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Marine reptile turnover during Jurassic-Cretaceous transition

From: Ben Creisler

A new online paper:

Roger B. J. Benson & Patrick S. Druckenmiller (2013)
Faunal turnover of marine tetrapods during the Jurassic–Cretaceous transition.
Biological Reviews (advance online publication)
DOI: 10.1111/brv.12038

Marine and terrestrial animals show a mosaic of lineage extinctions
and diversifications during the Jurassic–Cretaceous transition.
However, despite its potential importance in shaping animal evolution,
few palaeontological studies have focussed on this interval and the
possible climate and biotic drivers of its faunal turnover. In
consequence evolutionary patterns in most groups are poorly
understood. We use a new, large morphological dataset to examine
patterns of lineage diversity and disparity (variety of form) in the
marine tetrapod clade Plesiosauria, and compare these patterns with
those of other organisms. Although seven plesiosaurian lineages have
been hypothesised as crossing the Jurassic–Cretaceous boundary, our
most parsimonious topology suggests the number was only three. The
robust recovery of a novel group including most Cretaceous
plesiosauroids (Xenopsaria, new clade) is instrumental in this result.
Substantial plesiosaurian turnover occurred during the
Jurassic–Cretaceous boundary interval, including the loss of
substantial pliosaurid, and cryptoclidid diversity and disparity,
followed by the radiation of Xenopsaria during the Early Cretaceous.
Possible physical drivers of this turnover include climatic
fluctuations that influenced oceanic productivity and diversity: Late
Jurassic climates were characterised by widespread global monsoonal
conditions and increased nutrient flux into the opening
Atlantic-Tethys, resulting in eutrophication and a highly productive,
but taxonomically depauperate, plankton. Latest Jurassic and Early
Cretaceous climates were more arid, resulting in oligotrophic ocean
conditions and high taxonomic diversity of radiolarians, calcareous
nannoplankton and possibly ammonoids. However, the observation of
discordant extinction patterns in other marine tetrapod groups such as
ichthyosaurs and marine crocodylomorphs suggests that clade-specific
factors may have been more important than overarching extrinsic
drivers of faunal turnover during the Jurassic–Cretaceous boundary