The Oldest Known Crinoids (early Ordovician, Utah) and a New Crinoid Plate Homology System

The Oldest Known Crinoids (early Ordovician, Utah) and a New Crinoid Plate Homology System PDF

Author: Thomas Edgar Guensburg

Publisher:

Published: 2003

Total Pages: 43

ISBN-13: 9780877104582

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Six new primitive genera from the Early Ordovician of western Utah significantly advance our understanding of early crinoid history. Two of the new genera are the oldest crinoids (early Ibexian, early Tremadoc) and represent a previously unknown protocrinoid evolutionary grade, differing from other crinoids in having a nonstandardized dorsal cup and arms bearing ambulacral floor plates. Titanocrinus sumralli, new genus and species, has hundreds of unorganized mid-cup and interbrachial plates separating the cup-base basal circlet and the ray plates. Glenocrinus globularis, new genus and species, has similar plating with a more compact globular cup and fewer mid-cup plates, and is near the origin of diplobathrid camerates. A third taxon, Eknomocrinus wahwahensis, new genus and species, from the same lower stratigraphic interval, is a stem-group monocyclic camerate crinoid with standardized but irregular cup plating and other emergent crinoid traits shared with protocrinoids. Three new camerates from higher in the section are more derived. Cnemecrinus fillmorensis, new genus and species, and Habrotecrinus ibexensis, new genus and species, both latest Ibexian (middle Arenig), are monocyclic camerates. The latter taxon has unique accessory plates and major cup plate shapes. The fossil record indicates rapid diversification of disparid, cladid, and camerate crinoids by the end of the middle Ibexian (late Tremadoc), each arising independently from the protocrinoid stem group. Evidence from ontogeny, cup-stem and radial orientation, and now, early morphologic transitions necessitates revision of long used skeletal terminology. Dual ray and cup-base references for plate homologies, rather than the traditional ray-only model, are consistent with this evidence. Consequently, infrabasals are redefined as the cup-base circlet of both dicyclic and monocyclic crinoids. The use of basals is restricted to plates between infrabasals and radials of dicyclic (and tricyclic) crinoids. Traditional classifications emphasizing cup plate circlet number is unreliable early in the crinoid record; instead, posterior and interray cup morphology provides the most consistent phylogenetic information.

Echinoderm Paleobiology

Echinoderm Paleobiology PDF

Author: William I. Ausich

Publisher: Indiana University Press

Published: 2008-07-18

Total Pages: 474

ISBN-13: 0253351286

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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 Great Ordovician Biodiversification Event

The Great Ordovician Biodiversification Event PDF

Author: B. D. Webby

Publisher: Columbia University Press

Published: 2004

Total Pages: 497

ISBN-13: 0231126786

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Two of the greatest evolutionary events in the history of life on Earth occurred during Early Paleozoic time. The first was the Cambrian explosion of skeletonized marine animals about 540 million years ago. The second was the "Great Ordovician Biodiversification Event," which is the focus of this book. This is the first book devoted specifically to establishing the global patterns of differentiation of Ordovician biotas through time and space. It provides extensive genus- and species-level diversity data for the many Ordovician fossil groups and presents an evaluation of how each group diversified, with assessments of patterns of change, and rates of origination and extinction.

Niche Evolution and Phylogenetic Community Paleoecology of Late Ordovician Crinoids

Niche Evolution and Phylogenetic Community Paleoecology of Late Ordovician Crinoids PDF

Author: Selina R. Cole

Publisher: Cambridge University Press

Published: 2022-05-26

Total Pages: 88

ISBN-13: 1108898947

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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 Lagerstätte (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.

Early Palaeozoic Biogeography and Palaeogeography

Early Palaeozoic Biogeography and Palaeogeography PDF

Author: D.A.T. Harper

Publisher: Geological Society of London

Published: 2014-01-27

Total Pages: 485

ISBN-13: 1862393737

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The Early Palaeozoic was a critical interval in the evolution of marine life on our planet. Through a window of some 120 million years, the Cambrian Explosion, Great Ordovician Biodiversification Event, End Ordovician Extinction and the subsequent Silurian Recovery established a steep trajectory of increasing marine biodiversity that started in the Late Proterozoic and continued into the Devonian. Biogeography is a key property of virtually all organisms; their distributional ranges, mapped out on a mosaic of changing palaeogeography, have played important roles in modulating the diversity and evolution of marine life. This Memoir first introduces the content, some of the concepts involved in describing and interpreting palaeobiogeography, and the changing Early Palaeozoic geography is illustrated through a series of time slices. The subsequent 26 chapters, compiled by some 130 authors from over 20 countries, describe and analyse distributional and in many cases diversity data for all the major biotic groups plotted on current palaeogeographic maps. Nearly a quarter of a century after the publication of the ‘Green Book’ (Geological Society, London, Memoir12, edited by McKerrow and Scotese), improved stratigraphic and taxonomic data together with more accurate, digitized palaeogeographic maps, have confirmed the central role of palaeobiogeography in understanding the evolution of Early Palaeozoic ecosystems and their biotas.

Fossil Crinoids

Fossil Crinoids PDF

Author: Hans Hess

Publisher: Cambridge University Press

Published: 2002

Total Pages: 310

ISBN-13: 9780521524407

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Crinoids have graced the oceans for more than 500 million years. Among the most attractive fossils, crinoids had a key role in the ecology of marine communities through much of the fossil record, and their remains are prominent rock forming constituents of many limestones. This is the first comprehensive volume to bring together their form and function, classification, evolutionary history, occurrence, preservation and ecology. The main part of the book is devoted to assemblages of intact fossil crinoids, which are described in their geological setting in twenty-three chapters ranging from the Ordovician to the Tertiary. The final chapter deals with living sea lilies and feather stars. The volume is exquisitely illustrated with abundant photographs and line drawings of crinoids from sites around the world. This authoritative account recreates a fascinating picture of fossil crinoids for paleontologists, geologists, evolutionary and marine biologists, ecologists and amateur fossil collectors.

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