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Diandongosaurus (Sauropterygia) revised (free pdf) + end-Triassic extinctions + Caseid phylogeny



Ben Creisler
bcreisler@gmail.com


A number of recent non-dino papers:

LIU Xue-Qing, LIN Wen-Bin, Olivier RIEPPEL, SUN Zuo-Yu, LI Zhi-Guang,
LU Hao & JIANG Da-Yong (2015)
A new specimen of Diandongosaurus acutidentatus (Sauropterygia) from
the Middle Triassic of Yunnan, China. (in Chinese)
Vertebrata PalAsiatica (advance online publication)
http://www.ivpp.cas.cn/cbw/gjzdwxb/pressonline/201509/t20150916_4425780.html

Free pdf:

http://www.ivpp.cas.cn/cbw/gjzdwxb/pressonline/201509/P020150916504251471343.pdf



A new nearly complete specimen of Diandongosaurus acutidentatus Shang
et al., 2011 is described from the Upper Member of the Guanling
Formation (Anisian, Middle Triassic) of Luoping, Yunnan Province. With
the new information derived from the new specimen, some elements of
the skeleton that were either uncertain or controversial in the
previous studies are confirmed and discussed, and the diagnosis of D.
acutidentatus is revised. The result of our phylogenetic analysis
suggests that Diandongosaurus is an eosauropterygian, closely related
to the Eusauropterygia.

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Free pdf:

Spencer G. Lucas & Lawrence H. Tanner (2015)
End-Triassic nonmarine biotic events.
Journal of Palaeogeography (advance online publication)
doi:10.1016/j.jop.2015.08.010
http://www.sciencedirect.com/science/article/pii/S2095383615000218



The Late Triassic was a prolonged interval of elevated extinction
rates and low origination rates that manifested themselves in a series
of extinctions during Carnian, Norian and Rhaetian time. Most of these
extinctions took place in the marine realm, particularly affecting
radiolarians, conodonts, bivalves, ammonoids and reef-building
organisms. On land, the case for a Late Triassic mass extinction is
much more tenuous and has largely focused on tetrapod vertebrates
(amphibians and reptiles), though some workers advocate a sudden
end-Triassic (TJB) extinction of land plants. Nevertheless, an
extensive literature does not identify a major extinction of land
plants at the TJB, and a comprehensive review of palynological records
concluded that TJB vegetation changes were non-uniform (different
changes in different places), not synchronous and not indicative of a
mass extinction of land plants. Claims of a substantial perturbation
of plant ecology and diversity at the TJB in East Greenland are
indicative of a local change in the paleoflora largely driven by
lithofacies changes resulting in changing taphonomic filters. Plant
extinctions at the TJB were palaeogeographically localized events, not
global in extent. With new and more detailed stratigraphic data, the
perceived TJB tetrapod extinction is mostly an artifact of coarse
temporal resolution, the compiled correlation effect. The amphibian,
archosaur and synapsid extinctions of the Late Triassic are not
concentrated at the TJB, but instead occur stepwise, beginning in the
Norian and extending into the Hettangian. There was a disruption of
the terrestrial ecosystem across the TJB, but it was more modest than
generally claimed. The ecological severity of the end-Triassic
nonmarine biotic events are relatively low on the global scale. Biotic
turnover at the end of the Triassic was likely driven by the CAMP
eruptions, which caused significant environmental perturbations
(cooling, warming, acidification) through outgassing, but the effects
on the nonmarine biota appear to have been localized, transient and
not catastrophic. Long-term changes in the terrestrial biota across
the TJB are complex, diachronous and likely climate driven
evolutionary changes in the context of fluctuating background
extinction rates, not a single, sudden or mass extinction.

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Marco Romano and Umberto Nicosia (2015)
Cladistic analysis of Caseidae (Caseasauria, Synapsida): using the
gap-weighting method to include taxa based on incomplete specimens.
Palaeontology (advance online publication)
DOI: 10.1111/pala.12197
http://onlinelibrary.wiley.com/doi/10.1111/pala.12197/abstract

Occupying the role of primary consumer and having an early–middle
Permian age range, caseids (Caseasauria, Synapsida) are fundamental to
the interpretation of the early history of terrestrial vertebrate
ecosystems. Despite this importance, no comprehensive, species-level
phylogenetic study of Caseidae has yet been performed. Herein, we
present a phylogenetic analysis of the group, using gap weighting to
include poorly known taxa. Besides the description and comments on the
resultant topologies, some more general issues concerning cladistic
methodologies are briefly addressed. This study highlights the
importance of a total-evidence approach, including as many
within-group taxa and characters as possible. Continuously varying
characters, in the form of indices derived from measurement of
individual skeletal elements, proved to be highly important, adding
significantly to the resolution of, and support for, recovered trees.
The utility of the postcranial skeleton in understanding relationships
among basal synapsids is highlighted.




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