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Triassic marine predators during mass extinction recovery

From: Ben Creisler

New in PLoS ONE:

Torsten M. Scheyer, Carlo Romano, Jim Jenks & Hugo Bucher (2014)
Early Triassic Marine Biotic Recovery: The Predators' Perspective.
PLoS ONE 9(3): e88987.

Examining the geological past of our planet allows us to study periods
of severe climatic and biological crises and recoveries, biotic and
abiotic ecosystem fluctuations, and faunal and floral turnovers
through time. Furthermore, the recovery dynamics of large predators
provide a key for evaluation of the pattern and tempo of ecosystem
recovery because predators are interpreted to react most sensitively
to environmental turbulences. The end-Permian mass extinction was the
most severe crisis experienced by life on Earth, and the common
paradigm persists that the biotic recovery from the extinction event
was unusually slow and occurred in a step-wise manner, lasting up to
eight to nine million years well into the early Middle Triassic
(Anisian) in the oceans, and even longer in the terrestrial realm.
Here we survey the global distribution and size spectra of Early
Triassic and Anisian marine predatory vertebrates (fishes, amphibians
and reptiles) to elucidate the height of trophic pyramids in the
aftermath of the end-Permian event. The survey of body size was done
by compiling maximum standard lengths for the bony fishes and some
cartilaginous fishes, and total size (estimates) for the tetrapods.
The distribution and size spectra of the latter are difficult to
assess because of preservation artifacts and are thus mostly discussed
qualitatively. The data nevertheless demonstrate that no significant
size increase of predators is observable from the Early Triassic to
the Anisian, as would be expected from the prolonged and stepwise
trophic recovery model. The data further indicate that marine
ecosystems characterized by multiple trophic levels existed from the
earliest Early Triassic onwards. However, a major change in the
taxonomic composition of predatory guilds occurred less than two
million years after the end-Permian extinction event, in which a
transition from fish/amphibian to fish/reptile-dominated higher
trophic levels within ecosystems became apparent.