Onthophagus pilauco sp. nov. (Coleoptera, Scarabaeidae): evidence of beetle extinction in the Pleistocene–Holocene transition in Chilean Northern Patagonia

The South American Pleistocene–Holocene transition has been characterized by drastic climatic and diversity changes. These rapid changes induced one of the largest and most recent extinctions in the megafauna at the continental scale. However, examples of the extinction of small animals (e.g., insects) are scarce, and the underlying causes of the extinction have been little studied. In this work, a new extinct dung beetle species is described from a late Pleistocene sequence (~15.2 k cal yr BP) at the paleoarcheological site Pilauco, Chilean Northern Patagonia. Based on morphological characters, this fossil is considered to belong to the genus Onthophagus Latreille, 1802 and named Onthophagus pilaucosp. nov. We carried out a comprehensive revision of related groups, and we analyzed the possible mechanism of diversification and extinction of this new species. We hypothesize that Onthophagus pilaucosp. nov. diversified as a member of the osculatii species-complex following migration processes related to the Great American Biotic Interchange (~3 Ma). The extinction of O. pilaucosp. nov. may be related to massive defaunation and climatic changes recorded in the Plesitocene-Holocene transition (12.8 k cal yr BP). This finding is the first record of this genus in Chile, and provides new evidence to support the collateral-extinction hypothesis related to the defaunation.

New radiometric 40Ar–39Ar dates and faunistic analyses refine evolutionary dynamics of Neogene vertebrate assemblages in southern South America

The vertebrate fossil record of the Pampean Region of Argentina occupies an important place in South American vertebrate paleontology. An abundance of localities has long been the main basis for constructing the chronostratigraphical/geochronological scale for the late Neogene–Quaternary of South America, as well as for understanding major patterns of vertebrate evolution, including the Great American Biotic Interchange. However, few independently-derived dates are available for constraining this record. In this contribution, we present new 40Ar/39Ar dates on escorias (likely the product of meteoric impacts) from the Argentinean Atlantic coast and statistically-based biochronological analyses that help to calibrate Late Miocene–Pliocene Pampean faunal successions. For the type areas of the Montehermosan and Chapadmalalan Ages/Stages, our results delimit their age ranges to 4.7–3.7 Ma and ca. 3.74–3.04 Ma, respectively. Additionally, from Buenos Aires Province, dates of 5.17 Ma and 4.33 Ma were recovered for “Huayquerian” and Montehermosan faunas. This information helps to better calibrate important first appearances of allochthonous taxa in South America, including one of the oldest records for procyonids (7.24–5.95 Ma), cricetids (6.95–5.46 Ma), and tayassuids (> 3.74 Ma, oldest high-confidence record). These results also constrain to ca. 3 Ma the last appearances of the autochthonous sparassodonts, as well as terror birds of large/middle body size in South America. South American faunal turnover during the late Neogene, including Late Pliocene extinctions, is interpreted as a consequence of knock-on effects from global climatic changes and initiation of the icehouse climate regime.

A Pliocene–Pleistocene continental biota from Venezuela

The Pliocene–Pleistocene transition in the Neotropics is poorly understood despite the major climatic changes that occurred at the onset of the Quaternary. The San Gregorio Formation, the younger unit of the Urumaco Sequence, preserves a fauna that documents this critical transition. We report stingrays, freshwater bony fishes, amphibians, crocodiles, lizards, snakes, aquatic and terrestrial turtles, and mammals. A total of 49 taxa are reported from the Vergel Member (late Pliocene) and nine taxa from the Cocuiza Member (Early Pleistocene), with 28 and 18 taxa reported for the first time in the Urumaco sequence and Venezuela, respectively. Our findings include the first fossil record of the freshwater fishes Megaleporinus, Schizodon, Amblydoras, Scorpiodoras, and the pipesnake Anilius scytale, all from Pliocene strata. The late Pliocene and Early Pleistocene ages proposed here for the Vergel and Cocuiza members, respectively, are supported by their stratigraphic position, palynology, nannoplankton, and 86Sr/88Sr dating. Mammals from the Vergel Member are associated with the first major pulse of the Great American Biotic Interchange. In contrast to the dry conditions prevailing today, the San Gregorio Formation documents mixed open grassland/forest areas surrounding permanent freshwater systems, following the isolation of the northern South American basin from western Amazonia. These findings support the hypothesis that range contraction of many taxa to their current distribution in northern South America occurred rapidly during at least the last 1.5 million years.

<i>Selenogonus narinoensis</i> Stirton, 1947 (Tayassuidae, Cetartiodactyla, Mammalia): taxonomic status and paleobiogeographic implications

The species Selenogonus narinoensis was described by Stirton (1947) based on a single specimen which comes from sediments cropping out in the Cocha Verde locality, Nariño Department (Colombia), tentatively referred to the late Pliocene–Pleistocene (MGN 931; IGM p002118, Museo Geológico Nacional, Servicio Geológico Colombiano, Bogotá). However, morphological studies and comparative morphometric observations of the specimen suggest that (1) no diagnostic character supports the validity of the species Selenogonus narinoensis (here considered species inquirenda); (2) a combination of features (e.g., the mandibular condyle located behind the posterior edge of the vertical mandibular ramus, the angular process which projects laterally outwards, a bunolophodont crown morphology, a mesodont crown height, and a simple crown morphology of the third lobe of m3) indicates it belongs to the genus Platygonus; (3) this specimen corresponds to one of the largest South American peccaries; (4) taking into account certain anatomical characters as well as its morphometric range, this specimen is assigned to Platygonus cf. marplatensis. Even though the stratigraphic provenance of the specimen is still doubtful, it can be proposed that (1) it could be one of the most ancient records of tayassuids in South America, as would be expected given its geographical position, and (2) considering the new taxonomic proposal, this specimen represents the first record of Platygonus cf. marplatensis in Colombia and represents one of the northernmost South American records of the genus. This new interpretation would be of great relevance in the Great American Biotic Interchange due to its strategic geographical proximity to the Isthmus of Panama.

Quaternary proboscidean (Mammalia) remains of the UIS Geological Museum, Colombia

Proboscideans arrived in South America from North America during the Great American Biotic Interchange, becoming one of the most representative animals of the megafauna that inhabited this continent throughout the Quaternary. In Colombia, the abundance of their remains contrasts with scarce scientific descriptions and publications. This paper identifies dental and postcranial proboscidean fossils from the Center and Northeast of Colombia. The fossil remains were identified as molars (six), a tusk, cervical vertebrae, and a distal part of the right humerus. The tusk was assigned to Notiomastodon platensis, while the other remains were assigned to Gomphotheriidae, with at least six individuals: two immatures, two subadults, and two older adults – mature and senile. Keywords: South America, megamammals, taxonomy, Gomphotheriidae, Notiomastodon platensis.

Biogeography a key influence on distal forelimb variation in horses through the Cenozoic

Locomotion in terrestrial tetrapods is reliant on interactions between distal limb bones (e.g. metapodials and phalanges). The metapodial–phalangeal joint in horse (Equidae) limbs is highly specialized, facilitating vital functions (shock absorption; elastic recoil). While joint shape has changed throughout horse evolution, potential drivers of these modifications have not been quantitatively assessed. Here, I examine the morphology of the forelimb metacarpophalangeal (MCP) joint of horses and their extinct kin (palaeotheres) using geometric morphometrics and disparity analyses, within a phylogenetic context. I also develop a novel alignment protocol that explores the magnitude of shape change through time, correlated against body mass and diet. MCP shape was poorly correlated with mass or diet proxies, although significant temporal correlations were detected at 0–1 Myr intervals. A clear division was recovered between New and Old World hipparionin MCP morphologies. Significant changes in MCP disparity and high rates of shape divergence were observed during the Great American Biotic Interchange, with the MCP joint becoming broad and robust in two separate monodactyl lineages, possibly exhibiting novel locomotor behaviour. This large-scale study of MCP joint shape demonstrates the apparent capacity for horses to rapidly change their distal limb morphology to overcome discrete locomotor challenges in new habitats.

Applications of 3D Paleontological Data at the Florida Museum of Natural History

The past decade has seen an exponential increase of innovative applications of 3D technology in the geosciences. Here, we present a case study from the Florida Museum of Natural History applied to the multidisciplinary field of paleontology. We have deployed 3D scanning and printing techniques for the purposes of scientific research, formal education, and informal outreach. Depending on the application of the 3D file, different techniques are utilized to create high-fidelity models of physical fossil specimens or geologic field sites. These techniques include X-ray CT scans, surface scans, and photogrammetry, all of which produce 3D models that vary in resolution and scale. Novel paleontological research applied non-destructive CT scanning to explore the internal anatomy of fossil museum specimens, additionally, 3D models are being used to create K–12 curricula aligned with national and state-specific education standards that are implemented in formal classroom settings. Many of these lessons are part of the NSF-funded iDigFossils project, which aims to evaluate students’ motivation and interest towards science, technology, engineering, and mathematics after participating in integrated 3D printing and paleontology lessons. Specifically, lessons on dinosaur trackways, horse evolution, and the Great American Biotic Interchange teach geologic concepts such as deep time, taphonomy, plate tectonics, and evolutionary trends. The same 3D models developed for these K–12 lessons have been used during Florida Museum’s outreach events to engage broad audiences with hands-on exhibits and activities. All 3D files are stored on open-access, online repositories, providing accessibility to fossil specimens and field sites. The application of 3D technology for the study of fossils and paleontology will continue to expand the impact of scientific discoveries for basic research as well as for broader impacts on society.

Disproportionate extinction of South American mammals drove the asymmetry of the Great American Biotic Interchange

The interchange between the previously disconnected faunas of North and South America was a massive experiment in biological invasion. A major gap in our understanding of this invasion is why there was a drastic increase in the proportion of mammals of North American origin found in South America. Four nonmutually exclusive mechanisms may explain this asymmetry: 1) Higher dispersal rate of North American mammals toward the south, 2) higher origination of North American immigrants in South America, 3) higher extinction of mammals with South American origin, and 4) similar dispersal rate but a larger pool of native taxa in North versus South America. We test among these mechanisms by analyzing ∼20,000 fossil occurrences with Bayesian methods to infer dispersal and diversification rates and taxonomic selectivity of immigrants. We find no differences in the dispersal and origination rates of immigrants. In contrast, native South American mammals show higher extinction. We also find that two clades with North American origin (Carnivora and Artiodactyla) had significantly more immigrants in South America than other clades. Altogether, the asymmetry of the interchange was not due to higher origination of immigrants in South America as previously suggested, but resulted from higher extinction of native taxa in southern South America. These results from one of the greatest biological invasions highlight how biogeographic processes and biotic interactions can shape continental diversity.