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Avian respiration + post-Cretaceous "age of fishes" + Deccan eruptions + more



Ben Creisler
bcreisler@gmail.com


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


John N. Maina (2015)
The design of the avian respiratory system: development, morphology
and function.
Journal of Ornithology (advance online publication)
DOI: 10.1007/s10336-015-1263-9
http://link.springer.com/article/10.1007/s10336-015-1263-9



The avian respiratory apparatus is separated into a gas exchanger (the
lung) and ventilators (the air sacs). Synchronized bellows-like
movements of the cranial and caudal air sacs ventilate the lung
continuously and unidirectionally in a caudocranial direction. With
the lungs practically rigid, after their insertion into the ribs and
the vertebrae and on attaching to the membranous horizontal septum,
surface tension is not a constraining factor to the intensity that the
gas exchange tissue can subdivide. Delicate, transparent, capacious
and avascular, the air sacs are not directly involved in gas exchange.
The airway system comprises of a three-tiered system of passageways,
namely a primary bronchus, the secondary bronchi and the tertiary
bronchi (parabronchi). The crosscurrent system is formed by the
perpendicular arrangement between the mass (convective) air flow in
the parabronchial lumen and the centripetal (inward) flow of the
venous blood in the exchange tissue; the countercurrent system
consists of the centrifugal (outward) flow of air from the
parabronchial lumen into the air capillaries and the centripetal
(inward) flow of blood in the blood capillaries, and; the
multicapillary serial arterialization system is formed by the blood
capillaries and the air capillaries where venous blood is oxygenated
in succession at the infinite number of points where the respiratory
units contact exchange tissue. Together with the aforementioned
systems, features like large capillary blood volume, extensive
respiratory surface area and thin blood-gas barrier accord high
pulmonary diffusing capacity of O2 that supports the high metabolic
capacities and energetic lifestyles of birds.

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João Francisco Botelho, Daniel Smith-Paredes & Alexander O. Vargas (2015)
Altriciality and the Evolution of Toe Orientation in Birds.
Evolutionary Biology (advance online publication)
DOI: 10.1007/s11692-015-9334-7
http://link.springer.com/article/10.1007/s11692-015-9334-7



Specialized morphologies of bird feet have evolved several times
independently as different groups have become zygodactyl,
semi-zygodactyl, heterodactyl, pamprodactyl or syndactyl. Birds have
also convergently evolved similar modes of development, in a spectrum
that goes from precocial to altricial. Using the new context provided
by recent molecular phylogenies, we compared the evolution of foot
morphology and modes of development among extant avian families.
Variations in the arrangement of toes with respect to the anisodactyl
ancestral condition have occurred only in altricial groups. Those
groups represent four independent events of super-altriciality and
many independent transformations of toe arrangements (at least four
zygodactyl, three semi-zygodactyl, one heterodactyl, one pamprodactyl
group, and several syndactyl). We propose that delayed skeletal
maturation due to altriciality facilitates the epigenetic influence of
embryonic muscular activity over developing toes, allowing for
repeated evolution of innovations in their morphology.

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Gerald Mayr (2015)
A reassessment of Eocene parrotlike fossils indicates a previously
undetected radiation of zygodactyl stem group representatives of
passerines (Passeriformes).
Zoologica Scripta (advance online publication)
DOI: 10.1111/zsc.12128
http://onlinelibrary.wiley.com/doi/10.1111/zsc.12128/abstract



In the past years, various Eocene fossil birds were described as stem
group representatives of the zygodactyl Psittaciformes (parrots).
These birds show quite disparate morphologies, which cast some doubt
on the correct assignment of all of them to the psittaciform stem
group. A reassessment of their affinities is further needed, because
it was recently proposed that among extant birds, Psittaciformes and
Passeriformes (passerines) form a clade and that passerines possibly
derived from a zygodactyl ancestor. Here, phylogenetic analyses are
performed, which for the first time also include representatives of
the Zygodactylidae, the extinct zygodactyl sister taxon of the
Passeriformes. The early Eocene Psittacopes was originally described
as a stem group representative of Psittaciformes. However, none of the
present analyses supported psittaciform affinities for Psittacopes and
instead recovered this taxon in a clade together with zygodactylids
and passerines. Also part of this clade are the early Eocene taxa
Pumiliornis and Morsoravis, and it is detailed that Psittacopes and
the long-beaked and presumably nectarivorous Pumiliornis, with which
it has not yet been compared, are very similar in their postcranial
osteology. The present analysis corroborates the hypothesis of a
zygodactyl stem species of passerines. To account for these results,
Psittacopes is here assigned to a new higher-level taxon and a new
name is also introduced for the clade including Zygodactylidae and
Passeriformes.

