Mukupirna nambensis gen. et sp. nov.
Robin M. D. Beck, Julien Louys, Philippa Brewer, Michael Archer, Karen H. Black & Richard H. Tedford (2020)
A new family of diprotodontian marsupials from the latest Oligocene of Australia and the evolution of wombats, koalas, and their relatives (Vombatiformes).
Scientific Reports 10, Article number: 9741
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https://doi.org/10.1038/s41598-020-66425-8https://www.nature.com/articles/s41598-020-66425-8We describe the partial cranium and skeleton of a new diprotodontian marsupial from the late Oligocene (~26â25âMa) Namba Formation of South Australia. This is one of the oldest Australian marsupial fossils known from an associated skeleton and it reveals previously unsuspected morphological diversity within Vombatiformes, the clade that includes wombats (Vombatidae), koalas (Phascolarctidae) and several extinct families. Several aspects of the skull and teeth of the new taxon, which we refer to a new family, are intermediate between members of the fossil family Wynyardiidae and wombats. Its postcranial skeleton exhibits features associated with scratch-digging, but it is unlikely to have been a true burrower. Body mass estimates based on postcranial dimensions range between 143 and 171âkg, suggesting that it was ~5 times larger than living wombats. Phylogenetic analysis based on 79 craniodental and 20 postcranial characters places the new taxon as sister to vombatids, with which it forms the superfamily Vombatoidea as defined here. It suggests that the highly derived vombatids evolved from wynyardiid-like ancestors, and that scratch-digging adaptations evolved in vombatoids prior to the appearance of the ever-growing (hypselodont) molars that are a characteristic feature of all post-Miocene vombatids. Ancestral state reconstructions on our preferred phylogeny suggest that bunolophodont molars are plesiomorphic for vombatiforms, with full lophodonty (characteristic of diprotodontoids) evolving from a selenodont morphology that was retained by phascolarctids and ilariids, and wynyardiids and vombatoids retaining an intermediate selenolophodont condition. There appear to have been at least six independent acquisitions of very large (>100âkg) body size within Vombatiformes, several having already occurred by the late Oligocene.
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http://sciencepress.mnhn.fr/sites/default/files/articles/pdf/g2020v42a16.pdfAmphicyonidae Trouessart, 1885 are among the oldest known carnivoran groups, with the oldest representatives in Europe belonging to the genus Cynodictis Bravard & Pomel, 1850. This genus, discovered in the middle of the 19th century, presents a particularly confusing taxonomic history. Early on it was subject to taxonomic inflation, but now its diversity is reduced to six species. It is therefore interesting to question the relevance of dental characteristics, knowing that these structures have, very often, been the only anatomical elements used for the description of extinct mammalian taxa. Thanks to the several deposits of the Quercy Phosphorites, many crania of Cynodictis are available, allowing us to address this issue. In this comparative study, several skulls belonging to this genus are compared. Finally, we describe a new species, Cynodictis peignei n. sp., and discuss the relevance of cranial characters in comparison with dental characters and the ecological information from these structures.
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Organismal interactions drive the accumulation of diversity by influencing species ranges, morphology, and behavior. Interactions vary from agonistic to cooperative and should result in predictable patterns in trait and range evolution. However, despite a conceptual understanding of these processes, they have been difficult to model, particularly on macroevolutionary timescales and across broad geographic spaces. Here we investigate the influence of biotic interactions on trait evolution and community assembly in monitor lizards (Varanus). Monitors are an iconic radiation with a cosmopolitan distribution and the greatest size disparity of any living terrestrial vertebrate genus. Between the colossal Komodo dragon Varanus komodoensis and the smallest Australian dwarf goannas, Varanus length and mass vary by multiple orders of magnitude. To test the hypothesis that size variation in this genus was driven by character displacement, we extended existing phylogenetic comparative methods which consider lineage interactions to account for dynamic biogeographic history and apply these methods to Australian monitors and marsupial predators. Incorporating both exon-capture molecular and morphological datasets we use a combined evidence approach to estimate the relationships among living and extinct varaniform lizards. Our results suggest that communities of Australian Varanus show high functional diversity as a result of continent-wide interspecific competition among monitors but not with faunivorous marsupials. We demonstrate that patterns of trait evolution resulting from character displacement on continental scales are recoverable from comparative data and highlight that these macroevolutionary patterns may develop in parallel across widely distributed sympatric groups.
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Indah B. Huegele and Steven R. Manchester (2020)
An Early Paleocene Carpoflora from the Denver Basin of Colorado, USA, and Its Implications for Plant-Animal Interactions and Fruit Size Evolution.
International Journal of Plant Sciences 181(6): Â646â665
DOI: 10.1086/707727
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https://www.journals.uchicago.edu/doi/pdfplus/10.1086/707727Premise of research.Fossil fruit and seed floras are valuable because of the wealth of taxonomic characters that they can provide, but they are rare in the Cenozoic of North America. Here, we document a fossil fruit and seed flora from the Paleocene Denver Formation of the Denver Basin, Littleton, Colorado, representing the first account of an early Paleocene carpoflora in North America. This locality has previously yielded a rich and well-studied therian and sauropsid fauna confirming a Puercan age. In conjunction with these vertebrate records, the Littleton flora serves as an ecological snapshot of a transitional time in both angiosperm and vertebrate lineages following the K-T mass extinction event.
