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Origin and Early Radiation of Archosauriforms

Ben Creisler

New in PLoS ONE:

Massimo Bernardi, Hendrik Klein, Fabio Massimo Petti & Martín D. Ezcurra (2015)
The Origin and Early Radiation of Archosauriforms: Integrating the
Skeletal and Footprint Record.
PLoS ONE 10(6): e0128449.

We present a holistic approach to the study of early archosauriform
evolution by integrating body and track records. The ichnological
record supports a Late Permian–Early Triassic radiation of
archosauriforms not well documented by skeletal material, and new
footprints from the Upper Permian of the southern Alps (Italy) provide
evidence for a diversity not yet sampled by body fossils. The
integrative study of body fossil and footprint data supports the
hypothesis that archosauriforms had already undergone substantial
taxonomic diversification by the Late Permian and that by the Early
Triassic archosauromorphs attained a broad geographical distribution
over most parts of Pangea. Analysis of body size, as deduced from
track size, suggests that archosauriform average body size did not
change significantly from the Late Permian to the Early Triassic. A
survey of facies yielding both skeletal and track record indicate an
ecological preference for inland fluvial (lacustrine) environments for
early archosauromorphs. Finally, although more data is needed, Late
Permian chirotheriid imprints suggest a shift from sprawling to erect
posture in archosauriforms before the end-Permian mass extinction
event. We highlight the importance of approaching palaeobiological
questions by using all available sources of data, specifically through
integrating the body and track fossil record.