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Non-Dino Papers: Big Mesozoic placentals, Cretaceous climate

From: Ben Creisler

Some recent non-dino papers that may be of interest:

Mesozoic placental mammals bigger than thought

J. Romiguier, V. Ranwez, E.J.P. Douzery and N. Galtier (2012)
Genomic evidence for large, long-lived ancestors to placental mammals.
Molecular Biology and Evolution (advance online pubication)
doi: 10.1093/molbev/mss211

It is widely assumed that our mammalian ancestors, which lived in the
Cretaceous era, were tiny animals that survived massive asteroid
impacts in shelters, and evolved into modern forms after dinosaurs
went extinct, 65 Mya. The small size of most Mesozoic mammalian
fossils essentially supports this view. Paleontology, however, is not
conclusive regarding the ancestry of extant mammals, because
Cretaceous and Paleocene fossils are not easily linked to modern
lineages. Here we use full-genome data to estimate the longevity and
body mass of early placental mammals. Analysing 36 fully-sequenced
mammalian genomes, we reconstruct two aspects of the ancestral genome
dynamics, namely GC-content evolution and non-synonymous over
synonymous rate ratio. Linking these molecular evolutionary processes
to life history traits in modern species, we estimate that early
placental mammals had a life-span above 25 years, and a body mass
above one kilogram. This is similar to current primates,
cetartiodactyls or carnivores, but markedly different from mice or
shrews, challenging the dominant view about mammalian origin and
evolution. Our results imply that long-lived mammals existed in the
Cretaceous era, and were the most successful in evolution, opening new
perspectives about the conditions for survival to the
Cretaceous-Tertiary crisis.

News story:



William W. Haya & Sascha Floegel (2012)
New thoughts about the Cretaceous climate and oceans.
Earth-Science Reviews (advance online publication)

Several new discoveries suggest that the climate of the Cretaceous may
have been more different from that of today than has been previously
supposed. Detailed maps of climate sensitive fossils and sediments
compiled by Nicolai Chumakov and his colleagues in Russia indicate
widespread aridity in the equatorial region during the Early
Cretaceous. The very warm ocean temperatures postulated for the
Mid-Cretaceous by some authors would likely have resulted in
unacceptable heat stress for land plants at those latitudes, however,
and may be flawed.

Seasonal reversals of the atmospheric pressure systems in the Polar
Regions are an oversimplification. However, seasonal pressure
difference between 30° and 60° latitude become quite pronounced, being
more than 25 hPa in winter and less than 10 hPa in summer. This
results in inconstant winds, affecting the development of the
gyre-limiting frontal systems that control modern ocean circulation.
The idea of Hasegawa et al. (2011) who suggest a drastic reduction in
the size of the Hadley cells during the warm Cretaceous greenhouse is
supported by several numerical climate simulations. Rapid contraction
of the Hadley cell such that its sinking dry air occurs at 15° N
latitude rather than 30° N is proposed to occur at a threshold of
1,000 ppmv CO2 in the atmosphere. This change will probably be reached
in the next century.

Avian limbs
This paper was posted earlier but the pdf is now open access:

Ryohei Seki, Namiko Kamiyama, Ayumi Tadokoro, Naoki Nomura, Takanobu
Tsuihiji Makoto Manabe and Koji Tamura (2012)
Evolutionary and Developmental Aspects of Avian-Specific Traits in
Limb Skeletal Pattern.
Zoological Science 29(10):631-644. 2012
doi: http://dx.doi.org/10.2108/zsj.29.631

Earliest turtles from Poland

This paper in JVP was cited earlier:

Tomasz Sulej, Grzegorz Niedźwiedzki & Robert Bronowicz (2012)
A new Late Triassic vertebrate fauna from Poland with turtles,
aetosaurs, and coelophysoid dinosaurs.
Journal of Vertebrate Paleontology 23 (5): 1033-1041

A video can now be seen at:



Plant genus became important in Triassic; pdf is open access:

Yi Zhang, ShaoLin Zheng and Serge V. Naugolnykh (2012)
A new species of Lepidopteris discovered from the Upper Permian of
China with its stratigraphic and biologic implications.
SOI: 10.1007/s11434-012-5282-0

A new species Lepidopteris baodensis sp. nov. belonging to the family
Peltaspermaceae and represented by two ultimate pinnae in the
collection under study, was recently discovered at the Baijiagou of
Baode, Shanxi, China, from the Upper Permian Sunjiagou Formation. The
lower surface of the ultimate rachis, the midrib and secondary veins
is covered with triangular, trapezoid, rounded, or ligulate
subepidermal swellings, which show different natures from intercalary
pinnules. Lepidopteris is one of typical elements of the Late Permian
Euramerican flora. Since Schimper erected the genus Lepidopteris in
1869, the entire epidermal structure of subepidermal swellings had
been unclear. The new species L. baodensis clearly showing the
distinguished epidermal structure of subepidermal swellings, not only
enlarges and supplements our knowledge in biology and taxonomy of
Lepidopteris as well as the Upper Permian stratigraphy of China, but
also provides an opportunity to understand the relationship between
Euramerican floras and Cathaysian floras in paleoclimatic,
paleoenvironmental and paleogeographic context.

Discussion of Permian-Triassic extinction and importance of
Lepidopteris in recovery: