. Additionally, it highlights that the Scaphonyx-Exaeretodon-Herrerasaurus biozone in Ischigualasto exhibits similar cynodont diversity to contemporaneous zones in Southern Brazil, challenging previous assumptions about biogeographical patterns during this time.
Proterochampsia: an endemic archosauriform clade from South America
Proterochampsia, a distinct group of crocodile-like archosauriforms, has been identified as endemic to the late Middle and early Late Triassic periods in South America. This clade, which includes genera such as Cerritosaurus, Proterochampsa, Chanaresuchus, Gualosuchus, and Tropidosuchus, was traditionally confused with crocodilians but has since been clarified through new discoveries and phylogenetic studies to be a non-archosaurian archosauriform. Proterochampsia is considered a potential successive sister-taxa of the crown group Archosauria, shedding light on the evolutionary relationships among Triassic archosaurs. The research, based on fossils from the Ischigualasto-Villa Unión Basin in Argentina and the Parana Basin in Brazil, provides significant insights into the biodiversity and evolutionary history of this region during the Triassic period.
A new proterochampsidChanaresuchus ischigualastensis(Diapsida, Archosauriformes) in the early Late Triassic Ischigualasto Formation, Argentina
Paleontologists have identified a new species of proterochampsid, Chanaresuchus ischigualastensis, within the early Late Triassic Ischigualasto Formation in Argentina. This discovery sheds light on the evolutionary relationships between crocodile-like archosauriforms and the crown group Archosauria, challenging long-held assumptions about their phylogenetic connections. The research employed detailed morphological analysis of fossil specimens to establish the new taxon, contributing significantly to our understanding of prehistoric ecosystems in the region. The Ischigualasto Formation serves as a critical window into Triassic biodiversity.
Basal sauropodomorphs from the Ischigualasto Formation
A new phylogenetic analysis of basal sauropodomorphs from the Ischigualasto Formation, including Eoraptor lunensis, Panphagia protos, and Chromogisaurus novasi, confirms Chromogisaurus as a distinct genus while revealing a weak but structured evolutionary branching at the base of Sauropodomorpha. The study positions Panphagia as the most basal sauropodomorph, followed by Eoraptor, Pampadromaeus, and a clade grouping Chromogisaurus with Saturnalia. This challenges earlier assumptions about the parafiletic nature of early sauropodomorphs. The research combines detailed skeletal analysis of Chromogisaurus novasi's holotype with comparative morphology to refine taxonomic distinctions and phylogenetic relationships, offering new insights into the evolutionary trajectory of these early dinosaurs.
Braincase of Panphagia protos (Dinosauria, Sauropodomorpha)
A partial braincase of the basal sauropodomorph dinosaur Panphagia protos from the mid-Carnian Ischigualasto Formation reveals early evolutionary traits in sauropodomorphs. The disarticulated specimen, including frontal, parietal, prootic, and supraoccipital bones, lacks derived features such as a broad frontal or reduced tympanic/floccular recesses seen in more advanced species. This suggests Panphagia represents an early stage in sauropodomorph evolution, providing insights into the transition from primitive to specialized forms during the Late Triassic.
Hind limb osteology of Gracilisuchus stipanicicorum (Archosauria: Pseudosuchia)
A detailed osteological analysis of the hind limb and pelvic girdle of Gracilisuchus stipanicicorum, a Triassic pseudosuchian archosaur from Argentina, reveals new insights into its anatomical features and evolutionary relationships. The study describes previously underdescribed or misinterpreted regions, providing a more comprehensive understanding of this extinct taxon. While Gracilisuchus shares morphological traits with non-crocodyliform crocodylomorphs—such as the poorly developed femoral fourth trochanter and an underdeveloped femoral head—it lacks key features (e.g., an imperforated acetabulum) that would place it within Crocodylomorpha. These findings tentatively support its affiliation with Sphenosuchia, a clade of early crocodylomorphs, positioning Gracilisuchus as a sister taxon to this group rather than a direct ancestor.
Large-Diameter Burrows of the Triassic Ischigualasto Basin, NW Argentina: Paleoecological and Paleoenvironmental Implications
Researchers have uncovered large-diameter ichnofossils in the Upper Triassic Ischigualasto and Los Colorados formations of northwestern Argentina, revealing early Mesozoic fossorial behavior. Three distinct morphotypes were identified: two likely constructed by tetrapods, given their tunnel networks, and a third with a complex, calcareous structure suggesting combined plant/animal interactions. These burrows, associated with fluvial overbank lithologies deposited under arid conditions, indicate that vertebrates used burrowing to cope with extreme seasonal or perpetual dryness during Pangean climates. Comparisons of burrow morphology with paleovertebrate fauna suggest small carnivorous cynodonts like Ecteninion or Probelesodon as possible architects for Morphotype 1, while the architect for Morphotype 2 remains uncertain due to size mismatches.
