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Sphenacodontia tooth structure + other non-dino papers



Ben Creisler
bcreisler@gmail.com

A number of recent non-dino items that may be of interest:


Kirstin S. Brink, Aaron R. H. LeBlanc & Robert R. Reisz (2014)
First record of plicidentine in Synapsida and patterns of tooth root
shape change in Early Permian sphenacodontians.
Naturwissenschaften (advance online publication)
DOI: 10.1007/s00114-014-1228-5
http://link.springer.com/article/10.1007/s00114-014-1228-5

Recent histological studies have revealed a diversity of dental
features in Permo-Carboniferous tetrapods. Here, we report on the
occurrence of plicidentine (infolded dentine around the base of the
tooth root) in Sphenacodontia, the first such documentation in
Synapsida, the clade that includes mammals. Five taxa were examined
histologically, Ianthodon schultzei, Sphenacodon ferocior, Dimetrodon
limbatus, Dimetrodon grandis, and Secodontosaurus obtusidens. The
tooth roots of Ianthodon possess multiple folds, which is generally
viewed as the primitive condition for amniotes. Sphenacodon and D.
limbatus have distinctive “four-leaf clover”-shaped roots in cross
section, whereas Secodontosaurus has an elongate square shape with
only subtle folding. The most derived and largest taxon examined in
this study, D. grandis, has rounded roots in cross section and
therefore no plicidentine. This pattern of a loss of plicidentine in
sphenacodontids supports previous functional hypotheses of
plicidentine, where teeth with shallow roots require folds to increase
the area of attachment to the tooth-bearing element, whereas teeth
with long roots do not. This pattern may also reflect differences in
diet between co-occurring sphenacodontids as well as changes in
feeding niche through time, specifically in the apex predator
Dimetrodon.

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Malcolm B. Hart (2014)
The 'Otter Sandstone River' of the mid-Triassic and its vertebrate fauna.
Proceedings of the Geologists' Association (advance online publication)
DOI: 10.1016/j.pgeola.2014.08.002
http://www.sciencedirect.com/science/article/pii/S0016787814000601

The Triassic succession of the East Devon coastline is a key component
of the Jurassic Coast World Heritage Site. Within these strata are the
sediments deposited by two major river systems: the Budleigh Salterton
Pebble Beds and the Otter Sandstone Formation. The latter are
significant as both a reservoir for the Dorset oilfields near Wareham
and as a source of significant numbers of vertebrate fossils. The
Otter Sandstone Formation, of Anisian (Middle Triassic) age, has a
lower part formed of aeolian sands but these pass upwards into a
series of river channel deposits. These river channels, which are best
seen between the mouth of the River Otter and Ladram Bay, contain a
series of classic features such as erosive channel bases, channel lag
deposits, de-watering structures, calcified root systems (rhizoliths),
reworked calcretes and (rare) overbank mudstones. The rivers that
formed the various braided channel deposits flowed northwards or
north-eastwards and there are at least 4 or 5 separate channel units
within the Ladram Bay area. The Otter Sandstone Formation has yielded
a great many rhynchosaur fragments and at least one partial skeleton.
This juvenile individual appears to have fallen into one of the
channels, resulting in the loss of its head (skull), as this was not
recovered when the specimen was found by the author in 1990. This
important specimen of Fodonyx spenceri (Benton, 1990) is housed in the
Royal Albert Memorial Museum in Exeter.

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Open Access:

André Nel, Patricia Nel, Régis Krieg-Jacquier, Jean-Marc Pouillon &
Romain Garrouste (2014)
Exceptionally preserved insect fossils in the Late Jurassic lagoon of
Orbagnoux (Rhône Valley, France).
PeerJ 2:e510
doi: http://dx.doi.org/10.7717/peerj.510
https://peerj.com/articles/510/

The Late Kimmeridgian marine limestones of the area around Orbagnoux
(Rhône, France) are well known for their fish fauna and terrestrial
flora. Here we record the first insects and their activities (mines on
leaves and trails in sediments) from these layers, including the
oldest record of the gerromorphan bugs, as a new genus and species
Gallomesovelia grioti, attributed to the most basal family
Mesoveliidae and subfamily Madeoveliinae. These new fossils suggest
the presence of a complex terrestrial palaeoecosystem on emerged lands
near the lagoon where the limestones were deposited. The exquisite
state of preservation of these fossils also suggests that these
outcrops can potentially become an important Konservat-Lagerstätte for
the Late Jurassic of Western Europe.

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Sara Callegaro, Don R. Baker, Angelo De Min, Andrea Marzoli, Kalotina
Geraki, Hervé Bertrand, Cecilia Viti, and Fabrizio Nestola (2014)
Microanalyses link sulfur from large igneous provinces and Mesozoic
mass extinctions.
Geology (advance online publication)
doi: 10.1130/G35983.1
http://geology.gsapubs.org/content/early/2014/08/28/G35983.1.abstract



Volcanic gases can have devastating impacts on Earth's environment and
life. However, measurement of volatile elements in prehistoric magmas
is challenging. We present a new method for determining sulfur
contents in magmas using its concentrations in clinopyroxenes and an
experimentally determined crystal-melt partition coefficient. Using
this method we compared magmatic sulfur contents in the
Paraná-Etendeka large igneous province (LIP; South America) and two
other similarly sized LIPs, the Central Atlantic magmatic province
(CAMP) and the Deccan Traps (India). We found that the CAMP and Deccan
Traps, both associated with major extinction events, contained high
magmatic sulfur concentrations, up to 1900 ppm. Conversely, the
Paraná-Etendeka LIP, lacking significant environmental effects, had
substantially lower magmatic sulfur concentrations, less than 800 ppm.

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Victoria A. Hudspith, Susan M. Rimmer and Claire M. Belcher (2014)
Latest Permian chars may derive from wildfires, not coal combustion.
Geology (advance online publication)
doi: 10.1130/G35920.1
http://geology.gsapubs.org/content/early/2014/08/28/G35920.1.abstract



The Permian-Triassic boundary extinction event was the largest
biological crisis of the Phanerozoic. One of the principle triggers
for the mass extinction is thought to be greenhouse warming resulting
from the release of CH4 from basalt-coal interaction during the
extensive Siberian Traps (Russia) eruptions. Observations of organic
matter interpreted to be coal combustion products (fly ash) in latest
Permian marine sediments have been used to support this hypothesis.
However, this interpretation is dependent upon vesicular chars being
fly ash (coal combustion derived) and not formed by alternative
mechanisms. Here we present reflectance microscopy images of vesicular
chars from Russian Permian coals, and chars from modern tundra,
peatland, and boreal forest fires, to demonstrate that despite a
difference in precursor fuels, wildfires are capable of generating
vesicular chars that are morphologically comparable to end-Permian fly
ash. These observations, coupled with extensive global evidence of
wildfires during this time interval, call into question the
contribution of coal combustion to the end-Permian extinction event.

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