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Plesiochelyid turtles from Late Jurassic of UK + gigantism + more non-dino papers

Ben Creisler

Some recent non-dino papers that may be of interest:

In open access:

Jérémy Anquetin & Sandra D. Chapman (2016)
First report of Plesiochelys etalloni and Tropidemys langii from the
Late Jurassic of the UK and the palaeobiogeography of plesiochelyid
Royal Society Open Science 3: 150470
DOI: 10.1098/rsos.15047

Plesiochelyidae is a clade of relatively large coastal marine turtles
that inhabited the shallow epicontinental seas that covered western
Europe during the Late Jurassic. Although the group has been reported
from many deposits, the material is rarely identified at the species
level. Here, we describe historical plesiochelyid material from the
Kimmeridge Clay Formation of England and compare it with
contemporaneous localities from the continent. An isolated basicranium
is referred to the plesiochelyid Plesiochelys etalloni based notably
on the presence of a fully ossified pila prootica. This specimen
represents the largest individual known so far for this species and is
characterized by remarkably robust features. It is, however, uncertain
whether this represents an ontogenetic trend towards robustness in
this species, some kind of specific variation (temporal, geographical
or sexual), or an abnormal condition of this particular specimen. Four
other specimens from the Kimmeridge Clay are referred to the
plesiochelyidTropidemys langii. This contradicts a recent study that
failed to identify this species in this formation. This is the first
time, to the best of our knowledge, that the presence of Plesiochelys
etalloni and Tropidemys langii is confirmed outside the Swiss and
French Jura Mountains. Our results indicate that some plesiochelyids
had a wide palaeobiogeographic distribution during the Kimmeridgian.

In open access:

Geerat J. Vermeij (2016)
Gigantism and Its Implications for the History of Life.
PLoS ONE 11(1): e0146092.

Gigantism—very large body size—is an ecologically important trait
associated with competitive superiority. Although it has been studied
in particular cases, the general conditions for the evolution and
maintenance of gigantism remain obscure. I compiled sizes and dates
for the largest species in 3 terrestrial and 7 marine trophic and
habitat categories of animals from throughout the Phanerozoic. The
largest species (global giants) in all categories are of
post-Paleozoic age. Gigantism at this level appeared tens to hundreds
of millions of years after mass extinctions and long after the origins
of clades in which it evolved. Marine gigantism correlates with high
planktic or seafloor productivity, but on land the correspondence
between productivity and gigantism is weak at best. All global giants
are aerobically active animals, not gentle giants with low metabolic
demands. Oxygen concentration in the atmosphere correlates with
gigantism in the Paleozoic but not thereafter, likely because of the
elaboration of efficient gas-exchange systems in clades containing
giants. Although temperature and habitat size are important in the
evolution of very large size in some cases, the most important (and
rare) enabling circumstance is a highly developed ecological
infrastructure in which essential resources are abundant and
effectively recycled and reused, permitting activity levels to
increase and setting the stage for gigantic animals to evolve.
Gigantism as a hallmark of competitive superiority appears to have
lost its luster on land after the Mesozoic in favor of alternative
means of achieving dominance, especially including social organization
and coordinated food-gathering.


Collin S. VanBuren and David C. Evans (2016)
Evolution and function of anterior cervical vertebral fusion in tetrapods.
Biological Reviews (advance online publication)
DOI: 10.1111/brv.12245

