Patterns of diversification and timing of evolution within Neoaves, which includes almost 95% of all bird species, are virtually unknown. On the other hand, molecular data consistently indicate a Cretaceous origin of many neoavian lineages and the fossil record seems to support an Early Tertiary diversification. Here, we present the first well-resolved molecular phylogeny for Neoaves, together with divergence time estimates calibrated with a large number of stratigraphically and phylogenetically welldocumented fossils. Our study defines several well-supported clades within Neoaves. The calibration results suggest that Neoaves, after an initial split from Galloanseres in Mid-Cretaceous, diversified around or soon after the K/T boundary. Our results thus do not contradict palaeontological data and show that there is no solid molecular evidence for an extensive preTertiary radiation of Neoaves.

Zoogeographic, palaeontological and biochemical data support a Southern Hemisphere origin for passerine birds, while accumulating molecular data suggest that most extant avian orders originated in the midLate Cretaceous. We obtained DNA sequence data from the nuclear c-myc and RAG-1 genes of the major passerine groups and here we demonstrate that the endemic New Zealand wrens (Acanthisittidae) are the sister taxon to all other extant passerines, supporting a Gondwanan origin and early radiation of passerines. We propose that (i) the acanthisittids were isolated when New Zealand separated from Gondwana (ca. 82-85 Myr ago), (ii) suboscines, in turn, were derived from an ancestral lineage that inhabited western Gondwana, and (iii) the ancestors of the oscines (songbirds) were subsequently isolated by the separation of Australia from Antarctica. The later spread of passerines into the Northern Hemisphere reflects the northward migration of these former Gondwanan elements.

Flight speed is expected to increase with mass and wing loading among flying animals and aircraft for fundamental aerodynamic reasons. Assuming geometrical and dynamical similarity, cruising flight speed is predicted to vary as (body mass)1/6 and (wing loading)1/2 among bird species. To test these scaling rules and the general importance of mass and wing loading for bird flight speeds, we used tracking radar to measure flapping flight speeds of individuals or flocks of migrating birds visually identified to species as well as their altitude and winds at the altitudes where the birds were flying. Equivalent airspeeds (airspeeds corrected to sea level air density, U e) of 138 species, ranging 0.01–10 kg in mass, were analysed in relation to biometry and phylogeny. Scaling exponents in relation to mass and wing loading were significantly smaller than predicted (about 0.12 and 0.32, respectively, with similar results for analyses based on species and independent phylogenetic contrasts). These low scaling exponents may be the result of evolutionary restrictions on bird flight-speed range, counteracting too slow flight speeds among species with low wing loading and too fast speeds among species with high wing loading. This compression of speed range is partly attained through geometric differences, with aspect ratio showing a positive relationship with body mass and wing loading, but additional factors are required to fully explain the small scaling exponent of U e in relation to wing loading. Furthermore, mass and wing loading accounted for only a limited proportion of the variation in U e. Phylogeny was a powerful factor, in combination with wing loading, to account for the variation in U e. These results demonstrate that functional flight adaptations and constraints associated with different evolutionary lineages have an important influence on cruising flapping flight speed that goes beyond the general aerodynamic scaling effects of mass and wing loading.

The development of distinct regions in the amniote vertebral column results from somite formation and Hox gene expression, with the adult morphology displaying remarkable variation among lineages. Mammalian regionalization is reportedly very conservative or even constrained, but there has been no study investigating vertebral count variation across Amniota as a whole, undermining attempts to understand the phylogenetic, ecological, and developmental factors affecting vertebral column variation. Here, we show that the mammalian (synapsid) and reptilian lineages show early in their evolutionary histories clear divergences in axial developmental plasticity, in terms of both regionalization and meristic change, with basal synapsids sharing the conserved axial configuration of crown mammals, and basal reptiles demonstrating the plasticity of extant taxa. We conducted a comprehensive survey of presacral vertebral counts across 436 recent and extinct amniote taxa. Vertebral counts were mapped onto a generalized amniote phylogeny as well as individual ingroup trees, and ancestral states were reconstructed by using squared-change parsimony. We also calculated the relationship between presacral and cervical numbers to infer the relative influence of homeotic effects and meristic changes and found no correlation between somitogenesis and Hox-mediated regionalization. Although conservatism in presacral numbers characterized early synapsid lineages, in some cases reptiles and synapsids exhibit the same developmental innovations in response to similar selective pressures. Conversely, increases in body mass are not coupled with meristic or homeotic changes, but mostly occur in concert with postembryonic somatic growth. Our study highlights the importance of fossils in large-scale investigations of evolutionary developmental processes.omitogenesis, somatic growth, and Hox gene expression are primary factors driving the formation of the vertebrate body axis (1, 2). Somitogenesis occurs via the rhythmic budding of embryonic somites from the anterior part of the presomitic mesoderm, until a point when the latter has shrunk to such a degree that no further somites can be formed (3). Periodic somite formation is controlled by a molecular oscillator or "segmentation clock" (4), whereas the speed of the clock is highly variable across different vertebrate lineages. For example, the segmentation clock in snakes ticks much faster than in a mouse, resulting in a higher number of relatively smaller somites (3). Because the ossified vertebrae are derived from the embryonic somites through resegmentation (1), vertebral numbers can provide insights into the speed of the segmentation clock and the pattern of somitogenesis. In addition, the relative size of vertebrae relative to the number of vertebrae provides information about the rate of somatic growth (5, 6).Besides the marked variation in the number and sizes of vertebrae, the vertebrate body axis is also highly regionalized. In tetrapods, this regionalization is expressed in the formatio...

The ground tit (Parus humilis) is endemic to the Tibetan plateau. It is a member of family Paridae but it was long thought to be related to the ground jays because of their morphological similarities. Here we present the ground tit's genome and re-sequence two tits and one ground jay, to clarify this controversially taxonomic status and uncover its genetic adaptations to the Tibetan plateau. Our results show that ground tit groups with two tits and it diverges from them between 7.7 and 9.9 Mya. Compared with other avian genomes, ground tit shows expansion in genes linked to energy metabolism and contractions in genes involved in immune and olfactory perception. We also found positively selected and rapidly evolving genes in hypoxia response and skeletal development. These results indicated that ground tit evolves basic strategies and 'tit-to-jay' change for coping with the life in an extreme environment.