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Temnospondyl bone histology and skull ornamentation + Eastern European Permian Theromorpha



Ben Creisler
bcreislerF@gmail.com


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


Julia B. Mchugh  (2015)
Paleohistology of Micropholis stowi (Dissorophoidea) and Lydekkerina
huxleyi (Lydekkerinidae) humeri from the Karoo Basin of South Africa,
and implications for bone microstructure evolution in temnospondyl
amphibians.
Journal of Vertebrate Paleontology (advance online publication)
DOI:10.1080/02724634.2014.902845
http://www.tandfonline.com/doi/full/10.1080/02724634.2014.902845#.VMu1zmjF_To


Temnospondyl amphibians are a large and diverse group of early
tetrapods, whose paleohistology has been incompletely studied. Here,
humeri of Micropholis stowi and Lydekkerina huxleyi from the Karoo
Basin of South Africa (Katberg Formation) were thin–sectioned for
paleohistological analysis. Diaphyseal bone histology of both taxa
exhibits a convergence to fibrolamellar tissue and an absence of lines
of arrested growth; additionally, medullary cavities free of
trabeculae support terrestrial lifestyles in both Micropholis and
Lydekkerina. The presence of azonal tissue in Micropholis is unlike
that of other dissorophoids or extant caudatans, suggesting an
adaptation to local conditions in the Early Triassic of the Karoo
Basin, as well as a complicated and incompletely studied pattern of
histological evolution in dissorophoids. Additionally, the propodial
histology of these and 12 other taxa were assessed through different
broad–scale phylogenetic hypotheses for Temnospondyli. Results reveal
convergence towards sustained, non–cyclical growth and an absence of
lines of arrested growth in the diaphyses of Early Triassic
temnospondyls. The optimization of histological traits on to existing
phylogenetic hypotheses is equally parsimonious between the different
topologies. Homoplasy among histological characters suggests that
evolutionary history in this group is overshadowed by developmental
plasticity in bone microstructure, potentially due to environmental
and biomechanical constraints. However, the interpretation of these
data is limited by small sample size, and increased sampling is
required to validate the patterns revealed in this study.


http://zoobank.org/urn:lsid:zoobank.org:pub:7CF4CD42–3C8B–43F3–83A1–7C611C5CDBB8

***

B. I. Morkovin (2015)
On the development of surface ornamentation of skull bones in the
ontogeny of Early Triassic benthosuchids (Amphibia, Temnospondyli).
Paleontological Journal 49(1): 57-69
DOI: 10.1134/S0031030115010074
http://link.springer.com/article/10.1134/S0031030115010074

The rate of developmental changes in ornamentation of the dermal skull
observed at the submature stages of the trematosauroid Benthosuchus
(Amphibia, Temnospondyli) shows a wide range of individual variation
divided into two dominant modes. The analysis of this variation based
on comparisons within samples of two dermal bones (supratemporal and
squamosal) displays that such a bimodality is distinctly expressed at
the earliest known growth stage and tends to disappear with age.



=======

M. F. Ivakhnenko (2015)
Patterns of changes in Theromorph taxa of Permian terrestrial
communities of Eastern Europe.
Paleontological Journal 49(1): 70-78
DOI: 10.1134/S0031030115010050
http://link.springer.com/article/10.1134/S0031030115010050

The evolution of Late Permian tetrapod communities which include
Theromorpha is examined in the territory of Eastern Europe. It is
noteworthy that changes in the taxonomic composition of analogous
ecobiomorph groups are connected with certain biotic or abiotic
factors. The analysis of these factors allows the recognition of
presumable causes of the crises in communities, which are determined
to a greater or lesser extent by taxonomic changes. It is shown that
the crisis in the middle of the Permian was caused primarily by
abiotic (tectonic) reasons, while the crisis at the end of the Permian
was complex, determined by a combination of biotic, local tectonic,
and global factors.

=====

In open access:

Vincent J. Lynch, Mauris C. Nnamani, Aurélie Kapusta, Kathryn Brayer,
Silvia L. Plaza, Erik C. Mazur, Deena Emera, Shehzad Z. Sheikh, Frank
Grützner, Stefan Bauersachs, Alexander Graf, Steven L. Young, Jason D.
Lieb, Francesco J. DeMayo, Cédric Feschotte & Günter P. Wagner (2015)
 Ancient Transposable Elements Transformed the Uterine Regulatory
Landscape and Transcriptome during the Evolution of Mammalian
Pregnancy.
Cell Reports (advance online publication)
DOI: doi:10.1016/j.celrep.2014.12.052
http://www.sciencedirect.com/science/article/pii/S221112471401105X

Highlights

Thousands of genes gained uterine expression during the origins of pregnancy
Genes that mediate maternal-fetal immunotolerance evolved expression
in Eutherians
Ancient transposable elements donated cis-regulatory elements to recruited genes
Ancient transposable elements coordinate the uterine progesterone response

Summary

A major challenge in biology is determining how evolutionarily novel
characters originate; however, mechanistic explanations for the origin
of new characters are almost completely unknown. The evolution of
pregnancy is an excellent system in which to study the origin of
novelties because mammals preserve stages in the transition from egg
laying to live birth. To determine the molecular bases of this
transition, we characterized the pregnant/gravid uterine transcriptome
from tetrapods to trace the evolutionary history of uterine gene
expression. We show that thousands of genes evolved endometrial
expression during the origins of mammalian pregnancy, including genes
that mediate maternal-fetal communication and immunotolerance.
Furthermore, thousands of cis-regulatory elements that mediate
decidualization and cell-type identity in decidualized stromal cells
are derived from ancient mammalian transposable elements (TEs). Our
results indicate that one of the defining mammalian novelties evolved
from DNA sequences derived from ancient mammalian TEs co-opted into
hormone-responsive regulatory elements distributed throughout the
genome.


News story:
http://www.sciencedaily.com/releases/2015/01/150129125501.htm