Osteology ofEoraptor lunensis(Dinosauria, Sauropodomorpha)
A detailed osteological analysis of the basal sauropodomorph dinosaur Eoraptor lunensis, based on nearly complete skeletal remains from Argentina's Ischigualasto Formation, reveals distinctive anatomical features that differentiate it from contemporaneous theropods like Eodromaeus murphi. Key findings include a lightly built skull with enlarged external naris and unique antorbital fossa morphology, robust long bones in the hind limbs, and a twisted first phalanx of the pollex in the manus—a trait shared with other basal sauropodomorphs but absent in theropods. The study also highlights rudimentary palatal teeth on the pterygoid and vertically oriented marginal denticles, providing new insights into early dinosaur evolutionary diversification within the UNESCO-listed Ischigualasto/Talampaya Natural Parks.
Proterochampsa barrionuevoi (Archosauriformes: Proterochampsia) from the Late Triassic (Carnian) of Argentina and a phylogenetic analysis of Proterochampsia
A restudy of Proterochampsa barrionuevoi, a proterochampsian archosauriform from the Late Triassic Ischigualasto Formation in Argentina, reveals distinct autapomorphies that diagnose the genus. These include unique cranial features such as prominent dermal sculpturing with ridges and nodular protuberances, a hook-like quadratojugal projection, and specific morphological traits of the premaxilla, maxilla, and angular. The study also identifies Proterochampsa nodosa as a valid species, distinguished by fewer cranial ridges with larger protuberances and other cranial characteristics. Phylogenetic analysis supports the monophyly of Proterochampsia, a group that includes Proterochampsa, Chanaresuchus bonapartei, Gualosuchus reigi, Tropidosuchus romeri, and Cerritosaurus binsfeldi. The temporal separation between basal proterochampsians (Proterochampsa and Cerritosaurus) with earliest records in the Late Triassic and other members (Chanaresuchus, Gualosuchus, Tropidosuchus) from the Middle Triassic suggests a hidden diversity of Proterochampsia in the Middle Triassic.
Vertebrate succession in the Ischigualasto Formation
A comprehensive analysis of the Ischigualasto Formation in Argentina reveals that vertebrate diversity and abundance gradually declined over time due to climatic deterioration, with only one abrupt faunal shift. The study, based on 848 fossil specimens representing 29 taxa, identified two new basal dinosauromorphs—an unnamed lagerpetid and a silesaurid, Ignotosaurus fragilis—expanding the known fauna of this Upper Triassic ecosystem. Radioisotopic dating of ash layers provided a precise chronological framework, enabling the detection of subtle changes in faunal composition across three biozones. Notably, the dominant cynodont Exaeretodon was replaced by the rare dicynodont Jachaleria at the end of the second biozone, marking the only abrupt shift in this otherwise gradual decline.
Vertebrate taphonomy of the Ischigualasto Formation
A comprehensive analysis of vertebrate taphonomy in the Ischigualasto Formation reveals distinct preservation trends linked to sedimentary facies and stratigraphic position, reflecting basin evolution and paleoclimate. Fossils are predominantly concentrated along basin margins, with floodplain deposits preserving 88% of occurrences, ranging from unidentifiable fragments to articulated skeletons. Coarser-grained fluvial channel deposits account for 12%, including well-preserved cynodont skulls. The basal La Peña Member shows highly weathered, disarticulated fossils with hematitic permineralization, while the overlying Cancha de Bochas Member (65% of occurrences) features calcite-permineralized remains from isolated bones to complete skeletons. The Valle de la Luna Member preserves a unique association of vertebrate and plant fossils under wetter conditions, marked by superficial and penetrating hematite precipitation. The uppermost Quebrada de la Sal Member is nearly barren of fossil remains.
A Basal Dinosaur from the Dawn of the Dinosaur Era in Southwestern Pangaea
A new basal theropod dinosaur, previously unidentified, was discovered in the Ischigualasto Formation of northwestern Argentina, shedding light on the dawn of the dinosaur era around 230 million years ago. This finding challenges the traditional view that dinosaurs rose to dominance by replacing non-dinosaurian herbivores, as the study reveals a sequential extinction pattern unrelated to increasing dinosaur diversity. Researchers also reassessed Eoraptor, reclassifying it as a basal sauropodomorph, and divided the faunal record into biozones using (40)Ar/(39)Ar dating techniques. This work provides critical insights into the ecological dynamics of southwestern Pangaea during the Late Triassic.
