Abstract The Cambrian edrioasteroid “Totiglobus” spencensis Wen et al., 2019 is redescribed on the basis of a new and exquisitely preserved specimen from Wuliuan Spence Shale Member, Langston Formation (Utah). This occurrence associated with soft-body preservation several invertebrate groups other shelly fossils. description “ T. ” was originally based single poorly specimen. As result, some its features, such as curvature ambulacra morphology floor cover plates, were misinterpreted or...

Comparison of echinoderm faunas from two partly coeval Early Ordovician units, the Fillmore Formation western Utah and Ninemile Shale central southern Nevada, indicates that distribution echinoderms during initial radiation Paleozoic Evolutionary Fauna was substrate-controlled. Attached echinoderms, such as crinoids edrioasteroids, are much more common on hard substrates in shallow-water Fillmore, whereas vagile forms, rhombiferans mitrate stylophorans, found soft both deeper-water Ninemile....

Research Article| May 01, 1992 Rise of echinoderms in the Paleozoic evolutionary fauna: Significance paleoenvironmental controls Thomas E. Guensburg; Guensburg 1Physical Science Division, Rock Valley College, Rockford, Illinois 61111 Search for other works by this author on: GSW Google Scholar James Sprinkle 2Department Geological Sciences, University Texas, Austin, Texas 78713-7909 Author and Article Information Publisher: Society America First Online: 02 Jun 2017 Online ISSN: 1943-2682...

Abstract The palaeobiogeographical distribution of the six major clades Ordovician echinoderms (asterozoans, blastozoans, crinoids, echinozoans, edrioasteroids and stylophorans) is analysed based on a comprehensive up-to-date database compiling 3701 occurrences (1938 species recorded from 331 localities) both complete specimens isolated ossicles. Although historically biased towards limited number regions (Europe, North America, Russia), resulting dataset makes it possible to identify main...

The Kanosh Shale (Upper Arenig, Lower Ordovician) of west-central Utah. USA. contains abundant carbonate hardgrounds and one the earliest diverse hardground communities. were formed through a combination processes including development early digenetic nodules in clay sediments which exhumed concentrated as lags by storms. These cobble deposits. together with plentiful biogenic metrical. cemented inorganically precipitated calcite on sea floor. forming intraformational conglomerate...

Apektocrinus ubaghsi new genus and species is a monospecific taxon assigned to the family Apektocrinidae based on additional preparation of single previously studied specimen. among oldest known crinoids (Early Tremadoc, Early Ordovician). Although expressing crinoid apomorphies, it interpreted as retaining plesiomorphies in its arms reflecting early edrioasteroid rather than blastozoan (eocrinoid) ancestry. Apomorphies represent basal cladid (crownward) levels phylogeny. Restudy fortifies...

Although echinoderm debris is locally common, articulated specimens are rare in Late Cambrian rocks from the Great Basin and Rocky Mountains of western United States mostly associated with hardgrounds. The fauna, including cornute stylophorans, trachelocrinid eocrinoids, solute homoiosteleans, edrioasteroids, includes several members archaic Evolutionary Fauna, which had already passed its maximum diversity for echinoderms. In addition to low diversity, specimen abundance very low, averaging...

Research Article| February 01, 2001 Earliest crinoids: New evidence for the origin of dominant Paleozoic echinoderms Thomas E. Guensburg; Guensburg 1Physical Science Division, Rock Valley College, Rockford, Illinois 61114, USA Search other works by this author on: GSW Google Scholar James Sprinkle 2Department Geological Sciences, University Texas, Austin, Texas 78712, Author and Article Information Publisher: Society America Received: 27 Jul 2000 Revision 30 Oct Accepted: 03 Nov First...

Echinoderms underwent a major two-part radiation that produced all of the groups found in fossil record between Early Cambrian and Middle Ordovician. A small initial about nine classes containing low-diversity members Evolutionary Fauna. These were characterized by primitive morphology, simple ambulacral feeding structures, early development multiplated stalk or stem for attachment to skeletal fragments on soft substrate. Several became extinct at end Cambrian, leaving Late as gap very low...

