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Late Jurassic–Early Cretaceous transition: protracted faunal and ecological turnover (free pdf)

Ben Creisler

A new paper in open access:

Jonathan P. Tennant, Philip D. Mannion, Paul Upchurch, Mark D. Sutton
and Gregory D. Price (2016)
Biotic and environmental dynamics through the Late Jurassic–Early
Cretaceous transition: evidence for protracted faunal and ecological
Biological Reviews (advance online publication)
DOI: 10.1111/brv.12255
http: //  onlinelibrary.wiley.com/doi/10.1111/brv.12255/abstract

http: // onlinelibrary.wiley.com/doi/10.1111/brv.12255/epdf

The Late Jurassic to Early Cretaceous interval represents a time of
environmental upheaval and cataclysmic events, combined with
disruptions to terrestrial and marine ecosystems. Historically, the
Jurassic/Cretaceous (J/K) boundary was classified as one of eight mass
extinctions. However, more recent research has largely overturned this
view, revealing a much more complex pattern of biotic and abiotic
dynamics than has previously been appreciated. Here, we present a
synthesis of our current knowledge of Late Jurassic–Early Cretaceous
events, focusing particularly on events closest to the J/K boundary.
We find evidence for a combination of short-term catastrophic events,
large-scale tectonic processes and environmental perturbations, and
major clade interactions that led to a seemingly dramatic faunal and
ecological turnover in both the marine and terrestrial realms. This is
coupled with a great reduction in global biodiversity which might in
part be explained by poor sampling. Very few groups appear to have
been entirely resilient to this J/K boundary ‘event’, which hints at a
‘cascade model’ of ecosystem changes driving faunal dynamics. Within
terrestrial ecosystems, larger, more-specialised organisms, such as
saurischian dinosaurs, appear to have suffered the most. Medium-sized
tetanuran theropods declined, and were replaced by larger-bodied
groups, and basal eusauropods were replaced by neosauropod faunas. The
ascent of paravian theropods is emphasised by escalated competition
with contemporary pterosaur groups, culminating in the explosive
radiation of birds, although the timing of this is obfuscated by
biases in sampling. Smaller, more ecologically diverse terrestrial
non-archosaurs, such as lissamphibians and mammaliaforms, were
comparatively resilient to extinctions, instead documenting the
origination of many extant groups around the J/K boundary. In the
marine realm, extinctions were focused on low-latitude, shallow marine
shelf-dwelling faunas, corresponding to a significant eustatic
sea-level fall in the latest Jurassic. More mobile and ecologically
plastic marine groups, such as ichthyosaurs, survived the boundary
relatively unscathed. High rates of extinction and turnover in other
macropredaceous marine groups, including plesiosaurs, are accompanied
by the origin of most major lineages of extant sharks. Groups which
occupied both marine and terrestrial ecosystems, including
crocodylomorphs, document a selective extinction in shallow marine
forms, whereas turtles appear to have diversified. These patterns
suggest that different extinction selectivity and ecological processes
were operating between marine and terrestrial ecosystems, which were
ultimately important in determining the fates of many key groups, as
well as the origins of many major extant lineages. We identify a
series of potential abiotic candidates for driving these patterns,
including multiple bolide impacts, several episodes of flood basalt
eruptions, dramatic climate change, and major disruptions to oceanic
systems. The J/K transition therefore, although not a mass extinction,
represents an important transitional period in the co-evolutionary
history of life on Earth.