Order Inde sterminate Family Trachelocrinidae new family Genus Trachelocrinus Ulrich, 1929 Trachelocrinus resseri Ulrich Burgess Shale "Arms" Order Indeterminate Family Cryptocrinitidae Bassler, 1938 Genus Cryptoc rinites von Buch, Family Meristoschismatidae new family 156 Genus Meristoschisma new -genus 156 Meristoschisma hudsoni new species Meristoschisma fayi new -species 168 Class Rhombifera Zittel, 1879 -170 Class Blastoidea Say, 1825 e S (i Order Fissiculata(?) Jaekel, 1918 173 Family Indeterminate 173 Possible Ordovician Blastoid(? >) Plate from Nevada -. 173 Subphylum Crinozoa Matsumoto, 1929 (restricted herein) eee ey (11 7/! Class Crinoidea Miller, 1821. 175 Subclass Indeterminate -7/7 Order Indeterminate NG (7/ Family Echmatocrinidae new family 177 Genus Echmatocrinus new genus 177 Echmatocrinus brachiatus new species __ Class, Order, and Family Indeterminate 183 Cystidea nugatula Barrande, T8872 cae hee 183 Class Paracrinoidea Regnell, 1945 184 Unassigned Crinozoan or Blastozoan Class 186 Class Diploporita Miiller, 1854 186 Class Removed from the Blastozoa and Grinozoa. =e) 2 ee 187 Class Edrioblastoidea Fay, 1962 _.__ 187 References). 02.2. se eee 189 Appendix 1-Locality Index 193 Plate Descriptions). -ee 198 BLASTOZOAN ECHINODERMS e Sprinkle 3 logical Survey, Denver; Martin L. Anné and his family; Kraig Derstler; Lyle D. Cambell, then a graduate student at Frank-
The distribution of all known Cambrian echinoderm taxa, encompassing both articulated specimens and taxonomically diagnostic isolated ossicles, is documented for the first time. The database described by 2011 comprises 188 species recorded from 65 formations from around the world. Formations that have yielded articulated echinoderms are unequally distributed in space and time. Only Laurentia and West Gondwana provide reasonably complete records at the resolution of Stage. The review of the biogeographical distributions of the eight major echinoderm clades shows that faunas from Laurentia and Northeast Gondwana (China and Korea) are distinct from those of West Gondwana and Southeast Gondwana (Australia); other regions are too poorly sampled to make firm palaeobiogeographical statements. Analysis of alpha diversity (species per formation) shows that diversity rose initially to Cambrian Stage 5, declined into Guzhangian and Paibian before returning to Stage 5 levels by the end of the Cambrian. This pattern is replicated in Laurentia and West Gondwana. We show that taxonomically diagnostic ossicles found in isolation typically occur significantly earlier than the first articulated specimens of the same taxa and provide important information on the first occurrence and palaeobiogeographical distribution of key taxa, and of the phylum as a whole.Supplementary material:Articulated Cambrian echinoderms and Isolated plates of Cambrian echinoderms are provided at:http://www.geolsoc.org.uk/SUP18668
Apektocrinus ubaghsinew genus and species is a monospecific taxon assigned to the new family Apektocrinidae based on additional preparation of a single previously studied specimen.Apektocrinusis among the oldest known crinoids (Early Tremadoc, Early Ordovician). Although expressing crinoid apomorphies, it is interpreted as retaining plesiomorphies in its arms reflecting early edrioasteroid rather than blastozoan (eocrinoid) ancestry. Apomorphies represent basal crinoid and cladid (crownward) levels of phylogeny.Restudy fortifies previous reports of the presence of a basal echinoderm plesiomorphy; floor plates above brachials in the arms ofApektocrinus, as well as in other approximately contemporary crinoids.Apektocrinusfurnishes the first record of podial basins in crinoid arms. Arms and calyx ofApektocrinusmerge gradually, facilitated by continuations of interbrachials (extraxial body plates) extending onto the arms and separating floor plates from brachials. These arm interbrachials, which diminish and pinch out distally as floor plates nestle into the brachial (adoral) groove, have not been recognized as such in crinoids.
Although echinoderm debris is locally common, articulated specimens are rare in Late Cambrian rocks from the Great Basin and Rocky Mountains of the western United States and are mostly associated with hardgrounds. The fauna, including cornute stylophorans, trachelocrinid eocrinoids, solute homoiosteleans, and rare edrioasteroids, includes several members of the archaic Cambrian Evolutionary Fauna, which had already passed its maximum diversity for echinoderms. In addition to the low diversity, articulated specimen abundance is very low, averaging only about one-tenth that found in overlying Lower Ordovician units. The transition between the Cambrian and Paleozoic Evolutionary Faunas for echinoderms in North America apparently occurred rapidly very close to the Cambrian-Ordovician boundary, because no unequivocal examples of the Paleozoic fauna (such as crinoids, glyptocystitid rhombiferans, asteroids, or echinoids) were found in the Late Cambrian sections.New taxa include several cothurnocystid stylophorans assigned to Acuticarpus delticus, new genus and species, Acuticarpus? republicensis, new species, and Archaeocothurnus goshutensis, new genus and species; Scotiaecystis? species, a poorly preserved cornute stylophoran with lamellipores; Minervaecystis? species, a fragmentary solute homoiostelean based on several steles; Tatonkacystis codyensis, new genus and species, a well-preserved trachelocrinid eocrinoid with five unbranched arms bearing numerous brachioles; an unnamed, poorly preserved, epispire-bearing eocrinoid; an unnamed, poorly preserved, globular eocrinoid? lacking epispires; and an unnamed, heavily weathered, edrioasterid edrioasteroid. Nearly all holdfasts found in these Upper Cambrian units are single-piece blastozoan types, probably belonging to trachelocrinid and other eocrinoids. Distinctive columnals and thecal plates of several additional undescribed eocrinoids and other echinoderms were locally abundant and are also described.
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