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Santana Formation feathers + large marine vertebrate taphonomy in Utah + more papers



Ben Creisler
bcreisler@gmail.com

A number of recent semi- and non-dino papers that may be of interest:



Gustavo M. E. M. Prado, Luiz Eduardo Anelli, Guilherme Raffaelli Romero (2015)
New occurrences of fossilized feathers: systematics, taphonomy, and
paleoecology of the Santana Formation of the Araripe Basin
(Cretaceous), NE, Brazil.
PeerJ PrePrints 3:e1425
https://dx.doi.org/10.7287/peerj.preprints.1170v1

Feathers are the most complex and diversified integuments in
vertebrates. Their complexity are provided by the different forms and
functions, and they occur both in non-avian and avian-dinosaurs.
Despite their rareness, feathers are found throughout the world, and
the Santana Formation (comprised by Crato and Romualdo formations) of
the Araripe Basin is responsible for the majority of these records in
Brazil. Most occurrences is consisted by isolated feathers, where
downy-feathers is the recurrent morphotype, two coelurosaurs and one
enantiornithe bird. The sedimentary deposition of this unit is
consisted by a lacustrine (Crato Fm) and lagoonal (Romualdo Fm)
environments, where reducing conditions prevailed, precluding the
activity of bottom dwelling organisms that favored the exquisite
preservation. Despite the arid and hot conditions during the
Cretaceous, life teemed in the adjacency of both paleolakes, however,
feathered non-avian dinosaurs were not found yet in the Crato Member.
By the great diversity of life that existed in the paleolake
surroundings, is possible to recognize, through the fossil record,
that a complex and diversified trophic chain was well established
during the time period of sedimentation of this unit. When the remains
reached the bottom of the paleolakes, the subsequent isolation from
the environment allowed their preservation. In this work, three
fossilized feathers, consisted of two downy and one contour feather,
extracted from the laminated limestone of the Crato Member of the
Santana Formation, were described and identified according to
morphological and evolutionary models. We also used the terminology
commonly applied to extant organisms. Relying on the fossil record of
this unit and the adjacencies formations and basins (by autochthonous
condition), taxonomic inferences can be made when the lowest hierarchy
level is considered, and hence, is possible to propose the plausible
taxa that could bear these elements. Taphonomic and paleoecological
aspects, such as the preservation of these structures, and the
presence of dinosaurs, were also reviewed, as well as the future
perspectives about the study of these elements. Despite the virtual
low significance, the pragmatical study of fossilized feathers, can
help with the understanding of the evolution and paleobiology of
dinosaurs, especially on the South Hemisphere.


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Rebecca L. Schmeisser McKean & David D. Gillette (2015)
Taphonomy of large marine vertebrates in the Upper Cretaceous
(Cenomanian-Turonian) Tropic Shale of southern Utah.
Cretaceous Research 56: 278–292
doi:10.1016/j.cretres.2015.05.009
http://www.sciencedirect.com/science/article/pii/S0195667115300021

Highlights
Physical factors were dominant in marine vertebrate preservation in
the Tropic Shale.
Teeth and other durable elements are most common in the formation.
Significant post-burial alteration affected marine vertebrate skeletal material.
The paleoenvironment was low-energy marine with weak bottom currents.
Substrate firmness and benthic oxygen varied throughout deposition of the shale.



Abstract
Sediments from the Upper Cretaceous (Cenomanian-Turonian) Tropic Shale
were deposited along the western margin of the Western Interior
Seaway, in present-day southern Utah. Marine vertebrates from this
formation include plesiosaurs, mosasaurs, bony fish, sharks, and
turtles. They are concentrated in the lower portion of the Tropic
Shale, mostly between Bentonites B and D. Study of the taphonomic
condition of these vertebrates has contributed to an understanding of
how they were preserved as well as a detailed paleoenvironment for the
Tropic Shale. Physical factors played the dominant role in their
preservation, with robust and durable skeletal elements, such as teeth
and vertebrae, being most common within the shale. Isolated bones and
teeth are also relatively common within the formation, while complete
and nearly complete skeletons are more rare. Biological factors played
a less dominant role, with no evidence of epifaunal or infaunal
activity preserved with any of the skeletal remains. In addition,
scavenging marks (both bite and gnaw marks) are relatively uncommon,
typically only being found on more complete specimens. A signature of
post-burial alteration can be recognized as low levels of abrasion,
weathering, and compression and high levels of fracturing of
vertebrate skeletal material. Slightly higher levels of abrasion and
weathering occur to the west, closer to the ancient shoreline,
suggesting some pre-burial alteration. The preservation of marine
vertebrates in the Tropic Shale suggests a low energy marine
environment with some weak bottom currents and low levels of benthic
oxygen. The substrate ranged from soft and soupy to firm, with
moderate sedimentation rates resulting in relatively rapid burial.


