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Wupus agilis (Early Cretaceous) of Chongqing, China as large avian trace fossil

Ben Creisler

New in PLoS ONE:

Lida Xing, Lisa G. Buckley, Richard T. McCrea, Martin G. Lockley,
Jianping Zhang, Laura Piñuela, Hendrik Klein & Fengping Wang (2015)
Reanalysis of Wupus agilis (Early Cretaceous) of Chongqing, China as a
Large Avian Trace: Differentiating between Large Bird and Small
Non-Avian Theropod Tracks.
PLoS ONE 10(5): e0124039
doi: 10.1371/journal.pone.0124039

Trace fossils provide the only records of Early Cretaceous birds from
many parts of the world. The identification of traces from large avian
track-makers is made difficult given their overall similarity in size
and tridactyly in comparison with traces of small non-avian theropods.
Reanalysis of Wupus agilis from the Early Cretaceous (Aptian-Albian)
Jiaguan Formation, one of a small but growing number of known
avian-pterosaur track assemblages, of southeast China determines that
these are the traces of a large avian track-maker, analogous to extant
herons. Wupus, originally identified as the trace of a small non-avian
theropod track-maker, is therefore similar in both footprint and
trackway characteristics to the Early Cretaceous (Albian) large avian
trace Limiavipes curriei from western Canada, and Wupus is reassigned
to the ichnofamily Limiavipedidae. The reanalysis of Wupus reveals
that it and Limiavipes are distinct from similar traces of small to
medium-sized non-avian theropods (Irenichnites, Columbosauripus,
Magnoavipes) based on their relatively large footprint length to pace
length ratio and higher mean footprint splay, and that Wupus shares
enough characters with Limiavipes to be reassigned to the ichnofamily
Limiavipedidae. The ability to discern traces of large avians from
those of small non-avian theropods provides more data on the diversity
of Early Cretaceous birds. This analysis reveals that, despite the
current lack of body fossils, large wading birds were globally
distributed in both Laurasia and Gondwana during the Early Cretaceous.