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Chirotheriid footprints from Middle Triassic of Italy + Toarcian Anoxic Event and ichthyosaur body size

Ben Creisler

Two recent papers not yet mentioned:

G .Santi, A. Lualdi,  A. Decarlis,  U. Nicosia &  A. Ronchi (2015)
Chirotheriid footprints from the Lower-Middle Triassic of the
Briançonnais Domain (Pelite di Case Valmarenca, Western Liguria, NW
Bollettino della Società Paleontologica 54(2): 81-90.

Herein are described the first vertebrate footprints discovered in
sediments of Early-Middle Triassic age of the Pelite di Case
Valmarenca (Briançonnais Domain, Western Liguria, Northern Italy).
The tracks are attributed to an archosaur trackmaker and assigned to
the ichnofamily Chirotheriidae. The poor state of preservation has
hindered ichnospecific assignment; however, the find is significant,
because it allows the distribution of these archosaurs to be updated
within the Triassic of Europe. Biochronologically, the footprints of
the Ligurian Briançonnais can be assigned to the Biochrone II or the
“Chirothere assemblage zone” indicating an early Anisian age.


Erin E. Maxwell and Peggy Vincent (2015)
Effects of the early Toarcian Oceanic Anoxic Event on ichthyosaur body
size and faunal composition in the Southwest German Basin.
Paleobiology (advance online publication)
DOI: http://dx.doi.org/10.1017/pab.2015.34

The Early Jurassic Toarcian Oceanic Anoxic Event is considered one of
the most dramatic environmental perturbations of the Mesozoic. An
elevated extinction rate among marine invertebrates accompanied rapid
environmental changes, but effects on large vertebrates are less
understood. We examined changes in ichthyosaur body size in the
Posidonia Shale of the Southwest German Basin spanning the extinction
interval to assess how environmental changes and biotic crisis among
prey species affected large reptiles. We report no species-level
extinction among the ichthyosaurs coinciding with peak invertebrate
extinction. Large ichthyosaurs were absent from the fauna during the
extinction interval, but became more abundant in the immediate
aftermath. Stenopterygius quadriscissus, the most abundant species
during the extinction interval, increased in body size after the
biotic event. Rapid invasion by large taxa occurred immediately
following the extinction event at the end of the first ammonite zone
of the early Toarcian. Greater mobility permitting exploitation of
ephemeral resources and opportunistic feeding behavior may minimize
the impacts of environmental change on large vertebrates.