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Permian-Triassic transition in southern Europe + genome size in sarcopterygians + fossil melanosomes

Ben Creisler

Some recent non-dino papers:

Eudald Mujal, Nicola Gretter, Ausonio Ronchi, José López-Gómez,
Jocelyn Falconnet, José B. Diez, Raúl De la Horra, Arnau Bolet, Oriol
Oms, Alfredo Arche, José F. Barrenechea, J. -Sébastien Steyer & Josep
Fortuny (2015)
Constraining the Permian/Triassic transition in continental
environments: Stratigraphic and paleontological record from the
Catalan Pyrenees (NE Iberian Peninsula).
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)


The Pyrenean Permian-Triassic boundary based on stratigraphical and
paleontological data
First synapsid caseid fossil from the Middle Permian of the Iberian Peninsula
A diverse tetrapod ichnoassamblege from the late Early-early Middle Triassic


The continental Permian-Triassic transition in southern Europe
presents little paleontological evidence of the Permian mass
extinction and the subsequent faunal recovery during the early stages
of the Triassic. New stratigraphic, sedimentological and
paleontological analyses from Middle-Upper Permian to Lower-Middle
Triassic deposits of the Catalan Pyrenees (NE Iberian Peninsula) allow
to better constrain the Permian-Triassic succession in the Western
Tethys basins, and provide new (bio-) chronologic data. For the first
time, a large vertebra attributed to a caseid synapsid from the
?Middle Permian is reported from the Iberian Peninsula - one of the
few reported from western Europe. Osteological and ichnological
records from the Triassic Buntsandstein facies reveal a great tetrapod
ichnodiversity, dominated by small to medium archosauromorphs and
lepidosauromorphs (Rhynchosauroides cf. schochardti, R. isp. 1 and 2,
Prorotodactylus-Rotodactylus, an undetermined Morphotype A and to a
lesser degree large archosaurians (chirotheriids), overall suggesting
a late Early Triassic-early Middle Triassic age. This is in agreement
with recent palynological analyses in the Buntsandstein basal beds
that identify different lycopod spores and other bisaccate and
taeniate pollen types of late Olenekian age (Early Triassic). The
Permian caseid vertebra was found in a playa-lake setting with a low
influence of fluvial water channels and related to the distal parts of
alluvial fans. In contrast, the Triassic Buntsandstein facies
correspond to complex alluvial fan systems, dominated by high-energy
channels and crevasse splay deposits, hence a faunal and environmental
turnover is observed. The Pyrenean biostratigraphical data show
similarities with those of the nearby Western Tethys basins, and can
be tentatively correlated with North African and European basins. The
Triassic Pyrenean fossil remains might rank among the continental
oldest records of the Western Tethys, providing new keys to decipher
the Triassic faunal biogeography and recovery.


Chris Organ, Mikayla Struble, Aurore Canoville, Vivian de Buffrénil &
Michel Laurin (2015)
Macroevolution of genome size in sarcopterygians during the water–land
Comptes Rendus Palevol (advance online publication)

Genome size spans over a 300-fold range among vertebrates (132 pg for
Protopterus aethiopicus, the marbled lungfish, and 0.35 pg for
Tetraodon nigroviridis, the green spotted pufferfish). While
phylogenetic analysis of genome size has helped clarify how this
variation evolved in multiple tetrapod groups, the ancestral tetrapod
condition still remains poorly characterized, and this obscures our
understanding of character state polarity and macroevolutionary trends
in genome size. To address this problem, we used phylogenetic
comparative methods to analyze paleohistological data from eight taxa
of the Middle and Late Paleozoic to the Early Mesozoic:
Eusthenopteron, Ichthyostega, Acheloma, Eryops, Trimerorhachis,
Wetlugasaurus, an unidentified dissorophoid, and Chroniosaurus. Five
other extinct taxa were included from previous studies to better frame
our results, including Marmorerpeton, Cardiocephalus, Diplocaulus, an
unidentified basal sauropsid, and Mycterosaurus. We augmented a
previously reported histological and genome size data set (including
data from 14 lissamphibians, three testudines, Sphenodon, five
squamates, two crocodilians, 11 birds, and 22 mammals) with genome
size and histological data from extant Latimeria and three extant
actinopterygians. Our results suggest that all eight of the newly
analyzed extinct taxa had genome sizes ranging between 3.2 and 3.9 pg.
These results imply that basal tetrapods had genome sizes (and
underlying genomic architectures) similar to extant mammals and
lepidosaurs. We find no major shifts in genome size during the
tetrapod water-to-land transition. Our analysis suggests that
Eusthenopteron and Ichthyostega had genome sizes well within the range
of extant actinopterygians and Latimeria, despite several whole-genome
duplications in actinopterygians.

Jakob Vinther (2015)
Fossil melanosomes or bacteria? A wealth of findings favours melanosomes.
BioEssays (advance online publication)
DOI: 10.1002/bies.201500168

The discovery of fossil melanosomes has resulted in a wealth of
research over the last 7 years, notably the reconstruction of colour
in dinosaurs and fossil mammals. In spite of these discoveries some
authors persist in arguing that the observed microbodies could
represent preserved bacteria. They contend that bacteria fossilise
easily and everywhere, which means that one can never be certain that
a microbody is a melanosome without an extraordinary burden of
evidence. However, this critique mischaracterises the morphological
and structural evidence for interpreting microbodies as fossil
melanosomes, and hence the basis for using them in reconstructing
prehistoric colours. The claims for bacterial omnipresence in the
fossil record are themselves not supported, thus tipping the scales
strongly towards melanosomes in the bacteria-versus-melanosome