[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Deltavjatia (Permian pareiasaur) redescribed and other non-dino papers



From: Ben Creisler
bcreisler@gmail.com

A number of recent non-dino papers that may be of interest to some on the DML:


Deltavjatia

Linda A. Tsuji  (2013)
Anatomy, cranial ontogeny and phylogenetic relationships of the
pareiasaur Deltavjatia rossicus from the Late Permian of central
Russia.
Earth and Environmental Science Transactions of the Royal Society of
Edinburgh (advance online publication)
DOI: http://dx.doi.org/10.1017/S1755691013000492
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9095434&fulltextType=RA&fileId=S1755691013000492

New material of the pareiasaur Deltavjatia rossicus from the
Kotel'nich locality, Kirov Province, Russia, is described in detail.
The taxon is characterised by a distinctive pattern of dermal
sculpture and the exaggerated embayment of the posterior skull roof,
resulting in the dorsal exposure of the braincase. Postcranially,
Deltavjatia shares some aspects of its morphology with basal
pareiasaurs, including the osteoderm pattern. Features such as the
forward-slanting and pointed iliac blade are shared with
stratigraphically younger, more derived forms. Well-preserved material
of the taxon spans a wide size-range, allowing an assessment of
ontogenetic trends. A geometric morphometric analysis of the skull
roof of Deltavjatia reveals an allometric increase in snout length and
postorbital area, a result that can serve as a basis for examining
morphological trends within pareiasaurs. A reassessment of
pareiasauromorph relationships, using both parsimony and Bayesian
methods of phylogenetic inference, recovers similar topologies in both
cases. Four Bayesian analyses were completed, with and without a
gamma-shaped parameter and with and without the inclusion of
autapomorphies. Despite differing taxon and outgroup selection, the
recovered topologies are similar to previous phylogenies of
pareiasaurian relationships, with Deltavjatia appearing as a
relatively basal taxon.

===


Early tetrapod hyobranchial apparatus


Florian Witzmann (2013)
Phylogenetic patterns of character evolution in the hyobranchial
apparatus of early tetrapods.
Earth and Environmental Science Transactions of the Royal Society of
Edinburgh (advance online publication)
DOI: http://dx.doi.org/10.1017/S1755691013000480
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9095430&fulltextType=RA&fileId=S1755691013000480


The morphologies of the hyobranchial apparatus in early tetrapods are
reviewed, based primarily on first-hand examination and supplemented
by published descriptions. The basic arrangement of the “aquatic”
hyobranchium, with four pairs of branchial arches and internal gills,
was conserved to a remarkable degree across the fish–to–tetrapod
transition and was retained in further evolution in adults of several
tetrapod lineages. Thus, a fish-like hyobranchium in basal tetrapods
does not necessarily represent a larval or paedomorphic character,
respectively, as was often suggested in analogy to extant salamanders.
Rather, it represents the plesiomorphic state of the adult
hyobranchium in tetrapods. The changes in the hyobranchium during the
fish–to–tetrapod transition include the reduction of the number of
skeletal elements and their morphological simplification. In all three
presently discussed scenarios of lissamphibian origin, the
temnospondyl, lepospondyl and diphyly hypotheses, the internal gills
were reduced independently within temnospondyls and on the amniote
stem below seymouriamorphs. Evidence of remodelling into a true
“terrestrial” hyobranchium, with reduction of the posterior branchial
arches and modification to support terrestrial tongue feeding, is
scarce in early tetrapods. It evolved within temnospondyls in
zatracheids, amphibamids and lissamphibians, as well as once or
several times in early amniotes or in their immediate stem-forms.

===

Alligator osteoderms

Irene Chen, Wen Yang & Marc A. Meyers (2013)
Alligator Osteoderms: Mechanical Behavior and Hierarchical Structure.
Materials Science and Engineering: C (advance online publication)
doi: http://dx.doi.org/10.1016/j.msec.2013.11.024
http://www.sciencedirect.com/science/article/pii/S0928493113006371

Osteoderms are bony scutes embedded underneath the dermal layers of
the skin acting as a protection of the alligator (Archosauria,
Crocodylia) internal organs and tissues. Additionally, these scutes
function as an aid in temperature regulation. The scutes are
inter-connected by fibrous connective tissue. They have properties
similar to bone and thus have the necessary toughness to provide
protection against predators. The scutes consist of hydroxyapaptite
and have a porosity of approximately 12%. They have a disc-like
morphology with a ridge along the middle of the plate, called the
keel; the outer perimeter of the disc has depressions, grooves, and
jagged edges which anchor the collagen and act as sutures.
Computerized tomography reveals the pattern of elongated pores, which
emanate from the keel in a radial pattern. Micro-indentation
measurements along the cross-section show a zigzag behavior due to the
porosity. Compression results indicate that the axial direction is the
strongest (UTS ~ 67 MPa) and toughest (11 MJ/m3); this is the
orientation in which they undergo the largest external compression
forces from predator teeth. Toughening mechanisms are identified
through observation of the damage progression and interpreted in
mechanistic terms. They are: flattening of pores, microcrack opening,
and microcrack growth and coalescence. Collagen plays an essential
role in toughening and plasticity by providing bridges that impede the
opening of the cracks and prevent their growth.

