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K-Pg impact effects mapped on Gulf of Mexico sea floor + Winton Formation climate + more

Ben Creisler

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

Free pdf:

Charles K. Paull, David W. Caress, Roberto Gwiazda, Jaime
Urrutia-Fucugauchi, Mario Rebolledo-Vieyra, Eve Lundsten, Krystle
Anderson, Esther J. Sumner (2014)
Cretaceous-Paleogene boundary exposed: Campeche Escarpment, Gulf of Mexico.
Marine Geology (advance online publication)
DOI: 10.1016/j.margeo.2014.10.002


First detailed map of Campeche Escarpment.
Escarpment is as little as 130 km from Chicxulub impact crater.
Strata spanning Cretaceous-Paleogene (K-Pg) boundary are exposed along
Escarpment is a source for K-Pg debris flow, largest debris flow
deposit on Earth.
Results of first science cruise of the Schmidt Ocean Institute vessel
R/V Falkor.


We present the first multibeam bathymetric maps of the Campeche
Escarpment; a Mesozoic carbonate platform in the Gulf of Mexico, which
represents the closest Cretaceous-Paleogene (K-Pg) boundary outcrops
to the Chicxulub impact structure. The impact of an
extraterrestrial-body ~ 65 million years ago on top of this platform
is implicated in the end of the Cretaceous mass extinction and caused
the largest debris flow yet described on Earth, which is found across
the floor of the Gulf of Mexico and the Caribbean Sea. The location of
the K-Pg boundary has been identified in the escarpment face by
combining the new multibeam data with existing information from
boreholes. The boundary is represented by an abrupt change in gradient
on the escarpment face. The morphology of the escarpment combined with
seismic data reveals that a significant amount of material is missing
from the face, which failed catastrophically due to seismic shaking
produced by the impact. The escarpment face is inferred to be an
important source for the extensive debris flows triggered by the
impact, whose deposits are found throughout much of the Gulf of Mexico
that were triggered by the impact.

Tamara L. Fletcher, Patrick T. Moss & Steven W. Salisbury (2014)
Wood growth indices as climate indicators from the Upper Cretaceous
(Cenomanian–Turonian) portion of the Winton Formation, Australia.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
DOI: 10.1016/j.palaeo.2014.10.012


Provides evidence for oscillations in the wood indices in the early
Late Cretaceous
Explores the importance of the type of 'error' used in mean
sensitivity reporting
Provides indicators of flooding in the upper portion of the Winton Formation


Although the mid- to Late Cretaceous is regarded as a global warm
period, increasingly a more complex picture of warming and cooling is
emerging. New techniques allow more precise dating of terrestrial
localities, opening opportunities for using climate proxy approaches
on terrestrial fauna and flora to better capture the complexity of
Cretaceous climate. Here an attempt is made to understand the
seasonality and inter-annual variability of two newly dated localities
from the upper preserved portion (Cenomanian–Turonian) of the Winton
Formation, Australia. Primarily quantitative approaches to
palaeodendrology are used. The results suggest both seasonality and
high variability in climate conditions that affect growth between
years, including evidence for floods. The longest series (QM F44338)
suggests oscillatory patterns of good and poor growth in a 15 year
alternating cycle similar to the contemporary Pacific Decadal
Oscillation, although other potential explanations should be
considered and tested.


Hengye Wei, Jun Shen, Shane D. Schoepfer, Leo Krystyn, Sylvain Richoz
& Thomas J. Algeo (2014)
Environmental controls on marine ecosystem recovery following mass
extinctions, with an example from the Early Triassic.
Earth-Science Reviews (advance online publication)
DOI: 10.1016/j.earscirev.2014.10.007

