A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight

PeerJ - Tập 7 - Trang e7247
Scott Hartman1, Mickey Mortimer2, William R. Wahl3, Dean R. Lomax4, Jessica Lippincott3, David M. Lovelace5
1Department of Geoscience, University of Wisconsin-Madison, Madison, WI, USA
2Independent, Maple Valley, WA, USA
3Wyoming Dinosaur Center, Thermopolis, WY, USA
4School of Earth and Environmental Sciences, The University of Manchester, Manchester, UK
5University of Wisconsin Geology Museum, University of Wisconsin-Madison, Madison, WI, USA

Tóm tắt

The last two decades have seen a remarkable increase in the known diversity of basal avialans and their paravian relatives. The lack of resolution in the relationships of these groups combined with attributing the behavior of specialized taxa to the base of Paraves has clouded interpretations of the origin of avialan flight. Here, we describeHesperornithoides miesslerigen. et sp. nov., a new paravian theropod from the Morrison Formation (Late Jurassic) of Wyoming, USA, represented by a single adult or subadult specimen comprising a partial, well-preserved skull and postcranial skeleton. Limb proportions firmly establishHesperornithoidesas occupying a terrestrial, non-volant lifestyle. Our phylogenetic analysis emphasizes extensive taxonomic sampling and robust character construction, recovering the new taxon most parsimoniously as a troodontid close toDaliansaurus,Xixiasaurus, andSinusonasus. Multiple alternative paravian topologies have similar degrees of support, but proposals of basal paravian archaeopterygids, avialan microraptorians, andRahonavisbeing closer to Pygostylia than archaeopterygids or unenlagiines are strongly rejected. All parsimonious results support the hypothesis that each early paravian clade was plesiomorphically flightless, raising the possibility that avian flight originated as late as the Late Jurassic or Early Cretaceous.

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