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Books > Earth & environment > Earth sciences > Palaeontology > General
Fossil crinoids are exceptionally suited to deep-time studies of
community paleoecology and niche partitioning. By merging
ecomorphological trait and phylogenetic data, this Element
summarizes niche occupation and community paleoecology of crinoids
from the Bromide fauna of Oklahoma (Sandbian, Upper Ordovician).
Patterns of community structure and niche evolution are evaluated
over a ~5 million-year period through comparison with the Brechin
Lagerstatte (Katian, Upper Ordovician). The authors establish
filtration fan density, food size selectivity, and body size as
major axes defining niche differentiation, and niche occupation is
strongly controlled by phylogeny. Ecological strategies were
relatively static over the study interval at high taxonomic scales,
but niche differentiation and specialization increased in most
subclades. Changes in disparity and species richness indicate the
transition between the early-middle Paleozoic Crinoid Evolutionary
Faunas was already underway by the Katian due to ecological drivers
and was not triggered by the Late Ordovician mass extinction.
Studies of Sr isotopic composition of thousands of samples of
marine sediments and fossils have yielded a curve of 87Sr/86Sr
versus age for seawater Sr that extends back to 1 billion years.
The ratio has fluctuated with large amplitude during this time
period, and because the ratio is always uniform in the oceans
globally at any one time, it is useful as a stratigraphic
correlation and age-dating tool. The ratio also appears to reflect
major tectonic and climatic events in Earth history and hence
provides clues as to the causes, timing, and consequences of those
events. The seawater 87Sr/86Sr ratio is generally high during
periods marked by continent-continent collisions, and lower when
continental topography is subdued, and seafloor generation rates
are high. There is evidence that major shifts in the seawater ratio
can be ascribed to specific orogenic events and correlate with
large shifts in global climate.
Imaging and visualizing fossils in three dimensions with tomography
is a powerful approach in paleontology. Here, the authors introduce
select destructive and non-destructive tomographic techniques that
are routinely applied to fossils and review how this work has
improved our understanding of the anatomy, function, taphonomy, and
phylogeny of fossil echinoderms. Building on this, this Element
discusses how new imaging and computational methods have great
promise for addressing long-standing paleobiological questions.
Future efforts to improve the accessibility of the data underlying
this work will be key for realizing the potential of this virtual
world of paleontology.
The study of echinoid evolution, diversity, and ecology has always
suffered from the fact that they are represented by taxa showing
widely differing architectural designs of their multi-plated
skeletons, inhabiting a large range of marine paleoenvironments,
which result in highly varying taphonomic biases dictating their
presence and recognition. This Element addresses the taphonomy of
echinoids and includes: a general introduction to the morphological
features of echinoids that play a role in their preservation; a
review of processes which play an important role in the
differential preservation of both regular and irregular echinoids
including predation and transport; a summary of taphonomic pathways
included in actualistic studies for recent sea urchins and then
reconstructed for fossil taxa; and finally, a case study of the
variation of echinoid taphonomy across a shelf gradient using the
rich Miocene echinoid fauna of Sardinia.
Molybdenum (Mo) is a widely used trace metal for investigating
redox conditions. However, unanswered questions remain that
concentration and bulk isotopic analysis cannot specially answer.
Improvements can be made by combining new geochemical techniques to
traditional methods of Mo analysis. In this Element, we propose a
refinement of Mo geochemistry within aquatic systems, ancient
rocks, and modern sediments through molecular geochemistry
(systematically combining concentration, isotope ratio, elemental
mapping, and speciation analyses). Specifically, to intermediate
sulfide concentrations governing Mo behavior below the
'switch-point' and dominant sequestration pathways in low oxygen
conditions. The aim of this work is to 1) aid and improve the
breadth of Mo paleoproxy interpretations by considering Mo
speciation and 2) address outstanding research gaps concerning Mo
systematics (cycling, partitioning, sequestration, etc.). The Mo
paleoproxy has potential to solve ever complex research questions.
By using molecular geochemical recommendations, improved Mo
paleoproxy interpretations and reconstruction can be achieved.
Every fossil tells a story. Best-selling paleontology author Donald
R. Prothero describes twenty-five famous, beautifully preserved
fossils in a gripping scientific history of life on Earth.
Recounting the adventures behind the discovery of these objects and
fully interpreting their significance within the larger fossil
record, Prothero creates a riveting history of life on our planet.
The twenty-five fossils portrayed in this book catch animals in
their evolutionary splendor as they transition from one kind of
organism to another. We witness extinct plants and animals of
microscopic and immense size and thrilling diversity. We learn
about fantastic land and sea creatures that have no match in nature
today. Along the way, we encounter such fascinating fossils as the
earliest trilobite, Olenellus; the giant shark Carcharocles; the
"fishibian" Tiktaalik; the "Frogamander" and the "Turtle on the
Half-Shell"; enormous marine reptiles and the biggest dinosaurs
known; the first bird, Archaeopteryx; the walking whale
Ambulocetus; the gigantic hornless rhinoceros Paraceratherium, the
largest land mammal that ever lived; and the Australopithecus
nicknamed "Lucy," the oldest human skeleton. We meet the scientists
and adventurers who pioneered paleontology and learn about the
larger intellectual and social contexts in which their discoveries
were made. Finally, we find out where to see these splendid fossils
in the world's great museums. Ideal for all who love prehistoric
landscapes and delight in the history of science, this book makes a
treasured addition to any bookshelf, stoking curiosity in the
evolution of life on Earth.
Macroevolutionary inference has historically been treated as a
two-step process, involving the inference of a tree, and then
inference of a macroevolutionary model using that tree. Newer
models blend the two steps. These methods make more complete use of
fossils than the previous generation of Bayesian phylogenetic
models. They also involve many more parameters than prior models,
including parameters about which empiricists may have little
intuition. In this Element, we set forth a framework for fitting
complex, hierarchical models. The authors ultimately fit and use a
joint tree and diversification model to estimate a dated phylogeny
of the Cincta (Echinodermata), a morphologically distinct group of
Cambrian echinoderms that lack the fivefold radial symmetry
characteristic of extant members of the phylum. Although the
phylogeny of cinctans remains poorly supported in places, this
Element shows how models of character change and diversification
contribute to understanding patterns of phylogenetic relatedness
and testing macroevolutionary hypotheses.
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