The origin of birds from non-avian theropod dinosaurs is one of the greatest transitions in evolution. Shortly after diverging from other theropods in the Late Jurassic, Mesozoic birds diversified into two major clades--the Enantiornithes and Ornithuromorpha--acquiring many features previously considered unique to the crown group along the way. Here, we present a comparative phylogenetic study of the patterns and modes of Mesozoic bird skeletal morphology and limb proportions. Our results show that the major Mesozoic avian groups are distinctive in discrete character space, but constrained in a morphospace defined by limb proportions. The Enantiornithines, despite being the most speciose group of Mesozoic birds, are much less morphologically disparate than their sister clade, the Ornithuromorpha--the clade that gave rise to living birds, showing disparity and diversity were decoupled in avian history. This relatively low disparity suggests that diversification of enantiornithines was characterized in exhausting fine morphologies, whereas ornithuromorphs continuously explored a broader array of morphologies and ecological opportunities. We suggest this clade-specific evolutionary versatility contributed to their sole survival of the end-Cretaceous mass extinction.
Footnotes
Electronic supplementary material is available online at
https://doi.org/10.6084/m9.figshare.c.5288869.
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We describe a new Procellaria petrel species from the late Pliocene of Taranaki, New Zealand. The new species is most similar morphologically to the White-Chinned Petrel (P. aequinoctialis), Spectacled Petrel (P. conspicillata) and the Westland Petrel (P. westlandica). Compared with those taxa, the new species has a deeper and shorter premaxilla, longer coracoid and shorter wings, while its legs are a similar size. Today, New Zealand is the centre of global diversity of the genus, with four breeding species. This is the first fossil species of Procellaria to be described from New Zealand, attesting to a reasonably long history of this genus in the region.
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David A. Duchene, Paola Montoya, Santiago Claramunt & Daniel A. Cadena (2021)
Flight demand and environmental niche are associated with molecular evolutionary rates in a large avian radiation.
bioRxiv 2020.01.16.908368 (preprint)
doi:
https://doi.org/10.1101/2020.01.16.908368https://www.biorxiv.org/content/10.1101/2020.01.16.908368v4Among the macroevolutionary drivers of molecular evolutionary rates, metabolic demands and environmental energy have been a central topic of discussion. The large number of studies examining these associations have found mixed results, and have rarely explored the interactions among various factors impacting molecular evolutionary rates. Taking the diverse avian family Furnariidae as a case study, we examined the association between several estimates of molecular evolutionary rates with proxies of metabolic demands imposed by flight (wing loading and the hand-wing index) and proxies of environmental energy across the geographic ranges of species (temperature and UV radiation). We found evidence that species that fly less have greater wing loading and this is associated with accelerated rates of mutation. An elongated wing morphology is associated with greater flight activity and with molecular signatures of positive selection or reduced population sizes. Meanwhile, environmental temperature and UV radiation interact to explain molecular rates at sites affected by selection and population size, contrary to the expectation of their impact on mutation rates. Our results suggest that the demands of flight and environmental energy pose multiple evolutionary pressures on the genome either by driving mutation rates or via their association with natural selection or population size.
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