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Jurassic and Cretaceous squamates of North America; moa diet; + other non-dino papers



From: Ben Creisler
bcreisler@gmail.com


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


Randall L. Nydam (2013)
Squamates from the Jurassic and Cretaceous of North America.
Palaeobiodiversity and Palaeoenvironments (advance online publication)
DOI: 10.1007/s12549-013-0129-5
http://link.springer.com/article/10.1007/s12549-013-0129-5

Squamates from the Mesozoic of North America have been collected since
the end of the nineteenth century. To date, the fossils are known to
occur in the Late Jurassic, Aptian-Albian, Cenomanian, Turonian,
Santonian, Campanian, and Maastrichtian. Most of the records are from
the Western Interior in the arid regions associated with the Rocky
Mountains. Geographically, these records extend from central Alberta,
Canada, south to northern Mexico. The earliest squamates are primitive
forms of scincoideans and anguimorphans from the Late Jurassic–Early
Cretaceous. At the beginning of the Late Cretaceous, the squamate
fauna in North America changes dramatically to include a much greater
diversity of taxa with a mix of lineages now extinct (e.g.
Polyglyphanodontini, Chamopsiidae, Contogeniidae) and lineages still
alive today (e.g. Anguidae, Xantusiidae, Platynota, Serpentes). The
greatest diversity appears to be during the late Campanian, but
diversity appears correlated with number of localities sampled and the
late Campanian is the best sampled horizon in the Mesozoic of North
America. The apparent sudden change in the North American squamate
fauna is coincident with similar changes to other vertebrates
(mammals, dinosaurs) and the opening of a land bridge with Asia. The
lack of taxonomic and systematic study of the squamates from the Early
Cretaceous of Asia makes comparison difficult, but it is likely that
introduction of Asian taxa into North America was responsible, at
least in part, for the relatively rapid change in the North American
fauna. The hypotheses of an additional invasion from Asia during the
Turonian is not supported, but the hypothesis of a second opening with
Asia during the Santonian is weakly supported by the appearance of an
iguanian in North America. Additional iguanians from the Campanian may
have evolved in situ or may have entered North America from Asia as
late as the mid-Campanian. Many of the most conspicuous lizards of the
Late Cretaceous (Polyglyphanodontini, Chamopsiidae,
paramacellodid-cordylid grade scincoideans) went extinct at the
terminal Cretaceous extinction event, while most of the anguimorphans
and snakes appear little affected. Amphisbaenians do not appear in
North America until after the early Paleocene.


===

Pavel P. Skutschas (2013)
Mesozoic salamanders and albanerpetontids of Middle Asia, Kazakhstan,
and Siberia.
Palaeobiodiversity and Palaeoenvironments (advance online publication)
DOI: 10.1007/s12549-013-0126-8
http://link.springer.com/article/10.1007/s12549-013-0126-8



Mesozoic terrestrial deposits containing diverse vertebrate
assemblages are widely distributed in Siberia (central and eastern
part of Russia), Middle Asia (Kyrgyzstan, Tajikistan, Turkmenistan and
Uzbekistan), and Kazakhstan. Twelve formations of Middle Jurassic
(Bathonian) to Late Cretaceous (Campanian) age in the region contain
salamanders (six in Middle Asia, two in Siberia and four in
Kazakhstan). In contrast to the situation in Euramerica,
albanerpetontids are extremely rare in the Mesozoic of Asia, where
their fossil record is limited to the Khodzhakul (Cenomanian) and
Bissekty (Turonian) formations, both in Uzbekistan. Salamanders in
Siberia are known from the Bathonian Itat Formation in the Krasnoyarsk
Region (the stem salamander Urupia monstrosa and two undescribed
taxa—a new stem salamander and a possible crown-group salamander) and
from the Aptian–Albian Ilek Formation in Kemerovo Province and the
Krasnoyarsk Region (the crown-group salamander Kiyatriton
leshchinskiyi and Caudata indet.). In the Jurassic of Middle Asia, the
stem salamanders Kokartus honorarius and Karauridae indet. are known
from the Bathonian–Callovian Balabansai Formation in Kyrgyzstan.
Younger records in Middle Asia are restricted to only two Late
Cretaceous genera of crown-group salamanders: the possible
cryptobranchoid Nesovtriton in the Bissekty Formation (Turonian) and
the cryptobranchid Eoscapherpeton in the Khodzhakul, Dzharakuduk,
Bissekty, and Aitym formations (collectively Cenomanian–Campanian) in
Uzbekistan and the Yalovach Formation (Santonian) in Tajikistan. In
Kazakhstan, salamanders are known from the Kimmeridgian Karabastau
Formation (the stem salamander Karaurus sharovi), the Turonian
Zhirkindek Formation (Caudata indet.), the Santonian–Campanian Bostobe
Formation (the cryptobranchid Eoscapherpeton, the possible proteid
“Bishara backa” and Caudata indet.) and the Campanian Darbasa
Formation (the cryptobranchid Eoscapherpeton). Cenomanian–Campanian
vertebrate assemblages in Middle Asia and Kazakhstan are characterised
by dominance of the cryptobranchid Eoscapherpeton.


