Gerrothorax (Triassic temnospondyl) growth (free pdf) and more non-dino papers

[Ben Creisler <bcreisler@gmail.com>]

From: Ben Creisler
bcreisler@gmail.com

A number of new non-dino papers (plus a video) that may be interest:

S. Sanchez & R. R. Schoch (2013)
Bone Histology Reveals a High Environmental and Metabolic Plasticity
as a Successful Evolutionary Strategy in a Long-Lived Homeostatic
Triassic Temnospondyl.
Evolutionary Biology (advance online publication)
DOI: 10.1007/s11692-013-9238-3
http://link.springer.com/article/10.1007/s11692-013-9238-3
NOTE: pdf is open access (for now)

Evolutionary stasis (long-term stability of morphology in an evolving
lineage) is a pattern for which explanations are usually elusive. The
Triassic tetrapod Gerrothorax pulcherrimus, a gill-bearing
temnospondyl, survived for 35 million years in the Germanic Basin of
Central Europe persisting throughout the dinosaur-dominated Late
Triassic period. This evolutionary stasis coincides with the
occurrence of this species in a wide range of habitats and
environmental conditions. By the combination of palaeoecological and
palaeohistological analyses, we found great ecological flexibility in
G. pulcherrimus and present substantial evidence of developmental and
metabolic plasticity despite the morphological stasis. We conclude
that G. pulcherrimus could show the capacity to settle in water bodies
too harsh or unpredictable for most other tetrapods. This would have
been made possible by a unique life history strategy that involved a
wide reaction norm, permitting adjustment to fluctuating conditions
such as salinity and level of nutrients. Growth rate, duration of
juvenile period, age at maturity, and life span were all subject to
broad variation within specimens of G. pulcherrimus in one single lake
and in between different lakes. In addition to providing a better
understanding of fossil ecosystems, this study shows the potential of
such a methodology to encourage palaeobiologists and evolutionary
biologists to consider the mechanisms of variation in extant and
fossil organisms by using a similar time-scope reference.

==

Silvia N Césari  and Carina E Colombi (2013)
A new Late Triasssic phytogeographical scenario in westernmost Gondwana.
Nature Communications 4, Article number: 1889
doi:10.1038/ncomms2917
http://www.nature.com/ncomms/journal/v4/n5/full/ncomms2917.html

Floral provincialism within the Southern Hemisphere during the Late
Triassic (230 Ma) is characterized by the Ipswich and Onslow
provinces, recognized originally in eastern Gondwana. However, new
palynological assemblages from the Ischigualasto Formation,
northwestern Argentina (231–225 Ma), change the phytogeographic
interpretation for the Carnian–Norian in the westernmost Gondwana,
which was previously considered part of the southern floral Ipswich
province. Here we show the presence of diagnostic Euramerican species
within assemblages dominated by Gondwanan taxa that allows us to refer
the palynofloras to the Onslow province. Our new data extend the
Onslow floral belt, previously recognized from the western edge of
Tethys to Timor, to the western margin of South America. This has
implications for palaeophytogeography, palaeoclimate reconstructions
and the palaeoecology of a Triassic ecosystem, which has yielded
significant vertebrate remains and is regarded important in the early
evolution of groups such as the Dinosauria.

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Mammals across K/Pg boundary in Montana (video talk)

Greg Wilson's talk Mammals Inherit the Earth  at Royal Tyrrell Museum
is about mammals across the K/Pg boundary and the mass extinction.

http://www.youtube.com/watch?v=8lFHHRqhS8k&list=UUFYePvzFqxxk1xTD3hMmogw&index=1

==

Adatte, Karl Föllmi, Izabella Ploch & Jörg Mutterlose (2013)
Reconstructing Valanginian (Early Cretaceous) mid-latitude vegetation
and climate dynamics based on spore-pollen assemblages.
Review of Palaeobotany and Palynology (advance online publication)
doi: http://dx.doi.org/10.1016/j.revpalbo.2013.05.003
http://www.sciencedirect.com/science/article/pii/S0034666713000912

Changes in terrestrial vegetation patterns during the Valanginian
(Early Cretaceous) and their link to major climatic and environmental
alterations are poorly studied. In this study, the spatial and
temporal changes in plant community structure are reconstructed based
on spore-pollen records from two mid-latitude sites located in the
Mid-Polish Trough (MPT, central Poland), and the Vocontian Basin (VB,
southeast France). Stratigraphic control is provided by δ13Ccarb
chemostratigraphy and calcareous nannofossil biostratigraphy.
Reconstruction of hinterland vegetation is based on palynological
investigations of 83 samples from hemipelagic (VB) and marginal marine
(MPT) sediments rich in terrestrial palynomorphs. A total of 45
palynomorph taxa were identified at generic level (30 spores, 15
pollen). Vegetation around the MPT was dominated by
araucarian/cupressacean conifers while that surrounding the VB was
dominated by drought-resistant cheirolepidiacean conifers. At both
sites the understorey and/or vegetation of open areas was dominated by
pteridophytes. An early Valanginian gradual trend towards humid
conditions at the MPT, well expressed by a distinct increase in the
spore-pollen ratio, culminates in a short-lived spore-maximum
stratigraphically located at the lower/upper Valanginian boundary. It
is characterized by low conifer abundances and high abundances of the
fern spore taxa Cyathidites, Leiotriletes and Gleicheniidites
accompanied by enhanced abundances of the pteridosperm pollen
Vitreisporites pallidus, whose parent plants are assumed to be
indicative of swamp habitats. The spore-maximum is coeval to a similar
peak observed in the VB, characterized by essentially the same taxa.
Here, the spore-maximum is preceded by a protracted phase of arid
conditions, characterized by low spore abundances and exceptionally
high numbers of the cheirolepidiacean conifer pollen Classopollis.
Changes in moisture, identified as the key climatic factor determining
trends and turnovers in vegetation, were probably controlled by a
monsoonal circulation. The supra-regional humid phase expressed by the
coeval spore maxima was probably induced by an intensified monsoonal
climate. The temporal influence of a northern hemisphere arid belt at
the VB, under the influence of the subtropical high-pressure belt, may
have caused the temporal drying not affecting the MPT site, located
further north.

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Miocene crocodylian diversity in South America

T. M. Scheyer, O. A. Aguilera, M. Delfino, D. C. Fortier, A. A.
Carlini, R. Sánchez, J. D. Carrillo-Briceño, L. Quiroz, and M. R.
Sánchez-Villagra.
Crocodylian diversity peak and extinction in the late Cenozoic of the
northern Neotropics.
Nature Communications 4, Article number: 1907
doi:10.1038/ncomms2940
http://www.nature.com/ncomms/journal/v4/n5/full/ncomms2940.html

Northern South America and South East Asia are today’s hotspots of
crocodylian diversity with up to six (mainly alligatorid) and four
(mainly crocodylid) living species respectively, of which usually no
more than two or three occur sympatrically. In contrast, during the
late Miocene, 14 species existed in South America. Here we show a
diversity peak in sympatric occurrence of at least seven species,
based on detailed stratigraphic sequence sampling and correlation,
involving four geological formations from the middle Miocene to the
Pliocene, and on the discovery of two new species and a new
occurrence. This degree of crocodylian sympatry is unique in the world
and shows that at least several members of Alligatoroidea and
Gavialoidea coexisted. By the Pliocene, all these species became
extinct, and their extinction was probably related to hydrographic
changes linked to the Andean uplift. The extant fauna is first
recorded with the oldest Crocodylus species from South America.