The evolution of vertebral fusion is a poorly understood phenomenon
that results in the loss of mobility between sequential vertebrae.
Non-pathological fusion of the anterior cervical vertebrae has evolved
independently in numerous extant and extinct mammals and reptiles,
suggesting that the formation of a ‘syncervical’ is an adaptation that
arose to confer biomechanical advantage(s) in these lineages. We
review syncervical anatomy and evolution in a broad phylogenetic
context for the first time and provide a comprehensive summary of
proposed adaptive hypotheses. The syncervical generally consists of
two vertebrae (e.g. hornbills, porcupines, dolphins) but can include
fusion of seven cervical vertebrae in some cetaceans. Based on the
ecologies of taxa with this trait, cervical fusion most often occurs
in fossorial and pelagic taxa. In fossorial taxa, the syncervical
likely increases the out-lever force during head-lift digging. In
cetaceans and ricochetal rodents, the syncervical may stabilize the
head and neck during locomotion, although considerable variation
exists in its composition without apparent variability in locomotion.
Alternatively, the highly reduced cervical vertebral centra may
require fusion to prevent mechanical failure of the vertebrae. In
birds, the syncervical of hornbills may have evolved in response to
their unique casque-butting behaviour, or due to increased head mass.
The general correlation between ecological traits and the presence of
a syncervical in extant taxa allows more accurate interpretation of
extinct animals that also exhibit this unique trait. For example,
syncervicals evolved independently in several groups of marine
reptiles and may have functioned to stabilize the head at the
craniocervical joint during pelagic locomotion, as in cetaceans.
Overall, the origin and function of fused cervical vertebrae is poorly
understood, emphasizing the need for future comparative biomechanical
studies interpreted in an evolutionary context.


Marcello Ruta and Matthew A. Wills (2016)
Comparable disparity in the appendicular skeleton across the
fish–tetrapod transition, and the morphological gap between fish and
tetrapod postcrania.
Palaeontology (advance online publication)
DOI: 10.1111/pala.12227

Appendicular skeletal traits are used to quantify changes in
morphological disparity and morphospace occupation across the
fish–tetrapod transition and to explore the informativeness of
different data partitions in phylogeny reconstruction. Anterior
appendicular data yield trees that differ little from those built from
the full character set, whilst posterior appendicular data result in
considerable loss of phylogenetic resolution and tree branch
rearrangements. Overall, there is a significant incongruence in the
signals associated with pectoral and pelvic data. The appendicular
skeletons of fish and tetrapods attain similar levels of morphological
disparity (at least when data are rarefied at the maximum sample size
for fish in our study) and occupy similarly sized regions of
morphospace. However, fish appear more dispersed in morphospace than
tetrapods do. All taxa show a heterogeneous distribution in
morphospace, and there is a clear separation between fish and
tetrapods despite the presence of several evolutionarily intermediate


In open access:

Héctor E. Ramírez-Chaves, Stephen W. Wroe, Lynne Selwood, Lyn A.
Hinds, Chris Leigh, Daisuke Koyabu, Nikolay Kardjilov & Vera
Weisbecker (2016)
Mammalian development does not recapitulate suspected key
transformations in the evolutionary detachment of the mammalian middle
Proceedings of the Royal Society B 283: 20152606
DOI: 10.1098/rspb.2015.2606

The ectotympanic, malleus and incus of the developing mammalian middle
ear (ME) are initially attached to the dentary via Meckel's cartilage,
betraying their origins from the primary jaw joint of land
vertebrates. This recapitulation has prompted mostly unquantified
suggestions that several suspected—but similarly unquantified—key
evolutionary transformations leading to the mammalian ME are
recapitulated in development, through negative allometry and
posterior/medial displacement of ME bones relative to the jaw joint.
Here we show, using µCT reconstructions, that neither allometric nor
topological change is quantifiable in the pre-detachment ME
development of six marsupials and two monotremes. Also, differential
ME positioning in the two monotreme species is not recapitulated. This
challenges the developmental prerequisites of widely cited
evolutionary scenarios of definitive mammalian middle ear (DMME)
evolution, highlighting the requirement for further fossil evidence to
test these hypotheses. Possible association between rear molar
eruption, full ME ossification and ME detachment in marsupials
suggests functional divergence between dentary and ME as a trigger for
developmental, and possibly also evolutionary, ME detachment. The
stable positioning of the dentary and ME supports suggestions that a
‘partial mammalian middle ear’ as found in many mammaliaforms—probably
with a cartilaginous Meckel's cartilage—represents the only
developmentally plausible evolutionary DMME precursor.