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Elizabeth C. Sibert and Richard D. Norris (2015)
New Age of Fishes initiated by the Cretaceous−Paleogene mass extinction.
Proceedings of the National Academy of Sciences (advance online publication)
doi:10.1073/pnas.1504985112
http://www.pnas.org/content/early/2015/06/23/1504985112.abstract?sid=a0adcf04-bddf-4eae-b1b6-276b8d80bb8c

Significance

Ray-finned fishes are the most diverse and ecologically dominant group
of vertebrates on the planet. Previous molecular phylogenies and
paleontological studies have shown that modern ray-finned fishes
(crown teleosts) radiated sometime in the Late Cretaceous or early
Paleogene. Our data suggest that crown teleosts came into their
current dominant ecological role in pelagic ecosystems immediately
following the Cretaceous−Paleogene mass extinction 66 million years
ago by filling newly vacated ecological niches and marking the
beginning of an "age of ray-finned fishes." Our study is, to our
knowledge, the first geographically comprehensive, high-resolution
study of marine vertebrate communities across the extinction.

Abstract

Ray-finned fishes (Actinopterygii) comprise nearly half of all modern
vertebrate diversity, and are an ecologically and numerically dominant
megafauna in most aquatic environments. Crown teleost fishes
diversified relatively recently, during the Late Cretaceous and early
Paleogene, although the exact timing and cause of their radiation and
rise to ecological dominance is poorly constrained. Here we use
microfossil teeth and shark dermal scales (ichthyoliths) preserved in
deep-sea sediments to study the changes in the pelagic fish community
in the latest Cretaceous and early Paleogene. We find that the
Cretaceous−Paleogene (K/Pg) extinction event marked a profound change
in the structure of ichthyolith communities around the globe: Whereas
shark denticles outnumber ray-finned fish teeth in Cretaceous deep-sea
sediments around the world, there is a dramatic increase in the
proportion of ray-finned fish teeth to shark denticles in the
Paleocene. There is also an increase in size and numerical abundance
of ray-finned fish teeth at the boundary. These changes are sustained
through at least the first 24 million years of the Cenozoic. This new
fish community structure began at the K/Pg mass extinction, suggesting
the extinction event played an important role in initiating the modern
"age of fishes."


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J. Sean Doody, Hugh James, Kim Colyvas, Colin R. Mchenry and Simon
Clulow (2015)
Deep nesting in a lizard, déjà vu devil's corkscrews: first helical
reptile burrow and deepest vertebrate nest.
Biological Journal of the Linnean Society (advance online publication)
DOI: 10.1111/bij.12589
http://onlinelibrary.wiley.com/doi/10.1111/bij.12589/abstract

Dating back to 255 Mya, a diversity of vertebrate species have
excavated mysterious, deep helical burrows called Daimonelix (devil's
corkscrews). The possible functions of such structures are manifold,
but their paucity in extant animals has frustrated their adaptive
explanation. We recently discovered the first helical reptile burrows,
created by the monitor lizard Varanus panoptes. The plugged burrows
terminated in nest chambers that were the deepest known of any
vertebrate, and by far the deepest of any reptile (mean = 2.3 m, range
= 1.0–3.6 m, N = 52). A significant positive relationship between soil
moisture and nest depth persisted at depths > 1 m, suggesting that
deep nesting in V. panoptes may be an evolutionary response to egg
desiccation during the long (approximately 8 months) dry season
incubation period. Alternatively, lizards may avoid shallower nesting
because even slight daily temperature fluctuations are detrimental to
developing embryos; our data show that this species may have the most
stable incubation environment of any reptile and possibly any
ectotherm. Soil-filled burrows do not support the hypothesis generated
for Daimonelix that the helix would provide more consistent
temperature and humidity as a result of limited air circulation in dry
palaeoclimates. We suggest that Daimonelix were used mainly for
nesting or rearing young, because helical burrows of extant
vertebrates are generally associated with a nest. The extraordinary
nesting in this lizard reflects a system in which adaptive hypotheses
for the function of fossil helical burrows can be readily tested.

