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https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2019.2474While morphological traits are often associated with multiple functions, it remains unclear how evolution balances the selective effects of different functions. Birds' beaks function not only in foraging but also in thermoregulating and singing, among other behaviours. Studies of beak evolution abound, however, most focus on a single function. Hence, we quantified relative contributions of different functions over an evolutionary timescale. We measured beak shape using geometric morphometrics and compared this trait with foraging behaviour, climatic variables and song characteristics in a phylogenetic comparative study of an Australasian radiation of songbirds (Meliphagidae). We found that both climate and foraging behaviour were significantly correlated with the beak shape and size. However, foraging ecology had a greater effect on shape, and climate had a nearly equal effect on size. We also found that evolutionary changes in beak morphology had significant consequences for vocal performance: species with elongate-shaped beaks sang at higher frequencies, while species with large beaks sang at a slower pace. The evolution of the avian beak exemplifies how morphological traits can be an evolutionary compromise among functions, and suggests that specialization along any functional axis may increase ecological divergence or reproductive isolation along others.
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https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2019.1745Incorporating extinct taxa in phylogenetic comparative methods is rapidly becoming invaluable in studies of character evolution. An increasing number of studies have evaluated the effects of extinct taxa, and different numbers of extinct taxa, on model selection and parameter estimation. Body mass is a well-studied phenotype, but individual mass estimates may vary dramatically depending on the particular measurement used. Here, we perform an analysis of body mass evolution in a large clade of principally arboreal birds, incorporating 76 extinct species. We evaluate how different methods for estimating body mass of extinct taxa, and different phylogenetic hypotheses, affect our understanding of the rate and pattern of body mass evolution. Our results show that model selection can vary dramatically depending on the phenotypic and phylogenetic hypothesis used in the reconstruction. Even small changes in phenotype estimates can lead to different model selection and, as a result, affect the inferred evolutionary history. The best-fit models support an increase in the rate of evolution following the KâPg boundary, with variation accumulating linearly through the Cenozoic. These results provide additional insight into the application of comparative models of evolution, as well as the evolutionary history of one of the most spectacular vertebrate radiations.
Gerald Mayr (2020)
Comparative morphology of the avian maxillary bone (os maxillare) based on an examination of macerated juvenile skeletons.
Acta Zoologica 101 (1): 24-38
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https://doi.org/10.1111/azo.12268https://onlinelibrary.wiley.com/doi/abs/10.1111/azo.12268For the first time, isolated maxillary bones of juvenile neornithine birds are examined and compared. Contrary to the anatomical terminology currently employed, the avian maxillare exhibits five rather than four processes. In addition to the praemaxillary, jugal, nasal, and maxillopalatine processes, all palaeognathous and many neognathous birds also have a palatine process. The occurrence of these processes is, however, variable across different clades and only few taxa exhibit a pentaradiate maxillare with all five processes. Within Neognathae, a great morphological variability exists in the shape of the maxillopalatine process, which is more easily studied in juvenile individuals, in which the bones of the beak and palate are not coâossified. In some Neognathae, a caudally facing recess is situated in the junction of the maxillopalatine and jugal processes, which is likely to be homologous to the pneumatic recess of palaeognathous birds. Several derived morphologies of potential phylogenetic significance for the characterization of neognathous clades are identified and major morphological transformations in the lineage leading towards modern birds are highlighted.
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Asmodochelys parhami gen. et sp. nov.
Resolving the phylogeny of sea turtles is uniquely challenging given the high potential for the unification of convergent lineages due to systematic homoplasy. Equivocal reconstructions of marine turtle evolution subsequently inhibit efforts to establish fossil calibrations for molecular divergence estimates and prevent the accurate reconciliation of biogeographic or palaeoclimatic data with phylogenetic hypotheses. Here we describe a new genus and species of marine turtle, Asmodochelys parhami, from the Upper Campanian Demopolis Chalk of Alabama and Mississippi, USA represented by three partial shells. Phylogenetic analysis shows that A. parhami belongs to the ctenochelyids, an extinct group that shares characteristics with both pan-chelonioids and pan-cheloniids. In addition to supporting Ctenochelyidae as a sister taxon of Chelonioidea, our analysis places Protostegidae outside of the Chelonioidea crown group and recovers Allopleuron hofmanni as a stem dermochelyid. Gap excess ratio (GER) results indicate a strong stratigraphic congruence of our phylogenetic hypothesis; however, the highest GER value is associated with the phylogenetic hypothesis of marine turtles which excludes Protostegidae from the Cryptodira crown group. Ancestral range estimations derived from our phylogeny imply a European or North American origin of Chelonioidea in the middle-to-late Campanian, approximately 20 Myr earlier than current molecular divergence studies suggest.
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Christian A. Perez-Martinez, Julia L. Riley & Martin J. Whiting (2019)
Uncovering the function of an enigmatic display: antipredator behaviour in the iconic Australian frillneck lizard.
