Zygodactylus grandei new species
N. Adam Smith, Aj M. DeBee & Julia A. Clarke (2018)
Systematics and phylogeny of the Zygodactylidae (Aves, Neognathae) with description of a new species from the early Eocene of Wyoming, USA.Â
PeerJ 6:e4950Â
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Zygodactylidae are an extinct lineage of perching birds characterized by distinct morphologies of the foot and wing elements. Although the clade has a complex taxonomic history, current hypotheses place Zygodactylidae as the sister taxon to Passeriformes (i.e., songbirds). Given the rather sparse fossil record of early passeriforms, the description of zygodactylid taxa is important for inferring potentially ancestral states in the largest radiation of living birds (i.e., the ~6,000 species of extant passeriforms). Despite the exceptional preservation of many specimens and considerable species diversity in Zygodactylidae, the relationships among species have not been previously evaluated in a phylogenetic context. Herein, we review the fossil record of Zygodactylidae from North America and describe five new well-preserved fossils from the early Eocene Green River Formation of Wyoming. Two specimens are identified as representing a new species and the first records of the taxon Zygodactylus outside Europe. Anatomical comparisons with previously named taxa and the results of phylogenetic analysis including newly described specimens and previously named zygodactylid taxa provide the first hypothesis of the species-level relationships among zygodactylids. The monophyly of Zygodactylidae is supported in these new analyses. However, the monophyly of Primozygodactylus and the taxonomic distinction between Zygodactylus and Eozygodactylus remain unresolved and would likely benefit from the description of additional specimens.
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Daniel J. Field and Allison Y. Hsiang (2018)
A North American stem turaco, and the complex biogeographic history of modern birds.
BMC Evolutionary Biology 18:102
Background
Earthâs lower latitudes boast the majority of extant avian species-level and higher-order diversity, with many deeply diverging clades restricted to vestiges of Gondwana. However, palaeontological analyses reveal that many avian crown clades with restricted extant distributions had stem group relatives in very different parts of the world.
Results
Our phylogenetic analyses support the enigmatic fossil bird Foro panarium Olson 1992 from the early Eocene (Wasatchian) of Wyoming as a stem turaco (Neornithes: Pan-Musophagidae), a clade that is presently endemic to sub-Saharan Africa. Our analyses offer the first well-supported evidence for a stem musophagid (and therefore a useful fossil calibration for avian molecular divergence analyses), and reveal surprising new information on the early morphology and biogeography of this clade. Total-clade Musophagidae is identified as a potential participant in dispersal via the recently proposed âNorth American Gatewayâ during the Palaeogene, and new biogeographic analyses illustrate the importance of the fossil record in revealing the complex historical biogeography of crown birds across geological timescales.
Conclusions
In the Palaeogene, total-clade Musophagidae was distributed well outside the range of crown Musophagidae in the present day. This observation is consistent with similar biogeographic observations for numerous other modern bird clades, illustrating shortcomings of historical biogeographic analyses that do not incorporate information from the avian fossil record.
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