===



Gerta Keller, Jahnavi Punekar & Paula Mateo (2015)
Upheavals during the Late Maastrichtian: Volcanism, climate and faunal
events preceding the end-Cretaceous mass extinction.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
doi:10.1016/j.palaeo.2015.06.034
http://www.sciencedirect.com/science/article/pii/S0031018215003478

Highlights

Deccan volcanism linked to KTB mass extinction.
Deccan phase-2 and phase-3 volcanism linked to extreme warming in C29r
and C29n, respectively.
Deccan phase-1 and Ninetyeast Ridge volcanism linked to extreme
warming in C31/C30n.
All three events marked by global high-stress environments and
disaster opportunist species.

Abstract

The late Maastrichtian was a time of major climate, evolution and
extinction extremes. Rapid climate warming of 2-3°C in intermediate
waters between 69.5-68 Ma (top C31r to base C30n) accompanied maximum
evolutionary diversification (43% increase, zone CF5 to low CF4) in
planktic foraminiferal history, followed immediately by a cluster of
extinctions. During the last 250 ky of the Maastrichtian (C29r, zones
CF2-CF1), rapid warming of 4°C in intermediate waters and 8°C on land
resulted in high-stress environments ending in the mass extinction.
The end-Cretaceous mass extinction is recorded in sediments between
massive Deccan lava flows in India and attributed to SO2 and CO2
outgassing leading to ocean acidification. The early late
Maastrichtian climate and faunal upheavals are not well known.

Here we document the faunal similarities of both events from the
Indian Ocean through the Tethys and Gulf of Mexico. Results show that
both extreme warm events are marked by high-stress environments
characterized by decreased abundance and diversity of large
specialized species and dwarfing, high abundance of low oxygen
tolerant species, and disaster opportunist surface dweller
Guembelitria blooms. The similarity in faunal response with the Deccan
warming of C29r (CF2-CF1) suggests volcanism was also responsible for
the warming and faunal upheaval of the early late Maastrichtian. Major
volcanic activity at this time included the onset of Deccan eruptions
and Ninetyeast Ridge volcanism. The role of the Chicxulub impact
appears to have been a contributing, rather than causal, factor in the
mass extinction.

==

Alicia Fantasia, Thierry Adatte, Jorge E. Spangenberg & Eric Font (2015)
Paleoenvironmental changes associated with Deccan Volcanism, examples
from terrestrial deposits from Central India.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
doi:10.1016/j.palaeo.2015.06.032
http://www.sciencedirect.com/science/article/pii/S0031018215003454



Highlights

Sediments within the main Deccan phase-2 (80%) are strongly affected
by volcanism
 Clay minerals suggest a semi-arid climate with strong seasonality
Strong degradation of organic matter correlates with the most
detrimental phase-2
High chemical alteration reflects increasing acid rains during Deccan phase-2
Strong biotic stress due to volcanism predisposed faunas to extinction
at the KPg

Abstract

We analysed the geochemical and mineralogical aspects of sedimentary
beds associated with Deccan volcanism exposed in the eastern part of
the volcanic sequence in the Jabalpur-Mandla-Chhindwara (JMC) sector
(Madyha Pradesh) and in the Nand-Dongargaon (ND) basin in Central
India. These sediments were deposited in terrestrial environments
before the onset of the volcanic activity or during periods of
quiescence in mainly alluvial-limnic to lacustrine facies. Deposited
at different stratigraphic levels within the Deccan lava pile, they
provide crucial evidence to evaluate environmental changes on land
induced by the onset of the volcanism in the central part of India.
Our results indicate that sediments (intertrappeans) deposited during
Deccan volcanism do not reflect the same depositional characteristics
as sediments (Lameta Formation) preceding volcanic eruptions. The
sedimentological and mineralogical observations indicate
alluvial-limnic environments under semi-arid climate during deposition
of the Lameta sediments. This could explain the low concentration of
organic matter, which probably underwent excessive
desiccation/oxidation processes under semi-arid conditions. The
eruption of Deccan volcanic flows severely affected environmental
conditions. Intertrappean sediments associated with Deccan phase-1 and
phase-2 were deposited in terrestrial to lacustrine environments under
semi-arid climates with dry and humid seasons, which are highlighted
by the predominance of smectites resulting from basalts alteration.
Organic matter is well preserved in the sediments deposited in phase-1
and indicates a mixed source with well-preserved lacustrine organic
matter and terrestrial inputs. The subsequent intertrappean sediments
within phase-2 are strongly influenced by Deccan volcanism
characterized by high volcanic content associated elements (Ti and Fe)
and high chemical alteration (CIA-K) that likely reflects increasing
acid rains rather than climatic change. In addition, a sharp decrease
in pollen and spores coupled with the appearance of fungi mark
increasing stress conditions, which is likely a direct result of
volcanic activity. Bulk organic geochemistry points to a strong
degradation of the autochtonous organic matter, suggesting that the
biomass was oxidized in acidic conditions triggered by intense
volcanic activity.

