A small, incomplete synsacrum from Ypresian (early Eocene) levels of the Cucullaea I Allomember (La Meseta Alloformation) on Marambio (Seymour) Island, Antarctica, is examined. The synsacrum, which is dorsoventrally depressed and laterally widened, preserves two complete and one incomplete fused vertebrae. It exhibits a crista ventralis synsacri instead of the more typical sulcus ventralis synsacri observed in most Neornithes. Notable features include the presence of large, oval foramina intervertebralia that pierce the corpus synsacri and lateral concavities. Extensive comparisons with a broad sample of extant and extinct birds, including representatives of Tinamiformes, Anseriformes, Podicipediformes, Rallidae, Charadriiformes, Gaviiformes, Sphenisciformes, Procellariiformes, Phalacrocoracidae, Strigiformes, Accipitriformes, Phorusrhacidae, Falconiformes, and Pelagornithidae, reveal partial similarities with certain Charadriiformes but no exact match among the studied taxa. Given its unique combination of characters and its incomplete nature, the material is referred as an indeterminate Neognathae. Although a more precise taxonomic assignment is not possible, this synsacrum provides novel anatomical information as evidence of a small marine bird or shorebird in the Eocene of Antarctica. It underscores the significance of fragmentary postcranial elements in reconstructing past ecosystems and reveals a greater complexity in the structure of these avian communities than previously recognized.
The Bryn Gwyn (Chubut Province, Patagonia, Argentina) is a classic fossiliferous site, long recognised for its Cenozoic vertebrate record. However, its invertebrate content remains poorly documented. The Lower Miocene Gaiman Formation, representing the “Patagonian Transgression”, has yielded abundant vertebrates, whereas invertebrate faunas were historically mentioned only briefly, mostly as molds. New material was collected following the most recent stratigraphical framework at the Bryn Gwyn locality. Fossiliferous levels were identified, and several specimens were described and studied using updated systematic arrangements. The Bryn Gwyn fossil invertebrate assemblage previously comprised only 11 taxa and a few higher-level groups. Our new study documents 27 genera or species-level taxa, nearly doubling the known diversity. A new species, namely Buccinanops halleri sp. nov., is also described. Several groups previously reported without precise determinations (e.g., bryozoans, gastropods, irregular echinoids) are now taxonomically resolved, and two additional higher-level groups, Brachiopoda and Scaphopoda, are recorded for the first time in the region. Comparisons with other Patagonian Cenozoic assemblages reveal strong faunal affinities with the time-equivalent Chenque and Monte León formations. These results substantially refine the taxonomic composition of the Bryn Gwyn invertebrate fossil fauna and provide a stronger basis for its inclusion in regional biostratigraphic correlations and paleoenvironmental reconstructions of the “Patagonian Transgression”.
Non-marine ostracods are environmental proxies widely used in Quaternary environmental and climatic reconstructions. In South America (Neotropical Region), extant Limnocytheridae is the third most diverse family, with Limnocythere species typically inhabiting hyposaline to mesosaline waters. The South American Transitional Zone (SATZ), is defined across South America by arid-semiarid climate, holding the Argentinean section five endemic Limnocythere species, representing highest diversity of Limnocythere and the speciation role of this transitional area. This study analyses the diversity, paleoecological traits and distribution of Quaternary Argentinean Limnocythere, describing Limnocythere perseverans sp. nov. from Laguna Llancanelo basin, Salina del Bebedero and Laguna Runtuyoc (Argentinean SATZ), providing a dichotomous key for the 13 Quaternary species found in Argentina. The new species differs from L. cusminskyae (Neotropical Region, humid Chaco-Pampean) and L. staplini (Nearctic Region), in valve morphology (valve shape and hinge structure) and ecological requirements. Limnocythere perseverans sp. nov. prefers sodium-chloride, sulfate or chloride-sulfate waters, segregated from L. cusminskyae living in sodium, bicarbonate-rich waters, and L. staplini found in bicarbonate-depleted waters. These differences highlight its value to reconstruct changes in salinity and water chemistry. The morphological similarities among these three species open questions on biogeographical aspects of aquatic ecology. Further research is necessary to assess whether these species evolved from a shared ancestor or are an example of morphological convergence derived by the adaptation to similar ecological pressures within the Neotropical and Nearctic regions.
