Bird Evolution: Convergence Fits the Bill

New fossils help pinpoint when some birds started relying on a seed-based diet and reveal that disparate bill shapes evolved repeatedly throughout bird evolutionary history

Wing Musculature Reconstruction in Extinct Flightless Auks (<i>Pinguinus</i> and <i>Mancalla</i>) Reveals Incomplete Convergence with Penguins (Spheniscidae) Due to Differing Ancestral States.

Despite longstanding interest in convergent evolution, factors that result in deviations from fully convergent phenotypes remain poorly understood. In birds, the evolution of flightless wing-propelled diving has emerged as a classic example of convergence, having arisen in disparate lineages including penguins (Sphenisciformes) and auks (Pan-Alcidae, Charadriiformes). Nevertheless, little is known about the functional anatomy of the wings of flightless auks because all such taxa are extinct, and their morphology is almost exclusively represented by skeletal remains. Here, in order to re-evaluate the extent of evolutionary convergence among flightless wing-propelled divers, wing muscles and ligaments were reconstructed in two extinct flightless auks, representing independent transitions to flightlessness: Pinguinus impennis (a crown-group alcid), and Mancalla (a stem-group alcid). Extensive anatomical data were gathered from dissections of 12 species of extant charadriiforms and 4 aequornithine waterbirds including a penguin. The results suggest that the wings of both flightless auk taxa were characterized by an increased mechanical advantage of wing elevator/retractor muscles, and decreased mobility of distal wing joints, both of which are likely advantageous for wing-propelled diving and parallel similar functional specializations in penguins. However, the conformations of individual muscles and ligaments underlying these specializations differ markedly between penguins and flightless auks, instead resembling those in each respective group's close relatives. Thus, the wings of these flightless wing-propelled divers can be described as convergent as overall functional units, but are incompletely convergent at lower levels of anatomical organization-a result of retaining differing conditions from each group's respective volant ancestors. Detailed investigations such as this one may indicate that, even in the face of similar functional demands, courses of phenotypic evolution are dictated to an important degree by ancestral starting points

The morphomolecular features of cholangiocarcinoma in the personalised era

Cholangiocarcinoma is a group of diverse invasive malignancies arising along the biliary tract. The outcomes for patients with cholangiocarcinoma remain poor but an understanding of molecular aberrations and subsequent targeted therapies to these have opened up new treatment prospects. This review describes the clinical and morphological features and classifications of intrahepatic and perihilar cholangiocarcinoma in addition to laying out the related landscape of the molecular pathology within cholangiocarcinoma. The importance of both a high index of suspicion of cholangiocarcinoma and preserving tissue whilst reporting to access molecular testing and personalised treatment pathways is emphasised

Preliminary paleoecological insights from the Pliocene avifauna of Kanapoi, Kenya: Implications for the ecology of <i>Australopithecus anamensis</i>

Fossil bird remains from the Pliocene hominin-bearing locality of Kanapoi comprise &gt;100 elements representing at least 10 avian families, including previously undescribed elements referred to the ‘giant’ Pliocene marabou stork Leptoptilos cf. falconeri. The taxonomic composition of the Kanapoi fossil avifauna reveals an assemblage with a substantial aquatic component, corroborating geological evidence of this locality's close proximity to a large, slow-moving body of water. Both the taxonomic composition and relative abundance of avian higher-level clades at Kanapoi stand in stark contrast to the avifauna from the slightly older (∼4.4 Ma vs. 4.2 Ma) hominin-bearing Lower Aramis Member of Ethiopia, which has been interpreted as representing a mesic woodland paleoenvironment far from water. In general, the taxonomic composition of the Kanapoi avifauna resembles that from the Miocene hominoid-bearing locality of Lothagam (though Kanapoi is more diverse), and the aquatic character of the Kanapoi avifauna supports the idea that the environmental conditions experienced by Australopithecus anamensis at Kanapoi were markedly different from those experienced by Ardipithecus ramidus at Aramis. Additionally, the relative abundance of marabou stork (Leptoptilos) remains at Kanapoi may suggest a longstanding commensal relationship between total-clade humans and facultatively scavenging marabous. Additional avian remains from nearby fossil localities (e.g., the Nachukui Formation), ranging in age from 3.26 to 0.8 Ma, reveal the long-term persistence of an aquatic avifauna in the region.</p

Residential radon exposure and lung cancer: variation in risk estimates using alternative exposure scenarios