===


Jamie R. Wood, Janet M. Wilmshurst, Sarah J. Richardson, Nicolas J.
Rawlence, Steven J. Wagstaff, Trevor H. Worthy, and Alan Cooper (2013)
Resolving lost herbivore community structure using coprolites of four
sympatric moa species (Aves: Dinornithiformes).
Proceedings of the National Academy of Sciences (advance online publication)
doi: 10.1073/pnas.1307700110
http://www.pnas.org/content/early/2013/09/25/1307700110.abstract?sid=19cab806-2830-46af-bb96-da50d737a3be

Knowledge of extinct herbivore community structuring is essential for
assessing the wider ecological impacts of Quaternary extinctions and
determining appropriate taxon substitutes for rewilding. Here, we
demonstrate the potential for coprolite studies to progress beyond
single-species diet reconstructions to resolving community-level
detail. The moa (Aves: Dinornithiformes) of New Zealand are an
intensively studied group of nine extinct herbivore species, yet many
details of their diets and community structuring remain unresolved. We
provide unique insights into these aspects of moa biology through
analyses of a multispecies coprolite assemblage from a rock overhang
in a montane river valley in southern New Zealand. Using ancient DNA
(aDNA), we identified 51 coprolites, which included specimens from
four sympatric moa species. Pollen, plant macrofossils, and plant aDNA
from the coprolites chronicle the diets and habitat preferences of
these large avian herbivores during the 400 y before their extinction
(∼1450 AD). We use the coprolite data to develop a paleoecological
niche model in which moa species were partitioned based on both
habitat (forest and valley-floor herbfield) and dietary preferences,
the latter reflecting allometric relationships between body size,
digestive efficiency, and nutritional requirements. Broad ecological
niches occupied by South Island giant moa (Dinornis robustus) and
upland moa (Megalapteryx didinus) may reflect sexual segregation and
seasonal variation in habitat use, respectively. Our results show that
moa lack extant ecological analogs, and their extinction represents an
irreplaceable loss of function from New Zealand’s terrestrial
ecosystems.

====

Joachim Enax, Helge-Otto Fabritius, Alexander Rack, Oleg Prymak, Dierk
Raabe & Matthias Epple (2013)
Characterization of crocodile teeth: Correlation of composition,
microstructure, and hardness.
Journal of Structural Biology (advance online publication)
doi:  http://dx.doi.org/10.1016/j.jsb.2013.09.018
http://www.sciencedirect.com/science/article/pii/S1047847713002591


Structure and composition of teeth of the saltwater crocodile
Crocodylus porosus were characterized by several high-resolution
analytical techniques. X-ray diffraction in combination with elemental
analysis and infrared spectroscopy showed that the mineral phase of
the teeth is a carbonated calcium-deficient nanocrystalline
hydroxyapatite in all three tooth-constituting tissues: Dentin,
enamel, and cementum. The fluoride content in the three tissues is
very low (<0.1 wt%) and comparable to that in human teeth. The mineral
content of dentin, enamel, and cementum as determined by
thermogravimetry is 71.3, 80.5, and 66.8 wt%, respectively.
Synchrotron X-ray microtomography showed the internal structure and
allowed to visualize the degree of mineralization in dentin, enamel,
and cementum. Virtual sections through the tooth and scanning electron
micrographs showed that the enamel layer is comparably thin (100-200
μm). The crystallites in the enamel are oriented perpendicularly to
the tooth surface. At the dentin-enamel-junction, the packing density
of crystallites decreases, and the crystallites do not display an
ordered structure as in the enamel. The microhardness was 0.60±0.05
GPa for dentin, 3.15±0.15 GPa for enamel, 0.26±0.08 GPa for cementum
close to the crown, and 0.31±0.04 GPa for cementum close to the root
margin. This can be explained with the different degree of
mineralization of the different tissue types and is comparable with
human teeth.