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[dinosaur] Evolution of the avian digital pattern + Xorazmortyx

Ben Creisler

Recent avian papers not yet mentioned:

(This paper gives wing digits as 2, 3, and 4...)

Kenta Kawahata, Ingrid Rosenburg Cordeiro, Shogo Ueda, Guojun Sheng, Yuuta Moriyama, Chika Nishimori, Reiko Yu, Makoto Koizumi, Masataka Okabe & Mikiko Tanaka (2019)
Evolution of the avian digital pattern.
Scientific Reports 9, Article number: 8560
DOI: https://doi.org/10.1038/s41598-019-44913-w

Free pdf:

Variation in digit number has occurred multiple times in the history of archosaur evolution. The five digits of dinosaur limbs were reduced to three in bird forelimbs, and were further reduced in the vestigial forelimbs of the emu. Regulation of digit number has been investigated previously by examining genes involved in anterior-posterior patterning in forelimb buds among emu (Dromaius novaehollandiae), chicken (Gallus gallus) and zebra finch (Taeniopygia guttata). It was described that the _expression_ of posterior genes are conserved among these three birds, whereas _expression_ of anterior genes Gli3 and Alx4 varied significantly. Here we re-examined the _expression_ pattern of Gli3 and Alx4 in the forelimb of emu, chicken and zebra finch. We found that Gli3 is expressed in the anterior region, although its range varied among species, and that the _expression_ pattern of Alx4 in forelimb buds is broadly conserved in a stage-specific manner. We also found that the dynamic _expression_ pattern of the BMP antagonist Gremlin1 (Grem1) in limb buds, which is critical for autopodial expansion, was consistent with the digital pattern of emu, chicken and zebra finch. Furthermore, in emu, variation among individuals was observed in the width of Grem1 _expression_ in forelimb buds, as well as in the adult skeletal pattern. Our results support the view that the signalling system that regulates the dynamic _expression_ of Grem1 in the limb bud contributes substantially to variations in avian digital patterns.


Xorazmortyx turkestanensis gen. et sp. nov.

Nikita V. Zelenkov & Andrey V. Panteleyev (2019)
A small stem-galliform bird (Aves: Paraortygidae) from the Eocene of Uzbekistan.
Comptes Rendus Palevol (advance online publication)
doi: https://doi.org/10.1016/j.crpv.2019.04.005

Landfowl (order Galliformes) are among the most characteristic birds of the modern avian faunas, but their early evolutionary history is insufficiently known. The diversity of previously described Eocene galliforms implies a great role of Eocene diversification in the early evolution of this group. However, almost nothing is known about the Eocene diversity of galliforms in Asia, even though this large continent with a variety of habitats might have played a significant role in their early evolution. Here we describe a partial coracoid from the LutetianâBartonian of Uzbekistan, which is the oldest diagnosable galliform bird in Asia, and is further the first landbird known from this geographical area. The specimen displays a unique morphology with few autapomorphies and an unexpected combination of similarities with the African genus Scopelortyx and Eurasian Paraortyx, and hence is described as a new taxon, Xorazmortyx turkestanensis gen. et sp. nov., within the extinct family Paraortygidae, being the first Asian representative of this clade. Similarities with the African genus Scopelortyx indicate a connection of land bird faunas between northern Africa/Arabia and Asia in the middle Eocene. Better dispersal abilities of the early galliforms Paraortygidae are inferred from the osteology of their pectoral girdle and the humerus, which do not show adaptations to the powerful burst take off (escape flight), characteristic of most modern Phasianidae.


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