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Pliosaurus, new giant species from England
From: Ben Creisler
New in PLoS ONE:
Roger B. J. Benson mail, Mark Evans, Adam S. Smith, Judyth Sassoon,
Scott Moore-Faye, Hilary F. Ketchum, and Richard Forrest (2013)
A Giant Pliosaurid Skull from the Late Jurassic of England.
PLoS ONE 8(5): e65989.
Pliosaurids were a long-lived and cosmopolitan group of marine
predators that spanned 110 million years and occupied the upper tiers
of marine ecosystems from the Middle Jurassic until the early Late
Cretaceous. A well-preserved giant pliosaurid skull from the Late
Jurassic Kimmeridge Clay Formation of Dorset, United Kingdom,
represents a new species, Pliosaurus kevani. This specimen is
described in detail, and the taxonomy and systematics of Late Jurassic
pliosaurids is revised. We name two additional new species, Pliosaurus
carpenteri and Pliosaurus westburyensis, based on previously described
relatively complete, well-preserved remains. Most or all Late Jurassic
pliosaurids represent a globally distributed monophyletic group (the
genus Pliosaurus, excluding ‘Pliosaurus’ andrewsi). Despite its high
species diversity, and geographically widespread, temporally extensive
occurrence, Pliosaurus shows relatively less morphological and
ecological variation than is seen in earlier, multi-genus pliosaurid
assemblages such as that of the Middle Jurassic Oxford Clay Formation.
It also shows less ecological variation than the pliosaurid-like
Cretaceous clade Polycotylidae. Species of Pliosaurus had robust
skulls, large body sizes (with skull lengths of 1.7–2.1 metres), and
trihedral or subtrihedral teeth suggesting macropredaceous habits. Our
data support a trend of decreasing length of the mandibular symphysis
through Late Jurassic time, as previously suggested. This may be
correlated with increasing adaptation to feeding on large prey.
Maximum body size of pliosaurids increased from their first appearance
in the Early Jurassic until the Early Cretaceous (skull lengths up to
2360 mm). However, some reduction occurred before their final
extinction in the early Late Cretaceous (skull lengths up to 1750 mm).