Nuevo Material Postcraneano deSaurosuchus galileiReig (Archosauria: Crurotarsi) del Triásico Superior del Centro-Oeste de Argentina
A rare, well-preserved postcranial skeleton of Saurosuchus galilei, a rauisuchid archosaur from the Late Triassic Ischigualasto Formation in Argentina, reveals key morphological traits that shed light on its evolutionary relationships and functional adaptations. The newly described material includes the proatlas-atlas-axis complex, an articulated vertebral column, and both scapulae, providing unprecedented insights into this group's skeletal structure. The cervical vertebrae exhibit a short, robust neck with anteroposterior compression and dorsoventrally elongated centra, while the dorsal region features keeled centra and expanded neural spines. The caudal series displays axially compressed centra with a ventral groove, and the scapulae are notably robust with a brief expansion and slightly curved blade. These findings contribute to understanding the morphological diversity of rauisuchids, aiding in morphofunctional and phylogenetic analyses.
Registro de la relación isotópica de carbono en la paleoflora de la Formación Ischigualasto (Triásico Superior), noroeste Argentino: implicaciones paleoatmosféricas
A detailed isotopic analysis of the Upper Triassic flora from Ischigualasto / Talampaya Natural Parks, Argentina, reveals a mean carbon isotope ratio (δ13C) of -25.4‰, consistent with C3 plants and indicating minimal diagenetic alteration. This value is enriched by ~3‰ compared to Middle Triassic plants, suggesting a disturbance in the global carbon cycle during the Early Mesozoic. The study also estimates a paleo-atmospheric isotopic composition of -6.1‰, differing slightly from marine carbonate proxies, possibly due to atmospheric CO2/O2 ratios or hydric stress. The research provides critical data for chemostratigraphic correlation and offers insights into paleoatmospheric conditions during the Carnian period (~225 Ma).
A new early dinosaur (Saurischia: Sauropodomorpha) from the Late Triassic of Argentina: a reassessment of dinosaur origin and phylogeny
A new early dinosaur species, Chromogisaurus novasi, has been discovered in the Late Triassic Ischigualasto Formation of Argentina, challenging traditional views on dinosaur diversity and dominance. This find reveals that dinosaurs first appeared as a diverse group, though numerically minor, with their numerical rise over other tetrapods occurring diachronously after an initial phase of low abundance but high diversity. Phylogenetic analysis places Chromogisaurus at the base of Sauropodomorpha within the Guaibasauridae family, introducing it as the first member of this group and naming a new subfamily, Saturnaliinae, which includes Chromogisaurus and Saturnalia. The study also reclassifies Eoraptor as the sister-taxon to Neotheropoda and herrerasaurids as non-eusaurischian saurischians, providing significant insights into early dinosaur evolution.
A new herrerasaurid (Dinosauria, Saurischia) from the Upper Triassic Ischigualasto Formation of northwestern Argentina
A new herrerasaurid dinosaur, Sanjuansaurus gordilloi, has been identified from the Upper Triassic Ischigualasto Formation in northwestern Argentina. This discovery challenges previous assumptions about the diversification of saurischian dinosaurs, suggesting that they were already widely diversified by the late Carnian period rather than increasing in diversity across the Carnian-Norian boundary. The research involved a phylogenetic analysis that placed Sanjuansaurus within Herrerasauridae, at the base of Theropoda, alongside other known taxa such as Herrerasaurus and Staurikosaurus. The study highlights the significant paleontological importance of the Ischigualasto/Talampaya Natural Parks, contributing to our understanding of early dinosaur evolution in southwestern Pangea.
A new species of Rhinella (Anura: Bufonidae) from Ischigualasto Provincial Park, San Juan, Argentina
Researchers have identified and described a new species of toad, Rhinella bernardoi, from the Ischigualasto Provincial Park in Argentina. This discovery adds to the granulosa group within the Rhinella genus, with distinct morphological features distinguishing it from related species such as R. bergi, R. fernandezae, and R. granulosa. The study also provides detailed osteological descriptions of the new species' skull and vertebral column, contributing valuable data on its geographic distribution and natural history. This finding expands our understanding of amphibian biodiversity in one of Argentina's UNESCO-listed parks.
Implications of the Newark Supergroup-based astrochronology and geomagnetic polarity time scale (Newark-APTS) for the tempo and mode of the early diversification of the Dinosauria
A high-resolution astrochronological framework (Newark-APTS) reveals that stage-level correlations of Late Triassic and Early Jurassic continental sequences were misaligned by up to 10 million years, challenging long-standing biostratigraphic assumptions. New U–Pb dating confirms the accuracy of these correlations, enabling precise dating of dinosaur diversification. Key findings include: no unequivocal Carnian-age dinosaurs; slow saurischian diversity increase in the Norian with no ornithischians; profound provinciality during the Norian and Rhaetian; persistence of classic biotic assemblages into the Rhaetian; a mid-Norian biotic transition coinciding with the Manicouagan impact; and globally homogenous, low-diversity Hettangian-Sinemurian communities. The study underscores the need for region-specific geochronologies to unravel dinosaur diversification patterns.
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