The recovery of marine ecosystems following a mass extinction event
involves an extended interval of increasing biotic diversity and
ecosystem complexity. The pace of recovery may be controlled by
intrinsic ecosystem or extrinsic environmental factors. Here, we
present an analysis of changes in marine conditions following the
end-Permian mass extinction with the objective of evaluating the role
of environmental factors in the protracted (~ 5-Myr-long) recovery of
marine ecosystems during the Early Triassic. Specifically, our study
examines changes in weathering, productivity, and redox proxies in
three sections in South China (Chaohu, Daxiakou, and Zuodeng) and one
in northern India (Mud). Our results reveal: 1) recurrent
environmental perturbations during the Early Triassic; 2) a general
pattern of high terrestrial weathering rates and more intensely
reducing marine redox conditions during the early Griesbachian, late
Griesbachian, mid-Smithian, and (more weakly) the mid-Spathian; 3)
increases in marine productivity during the aforementioned intervals
except for the early Griesbachian; and 4) stronger and more temporally
discrete intervals of environmental change in deepwater sections
(Chaohu and Daxiakou) relative to shallow and intermediate sections
(Zuodeng and Mud). Our analysis reveals a close relationship between
episodes of marine environmental deterioration and a slowing or
reversal of ecosystem recovery based on metrics of biodiversity,
within-community (alpha) diversity, infaunal burrowing, and ecosystem
tiering. We infer that the pattern and pace of marine ecosystem
recovery was strongly modulated by recurrent environmental
perturbations during the Early Triassic. These perturbations were
associated with elevated weathering and productivity fluxes, implying
that nutrient and energy flows were key influences on recovery. More
regular secular variation in deepwater relative to shallow-water
environmental conditions implies that perturbations originated at
depth (i.e., within the oceanic thermocline) and influenced the
ocean-surface layer irregularly. Finally, we compared patterns of
environmental disturbance and ecosystem recovery following the other
four “Big Five” Phanerozoic mass extinctions to evaluate whether
commonalities exist. In general, the pace of ecosystem recovery
depends on the degree of stability of the post-crisis marine


Free pdf:

Aleksandra V. Birn-Jeffery, Christian M. Hubicki, Yvonne Blum, Daniel
Renjewski, Jonathan W. Hurst and Monica A. Daley (2014)
Don't break a leg: running birds from quail to ostrich prioritise leg
safety and economy on uneven terrain.
Journal of Experimental Biology 217: 3786-3796

Cursorial ground birds are paragons of bipedal running that span a
500-fold mass range from quail to ostrich. Here we investigate the
task-level control priorities of cursorial birds by analysing how they
negotiate single-step obstacles that create a conflict between body
stability (attenuating deviations in body motion) and consistent leg
force–length dynamics (for economy and leg safety). We also test the
hypothesis that control priorities shift between body stability and
leg safety with increasing body size, reflecting use of active control
to overcome size-related challenges. Weight-support demands lead to a
shift towards straighter legs and stiffer steady gait with increasing
body size, but it remains unknown whether non-steady locomotor
priorities diverge with size. We found that all measured species used
a consistent obstacle negotiation strategy, involving unsteady body
dynamics to minimise fluctuations in leg posture and loading across
multiple steps, not directly prioritising body stability. Peak leg
forces remained remarkably consistent across obstacle terrain, within
0.35 body weights of level running for obstacle heights from 0.1 to
0.5 times leg length. All species used similar stance leg actuation
patterns, involving asymmetric force–length trajectories and
posture-dependent actuation to add or remove energy depending on
landing conditions. We present a simple stance leg model that explains
key features of avian bipedal locomotion, and suggests economy as a
key priority on both level and uneven terrain. We suggest that running
ground birds target the closely coupled priorities of economy and leg
safety as the direct imperatives of control, with adequate stability
achieved through appropriately tuned intrinsic dynamics.

Kathryn Knight (2014)
Running birds prioritise safety on uneven terrain.

M. B. J. Picasso (2014)
Ontogenetic Scaling of the Hindlimb Muscles of the Greater Rhea (Rhea
Anatomia, Histologia, Embryologia (advance online publication)
DOI: 10.1111/ahe.12158

The greater rhea (Rhea americana) is the largest South American bird.
It is a cursorial, flightless species with long powerful legs and
reduced forelimbs. The goal of this study was to explore how hindlimb
muscles scale with body mass during postnatal growth and to analyze
whether the specialized locomotion of this species affects the growth
of muscle masses. The mass of 19 muscles and body mass were weighed in
21 specimens ranging from 1-month-old individuals to adults. Seventeen
muscles scaled with positive allometry with respect to body mass,
whereas two muscles scaled isometrically. The predominance of positive
allometric growth in hindlimb muscles results in a limb with massive
and powerful muscles specialized to support a large body mass and to
attain relatively high running speeds. Analysis of muscle mass scaling
is a simple and useful way to compare possible differences between
locomotor styles, and it is valuable in studies that reconstruct the
paleobiology of extinct taxa.


