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Gomphodont cynodont stapes + Multituberculate iron-pigmented tooth enamel + more (free pdfs)



Ben Creisler
bcreisler@gmail.com

Some new non-dino papers in open access that may be of interest:

Leandro C. Gaetano  & Fernando Abdala (2015)
The Stapes of Gomphodont Cynodonts: Insights into the Middle Ear
Structure of Non-Mammaliaform Cynodonts.
PLoS ONE 10(7): e0131174.
doi:10.1371/journal.pone.0131174
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0131174


The stapes is known in several non-mammaliaform cynodonts, although it
has only been cursorily studied. Here we thoroughly analyze the
stapedial anatomy of several basal cynodonts in a phylogenetic
framework. Our study shows that the stapedial anatomy is more variable
than previously thought. The morphological variation of the stapes led
to the recognition of 11 phylogenetic characters that were included in
a total evidence data matrix centered in the analysis of gomphodont
cynodonts. Stapes morphology does not provide evidence to suggest a
direct connection between the stapes and a postquadrate tympanic
membrane (if present) and the hypothesis of a dorsal process as the
site of attachment of a small ligament or the stapedial muscle is
supported. The re-evaluation of the theories concerning the position
of the tympanic membrane in non-mammaliaform cynodonts allowed us to
conclude that the hypothetical postquadrate tympanic membrane
associated with the squamosal sulcus is at best relictual and most
likely non-functional (not connected with the stapes). The sound waves
were most likely transmitted to the stapes from a postdentary tympanic
membrane through the quadrate. Our analysis results in a better
understanding of the auditory system in basal cynodonts and its
evolution, highlighting the variability of the stapedial anatomy.

===

Thierry Smith & Vlad Codrea (2015)
Red Iron-Pigmented Tooth Enamel in a Multituberculate Mammal from the
Late Cretaceous Transylvanian “Haţeg Island”.
PLoS ONE 10(7): e0132550
DOI: 10.1371/journal.pone.0132550
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0132550

Mammals that inhabit islands are characterized by peculiar
morphologies in comparison to their mainland relatives. Here we report
the discovery of a partial skull associated with the lower jaws of a
Late Cretaceous (≈70 Ma) multituberculate mammal from the Carpathian
“Haţeg Island” of Transylvania, Romania. The mammal belongs to the
Kogaionidae, one of the rare families that survived the
Cretaceous—Paleogene mass extinction in Europe. The excellent
preservation of this specimen allows for the first time description of
the complete dentition of a kogaionid and demonstration that the
enigmatic Barbatodon transylvanicus presents a mosaic of primitive and
derived characters, and that it is phylogenetically basal among the
Cimolodonta. Another peculiarity is the presence of red pigmentation
in its tooth enamel. The red coloration is present on the anterior
side of the incisors and on the cusps of most of the teeth.
Energy-dispersive X-ray spectrometry (EDS) analysis reveals that the
pigmented enamel contains iron, as in living placentals. Such a red
pigmentation is known in living soricine shrews and many families of
rodents, where it is thought to increase the resistance of the enamel
to the abrasion that occurs during “grinding” mastication. The
extended pattern of red pigment distribution in Barbatodon is more
similar to that in eulipotyplan insectivores than to that in rodents
and suggests a very hard diet and, importantly, demonstrates that its
grasping incisors were not ever-growing. As inferred for other endemic
Transylvanian vertebrates such as dwarf herbivorous dinosaurs and
unusual theropod dinosaurs, insularity was probably the main factor of
survival of such a primitive mammalian lineage relative to other
mainland contemporaries of the Northern hemisphere.

===

Vincent Fernandez, Eric Buffetaut, Varavudh Suteethorn, Jean-Claude
Rage, Paul Tafforeau & Martin Kundrát (2015)
Evidence of Egg Diversity in Squamate Evolution from Cretaceous
Anguimorph Embryos.
PLoS ONE 10(7): e0128610
doi:10.1371/journal.pone.0128610
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0128610

Lizards are remarkable amongst amniotes, for they display a unique
mosaic of reproduction modes ranging from egg-laying to live-bearing.
Within this patchwork, geckoes are believed to represent the only
group to ever have produced fully calcified rigid-shelled eggs,
contrasting with the ubiquitous parchment shelled-eggs observed in
other lineages. However, this hypothesis relies only on observations
of modern taxa and fossilised gecko-like eggshells which have never
been found in association with any embryonic or parental remains. We
report here the first attested fossil eggs of lizards from the Early
Cretaceous of Thailand, combining hard eggshells with exquisitely
preserved embryos of anguimoph (e.g. Komodo dragons, mosasaurs). These
fossils shed light on an apparently rare reproduction strategy of
squamates, demonstrate that the evolution of rigid-shelled eggs are
not an exclusive specialization of geckoes, and suggest a high
plasticity in the reproductive organs mineralizing eggshells.