Since its founding in 1870, the Colegio Seminario San Rafael of Valparaiso has offered natural science-related courses, complemented by laboratory work. Thus, in 1881, five science "cabinets" were established within the school premises, and in 1886, the building that still houses them was inaugurated. The Museo Seminario Valparaiso (MSV) houses various natural history collections, among which a notable paleontological collection stands out, comprising paleobotanical, invertebrate, and vertebrate specimens. Within one of the oldest mineral collection showcases, associated with copper oxides and sulfides samples, a proximal fragment of a right sauropod ulna was found. This ulna must have been deposited long ago, which is proven when it is considered that the associated mineral specimens with collection register labels on the shelf dates between 1860 and 1896, and because this collection has not been modified and it has remained unchanged for over a century. On the other hand, it was only in the 1960s that the first formal descriptions of dinosaur bone records in Chile were made, based on indeterminate titanosaur remains from the informal unit "Estratos de Quebrada La Totora". Morphological comparisons of the ulna suggest affinities with the clade Titanosauria. Furthermore, based on its preservation characteristics, the provenance of the specimen is attributed to the Estratos de Quebrada La Totora, Coquimbo region. In this way, the specimen could represent the first discovery of a non-avian dinosaur in Chile and the first historical evidence of titanosaurs found in a Chilean museum collection.
Cranial muscles perform important roles triggering diverse paleobiological faculties, such as feeding, communication, alert postures, etc. Within Sauropoda, a clade with high specializations in skull architectures, and several partially complete skulls recovered, detailed reconstructions of the cranial muscles are mainly limited to two of the most famous taxa of the clade: Diplodocus and Camarasaurus. The cranial musculature for Dicraeosauridae, a minor group within the clade, has been gingerly described, based on the few suitable specimens. Herein, the craniomandibular, extrinsic eye, and cervicocranial musculatures of Bajadasaurus pronuspinax are inferred, resulting in the first detailed reconstruction for Dicraeosauridae on these muscular groups, and these are compared with previous inferences in Dicraeosauridae and with other Sauropoda and non-avian dinosaurs. The musculature of Bajadasaurus shows a shift of angle in the temporal musculature when passing through the inferior temporal window (probably indicating the presence of a cartilage for support), an important role of the orbitotemporal muscles in a hypothetical cranial kinesis (which, if true, would allow pseudo-palinal movements in a rostral directionduring the feeding process), an avian-like configuration of the eye muscles, and high lateroflexor moment arms for the skull-neck complex. Dicraeosauridae show clear osteological correlates for a high number of the craniomandibular and cervicocranial muscles, albeit some of these correlates might not be exclusively dedicated for musculature, and could be indicating the presence of alternative soft tissues.
South American Mesozoic vertebrate fossils are key in contrasting the classic North American and European views of clades evolution. During the last decades, several relevant findings of stegosaurian remains from Argentina show a greater diversity than previously thought. These include the early stegosaur Isaberrysaura from Los Molles Formation (Middle Jurassic) and indeterminate stegosaurian remains from the Cañadón Calcáreo (Upper Jurassic) and the La Amarga (Lower Cretaceous) formations, all from the Argentinian Patagonia. In addition to these scarce records, new remains from the Berriasian–Valanginian Bajada Colorada Formation of Neuquén Province (Argentina) are presented here. These consist of sacral vertebrae, dorsal ribs and several osteoderm types, including stegosaurian-like spines. The shape analysis of the sacral vertebrae, anatomic features (e.g., sacral vertebrae and ribs dorsoventrally compressed, and dorsal ribs with T-shaped proximal transversal section), and the morphologic disparity of the osteoderms, support an assignation to Thyreophora with affinities to Stegosauria. The finding of these remains in Bajada Colorada reinforces the presence of stegosaurs in Argentinian Patagonia during the Lower Cretaceous. Our explorations and research in Bajada Colorada also support that the historical absence of stegosaurian remains in Southern continents was an effect of searching and/or preservational biases, as other authors proposed. These new stegosaurian remains also support the presence of a transitional fauna in Bajada Colorada including both Jurassic and Cretaceous components.
