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Diapsid origin of turtles + biochronology for Triassic marine vertebrate faunas of Guizhou Province + more ,

Ben Creisler

Some additional recent (and not so recent) refs:

Rainer R. Schoch & Hans-Dieter Sues (2016)
The diapsid origin of turtles.
Zoology (advance online publication)
http: // www.sciencedirect.com/science/article/pii/S0944200616300046?np=y


New fossils from Germany reveal that turtles had ancestors with a diapsid skull.
The turtle plastron formed in part from thickened gastralia.
The closed anapsid skull of turtles evolved late in the stem group.
The traditional parareptile hypothesis of turtle origin is rejected.


The origin of turtles has been a persistent unresolved problem
involving unsettled questions in embryology, morphology, and
paleontology. New fossil taxa from the early Late Triassic of China
(Odontochelys) and the Late Middle Triassic of Germany (Pappochelys)
now add to the understanding of (i) the evolutionary origin of the
turtle shell, (ii) the ancestral structural pattern of the turtle
skull, and (iii) the phylogenetic position of Testudines. As has long
been postulated on the basis of molecular data, turtles evolved from
diapsid reptiles and are more closely related to extant diapsids than
to parareptiles, which had been suggested as stem group by some
paleontologists. The turtle cranium with its secondarily closed
temporal region represents a derived rather than a primitive condition
and the plastron partially evolved through the fusion of gastralia.


Zuoyu Sun, Dayong Jiang, Cheng Ji & Weicheng Hao (2016)
Integrated biochronology for Triassic marine vertebrate faunas of
Guizhou Province, South China.
Journal of Asian Earth Sciences 118: 101–110
http: // www.sciencedirect.com/science/article/pii/S1367912016300049


An integrated biochronology for Triassic reptile faunas of Guizhou was
Triassic vertebrate faunas of Guizhou are dated to the substage and zone levels.


The Middle and Upper Triassic marine deposits of Guizhou Province,
which yielded exceptionally well-preserved vertebrate faunas, are
further investigated. New age-diagnostic conodonts and ammonoids from
six measured sections, together with already published data, allow us
to construct an integrated biochronology straddling strata from the
upper Guanling Formation (Anisian, Middle Triassic) to the basal
Xiaowa Formation (Carnian, Upper Triassic). Age constrains for those
fossil Lagerstätten are now dated to the substage and zone levels: the
Panxian Fauna, within the conodont Nicoraella kockeli Zone and broadly
coexisted with the ammonoid 'Schreyerites' binodosus, is suggested as
latest Pelsonian (middle Anisian) in age; the Xingyi Fauna is assumed
to be not younger than the middle Longobardian (Late Ladinian) because
the conodont Paragondolella inclinata with free-blade and the ammonoid
Haoceras xingyiensis are recorded from slightly younger strata; the
conodont Paragondolella auriformis and the ammonoid Trachyceras
multituberculatum and Austrotrachyceras triadicum clearly indicate
that the Guanling Fauna is not older than Julian (early Carnian) in
age (time interval between Aon Zone or Aonoides Zone). With the new
biostratigraphic data, a relative sequence and correlation of the
Middle Triassic vertebrate faunas from Guizhou (South China) and Monte
San Giorgio (Southern Alps, Switzerland/Italy) is proposed.


Kévin Rey, Romain Amiot, François Fourel, Thomas Rigaudier, Fernando
Abdala, Michael O. Day, Vincent Fernandez, Frédéric Fluteau, Christian
France-Lanord, Bruce S. Rubidge, Roger M. Smith, Pia A. Viglietti,
Bernhard Zipfel & Christophe Lécuyer (2015)
Global climate perturbations during the Permo-Triassic mass
extinctions recorded by continental tetrapods from South Africa.
Gondwana Research (advance online publication)
http: // www.sciencedirect.com/science/article/pii/S1342937X15002439


We analyzed stable isotopes of Karoo Permo-Triassic vertebrate apatites.
Variation in δ18O and δ13C mimic those of conodont phosphates and
marine carbonates.
Both Late Permian mass extinctions are associated with climate deteriorations.


