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Iguanas breathe more like birds + Morrison Jurassic climate + other papers

Ben Creisler

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

Robert L. Cieri, Brent A. Craven, Emma R. Schachner, and C. G. Farmer (2014)
New insight into the evolution of the vertebrate respiratory system
and the discovery of unidirectional airflow in iguana lungs.
Proceedings of the National Academy of Sciences (advance online publication)

The avian respiratory system appears strikingly distinct from all
other animals. Purported key innovations underpinning avian patterns
of airflow are an enclosed intrapulmonary bronchus, intercameral
perforations, heterogeneous parenchyma; these traits allegedly
coevolved with separation of the cardiac ventricle into right and left
sides and are presumed to have been favored by selection because they
facilitate high activity metabolisms. In contradistinction to these
prevailing theories, here we show that unidirectional flow is present
in the lungs of the green iguana, an ectothermic animal with low
aerobic capacity, no intrapulmonary bronchus, and no intercameral
perforations. This discovery indicates a transformation in our
understanding of the evolution of the vertebrate respiratory system is

The generally accepted framework for the evolution of a key feature of
the avian respiratory system, unidirectional airflow, is that it is an
adaptation for efficiency of gas exchange and expanded aerobic
capacities, and therefore it has historically been viewed as important
to the ability of birds to fly and to maintain an endothermic
metabolism. This pattern of flow has been presumed to arise from
specific features of the respiratory system, such as an enclosed
intrapulmonary bronchus and parabronchi. Here we show unidirectional
airflow in the green iguana, a lizard with a strikingly different
natural history from that of birds and lacking these anatomical
features. This discovery indicates a paradigm shift is needed. The
selective drivers of the trait, its date of origin, and the
fundamental aerodynamic mechanisms by which unidirectional flow arises
must be reassessed to be congruent with the natural history of this
lineage. Unidirectional flow may serve functions other than expanded
aerobic capacity; it may have been present in the ancestral diapsid;
and it can occur in structurally simple lungs.


News stories:




SMU blog about Morrison Formation climate:


The paper posted online last March:

Timothy S. Myers, Neil J. Tabor and Nicholas A. Rosenau (2014)
Multiproxy approach reveals evidence of highly variable
paleoprecipitation in the Upper Jurassic Morrison Formation (western
United States).
GSA Bulletin (advance online publication)
doi: 10.1130/B30941.1

Elemental analyses of paleosol B horizons in the Upper Jurassic
Morrison Formation of the western United States provide estimates of
mean annual precipitation (MAP) and allow determination of humidity
regimes. Samples were collected from the lower Morrison Formation in
New Mexico and the upper Morrison Formation in Wyoming and Montana.
The chemical index of alteration minus potassium (CIA – K) and the
calcium and magnesium weathering index (CALMAG) were used to estimate
paleorainfall. CIA – K values calculated for paleosols without
shrink-swell (vertic) features correspond to MAP estimates between 800
and 1100 mm yr–1, with an average of 1000 mm yr–1. CALMAG values,
calculated for vertic paleosols, correspond to MAP estimates between
50 and 1200 mm yr–1, with an average of 700 mm yr–1. MAP estimates
from the older New Mexico strata indicate that early Morrison
environments were relatively arid. MAP estimates from the younger
Wyoming and Montana deposits reflect wetter conditions in the
northernmost part of the Morrison Formation, but the transition from
arid interior environments was abrupt. Humidity provinces inferred
from geochemical proxy-based estimates of evapotranspiration and
energy influx from precipitation range from semiarid to superhumid,
suggesting wetter conditions than the MAP estimates, but supporting
the relative differences in moisture among the three study areas.
Paleoprecipitation patterns within the Morrison depositional basin do
not match the modern latitudinal distribution of rainfall that arises
from zonal atmospheric circulation. Comparison with the Upper Jurassic
Lourinhã Formation in Portugal and the Vega Formation in Spain reveals
that MAP in Late Jurassic Portuguese environments was similar to that
in the wet northern part of the Morrison Formation, although more arid
conditions prevailed in some areas of Portugal. Inferred humidity
regimes for the Lourinhã Formation, which range from semiarid to
superhumid, also indicate small-scale geographic variability in
climate, although less pronounced than that observed in the Morrison
Formation. Paleoenvironments in northern Spain were similar to the
drier Morrison environments in the continental interior. Given the
abrupt climatic transitions inferred here for the Morrison Formation,
paleoprecipitation estimates derived from a geographically restricted
sample may reflect only local conditions and should not necessarily be
extrapolated to larger areas.