===

Kelli C. Trujillo & Bart J. Kowallis (2015)
Recalibrated Legacy 40Ar/39Ar Ages for the Upper Jurassic Morrison
Formation, Western Interior, U.S.A.
Geology of the Intermountain West 2(1): 1-8
http://www.utahgeology.org/resourcespace/pages/view.php?ref=467&search=%21collection3&order_by=date&sort=DESC&offset=0&archive=0&k&curpos=0

As a result of recent updating of decay constants and standard ages
used for 40Ar/39Ar dating, it is necessary to recalibrate legacy ages
obtained with older methods. These recalibrations bring legacy
40Ar/39Ar ages into better agreement with ages obtained using
238U/206Pb dating methods. We present nine recalibrated 40Ar/39Ar ages
for the Upper Jurassic Morrison Formation of the Western Interior,
U.S.A., along with the individual geographic and stratigraphic
locations for each sample. These recalibrated ages will be useful for
researchers looking to place better age constraints on the flora and
fauna of the Morrison Formation, as well as for those working to
understand stratigraphic relationships across the formation. The
recalibrated ages also can now be used reliably for comparisons with
newer 238U/206Pb ages obtained for the Morrison Formation.

===


Matt Williams, Michael J. Benton, and Andrew Ross (2015)
The Strawberry Bank Lagerstätte reveals insights into Early Jurassic life.
Journal of the Geological Society (advance online publication)
doi: 10.1144/jgs2014-144
http://jgs.lyellcollection.org/content/early/2015/06/29/jgs2014-144.abstract
http://jgs.lyellcollection.org/content/early/2015/06/29/jgs2014-144.full.pdf+html


The Strawberry Bank Lagerstätte provides a rich insight into Early
Jurassic marine vertebrate life, revealing exquisite anatomical detail
of marine reptiles and large pachycormid fishes thanks to exceptional
preservation, and especially the uncrushed, 3D nature of the fossils.
The site documents a fauna of Early Jurassic nektonic marine animals
(five species of fishes, one species of marine crocodilian, two
species of ichthyosaurs, cephalopods and crustaceans), but also over
20 species of insects. Unlike other fossil sites of similar age, the
3D preservation at Strawberry Bank provides unique evidence on palatal
and braincase structures in the fishes and reptiles. The age of the
site is important, documenting a marine ecosystem during recovery from
the end-Triassic mass extinction, but also exactly coincident with the
height of the Toarcian Oceanic Anoxic Event, a further time of turmoil
in evolution.




===


Sam Giles, Michael I. Coates, Russell J. Garwood, Martin D. Brazeau,
Robert Atwood, Zerina Johanson and Matt Friedman (2015)
Endoskeletal structure in Cheirolepis (Osteichthyes, Actinopterygii),
An early ray-finned fish.
Palaeontology (advance online publication)
DOI: 10.1111/pala.12182
http://onlinelibrary.wiley.com/doi/10.1111/pala.12182/abstract
http://onlinelibrary.wiley.com/doi/10.1111/pala.12182/pdf


As the sister lineage of all other actinopterygians, the Middle to
Late Devonian (Eifelian–Frasnian) Cheirolepis occupies a pivotal
position in vertebrate phylogeny. Although the dermal skeleton of this
taxon has been exhaustively described, very little of its endoskeleton
is known, leaving questions of neurocranial and fin evolution in early
ray-finned fishes unresolved. The model for early actinopterygian
anatomy has instead been based largely on the Late Devonian (Frasnian)
Mimipiscis, preserved in stunning detail from the Gogo Formation of
Australia. Here, we present re-examinations of existing museum
specimens through the use of high-resolution laboratory- and
synchrotron-based computed tomography scanning, revealing new details
of the neuro-cranium, hyomandibula and pectoral fin endoskeleton for
the Eifelian Cheirolepis trailli. These new data highlight traits
considered uncharacteristic of early actinopterygians, including an
uninvested dorsal aorta and imperforate propterygium, and corroborate
the early divergence of Cheirolepis within actinopterygian phylogeny.
These traits represent conspicuous differences between the
endoskeletal structure of Cheirolepis and Mimipiscis. Additionally, we
describe new aspects of the parasphenoid, vomer and scales, most
notably that the scales display peg-and-socket articulation and a
distinct neck. Collectively, these new data help clarify primitive
conditions within ray-finned fishes, which in turn have important
implications for understanding features likely present in the last
common ancestor of living osteichthyans.