A tarsometatarsus recovered from the lower Pleistocene levels of the La Esperanza Formation in Olavarría, Argentina, represents the first avian remains reported from this locality. Its morphology and size allow its assignment to Aramides cajaneus (Aves, Gruiformes), a species that still occurs in or near the area. Members of the genus Aramides are terrestrial birds closely associated with wetland environments, providing valuable paleoenvironmental insight into the conditions that prevailed in the region during the Pleistocene.
New specimens of Aturia (Nautilida) were collected from the late Eocene to early Oligocene deposits of the San Jacinto Formation near Ovejas (Sucre, northern Colombia). These specimens, alongside historical material collected from a nearby region, are identified as Aturia peruviana. The morphological analysis of the shell (the phragmocone and suture line characters) confirms that Aturia colombiana is a junior synonym of A. peruviana, in conformity with previous taxonomic proposals. Furthermore, the stratigraphic range of A. peruviana in Colombia is constrained to the upper Eocene to lower Oligocene, consistent with its documented occurrence in Peru.
Palaeontology in the state of Aguascalientes (México) has an extensive history dating back to 1799. However, it was not until the 1950s that Oswaldo Mooser began to formally describe the palaeontological biodiversity of the state, together with other palaeontologists such as Walter W. Dalquest, with whom he even described multiple new species from local discoveries. Much of the fossil material collected by Mooser was donated to different scientific collections, but the location of several specimens was never specified, and they were lost for decades, including holotypes. Bibliographic sources were consulted to trace the location of part of the Mooser’s collection. A total of four local, national, and foreign institutions were consulted to examine the palaeontological material, and a compilation of various fossils collected by Mooser in Aguascalientes was made, resulting in 76 original specimens of which nine are holotypes. Additional bibliographic sources were used to describe and reassess some specimens that had not been properly evaluated before. Previously published information of the fossil material was complemented, and the anatomical description of some specimens is also presented for the first time. Twenty new reports of unpublished fossils collected by Mooser are addressed in this work. The data obtained have implications for the evaluation of the examined taxa, as the specimens documented in this study still require intensive and specific analyses that cover aspects of their systematics, evolution, ecology, and natural history. Thus, the present work aims to serve as a basis for future palaeontological studies.
In the south-central area of Chubut Province, excellent outcrops of sedimentary rocks which comprise the main fill of the Golfo San Jorge Basin are well exposed. Within this basin, due their abundance of vertebrate fossil remains, stand out the Bajo Barreal Formation (early Cenomanian-late Turonian) and the Lago Colhue Huapi Formation (Coniacian-Maastrichtian). Although the record is largely dominated by saurischian dinosaurs, ornithischian fossils, particularly ornithopods, have increased in recent years. In this context, this contribution aims to increase our knowledge of the basal ornithopods Notohypsilophodon comodorensis and Sektensaurus sanjuanboscoi from the Bajo Barreal and Lago Colhue Huapi formations, respectively. Also, for the first time, aspects of the paleohistology are addressed and described for both ornithopods. Likewise, with the lines of evidence available at the moment and waiting new studies that better resolve the systematic relationships at the base of Ornithopoda, it is suggested that the elasmarians would have originated in eastern Gondwana probably during the early Cretaceous. Subsequently, they would have dispersed to western Gondwana where they attained larger body sizes. Finally, at least in central Patagonia, environmental selection is observed between basal ornithopods (elasmarians) and derived ones (hadrosaurids). The former would have developed in inland environments with climates with certain seasonality, while the hadrosaurids would have selected environments close to the sea and with a more homogeneous climate.