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David B. Kemp, David Selby & Kentaro Izumi (2020)
Direct coupling between carbon release and weathering during the Toarcian oceanic anoxic event.
Geology (advance online publication)
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https://doi.org/10.1130/G47509.1https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G47509.1/587600/Direct-coupling-between-carbon-release-andSilicate weathering represents a major feedback mechanism in the Earthâs climate system, helping to stabilize atmospheric CO2 levels and temperature on million-year time scales. On shorter time scales of greater relevance to understanding the fate of anthropogenic CO2, the efficacy and responsiveness of weathering is less clear. Here, we present high-resolution osmium-isotope data that reflect global chemical weathering from a stratigraphically thick record of the early Toarcian oceanic anoxic event (T-OAE; ca. 182 Ma). A pronounced decrease in the carbon-isotope composition of exogenic carbon reservoirs during this event has been linked to the large-scale release of 12C-enriched carbon. Our data indicate that the flux of radiogenic osmium to the oceans increased in lockstep with the decrease in carbon-isotope values, demonstrating a geologically synchronous coupling between massive carbon release and enhanced global continental crust weathering. We show that abrupt shifts in carbon isotopes, previously interpreted as millennial-scale methane hydrate melting or terrestrial carbon-release events, are coeval with rapid increases in weathering. Global weathering may have increased by >40% across each of these intervals of rapid carbon injection. Our results help to reconcile previous estimates of weathering change during the T-OAE, and support the view that, overall, global weathering rates may have increased six-fold through the entire event.
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Until recently, the biotic crisis that occurred within the Capitanian Stage (Middle Permian, ca. 262 Ma) was known only from equatorial (Tethyan) latitudes, and its global extent was poorly resolved. The discovery of a Boreal Capitanian crisis in Spitsbergen, with losses of similar magnitude to those in low latitudes, indicated that the event was geographically widespread, but further non-Tethyan records are needed to confirm this as a true mass extinction. The cause of this crisis is similarly controversial: While the temporal coincidence of the extinction and the onset of volcanism in the Emeishan large igneous province in China provides a clear link between those phenomena, the proximal kill mechanism is unclear. Here, we present an integrated fossil, pyrite framboid, and geochemical study of the Middle to Late Permian section of the Sverdrup Basin at Borup Fiord, Ellesmere Island, Arctic Canada. As in Spitsbergen, the Capitanian extinction is recorded by brachiopods in a chert/limestone succession 30â40 m below the Permian-Triassic boundary. The extinction level shows elevated concentrations of redox-sensitive trace metals (Mo, V, U, Mn), and contemporary pyrite framboid populations are dominated by small individuals, suggestive of a causal role for anoxia in the wider Boreal crisis. Mercury concentrationsâa proxy for volcanismâare generally low throughout the succession but are elevated at the extinction level, and this spike withstands normalization to total organic carbon, total sulfur, and aluminum. We suggest this is the smoking gun of eruptions in the distant Emeishan large igneous province, which drove high-latitude anoxia via global warming. Although the global Capitanian extinction might have had different regional mechanisms, like the more famous extinction at the end of the Permian, each had its roots in large igneous province volcanism.
Lily S. Pfeifer, Gerilyn S. Soreghan, StÃphane Pochat & Jean Van Den Driessche (2020)
Loess in eastern equatorial Pangea archives a dusty atmosphere and possible upland glaciation.
GSA Bulletin (advance online publication)
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https://doi.org/10.1130/B35590.1https://pubs.geoscienceworld.org/gsa/gsabulletin/article/doi/10.1130/B35590.1/587468/Loess-in-eastern-equatorial-Pangea-archives-aCarboniferous-Permian strata in basins within the Central Pangean Mountains in France archive regional paleoequatorial climate during a unique interval in geological history (Pangea assembly, ice-age collapse, megamonsoon inception). The voluminous (~1.5 km) succession of exclusively fine-grained red beds that comprises the Permian Salagou Formation (LodÃve Basin, France) has long been interpreted to record either lacustrine or fluvial deposition, primarily based on a local emphasis of subaqueous features in the upper ~25% of the section. In contrast, data presented here indicate that the lower-middle Salagou Formation is dominated by up to 15-m-thick beds of internally massive red mudstone with abundant pedogenic features (microscale) and no evidence of channeling. Up-section, limited occurrences of ripple and hummocky cross-stratification, and mudcracks record the intermittent influence of shallow water, but with no channeling nor units with grain sizes exceeding coarse silt. These data suggest that the most parsimonious interpretation for the Salagou Formation involves eolian transport of the sediment and ultimate deposition as loess in shallow, ephemeral lacustrine environments. Provenance analyses of the Salagou Formation indicate coarse-grained protoliths and, together with geochemical proxies (chemical index of alteration [CIA] and ÏNa) that correspond respectively to a low degree of chemical weathering and a mean annual temperature of ~4 ÂC, suggest that silt generation in this case is most consistent with cold-weathering (glacial and associated periglacial) processes in the Variscan highlands. Together with previous studies that detailed voluminous Permian loess in western equatorial Pangea, this work shows a globally unique distribution of dust at low latitudes that can be linked either directly to glaciated alpine terranes or to reworked and deflated deposits of other types (e.g., fluvial outwash) where fine-grained material was originally generated from glacial grinding in alpine systems. These results further support a revised model for early Permian climate, in which extratropical ice sheets coexisted with a semiarid tropics that may have hosted significant ice at moderate elevation.