More avian papers!
==========
Here within we describe the fifth know specimen of Protopteryx, contributing new anatomical information on this taxon derived from this new specimen and the holotype and paratype.
The new specimen includes well preserved feathers; two gaps in the right wing are interpreted as evidence of a sequential molt.
It appears a single primary and secondary are immature suggesting that molt patterns differed from those in neornithines and documented in Microraptor.
SEM reveals the preservation of eumelanosomes indicating the plumage was at least partly black.
Abstract
Protopteryx fengningensis is from the 130.7 Ma Huajiying Formation making it one of the oldest known enantiornithines. Contributing to its significance, this taxon is also commonly resolved as the basal-most enantiornithine in phylogenetic analyses. Protopteryx preserves several unusual morphologies that are otherwise absent in the Enantiornithes but common in the Ornithuromorpha such as the procoracoid and lateral processes on the coracoid and proximally convex humeral head. Thus, the morphology of this taxon hints at the morphology of the ornithothoracine common ancestor. Here we supplement existing data with information from a new specimen as well as new morphological data from the holotype and paratype. The new specimen preserves gaps in the right wing suggestive of a sequential molt. The presence of two gaps suggests that, unlike neornithines, primaries and secondaries molted simultaneously. This represents an intermediate condition between Microraptor, in which several feathers are growing simultaneously and sequentially, and modern birds with sequential molts, in which a single feather is replaced at a time. A single patch of feathers was sampled revealing preserved eumelanosomes, indicating that at least part of the remiges was darkly colored.
Gergely OsvÃth, Orsolya Vincze, Dragomir-Cosmin David, LÃszlà JÃcint Nagy, ÃdÃm Z Lendvai, Robert L. Nudds & PÃter L. Pap (2020)
Morphological characterization of flight feather shafts in four bird species with different flight styles.
Biological Journal of the Linnean Society, blaa108 (advance online publication)
doi:
https://doi.org/10.1093/biolinnean/blaa108https://academic.oup.com/biolinnean/article-abstract/doi/10.1093/biolinnean/blaa108/5877023Variation in rachis (central shaft) morphology in individual remiges (flight feathers) within and among species reflects adaptations to requirements imposed by aerodynamic forces, but the fine-scale variation of feather morphology across remiges is not well known. Here we describe how the shape of the rachis, expressed by the height/width ratio, changes along the longitudinal and lateral axis of the wing in four bird species with different flight styles: flapping-soaring (white storks), flapping-gliding (common buzzards), passerine-type (house sparrows) and continuous flapping (pygmy cormorants). Overall, in each wing feather, irrespective of species identity, rachis shape changed from circular to rectangular, from the base towards the feather tip. The ratio between the height and width of the calamus was similar across remiges in all species, whereas the ratio at the base, middle and tip of the rachis changed among flight feathers and species. In distal primaries of white storks and common buzzards, the ratio decreased along the feather shaft, indicating a depressed (wider than high) rachis cross section towards the feather tip, whereas the inner primaries and secondaries became compressed (higher than wide). In house sparrows, the rachis was compressed in each of the measurement points, except at the distal segment of the two outermost primary feathers. Finally, in pygmy cormorants, the width exceeds the height at each measurement point, except at the calamus. Our results may reflect the resistance of the rachis to in-plane and out-of-plane aerodynamic forces that vary across remiges and across study species. A link between rachis shape and resistance to bending from aerodynamic forces is further indicated by the change of the second moment of areas along the wing axes.