The Central Pampa plain (36 degrees-37 degrees S; 60 degrees-61 degrees W) presents numerous shallow lakes subjected to climatic dynamics and anthropogenic impacts during the Late Holocene, but few were analyzed. New studies are essential to provide an integral and regional analysis of these lakes evolution. In this context, a multi-indicator analysis including sedimentary and palynomorph (pollen and non-pollen) indicators was performed to reconstruct the paleoenvironmental evolution of Blanca Chica shallow lake during the past 1700 years. Four main lake condition stages were identified. Natural forcing dominated the period prior to 1880 CE, followed by a scenario characterized by the combined action of anthropic and natural forcings. Between 260-800 CE, laminated sediments and phytoplankton dominance point to a high-level, turbid, nutrient rich lake during a wet period. Between 800-1600 CE, massive sediments, increasing halophytic vegetation and decreasing phytoplankton indicate a lower water-lake level in a dry context. This drought scenario was intensified between 1660-1830 CE as suggested by massive mottled sediments, submerged macrophytes remains and filamentous chlorophytes. A shift to wetter conditions is indicated for 1830-2015 CE, by a perennial, turbid, eutrophic, high-level lake with massive organic sediments. The onset of agriculture and cattle was shown bya raise in pollen taxa (i.e., 1830) and increased sedimentation rates related to soils erosion which suggested intense anthropic activity. The change in the aquatic communities and sedimentology for the last 30 years allowed considering a shift to high anthropogenic impact combined with an increase in precipitation which generated an accelerated eutrophication of the lake.
The cheilostome bryozoan genus Cellaria is characterized by articulated, dichotomously branching colonies, which are composed of cylindrical internodes joined by cuticular nodes. The genus includes over 130 species, with approximately 70 taxa ranging from the late Paleocene to the Holocene. This study describes Cellaria daniana sp. nov., based on material collected from the Roca Formation, upper Danian (Paleocene) of northern Patagonia, Argentina, making it the earliest known occurrence of the genus. The most distinctive feature of C. daniana sp. nov. is its vicarious avicularium, which lacks mandibular pivots and exhibits a distally depressed cryptocyst, resembling that of C. stachi from the Eocene of Victoria, Australia. Cellaria stachi shows a great morphological similarity with C. daniana sp. nov., supporting a close biogeographic connection between South America and Australasia during the Early Cenozoic.
This contribution integrates palynofacies, organic geochemical and sedimentological analyses to characterize the depositional environment and the kerogen properties related to the hydrocarbon source potential of the Vaca Muerta Formation at the Mallin Quemado Norte (MQN) and Puerta Curaco (PC), Neuqu & eacute;n Basin, Argentina. Thirty-five outcrop samples were analyzed for palynofacies and total organic carbon (TOC). At MQN, five palynofacies types and sedimentological evidence suggest deposition mainly in an outer shelf marine environment with a variable continental input. At PC, three palynofacies types and sedimentological observations point to accumulation mainly in an outer ramp marine environment with minimal to moderate terrigenous input. Depositional processes involve an interplay of suspension settling from the water column (marine snow) and buoyant plumes, followed by reworking of the seafloor by bottom currents and sediment gravity flows. Under identical hydrodynamic flow conditions, equidimensional phytoclasts respond better to transport sorting than blade-shaped. The first documentation of high-relief organic spheres (HROS) in this unit points to redox oscillation between sulfidic and ferruginous anoxic microenvironments during early diagenesis. Low HROS percentages and crypto-bioturbated strata suggest that bottom waters were not strictly anoxic. Organic carbon preservation may be partly related to the role of extracellular polymeric substances as an organic matter encapsulator. The kerogen aligns with type III-IV, and TOC values are mainly high (MQN: up to 4.69%; PC: 4.9-10.4%). Although an over-mature state cannot be entirely ruled out (highly dark palynological matter), the poor preservation of the kerogen suggests a negligible hydrocarbon potential.
This paper presents the taphonomic and geoarchaeological study of a thin shell lens identified 3.2 km from the coast of San Sebastian Bay on the hilltop of the inland Cerro Bandurrias archaeological locality (Tierra del Fuego Province, Argentina). The biological assemblage of the shell lens comprises marine fauna (bivalves, gastropods, and fish) that may represent the remains of the occasional exploitation of littoral resources by hunter gatherers. However, since the lack of unequivocal anthropogenic signals, alternative non-anthropogenic hypotheses need to be also assessed. Indeed, the time frame of the shell lens (radiocarbon dated as ~6500 cal. years BP) indicates that the bioclast accumulation occurred during the Middle Holocene marine transgression with a different paleogeography, when the hill was part of a coastal landform (peninsula). The methodological design comprised the combination of different and independent sources of information and the techniques applied to assess competing genetic hypotheses. Based on compositional, taphonomic and sedimentological analyses, our research suggests that the most parsimonious explanation is that hunter gatherers were the primary agents of bioclast accumulation of the lens. Thus, this ephemeral archaeological evidence provides a new record for the human exploitation of littoral resources on the Atlantic coast of Isla Grande de Tierra del Fuego during the Middle Holocene. The conspicuous character of shells improves the archaeological visibility of short term, nonredundant past human occupations.