For many years the earliest record of class Crinoidea was a single late Tremadocian genus. In past decade, five crinoid genera were described from early and middle Tremadocian, near base Ordovician. Together these six represent diverse assemblage with all but one expressing existing subclass apomorphies. Two recently initially assigned to their own order (plesion) Protocrinoida not subclass. Here they are placed in camerates based on apomorphies tegmen complex. Protocrinoids exhibit...

Abstract The class Somasteroidea Spencer, 1951, is basal within the subphylum Asterozoa. Members are most readily recognized by presence of series rod-like so-called virgal ossicles extending laterally from each ambulacral ossicle. Five somasteroid genera and assigned to two families. Four Gondwanan, three these ( Chinianaster , Thoralaster Villebrunaster ) Lower Ordovician Tremadocian France one Archegonaster Middle upper Darriwilian Czech Republic. fifth genus, Ophioxenikos Laurentian...

Aspects of functional morphology are examined and lifestyles proposed for seven exceptionally well-preserved crinoids from the Middle Ordovician Lebanon Limestone, Tennessee. Potential ranges motion based on plate shapes, articular surfaces attachment, feeding structures. This diverse group includes disparid inadunates ( Columbicrinus crassus Tryssocrinus endotomitus ), a hybocrinid Hybocrinus bilateralis reteocrinids Reteocrinus polki R. variabilicaulis rhodocrinitid camerates Archaeocrinus...

Because of their complexity, potential for homoplasy, andsketchy fossil record, the evolutionary history early echinodermshas been problematic. Origins high ranktaxa continue to be vig-orously debated. Specifically,the dispute over origin crinoidsis particularly active, fuelled by recent discoveries. Twoschools thought now promote competing hypotheses.Inthe tra-ditional model, crinoids branch from earliest echinoderms thatbear feeding appendages, blastozoans (‘eocrinoids’ or...

Ophioxenikos langenheimi n. gen. and sp. (class Somasteroidea), Stibaraster ratcliffei sp., Cnemidactis ? macroadambulacralatus (both class Asteroidea) are new stelleroid echinoderms described from Lower Middle Ordovician strata of the western United States. clearly is at asteroid grade organization, although an early representative class. first fossil somasteroid recognized beyond Europe. It similar to Chinianaster Villebrunaster , ambulacral characters all three suggest affinities with...

Blake, D.B. & Guensburg, T.E. 1994 10 15: Predation by the Ordovician asteroid Promopalaeaster on a pelecypod. An Prornopalaeaster (Echinodermata: Asteroidea) wrapped about Cuneamya? (Mol-lusca: Pelecypoda) in extraoral feeding posture characteristic of Jurassic to modern members Asteriidae documents an early origin for this behavioral complex. Modern asteriids are convergent Promopalaeastet; there is no direct phylogenetic linkage between two. This fossil occurrence, combined with success...

Asteroids of all geologic ages share a single basic body form, surficial skeletal arrangement, and aspects water vascular construction. In almost described Paleozoic species, however, either podial pores to the interior arm were lacking, or they are directed laterally, above adambulacrals. They internal ambulacrals in known post-Paleozoic species Pennsylvanian Calliasterella. Certain features ambulacral arrangement also differ. Calliasterella is closest relative asteroids. Classifications...

Alphacrinus mansfieldi new genus and species from the Middle Tremadoc Series (Early Ibexian), near base of Ordovician, is oldest known disparid crinoid. A family, Alphacrinidae, receives this monospecific genus. Alphacrinus's character mosaic includes primitive traits unknown among other disparids, auguring for origin a more complexly plated, less standardized antecedent, echoing evolutionary progression documented camerates cladids. Disparids are diagnosed as those crinoids expressing an...

Abstract Intermediate morphologies of a new fossil crinoid shed light on the pathway by which crinoids acquired their distinctive arms. Apomorphies originating deep in echinoderm history among early nonblastozoan pentaradiate echinoderms distinguish Tremadocian (earliest Ordovician) arms from later taxa. The brachial series is separated ambulacra, part axial skeleton, lateral plate fields. Cover plates are arrayed two tiers, and floor expressed podial basins pores. Later during Early...