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Tomasz Brachanieca, Robert Niedźwiedzkib, Dawid Surmika, c, Tomasz
Krzykawskia, Krzysztof Szopaa, Przemysław Gorzelakc & Mariusz A.
Salamona (2015)
Coprolites of marine vertebrate predators from the Lower Triassic of
southern Poland.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
doi:10.1016/j.palaeo.2015.06.005
http://www.sciencedirect.com/science/article/pii/S0031018215003028


Highlights
Phosphatic coprolites were described from the Lower Triassic marine sediments
Marine vertebrate predators were likely producers of the described coprolites
Durophagous predation was intense during the Early Triassic
Intestinal parasitism was broadly distributed in the aftermath of the
P/T extinction


Abstract
Numerous coprolites are described for the first time herein from the
Lower Triassic (Olenekian) shallow marine sedimentary rocks in
southern Poland. X-ray Diffraction and geochemical analyses show that
they are preserved as calcium phosphate with small admixtures of
quartz and calcite. Additionally, SEM and thin section studies
revealed that they contain highly fragmented faunal remains (crinoids,
molluscs and vertebrates). The size, shape, geochemistry,
biostratigraphic distribution and co-occurrence with vertebrate
skeletal remains imply that the coprolites at hand were likely
produced by nothosaurids and the durophagous actinopterygian
(ray-finned) fish Colobodus. The large number of recorded coprolites
implies that durophagous predation has been intense during the Early
Triassic and suggests that the so-called Mesozoic Marine Revolution
probably started soon after the end-Permian extinction. Furthermore,
discovery of sinusoidal trails attributable to nematodes in some
coprolites implies that the intestinal parasitic associations with
these predators had already evolved by at least the Early Triassic.

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Jane Qiu (2015)
Dinosaur climate probed.
Science 348 (6240): 1185
DOI: 10.1126/science.348.6240.1185
http://news.sciencemag.org/earth/2015/06/dinosaur-climate-probed
http://www.sciencemag.org/content/348/6240/1185.summary

Well before an asteroid struck the planet some 66 million years ago,
Earth was already in turmoil, a record from an ancient lakebed in
northeastern China suggests. Investigators knew from ocean floor
sediments that the climate was unstable at the end of the Cretaceous
period, when the dinosaurs were making their last stand. But findings
from deep drilling in the Songliao Basin show that the climate swings
on land were far more drastic, with average annual temperatures going
up or down by as much as 20°C over tens of thousands of years—a
geological eyeblink. The findings support a growing consensus that a
one-two punch felled the dinosaurs and their contemporaries.

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Josep Fortuny, J.-Sébastien Steyer & Izzet Hoşgör (2015)
First occurrence of temnospondyls from the Permian and Triassic of
Turkey: Paleoenvironmental and paleobiogeographic implications.
Comptes Rendus Palevol (advance online publication)
doi:10.1016/j.crpv.2015.03.001
http://www.sciencedirect.com/science/article/pii/S1631068315000408

Permian and Triassic tetrapods are very rare in Turkey. Yet this group
bears important paleoenvironmental and paleogeographical signals to
better understand Pangean models, and especially the geodynamic
history of the Permian and Triassic in Turkey, which remains highly
debated. Here we present and describe the first temnospondyls from
Turkey (SE Anatolia) which consist of a Middle Permian branchiosaurid
and an Early Triassic stereospondyl. The branchiosaurid is the first
representative of its group in Gondwana and the first from the Middle
Permian: it therefore brings important paleogeographic implications
and supports the hypothesis that anamniotic tetrapods may have used
trans-Pangean migration routes between Europe and Gondwana. It also
brings new data to the debated depositional environment of the Permian
of SE Anatolia. The Triassic stereospondyl represents one of the few
tetrapods known from paleoequatorial areas and confirms a relatively
rapid faunal turnover of the anamniotic fauna after the
Permian-Triassic mass extinction.

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Aletrimyti gaskillae and Dvellacanus carrolli


Matt Szostakiwskyj, Jason D. Pardo & Jason S. Anderson (2015)
Micro-CT Study of Rhynchonkos stovalli (Lepospondyli, Recumbirostra),
with Description of Two New Genera.
PLoS ONE 10(6): e0127307.
doi:10.1371/journal.pone.0127307
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0127307


he Early Permian recumbirostran lepospondyl Rhynchonkos stovalli has
been identified as a possible close relative of caecilians due to
general similarities in skull shape as well as similar robustness of
the braincase, a hypothesis that implies the polyphyly of extant
lissamphibians. In order to better assess this phylogenetic
hypothesis, we studied the morphology of the holotype and three
specimens previously attributed to R. stovalli. With the use of
micro-computed x-ray tomography (μCT) we are able to completely
describe the external and internal cranial morphology of these
specimens, dramatically revising our knowledge of R. stovalli and
recognizing two new taxa, Aletrimyti gaskillae gen et sp. n. and
Dvellacanus carrolli gen et sp. n. The braincases of R. stovalli, A.
gaskillae, and D. carrolli are described in detail, demonstrating
detailed braincase morphology and new information on the
recumbirostran supraoccipital bone. All three taxa show fossorial
adaptations in the braincase, sutural articulations of skull roof
bones, and in the lower jaw, but variation in cranial morphology
between these three taxa may reflect different modes of head-first
burrowing behaviors and capabilities. We revisit the homology of the
supraoccipital, median anterior bone, and temporal bone of
recumbirostrans, and discuss implications of alternate interpretations
of the homology of these elements. Finally, we evaluate the
characteristics previously used to unite Rhynchonkos stovalli with
caecilians in light of these new data. These proposed similarities are
more ambiguous than previous descriptions suggest, and result from the
composite nature of previous descriptions, ambiguities in external
morphology, and functional convergence between recumbirostrans and
caecilians for head-first burrowing.

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