==

Alexander G. Polozov, Henrik H. Svensen, Sverre Planke, Svetlana N.
Grishina, Kirsten E. Fristad & Dougal A. Jerram (2015)
The Basalt Pipes Of The Tunguska Basin (Siberia, Russia): High
Temperature Processes And Volatile Degassing Into The End-Permian
Atmosphere.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
doi:10.1016/j.palaeo.2015.06.035
http://www.sciencedirect.com/science/article/pii/S003101821500348X

Highlights

More than three hundreds of mineralized diatremes are found in the
Tunguska Basin.
We claim that studied Sholokhovsk diatreme has a phreatomagmatic origin.
Halogen-enriched mineral assemblages originate from magma-brine interaction.
Diatremes acting as degassing channels for halogen-rich volatiles.
Gas venting throughout pipes in the Tunguska Basin triggered mass extinction.

Abstract

A number of mechanisms have been proposed to explain the end-Permian
crisis. Many of them explore the link between this catastrophe and the
Siberian Traps. We test the hypothesis that eruption of thermogenic
gas generated in contact aureoles around igneous sills intruded into
evaporite sequences of the Tunguska Basin triggered the crisis. In
particular, we test the idea that the aspect that breccia pipes
represent conduits for voluminous gas migration from the deep basins
to the atmosphere. This contribution sheds new light on the pipe
formation based on new field and borehole observations and electron
microscopy analyses. Of more than three hundred mapped
magnetite-bearing basalt pipes, 43 are classified as diatremes. The
diatremes are usually circular or elliptical, with multiple zones of
brecciation reaching the surface, sometimes with preserved in-filled
crater lakes. The pipe diameter on the surface varies from a few tens
meters for small single diatremes to about a kilometer. The largest
crater lake area is 2.7 km2. We have conducted a detailed study of the
breccias in the Sholokhovsk basalt pipe located within the Nepa potash
deposit in the Tunguska Basin, Siberia, Russia (about N 59° and E
107°) and find that the breccias are cemented by carbonate matrix
(calcite, dolomite) and halite. Breccia clasts are altered at various
temperatures, evidenced by growth of albite and garnet from basaltic
glass, and diopside, garnet, magnetite and chlorine–bearing amphibole
(up to 1.8% Cl) in altered magmatic clasts. These mineral assemblages
suggest high temperature interactions with evaporites within the pipe
conduits. The large number of pipes support that degassing of
halogen-rich volatiles was a widespread and violent process with
implications for the end-Permian crisis.

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S. Hergarten & T. Kenkmann (2015)
The number of impact craters on Earth: Any room for further discoveries?
Earth and Planetary Science Letters 425: 187–192
doi:10.1016/j.epsl.2015.06.009
http://www.sciencedirect.com/science/article/pii/S0012821X15003659

Highlights

The crater inventory at Earth's surface is probably complete above 6
km diameter.
Some 350 undiscovered craters between 0.25 km and 6 km wide should be present.
Long-term erosion rates might be closer to present-day rates than assumed.

Abstract

Only 128 impact craters exposed at Earth's surface have been found so
far, while new craters are discovered occasionally. Taking into
account the permanent consumption of craters by erosion we present the
first estimate on the number of impact craters that should be present
at Earth's surface. Our study yields no evidence for any systematic
incompleteness in the available inventory of the craters larger than
about 6 km in diameter exposed at the surface. In contrast, more than
90 craters in the diameter range from 1 km to 6 km should still be
waiting to be discovered, and even more than 250 between 0.25 km and 1
km diameter. The transition from a probably complete inventory above 6
km to a strongly incomplete record at smaller sizes may be related to
the difference between simple and complex craters. Beyond these
results on the terrestrial crater record, our findings tentatively
suggest that erosion rates on the 10 to 100 million year scale may be
closer to present-day erosion rates than previously assumed.

News:

http://news.sciencemag.org/earth/2015/06/earths-colossal-crater-count-complete?rss=1

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