Inter- and Intraspecific Morphological Variation of Crinoid Columnals in Relation to Water Depth in the Type Cincinnatian (upper Ordovician) PDF Download
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Author: Bradley L. Deline Publisher: ISBN: Category : Languages : en Pages : 84
Book Description
Crinoid columnals are a major constituent in the Upper Ordovician fossil assemblage of the Cincinnati Arch Region. Several species of Cincinnatian crinoids are identifiable based on columnal morphology alone. Disarticulated columnals of two crinoids were measured throughout a 68-meter section of the Kope and lower Fairview Formations to examine the relationship between columnal morphology and sea level fluctuations. The columnal diameter of two disparid crinoids increased in the upward shallowing sequence. Detrended Correspondence Analysis axis 1 scores computed using columnal measurements of two crinoids correlated significantly with a proxy for depth. Therefore, crinoid columnals may provide a metric for the study of small-scale sea level fluctuation in a depositional sequence. A larger scale study showed similar morphological shifts in five taxa of crinoids, but to differing degrees. The morphologic shifts in the columnals are likely due to differences in nutrient levels and flow regimes between depths.
Author: Bradley L. Deline Publisher: ISBN: Category : Languages : en Pages : 84
Book Description
Crinoid columnals are a major constituent in the Upper Ordovician fossil assemblage of the Cincinnati Arch Region. Several species of Cincinnatian crinoids are identifiable based on columnal morphology alone. Disarticulated columnals of two crinoids were measured throughout a 68-meter section of the Kope and lower Fairview Formations to examine the relationship between columnal morphology and sea level fluctuations. The columnal diameter of two disparid crinoids increased in the upward shallowing sequence. Detrended Correspondence Analysis axis 1 scores computed using columnal measurements of two crinoids correlated significantly with a proxy for depth. Therefore, crinoid columnals may provide a metric for the study of small-scale sea level fluctuation in a depositional sequence. A larger scale study showed similar morphological shifts in five taxa of crinoids, but to differing degrees. The morphologic shifts in the columnals are likely due to differences in nutrient levels and flow regimes between depths.
Author: Robert C. Frey Publisher: ISBN: Category : Animals, Fossil Languages : en Pages : 180
Book Description
Stratigraphic distribution, paleoecology, biogeography, and systematic paleontology of 50 species of Ordovician nautiloids from the midcontinent.
Author: Hans Hess Publisher: Cambridge University Press ISBN: 9780521524407 Category : Nature Languages : en Pages : 310
Book Description
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.
Author: James C. Brower Publisher: ISBN: 9780877102212 Category : Crinoidea, Fossil Languages : en Pages : 125
Book Description
This paper describes the crinoid fauna of the Benbolt and allied formations of eastern Tennessee and southwestern Virginia. One new genus and 14 new species are proposed. These are Ectenocrinus punctalus, n. sp., anulocrinus latus, n. sp., Ristnacrinus ? altobasalis, n. sp., Hybocrinus punctatocristatus, n. sp., H. perperamnominatus, n. sp., Palaeocrinus planobasalis, n. sp., P. avondalensis, n. sp., Carabocrinus stellifer, n. sp., C. micropunctatus, n. sp., Pararchaeocrinus convexus, n., sp., Paradiabolocrinus irregularis, n. gen., n. sp., P. sinuorugosus, n. gen., n. sp., Rhaphanocrinus simplex, n. sp., and Wilsonicrinus culmensiuosus, n. sp. Due to poorly preserved material, two new species are not formally described but are referred to Isotomocrinus and Diabolocrinus. Two previously described species, Archaeocrinus peculiaris Miller and Gurley and Geraocrinus sculptus Ulrich, are treated here. The crinoid proposed by Miller and Gurley as Indianocrinus punctatus is a broken hybocrinid with some plates missing; consequently, Indianocrinus is placed in synonymy with Hybocrinus and the species retained as H. punctatus (Miller and Gurley). The pores of the Tennessee and Virgina palaeocrinids are shown to be respiratory; in addition, the ontogeny of the pores is discussed. Diabolocrinus vesperalis (White) is considered a highly variable form which includes six previously erected "species". As indicated in the above tabulation, the fauna is dominated by archaeocrinids, hybocrinids, and peculiar dicyclic cyathocrinid inadunates. The greatest faunal affinities are with the Chazyan crinoids of New York and adjacent areas and with the presumably specialized crinoids (e.g., Ristnacrinus, Hybocrinus, Carabocrinus, and Palaeocrinus) suggests that Late Chazyan and Black River time was an epoch of evolutionary experimentation for crinoids. Three of the peculiar genera survived the Black River, and persisted into the Trenton of North America, but they all became extinct prior to the Upper Ordovician. Most of the Benbolt and allied formation genera which failed to survive after the Black River epoch in North America are "normal" crinoids such as Anulocrinus, Pararchaeocrinus, Paradiabolocrinus, and Diabolocrinus. Reconstruction of the environment of the crinoids suggests that they were rooted in a relatively soft substrate and lived in shallow water of normal marine salinity and high oxygen content which was alternatingly agitated and calm. Agitated conditions probably prevailed as most species show structures which are best interpreted as adaptations to rough water conditions. The only crinoids which do not exhibit such adaptations are Geraocrinus sculptus Ulrich, two Palaeocrinus species, and Rhaphanocrinus simplex, n. sp.
Author: Thomas Edgar Guensburg Publisher: ISBN: 9780877104582 Category : Animals, Fossil Languages : en Pages : 43
Book Description
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.
Author: Bradley L. Deline
Author: Bradley L. Deline
Author: John Michael Warn
Author: Raymond Cecil Moore
Author: Robert C. Frey
Author: Hans Hess
Author: Raymond Cecil Moore
Author: James C. Brower
Author: Allan Geoffrey Axon
Author: Thomas Edgar Guensburg
Author: Mike Foote