The echinoderms are an ideal group to understand evolution from a holistic, interdisciplinary framework. The genetic regulatory networks underpinning development in echinoderms are some of the best known for any model group. Additionally, the echinoderms have an excellent fossil record, elucidating in in detail the evolutionary changes underpinning morphological evolution. In this Element, the echinoderms are discussed as a model group for molecular palaeobiological studies, integrating what is known of their development, genomes, and fossil record. Together, these insights shed light on the molecular and morphological evolution underpinning the vast biodiversity of echinoderms, and the animal kingdom more generally.

Echinoderms elaborate a calcite skeleton composed of numerous plates with a distinct microstructure (stereom) that can be modelled into different shapes thanks to the use of a transient amorphous calcium carbonate (ACC) precursor phase and the incorporation of an intraorganic matrix during biomineralization. A variety of different types of stereom microarchitecture have been distinguished, each of them optimized for a specific function. For instance, a regular, galleried stereom typically houses collagenous ligaments, whereas an irregular, fine labyrinthic stereom commonly bears muscles. Epithelial tissues, in turn, are usually associated with coarse and dense stereom microfabrics. Stereom can be preserved in fossil echinoderms and a wide array of investigating methods are available. As many case studies have shown, a great deal of important paleobiological and paleoecological information can be decoded by studying the stereom microstructure of extinct echinoderms.

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 unique overview of current research on echinoderm evolution brings together a series of authoritative syntheses and reviews of this diverse marine invertebrate group which includes starfishes and sea urchins. Included in the 26 chapters are molecular biology, biochemistry, developmental biology, comparative anatomy, and palaeontology of the echinoderms.

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.

The history of life on earth is largely reconstructed from time-averaged accumulations of fossils. A glimpse at ecologic-time attributes and processes is relatively rare. However, the time-sensitive and predictability of echinoderm disarticulation makes them model organisms to determine post-mortem transportation and allows recognition of ecological-time data within paleocommunity accumulations. Unlike many other fossil groups, this has allowed research on many aspects of echinoderms and their paleocommunities, such as the distribution of soft tissues, assessment of the amount of fossil transportation prior to burial, determination of intraspecific variation, paleocommunity composition, estimation of relative abundance of taxa in paleocommunities, determination of attributes of niche differentiation, etc. Crinoids and echinoids have received the most amount of taphonomic research, and the patterns present in these two groups can be used to develop a more thorough understanding of all echinoderm clades.

This book provides a comprehensive synthesis of the range of biological information that can be retrieved from the fossilised skeletons of echinoids. The first half consists of a detailed explanation of the functional significance of skeletal structures and the inferences to be drawn from them about the living animals. This is followed by a discussion of the important evolutionary changes that have taken place and why they may have occurred. Finally, there is a section on how echinoids relate to other echinoderm groups.

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.

Sea urchins and other echinoderms, which have been studied intensively by developmental biologists for more than a century, are currently among the most prominent models for elucidating the genomic regulatory processes that control embryogenesis and the evolution of those processes. This volume contains reviews from the world's leading researchers who are using echinoderms to address these questions. Chapters focus on gene regulatory networks that drive the differentiation and morphogenesis of major embryonic tissues such as the skeleton, muscle, nervous system, immune system, pigment cells, and germ line, and on evolutionary insights from comparative studies of these networks across echinoderms and other taxa. Other chapters comprehensively review the architecture and evolution of the cell signaling pathways that establish the early embryonic axes and on recent evolutionary changes in gene networks that have led to dramatic changes in the life history modes of echinoderms. This volume provides a comprehensive, current picture of exciting research at the interface between developmental genomics and evolution from one of the research communities leading this work. - Contributions from leading investigators who use echinoderms as model organisms - Up-to-date reviews of developmental gene regulatory networks - Current work at the interface between developmental genomics and evolution

The proceedings of the Seventh International Echinoderm Conference, held at Atami, Japan, September 1990. In addition to sections covering ecology, evolution, reproduction, morphology, molecular biology, developmental biology, physiology, behavior, and paleontology, there are four plenary lectures a