Several studies of the marine sedimentary record have documented the
evolution of global climate during the Permo-Triassic mass extinction.
By contrast, the continental records have been less exploited due to
the scarcity of continuous sections from the latest Permian into the
Early Triassic. The South African Karoo Basin exposes one of the most
continuous geological successions of this time interval, thus offering
the possibility to reconstruct climate variations in southern Laurasia
from the Middle Permian to Middle Triassic interval. Both air
temperature and humidity variations were estimated using stable oxygen
(δ18Op) and carbon (δ13Cc) isotope compositions of vertebrate apatite.
Significant fluctuations in both δ18Op and δ13Cc values mimic those of
marine records and suggest that stable isotope compositions recorded
in vertebrate apatite reflect global climate evolution. In terms of
air temperature, oxygen isotopes show an abrupt increase of about + 8
°C toward the end of the Wuchiapingian. This occurred during a slight
cooling trend from the Capitanian to the Permo-Triassic boundary
(PTB). At the end of the Permian, an intense and fast warming of + 16
°C occurred and kept increasing during the Olenekian. These thermal
fluctuations may be related to the Emeishan (South China) and Siberian
volcanic paroxysms that took place at the end of the Capitanian and at
the end of the Permian, respectively. Vertebrate apatite δ13Cc partly
reflects the important fluctuations of the atmospheric δ13C values,
the differences with marine curves being likely due to the evolution
of local humidity. Both the oxygen and carbon isotope compositions
indicate that the PTB was followed by a warm and arid phase that
lasted 6 Ma before temperatures decreased, during the Late Anisian,
toward that of the end-Permian. Environmental fluctuations occurring
around the PTB that affected both continental and marine realms with
similar magnitude likely originated from volcanism and methane


Jason C. Sanford, John W. Snedden & Sean P. S. Gulick (2016)
The Cretaceous-Paleogene boundary deposit in the Gulf of Mexico:
Large-scale oceanic basin response to the Chicxulub impact.
Journal of Geophysical Research: Solid Earth (advance online publication)
DOI: 10.1002/2015JB012615
http: // onlinelibrary.wiley.com/doi/10.1002/2015JB012615/full

Hydrocarbon exploration in the last decade has yielded sufficient data
to evaluate the Gulf of Mexico basin response to the Chicxulub
asteroid impact. Given its passive marine setting and proximity to the
impact structure on the Yucatán Peninsula, the Gulf is the premier
locale in which to study the near-field geologic effect of a bolide
impact. We mapped a thick (dm- to hm-scale) deposit of carbonate
debris at the Cretaceous-Paleogene boundary that is ubiquitous in the
Gulf and readily identifiable on borehole and seismic data. We
interpret deposits seen in seismic and borehole data in the deepwater
Gulf to be predominately muddy debrites with minor turbidites based on
cores in the southeastern Gulf. Mapping of the deposit in the northern
Gulf of Mexico reveals that the impact redistributed roughly 1.05 ×
105 km3 of sediment therein, and over 1.98 × 105 km3 Gulf-wide.
Deposit distribution suggests that the majority of sediment derived
from coastal and shallow-water environments throughout the Gulf via
seismic and megatsunamic processes initiated by the impact. The Texas
shelf and northern margin of the Florida Platform were significant
sources of sediment, while the central and southern Florida Platform
underwent more localized platform collapse. Crustal structure of the
ancestral Gulf influenced post-impact deposition both directly and
indirectly through its control on salt distribution in the Louann Salt
Basin. Nevertheless, impact-generated deposition overwhelmed virtually
all topography and depositional systems at the start of the Cenozoic,
blanketing the Gulf with carbonate debris within days.