===

Early Cretaceous angiosperm from Virginia


Nathan A. Jud and Leo J. Hickey (2013)
Potomacapnos apeleutheron gen. et sp. nov., a new Early Cretaceous
angiosperm from the Potomac Group and its implications for the
evolution of eudicot leaf architecture.
American Journal of Botany (advance online publication)
doi: 10.3732/ajb.1300250
http://www.amjbot.org/content/early/2013/11/27/ajb.1300250.abstract


• Premise of the study: Eudicots diverged early in the evolution of
flowering plants and now comprise more than 70% of angiosperm species.
In spite of the importance of eudicots, our understanding of the early
evolution of this clade is limited by a poor fossil record and
uncertainty about the order of early phylogenetic branching. The study
of Lower Cretaceous fossils can reveal much about the evolution,
morphology, and ecology of the eudicots.

• Methods: Fossils described here were collected from Aptian sediments
of the Potomac Group exposed at the Dutch Gap locality in Virginia,
USA. Specimens were prepared by degaging, then described and compared
with leaves of relevant extant and fossil plants. We conducted a
phylogenetic analysis of morphological characters using parsimony
while constraining the tree search with the topology found through
molecular phylogenetic analyses.

• Key results: The new species is closely related to ranunculalean
eudicots and has leaf architecture remarkably similar to some living
Fumarioideae (Papaveraceae).

• Conclusions: These are the oldest eudicot megafossils from North
America, and they show complex leaf architecture reflecting
developmental pathways unique to extant eudicots. The morphology and
small size of the fossils suggest that they were herbaceous plants, as
is seen in other putative early eudicots. The absence of co-occurring
tricolpate pollen at Dutch Gap either (1) reflects low preservation
probability for pollen of entomophilous herbs or (2) indicates that
some leaf features of extant eudicots appeared before the origin of
tricolpate pollen.

Related news stories:

http://blogs.smithsonianmag.com/science/2013/11/this-could-be-the-oldest-flowering-plant-ever-found-in-north-america/#.Upjs-dhVTrg.twitter

http://phys.org/news/2013-12-evolution-civil-war-history-entwine.html

==

End-Permian mass extinction

Yue Wang , Peter M. Sadler , Shu-zhong Shen , Douglas H. Erwin ,
Yi-chun Zhang , Xiang-dong Wang , Wei Wang , James L. Crowley , and
Charles M. Henderson (2013)
Quantifying the process and abruptness of the end-Permian mass extinction.
Paleobiology 40(1): 113-129
doi: http://dx.doi.org/10.1666/13022
http://www.bioone.org/doi/abs/10.1666/13022

Studies of the end-Permian mass extinction have suggested a variety of
patterns from a single catastrophic event to multiple phases. But most
of these analyses have been based on fossil distributions from single
localities. Although single sections may simplify the interpretation
of species diversity, they are susceptible to bias from stratigraphic
incompleteness and facies control of preservation. Here we use a data
set of 1450 species from 18 fossiliferous sections in different
paleoenvironmental settings across South China and the northern
peri-Gondwanan region, and integrate it with high-precision
geochronologic data to evaluate the rapidity of the largest
Phanerozoic mass extinction. To reduce the Signor-Lipps effect, we
applied constrained optimization (CONOP) to search for an optimal
sequence of first and last occurrence datums for all species and
generate a composite biodiversity pattern based on multiple sections.
This analysis indicates that an abrupt extinction of 62% of species
took place within 200 Kyr. The onset of the sudden extinction is
around 252.3 Ma, just below Bed 25 at the Meishan section. Taxon
turnover and diversification rates suggest a deterioration of the
living conditions nearly 1.2 Myr before the sudden extinction. The
magnitude of the extinction was such that there was no immediate
biotic recovery. Prior suggestions of highly variable, multi-phased
extinction patterns reflect the impact of the Signor-Lipps effect and
facies-dependent occurrences, and are not supported following
appropriate statistical treatment of this larger data set.