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Dental formula in Late Cretaceous eutherian mammals + Thalassemys + Permian eruptions (free pdf)



Ben Creisler
bcreisler@gmail.com


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

Alexander O. Averianov & J. David Archibald (August 2015)
Evolutionary transition of dental formula in Late Cretaceous eutherian mammals.
The Science of Nature 102:56
DOI: 10.1007/s00114-015-1308-1
http://link.springer.com/article/10.1007/s00114-015-1308-1

Kulbeckia kulbecke, stem placental mammal from the Late Cretaceous of
Uzbekistan, shows a transitional stage of evolution in the dental
formula from five to four premolars. A non-replaced dP3/dp3 may occur
as individual variation. In other specimens, the lower premolars are
crowded with no space for development of dp3. As is evident from the
CT scanning of one juvenile specimen, the development of dp3 started
in a late ontogenetic stage and was confined to the pulp cavity of the
developing p2. This dp3 would have been resorbed in a later
ontogenetic stage, as the roots of p2 formed. The initial stage of
reduction of the third premolar can be traced to stem therians
(Juramaia and Eomaia), which have both dP3 and P3 present in the adult
dentition. Further delay in the development of dP3/dp3 led to the loss
of the permanent P3/p3 (a possible synapomorphy for Eutheria). The
dP3/dp3 was present during most of the adult stages in the Late
Cretaceous stem placentals Zhelestidae and Gypsonictops. This tooth is
totally absent in basal taxa of Placentalia, which normally have at
most four premolars.

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Adán Pérez-García (2015)
Largest shell of a basal eucryptodiran turtle reveals Late Jurassic
Thalassemys hugii in the British record.
Comptes Rendus Palevol (advance online publication)
doi:10.1016/j.crpv.2015.06.003
http://www.sciencedirect.com/science/article/pii/S1631068315001141

A British turtle specimen with the largest shell of a basal
eucryptodiran turtle recognized globally is presented and analyzed. It
belongs to Thalassemys hugii, the type species of both Thalassemys and
Thalassemydidae, a poorly-known European Late Jurassic clade. T. hugii
is recognized outside Central Europe for the first time. Therefore,
this finding offers new data on its geographical distribution and on
its intraspecific variability.

Blog:

http://godzillin.blogspot.com/2015/08/thalassemys-la-mayor-tortuga-de-las.html

===

In open access:

Seth D. Burgess and Samuel A. Bowring (2015)
High-precision geochronology confirms voluminous magmatism before,
during, and after Earth’s most severe extinction.
Science Advances 1(7): e1500470
DOI: 10.1126/sciadv.1500470
http://advances.sciencemag.org/content/1/7/e1500470


The end-Permian mass extinction was the most severe in the
Phanerozoic, extinguishing more than 90% of marine and 75% of
terrestrial species in a maximum of 61 ± 48 ky. Because of broad
temporal coincidence between the biotic crisis and one of the most
voluminous continental volcanic eruptions since the origin of animals,
the Siberian Traps large igneous province (LIP), a causal connection
has long been suggested. Magmatism is hypothesized to have caused
rapid injection of massive amounts of greenhouse gases into the
atmosphere, driving climate change and subsequent destabilization of
the biosphere. Establishing a causal connection between magmatism and
mass extinction is critically dependent on accurately and precisely
knowing the relative timing of the two events and the flux of magma.
New U/Pb dates on Siberian Traps LIP lava flows, sills, and
explosively erupted rocks indicate that (i) about two-thirds of the
total lava/pyroclastic volume was erupted over ~300 ky, before and
concurrent with the end-Permian mass extinction; (ii) eruption of the
balance of lavas continued for at least 500 ky after extinction
cessation; and (iii) massive emplacement of sills into the shallow
crust began concomitant with the mass extinction and continued for at
least 500 ky into the early Triassic. This age model is consistent
with Siberian Traps LIP magmatism as a trigger for the end-Permian
mass extinction and suggests a role for magmatism in suppression of
post-extinction biotic recovery.

News:

https://www.sciencenews.org/article/volcanic-activity-convicted-permian-extinction