The most direct way to derive risk estimates for residential radon progeny exposure is through epidemiologic studies that examine the association between residential radon exposure and lung cancer. However, the National Research Council concluded that the inconsistency among prior residential radon case-control studies was largely a consequence of errors in radon dosimetry. This paper examines the impact of applying various epidemiologic dosimetry models for radon exposure assessment using a common data set from the Iowa Radon Lung Cancer Study (IRLCS). The IRLCS uniquely combined enhanced dosimetric techniques, individual mobility assessment, and expert histologic review to examine the relationship between cumulative radon exposure, smoking, and lung cancer. The a priori defined IRLCS radon-exposure model produced higher odds ratios than those methodologies that did not link the subject\u27s retrospective mobility with multiple, spatially diverse radon concentrations. In addition, the smallest measurement errors were noted for the IRLCS exposure model. Risk estimates based solely on basement radon measurements generally exhibited the lowest risk estimates and the greatest measurement error. The findings indicate that the power of an epidemiologic study to detect an excess risk from residential radon exposure is enhanced by linking spatially disparate radon concentrations with the subject\u27s retrospective mobility

The changing face of birds from the age of the dinosaurs

PDF version As living dinosaurs, birds are the product of a long and complex evolutionary history that has given rise to more than 11,000 living species1. The past decade has witnessed a surge of interest in the evolution of the avian skull — a structure that is hugely variable across the diversity of living birds2. However, our ability to test hypotheses of how and when key transformations of the bird skull took place is limited if we can’t incorporate fossils into evolutionary models. Writing in Nature, O’Connor et al.3 report a stunning fossil-bird discovery from the age of the dinosaurs that reminds us of the crucial value of fossils for casting light on unexpected complexities in avian evolutionary history

Ecological selectivity and the evolution of mammalian substrate preference across the K-Pg boundary.

The Cretaceous-Paleogene (K-Pg) mass extinction 66 million years ago was characterized by a worldwide ecological catastrophe and rapid species turnover. Large-scale devastation of forested environments resulting from the Chicxulub asteroid impact likely influenced the evolutionary trajectories of multiple clades in terrestrial environments, and it has been hypothesized to have biased survivorship in favour of nonarboreal lineages across the K-Pg boundary. Here, we evaluate patterns of substrate preferences across the K-Pg boundary among crown group mammals, a group that underwent rapid diversification following the mass extinction. Using Bayesian, likelihood, and parsimony reconstructions, we identify patterns of mammalian ecological selectivity that are broadly similar to those previously hypothesized for birds. Models based on extant taxa indicate predominant K-Pg survivorship among semi- or nonarboreal taxa, followed by numerous independent transitions to arboreality in the early Cenozoic. However, contrary to the predominant signal, some or all members of total-clade Euarchonta (Primates + Dermoptera + Scandentia) appear to have maintained arboreal habits across the K-Pg boundary, suggesting ecological flexibility during an interval of global habitat instability. We further observe a pronounced shift in character state transitions away from plesiomorphic arboreality associated with the K-Pg transition. Our findings are consistent with the hypothesis that predominantly nonarboreal taxa preferentially survived the end-Cretaceous mass extinction, and emphasize the pivotal influence of the K-Pg transition in shaping the early evolutionary trajectories of extant terrestrial vertebrates.NS

Geospatial analysis of BECCS deployment potential in the U.S.

Negative emissions from bioenergy with carbon capture and storage (BECCS) has been identified as a potentially important carbon mitigation technology. To date, much of the technical work and discussion on BECCS have focused on land use change and bioenergy potential, while the CCS components – including capacity, injectivity, and location of potential storage sites – have been overlooked. A geospatial analysis of biomass production and storage sites in the U.S. is conducted to discuss BECCS deployment in the U.S. across a range of biomass production scenarios. U.S. Department of Energy provides national annual biomass production data from 2015 to 2040. Extrapolating the production trends across different yield scenarios to 2100 shows average annual CO2 production from agricultural residue and energy crop of 720-1,220 Mt CO2 yr-1 and cumulative production of 27-47 Gt CO2. Considering that the estimated storage capacity in the U.S. is ~3,000 Gt CO2, absolute storage capacity is not likely to be a constraint on BECCS. However, collocation of high-density biomass (\u3e25 MW per 100×100 km2) and high injection rate storage sites (\u3e5 Mt CO2 yr-1) in 2040 yields biomass CO2 injection potential of 140-360 Mt CO2 yr-1. This represents 9-39% of the total biomass feedstock in the U.S. To achieve a biomass CO2 injection potential greater than 360 Mt CO2 yr-1, transportation networks of either biomass or CO2 will be needed. The geospatial analysis conducted in this study highlights the importance of previously overlooked CCS components in global BECCS assessments and provides a framework for future studies. Please click Additional Files below to see the full abstract