The extraxial-axial theory (EAT) and universal elemental homology (UEH) are often portrayed as mutually exclusive hypotheses of homology within pentaradiate Echinodermata. EAT describes homology upon the echinoderm bauplan, interpreted through early post-metamorphic growth and growth zones, dividing it into axial regions generally associated with elements of the ambulacral system and extraxial regions that are not. UEH describes the detailed construction of the axial skeleton, dividing it into homologous plates and plate series based on symmetry, early growth, and function. These hypotheses are not in conflict; the latter is rooted in refinement of the former. Some interpretive differences arise because many of the morphologies described from eleutherozoan development are difficult to reconcile with Paleozoic forms. Conversely, many elements described for Paleozoic taxa by UEH, such as the peristomial border plates, are absent in eleutherozoans. This Element recommends these two hypotheses be used together to generate a better understanding of homology across Echinodermata.
This Element reviews the ecologies of skeletal trace-producing interactions on echinoids in Modern ecosystems and the recognition of those biogenic traces in the fossil record. This title is also available as Open Access on Cambridge Core.
Echinoderms are now considered as a biological and geological model that underlies researches of primary importance. The extent of the contributions made by the International Echinoderm Conferences to various fields of research is attested by the scope covered by presentation at the international conferences. These proceedings contain the complete papers or abstracts of all the presentations and posters presented at the eighth International Echinoderm Conference, held in Dijon, France in September, 1994. Coverage includes: general; extinct classes; crinoids; asteroids; ophiuroids; holothuroids; and echinoids.
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 paper, 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 five-fold 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.
The quantification of morphology through time is a vital tool in elucidating macroevolutionary patterns. Studies of disparity require intense effort but can provide insights beyond those gained using other methodologies. Over the last several decades, studies of disparity have proliferated, often using echinoderms as a model organism. Echinoderms have been used to study the methodology of disparity analyses and potential biases as well as documenting the morphological patterns observed in clades through time. Combining morphological studies with phylogenetic analyses or other disparate data sets allows for the testing of detailed and far-reaching evolutionary hypotheses.
The dominant faunal elements in shallow Paleozoic oceans, echinoderms are important to understanding these marine ecosystems. Echinoderms (which include such animals as sea stars, crinoids or sea lilies, sea urchins, sand dollars, and sea cucumbers) have left a rich and, for science, extremely useful fossil record. For various reasons, they provide the ideal source for answers to the questions that will help us develop a more complete understanding of global environmental and biodiversity changes. This volume highlights the modern study of fossil echinoderms and is organized into five parts: echinoderm paleoecology, functional morphology, and paleoecology; evolutionary paleoecology; morphology for refined phylogenetic studies; innovative applications of data encoded in echinoderms; and information on new crinoid data sets.
This book presents a comprehensive overview of the science of the history of life. Paleobiologists bring many analytical tools to bear in interpreting the fossil record and the book introduces the latest techniques, from multivariate investigations of biogeography and biostratigraphy to engineering analysis of dinosaur skulls, and from homeobox genes to cladistics. All the well-known fossil groups are included, including microfossils and invertebrates, but an important feature is the thorough coverage of plants, vertebrates and trace fossils together with discussion of the origins of both life and the metazoans. All key related subjects are introduced, such as systematics, ecology, evolution and development, stratigraphy and their roles in understanding where life came from and how it evolved and diversified. Unique features of the book are the numerous case studies from current research that lead students to the primary literature, analytical and mathematical explanations and tools, together with associated problem sets and practical schedules for instructors and students. “..any serious student of geology who does not pick this book off the shelf will be putting themselves at a huge disadvantage. The material may be complex, but the text is extremely accessible and well organized, and the book ought to be essential reading for palaeontologists at undergraduate, postgraduate and more advanced levels—both in Britain as well as in North America.” Falcon-Lang, H., Proc. Geol. Assoc. 2010 “...this is an excellent introduction to palaeontology in general. It is well structured, accessibly written and pleasantly informative .....I would recommend this as a standard reference text to all my students without hesitation.” David Norman Geol Mag 2010 Companion website This book includes a companion website at: www.blackwellpublishing.com/paleobiology The website includes: · An ongoing database of additional Practical’s prepared by the authors · Figures from the text for downloading · Useful links for each chapter · Updates from the authors
Chordate Origins and Evolution: The Molecular Evolutionary Road to Vertebrates focuses on echinoderms (starfish, sea urchins, and others), hemichordates (acorn worms, etc.), cephalochordates (lancelets), urochordates or tunicates (ascidians, larvaceans and others), and vertebrates. In general, evolution of these groups is discussed independently, on a larger scale: ambulacrarians (echi+hemi) and chordates (cephlo+uro+vert). Until now, discussion of these topics has been somewhat fragmented, and this work provides a unified presentation of the essential information. In the more than 150 years since Charles Darwin proposed the concept of the origin of species by means of natural selection, which has profoundly affected all fields of biology and medicine, the evolution of animals (metazoans) has been studied, discussed, and debated extensively. Following many decades of classical comparative morphology and embryology, the 1980s marked a turning point in studies of animal evolution, when molecular biological approaches, including molecular phylogeny (MP), molecular evolutionary developmental biology (evo-devo), and comparative genomics (CG), began to be employed. There are at least five key events in metazoan evolution, which include the origins of 1) diploblastic animals, such as cnidarians; 2) triploblastic animals or bilaterians; 3) protostomes and deuterostomes; 4) chordates, among deuterostomes; and 5) vertebrates, among chordates. The last two have received special attention in relation to evolution of human beings. During the past two decades, great advances have been made in this field, especially in regard to molecular and developmental mechanisms involved in the evolution of chordates. For example, the interpretation of phylogenetic relationships among deuterostomes has drastically changed. In addition, we have now obtained a large quantity of MP, evo-devo, and CG information on the origin and evolution of chordates. - Covers the most significant advances in this field to give readers an understanding of the interesting biological issues involved - Provides a unified presentation of essential information regarding each phylum and an integrative understanding of molecular mechanisms involved in the origin and evolution of chordates - Discusses the evolutionary scenario of chordates based on two major characteristic features of animals—namely modes of feeding (energy sources) and reproduction—as the two main forces driving animal evolution and benefiting dialogue for future studies of animal evolution