Giant Miocene caiman Mourasuchus

David Eric Tineo, Paula Bona, Leandro Martín Pérez, Gustavo Dardo
Vergani, Gloria González, Daniel Gustavo Poiré, Zulma Gasparini &
Pablo Legarreta (2014)
Palaeoenvironmental implications of the giant crocodylian Mourasuchus
(Alligatoridae, Caimaninae) in the Yecua Formation (late Miocene) of
Alcheringa (advance online publication)

Outcrops of the Yecua Formation (late Miocene) are exposed for
approximately 230 m along the La Angostura section of the Piraí River
(50 km southwest of Santa Cruz de la Sierra). These reveal massive
(argillic palaeosols) and laminated (quiet-water lacustrine and marsh
settings) mudstones interbedded with thin sandstones containing
microfossils, molluscs and vertebrate remains. Significantly, the
succession hosts a giant crocodylian, Mourasuchus (Alligatoridae,
Caimaninae), which is represented by both skull and postcranial
fragments found in association with freshwater turtles and fishes.
Mourasuchus was distributed widely from the middle Miocene of Colombia
to upper Miocene of Venezuela, Brazil and Argentina, suggesting
connections between major fluvial systems and an active mechanism for
dispersal of South American freshwater vertebrates during the Miocene.


Mongolian Cretaceous trees

Gongle Shi, Andrew B. Leslie, Patrick S. Herendeen, Niiden Ichinnorov,
Masamichi Takahashi, Patrick Knopf, and  Peter R. Crane (2014)
Whole-Plant Reconstruction and Phylogenetic Relationships of Elatides
zhoui sp. nov. (Cupressaceae) from the Early Cretaceous of Mongolia.
International Journal of Plant Sciences 175(8): 911-930
doi : http://www.jstor.org/stable/10.1086/677651

Premise of research. Exceptionally well-preserved lignified fossils
from the Early Cretaceous of Mongolia include abundant conifer leafy
shoots with attached pollen cones and seed cones. A whole-plant
reconstruction based on these fossils enables a critical evaluation of
the relationship of this extinct plant with extant conifers.

Methodology. Bulk lignite samples collected from the Tugrug lignite
mine were disaggregated in water, cleaned with hydrochloric and
hydrofluoric acids, washed, and dried in air. Fossils were then
examined using light and scanning electron microscopy. Pivotal
results. Elatides zhoui sp. nov. has helically arranged leaves with
two narrow lateral stomatal bands, predominantly on the adaxial leaf
surface. Pollen cones are usually borne laterally on shoots in tight
spirals; each microsporophyll bears three pollen sacs that produce
nonsaccate pollen with a small circular aperture. Seed cones have
numerous bract-scale complexes, each with a small membranous
ovuliferous scale and four to six seeds. Elatides zhoui is the most
completely understood of all described Elatides species, and major
features of seed cone and pollen cone morphology indicate that it is
most closely related to extant Cunninghamia, which today has two
species restricted to East Asia. Morphological cladistic analyses
using parsimony resolved an expanded Cunninghamioideae clade, which
includes extant Cunninghamia, E. zhoui, and other Cunninghamia-like
fossils, as the sister group to all other extant Cupressaceae sensu

Conclusions. Elatides zhoui provides further evidence for the
diversity of Cupressaceae sensu lato during the Cretaceous and
supports the hypothesis that cunninghamioid conifers in particular
were diverse and widespread during the early evolution of the