Actualistic taphonomic observations of guanaco carcasses resulting from two winter mass death events that occurred in 2020 and 2023 at various locations in the Coyle-Gallegos River interfluve (Santa Cruz, Argentina) provide valuable information about the formation of the fossil record. In this paper, we discuss how studying these die-offs allows us to monitor the formation of the so-called averaged samples. The longitudinal monitoring of carcass assemblages aggregated in different years forced us to change the scale of analysis, which gradually approached a controlled averaged sample. In this long-term study, we evaluate the main variables involved in the processes of guanaco carcass accumulation, such as the regularity and causes of massive accumulations, the locations of dead guanaco concentrations, the spatial superposition of deaths, and the variation in the size of bone patches due to processes such as carnivore action, trampling, and gravity sliding. For the analysis, we used the concepts of accumulation cycle, tempo, settling in, fossil stability, formational forcing, and retarding factors. Our results allow us to propose various conditions of bone preservation and identify spatial sectors with better burial opportunities, which are useful for constructing long-term viable analogous models, the usual ones of the archaeological and paleontological records.
The invasive bivalve Corbicula fluminea has been known in the Río de la Plata for approximately 40 years. This decadal time lapse fill a gap in taphonomic studies. Our study is the second to investigate taphonomic modifications on valves of this species in Uruguay, expanding the temporal resolution of the first. We divided the valve into four sectors and recorded fragmentation, periostracum loss, and corrasion, categorizing these attributes into three severity levels. We also observed no attempts at bioerosion and bioencrustation. The central sector is the most frequent among all samples, and the posterior one is the least frequent. The differences in damage were tested using the X2 test, the Bonferroni correction, and an average taphonomic score. We evaluated the extent of taphonomic damage over time by comparing the average taphonomic score using Kendall’s tau. The tests revealed several statistically significant differences. The umbonal and posterior sectors are differently represented, with the 2008 sample being different in both cases. The central and anterior sectors do not exhibit differences. Fragmentation exhibits differences in all sectors except the anterior over the years; category 0 is the most represented in all years and sectors. Periostracum damage shows no statistically significant differences in sectors or years; category 2 is the most represented. Corrasion differs among the three samples, varying over the years in different sectors; category 2 is the most represented. In conclusion, there are statistically significant differences in the sectors represented and in fragmentation. However, no linear trend was observed over the years.
Neotaphonomic studies of vertebrates provide information about the mechanisms and processes that can modify the original characteristics of skeletal elements and can be used as analogues for interpretations on the origin of archeological and paleontological assemblages. The neotaphonomic evaluation of non-ingested bones (leftover prey remains) and modified digested bones by the crowned eagle (Buteogallus coronatus Accipitriformes, Accipitridae) is presented. Bones were recovered from the nests located in the central–west La Pampa Province, Argentina. Leftover prey remains include representatives of Aves, Iguania, Ophidia, Cingulata, Lagomorpha, and Carnivora. Bones from pellets correspond to Ophidia, Rodentia, and osteoderms of two armadillos Chlamyphoridae (Xenarthra, Cingulata). Some of the latter correspond to pichi (Zaedyus pichiy Euphractinae), a common species that is usually located in the diet of B. coronatus. Zaedyus pichiy osteoderms, recovered from pellets, present modifications in the original ornamentation, as well as a reduction in their thickness. Various pellets also contained remains of pink fairy armadillo (Chlamyphorus truncatus, Chlamyphorinae), a small paradigmatic, nocturnal and fossorial species, endemic to centralwestern Argentina, which is recorded for the first time as part of this raptor diet. This first mention of Chl. truncatus being captured by the crowned eagle is relevant because it involves two little–known and sympatric species, in an area where this armadillo is endemic. Osteoderms of Chl. truncatus show an extreme degree of modification, and it is interpreted that its potential of preservation in the fossil record is very low.