Biological Journal of the Linnean Society, blz176
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https://doi.org/10.1093/biolinnean/blz176https://academic.oup.com/biolinnean/advance-article-abstract/doi/10.1093/biolinnean/blz176/5679583When faced with a predator, some animals engage in a deimatic display to startle the predator momentarily, resulting in a pause or retreat, thereby increasing their chance of escape. Frillneck lizards (Chlamydosaurus kingii) are characterised by a large, pronounced frill that extends from the base of the head to beyond the neck and, when displayed, can be up to six times the width of the head. We used behavioural assays with a model avian predator to demonstrate that their display conforms to deimatic display theory. First, juveniles and adults deployed the frill in encounters with a model predator. Second, the display revealed three colour patches (white and redâorange patches on the frill; yellow mouth palate) that facilitate a transition from a cryptic to a conspicuous state as perceived by a raptor visual system. Third, the display was performed with movements that amplified its effect. The frill area was larger in males than in females, which suggests that the frill might also be co-opted for maleâmale contests. If future research confirms a role of the frill in male agonistic interactions, frillneck lizards will be a rare case in which a structure has a dual function in a deimatic display and a sexually selected signal.
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Minimal annual rainfall in arid environments results in low productivity ecosystems with fluctuating food availability. Large mammalian predators that require frequent consumption of vertebrate prey tend to be less abundant in desert environments; however, such environments often support numerous largeâbodied carnivorous reptiles. Diet is a fundamental component of an animalâs ecology, and we explore the diets of three coexisting, sympatric Varanus species occurring in arid Australia: V. tristis, V. gouldii and V. panoptes. We hypothesized that the diet of varanids living in arid environments would primarily consist of relatively abundant invertebrate prey, and that vertebrate prey items would largely be limited to opportunistically consumed mammalian carrion and small reptilian species. All three Varanus species had high dietary overlap and broad, generalist diets. Invertebrate prey, particularly Orthoptera, were key to the diets of all three species. Vertebrate prey was infrequently consumed by all three Varanus species; however, when consumed, tended to comprise small reptilian species and mammalian carrion. Unlike large mammalian predators, varanids can survive on invertebrate prey and infrequent feeds and can aestivate when conditions become unfavourable, contributing to their success in arid environments.
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Yuewu Sun, ÂXiang Li, ÂQuanyou Liu, ÂMingda Zhang, ÂPeng Li, ÂRui Zhang Â& Xiao Shi (2019)
In search of the inland Carnian Pluvial Event: MiddleâUpper Triassic transition profile and UâPb isotopic dating in the Yanchang Formation in Ordos Basin, China
Geological Journal (advance online publication)
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https://doi.org/10.1002/gj.3691https://onlinelibrary.wiley.com/doi/10.1002/gj.3691The Carnian Pluvial Event (CPE) in the early Late Triassic is a global climate change. The CPE is not only recorded in the ocean but also on the continent. It has been wellâdocumented in the marine environments in Tethys and boreal areas. However, it is less reported for the terrestrial. As a global precipitation event, the CPE on the supercontinent Pangaea is related directly to the sudden increase in argillaceous transportation in the marine carbonate platform. Here, we report a chronological study of the Yunmeng profile in southâeastern Ordos Basin, China where the continuous lacustrine deposits developed with several tuff interlayers. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LAâICPâMS) UâPb isotopic dating of zircons from three bentonite samples show weighted mean ages of 234.1 Â 2.4 Ma, 234.8 Â 2.1 Ma, and 236.0 Â 1.7 Ma, respectively. Based on the review of isotopic dating, sedimentary and palaeontological characteristics of the Triassic Yanchang Formation, the Middle and Upper Triassic boundary is located at the bottom of Chang 7 oil layer (YC7) in the Yanchang Formation at the Yunmeng profile in the Ordos Basin. Therefore, the Yunmeng profile provides a potential case for understanding the inland CPE and might link the terrestrial and oceanic systems in the Carnian.
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Kyle W. Meyer, Sierra V. Petersen, Kyger C Lohmann, Joel D. Blum, Spencer J. Washburn, Marcus W. Johnson, James D. Gleason, Aaron Y. Kurz & Ian Z. Winkelstern Â(2019)
Biogenic carbonate mercury and marine temperature records reveal global influence of Late Cretaceous Deccan Traps.
Nature Communications 10, Article number: 5356
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https://doi.org/10.1038/s41467-019-13366-0 https://www.nature.com/articles/s41467-019-13366-0Free pdf:
https://www.nature.com/articles/s41467-019-13366-0.pdfThe climate and environmental significance of the Deccan Traps large igneous province of west-central India has been the subject of debate in paleontological communities. Nearly one million years of semi-continuous Deccan eruptive activity spanned the Cretaceous-Paleogene boundary, which is renowned for the extinction of most dinosaur groups. Whereas the Chicxulub impactor is acknowledged as the principal cause of these extinctions, the Deccan Traps eruptions are believed to have contributed to extinction patterns and/or enhanced ecological pressures on biota during this interval of geologic time. We present the first coupled records of biogenic carbonate clumped isotope paleothermometry and mercury concentrations as measured from a broad geographic distribution of marine mollusk fossils. These fossils preserve evidence of simultaneous increases in coastal marine temperatures and mercury concentrations at a global scale, which appear attributable to volcanic CO2 and mercury emissions. These early findings warrant further investigation with additional records of combined Late Cretaceous temperatures and mercury concentrations of biogenic carbonate.