Free pdf:

Gael J Kergoat, Patrice Bouchard, Anne-Laure Clamens, Jessica L
Abbate, Hervé Jourdan, Roula Jabbour-Zahab, Gwenaelle Genson, Laurent
Soldati & Fabien L Condamine (2014)
Cretaceous environmental changes led to high extinction rates in a
hyperdiverse beetle family.
BMC Evolutionary Biology 14: 220,
DOI: 10.1186/s12862-014-0220-1


As attested by the fossil record, Cretaceous environmental changes
have significantly impacted the diversification dynamics of several
groups of organisms. A major biome turnover that occurred during this
period was the rise of angiosperms starting ca. 125 million years ago.
Though there is evidence that the latter promoted the diversification
of phytophagous insects, the response of other insect groups to
Cretaceous environmental changes is still largely unknown. To gain
novel insights on this issue, we assess the diversification dynamics
of a hyperdiverse family of detritivorous beetles (Tenebrionidae)
using molecular dating and diversification analyses.


Age estimates reveal an origin after the Triassic-Jurassic mass
extinction (older than previously thought), followed by the
diversification of major lineages during Pangaean and Gondwanan
breakups. Dating analyses indicate that arid-adapted species
diversified early, while most of the lineages that are adapted to more
humid conditions diversified much later. Contrary to other insect
groups, we found no support for a positive shift in diversification
rates during the Cretaceous; instead there is evidence for an 8.5-fold
increase in extinction rates that was not compensated by a joint
increase in speciation rates.


We hypothesize that this pattern is better explained by the
concomitant reduction of arid environments starting in the
mid-Cretaceous, which likely negatively impacted the diversification
of arid-adapted species that were predominant at that time.

Free pdf:

Peter Uetz, Omar Torres-Carvajal, Aaron Bauer, Uri Roll and Shai Meiri (2014)
Late bloomers and baby boomers: ecological drivers of longevity in
squamates and the tuatara.
Global Ecology and Biogeography (advance online publication)
DOI: 10.1111/geb.12244


Longevity is an important life-history trait, directly linked to the
core attributes of fitness (reproduction and survival), yet
large-scale comparative studies quantifying its implications for the
ecology and life history of ectotherms are scarce. We tested the
allometry of longevity in squamates and the tuatara, and determined
how longevity is related to key environmental characteristics and
life-history traits. Predictions based on life-history theory are
expected to hold true for ectotherms, similarly to mammals and birds.




We assembled from the literature a dataset of the maximum longevities
of more than a thousand squamate species, representing c. 10% of their
known species diversity, their phylogenetic relationships and multiple
life-history and ecological variables. Correcting for phylogeny, we
modelled the link between squamate longevity and both key life-history
traits, such as body mass and age at first reproduction, and important
environmental factors, such as latitude and primary productivity
within species distributional ranges.


Large-bodied species live for longer than small ones, but body size
explains far less of the variance in longevity than it does in mammals
and birds. Accounting for body size, squamate brood frequency is
negatively correlated with longevity, while age at first reproduction
is positively correlated with longevity. This points to a continuum of
slow-to-fast life-history strategies. Squamates in high latitudes and
cold regions live for longer, probably because a shorter season of
activity translates to slower development, older age at first
reproduction and hence to increased longevity. Individuals live longer
in captivity than in the wild. Herbivorous and omnivorous squamates
live for longer than carnivorous ones. We postulate that low-quality
nutrition reduces growth rates, promotes a relative decline in
reproductive rates and thus prolongs life.

Main conclusions

Our results support key predictions from life-history theory and
suggest that reproducing more slowly and at older ages, being
herbivorous and, plausibly, lowering metabolism, result in increased