Over the past four decades, global actualistic taphonomy studies have grown significantly, driven by increased interest in present day patterns and processes of fossilization. South America has mirrored this trend, though the exact growth level is unclear. This study compiles actualistic taphonomy research in South America based on internationally accessible journal articles and book chapters using databases such as Web of Science, ResearchGate, Google Scholar, and Academia. Results revealed a steady rise in studies from 1985, with Argentina leading, followed by Brazil, Uruguay, and a few other countries with lesser representation. Terrestrial environments have seen the most extensive research, largely due to archaeologists and vertebrate paleontologists, with marine environments (mainly mollusk-based studies) following. Freshwater actualistic taphonomy began in 2006 and was the next most commonly represented, while estuarine and lagoonal environments were the least studied. Most research has been naturalistic: examining taphonomic patterns, taphofacies, live-dead fidelity, and time-averaging. However, experimental studies increased markedly after 2009. Synthesis papers appeared from 2007, reflecting the growing body of literature. Archaeological studies have been the most prolific, with vertebrate studies dominating the region’s actualistic taphonomy literature, followed by research on mollusks and lithics. Brachiopods, foraminifera, diatom, pollen, and phytoliths have developed less. Several groups, including plants, arthropods, worms, lichens, charcoal, pottery, rock art paintings, and sediments, remained poorly studied, highlighting the need for further research. This review underscores the significant progress made in South American actualistic taphonomy but also points to underrepresented environments and taxonomic groups that should be addressed in future studies.
The Chañares Formation in north-western Argentina has provided an impressive number of specimens of early archosauriforms, dicynodonts, and non-mammaliamorph cynodonts. However, there is a very low diversity of cynognathian cynodonts. Herein, we report on Pontognathus ignotus gen. et sp. nov., a small new traversodontid from the traditional Late Triassic Carnian levels of the unit. It differs from other traversodontids for lacking a maxillary platform lateral to the posterior postcanines and by presenting a unique combination of characters from the premaxilla, maxilla, and dentition (i.e., the precanine diastema; the placement of the paracanine fossa; the number of upper postcanines; the general outline of the upper postcanines crown in occlusal view; the shouldering between adjacent teeth; the expansion of the crown distolateral to the sectorial crest; the extension, limits and deepness of the occlusal basin; the distal ridge-like bulging at the base of the crown; the number and relative placement and development of the cusps). It is a relatively small taxon inferred to have occupied a specialized, small herbivorous/omnivorous role, which in this fauna is otherwise only shared by small individuals of the traversodontid Massetognathus pascuali.
The Museo de La Plata (MLP, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata) houses Antarctica's largest fossil vertebrate collection. This collection is a major international research resource and constitutes one of Antarctica's most important records of vertebrate history and evolution. The principal focus of this collection is on vertebrate fossils from the Antarctic Peninsula (Late Cretaceous and Paleogene of the James Ross Archipelago, NE Antarctic Peninsula and the Jurassic of the Antarctic Peninsula). The collection is estimated to consist of over 32,000 specimens, including fossils of fishes, anurans, marine reptiles (plesiosaurs and mosasaurs), avian and non-avian dinosaurs, turtles, and marine and terrestrial mammals. The collection comprises many complete and extraordinarily well-preserved skeletons and has 22 holotypes. It also contains several institutional icons, including the skeletons of the elasmosaurid plesiosaur Vegasaurus and several non-avian dinosaurs such as Antarctopelta and Trinisaura, as well as non-avian dinosaurs Vegavis and Conflicto. The MLP Antarctic fossil vertebrate collection dates from 1978; its importance lies not only in the fact that it is globally one of the main reference collections of Antarctic paleontological material but also in its high proportion of Mesozoic and Cenozoic faunas, which can be used to understand evolutionary dynamics, continental movements, and climatic changes over the past 80 Ma. The collection was made under the auspices and agreement between the Direccion Nacional del Antartico - Instituto Antartico Argentino and the Museo de La Plata in 1983.
