DOCSLIB.ORG

Early Silurian Graptolites from Southeastern Alaska and Their Correlation with Graptolitic Sequences in North America and the Arctic

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Early Silurian Graptolites from Southeastern Alaska and Their Correlation with Graptolitic Sequences in North America and the Arctic Early Silurian Graptolites From Southeastern Alaska and Their Correlation With Graptolitic Sequences in North America and the Arctic GEOLOGICAL SURVEY PROFESSIONAL PAPER 653 Early Silurian Graptolites From Southeastern Alaska and Their Correlation With Graptolitic Sequences in North America and the Arctic By MICHAEL CHURKIN, JR., and CLAIRE CARTER GEOLOGICAL SURVEY PROFESSIONAL PAPER 653 Descriptions and illustrations of $9 species of Graptoloidea and correlation of the assemblages with other graptolitic successions in North America, the Soviet Arctic, and Great Britain UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1970 UNITED STATES DEPARTMENT OF THE INTERIOR WALTER J. HICKEL, Secretary GEOLOGICAL SURVEY William T. Pecora, Director Library of Congress Catalog-card No. 78-605140 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price $1 (paper cover) CONTENTS Page Page Abstract-_ _________________________________________ 1 Standard graptolite zones for the Lower Silurian___-_._- 6 Introduction-______________________________________ 1 Lower Silurian graptolites in western North America-___ 6 Acknowledgments. ____ __--_-_________-____-__-______ 1 Systematic descriptions._____________________________ 13 Graptolites of the Descon Formation, southeastern Alaska__ _____________________________________ 2 Class Graptolithina.____________________________ 13 Description of the Descon Formation.________..___ 2 Order Graptoloidea_-___________---___-__-_- 13 Graywacke sandstone and banded mudstone___ 2 Family Diplograptidae__________________ 13 Conglomerate and sedimentary breccia. _______ 3 Family Dimorphograptidae______________ 33 Black chert and siliceous shale________________ 3 Family Monograptidae__________________ 34 Quartzo-feldspathic arenite.__________________ 3 Volcanic rocks,_____________________________ 3 References cited.___________________________________ 46 Stratigraphic relations to other units and age___--_- 3 Index ____.._______-__ __-_______-__-___---__-__--- 49 ILLUSTRATIONS [Plates 1-4 follow index] PLATE 1, Climacograptus, Pseudoclimacograptus, and Diplograptus. 2. Diplograptus, Glyptograptus, and Orthograptus. 3. Orthograptus, Petalograptus, Dimorphograptus, Akidograptus, and Monograptus. 4. Monograptus and Rastrites. Page FIGUBE 1. Geologic map of Prince of Wales Island area_________________--____-_--_-------_----_------_-------- 4 2. Index map showing Silurian graptolite localities_______________--_-_-----------_--------------------- 7 3. Correlation diagram showing graptolitic sequences-_____-__-_--___---__-_---------------------------- 9 4-5. Columnar sections showing graptolite localities: 4. Esquibel Island.________________-_________________-_------_-------_----------------------- 11 5. San Fernando Island.__________________________-_______-_-__--_---___--------------------- 12 6-19. Camera lucida drawings of: 6. Climacograptus. ________________-________________-_____-___-___-_-_-__-------------------- 13 7. Climacograptus- ________________-_______-____-__-_--__---_----_--------------------------- 17 8. Climacograptus and Pseudoclimacograptus. ______________________-_-__-__-----_----_--_------- 18 9. Diplograptus. __________________________________--___----___--_-_--__--------------------- 21 10. Glyptograptus and Diplograptus... _____________--__---_-----__-------_--_------------------- 22 11. Glyptograptus _______________________________________----_____--_--__-_-_----------------- 25 12. Glyptograptus and OrtAogrrapfus______---__--_----------------------------------------------- 26 13. ^.Orthograptus, Petalograptus, Dimorphograptus, and Akidograptus. ________-__------------------- 31 14. Dimorphograptus and Monograptus... ____________________-_______-._____------------_-------- 35 15. Monograptus... _______________________________________-______--------------------_------- 36 16. Monograptus_______________________________________-_--_______-___----------_----------- 38 17. Monograptus..- ________________________________________________-______----_--__----------- 40 18. Monograptus... _______________________________________________-____-_--_----------------- 41 19. Rastrites............ ___________ ______ _ _____________________.._-_-._--.-_--.---- 45 TABLES Page TABLE 1. Partial list of graptolites from northeastern Nevada showing British ranges and associations on single talus slabs--_-________________________________________________--_-___----_----------------------- 1 2. Silurian graptolite faunas from Prince of Wales Island area, Alaska__-____-_-__------------------------ 10 3. Lower Silurian graptolites of Alaska and Nevada showing a comparison of their zonal ranges to the same or similar species in Canada, Great Britain, and the Soviet Arctic.__________-_-----_------------------- ^ ill EARLY SILURIAN GRAPTOLITES FROM SOUTHEASTERN ALASKA AND THEIR CORRELATION WITH GRAPTOLITIG SEQUENCES IN NORTH AMERICA AND THE ARCTIC By MICHAEL CHURKIN, JR., and CLAIRE CARTER ABSTRACT Dimorphograptus (proximally uniserial and distally A succession of graptolite faunas across the Ordovician-Silurian biserial) together with the first monograptids were not boundary has been discovered in North America. The earliest reported in Ruedemann's (1947) cataloging of Nor^h Silurian graptolite zones, characterized by the association of American graptolites. the biserial graptolites Climacograptus, Glyptograptus, and Orthograptus, established much earlier in the Ordovician More recently, Ross, (1962) described several lower together with the first Silurian monograptids, Akidograptus and Silurian species from Illinois, but they are fragmentary Dimorphograptus are described for the first time in North and poorly preserved. Another lower, but not lowest, America. These new collections of Lower Silurian graptolites Silurian graptolite collection that has beautifully are from dark shales in southeastern Alaska and Nevada. The preserved specimens was recently made from talus in occurrence of Silurian graptolites in western North America is reviewed, and the Alaskan graptolite faunas are correlated a mine dump in Nevada (Kerr, 1962; Churkin and Kay, with other graptolitic successions in North America and the 1967). These graptolites are illustrated for the first Soviet Arctic. The Alaskan graptolite species and zonal succession time in this paper. are remarkably similar to that in the Birkhill Shales of Scotland, The senior author in the company of G. D. Eberleni the type section for the standard Lower Silurian graptolite and M. A. Lanphere made several discoveries of con­ zones. From Alaska, graptolite assemblages equivalent to the zones of Akidograptus acuminatus, Monograptus cyphus, and siderably older Silurian graptolite faunas in south­ Monograptus grcgarius are recognized and illustrated. In addition, eastern Alaska during the 1964 field season. Subse­ the following new graptolite species are established: Climaco­ quently in 1965, new lower Silurian graptolite localities graptus indivisus esquibelensis, C. innotatus obesus, C. tnedius were found by Eberleiii, A. T. Ovenshine, and Churkin. brevicaudatus, C. stenotelus, C. rectangularis abbreviatus, Diplo- The most important of these localities was revisited graptus mucroterminatus, D. elongatus, Glyptograptus tamariscus magnus, G. lanphcrei, G. laciniosits, G. gnomus, G. kayi, Ortho­ by Churkin in 1968, and the highest Ordovician grapto­ graptus eberleini, 0. insectiformis minutus, Dimorphograptus lites were found just below the previously known lowest physophora alaskensis, Monograptus calamistratus, M. budding- Silurian faunas, thus establishing the Ordovician- toni, M. noyesensis, M. kerri, M. hamatus, Rastrites orbitus. Silurian boundary. The earliest Silurian graptolite zones are present in some of these localities the first INTRODUCTION record of their occurrence in North America. The Graptolite faunas, especially from black shale se­ purpose of this paper is to describe this new material, quences bordering North America, show a remarkable briefly review the occurrence of Lower Silurian grapto­ similarity in species and faunal succession to the British lites in western North America and the Soviet Arctic, graptolites made famous first by Charles Lapworth, correlate the Alaskan graptolites within these areas, then by Elles and Wood (1901-18). In Australia and show the differences in associations of certain (Thomas, 1960), Asia (Sun, 1933; Hsii, 1934; Obut, critical graptolite species that most likely reflect 1959, 1960), and North Africa (Waterlot, 1945), where changes in their stratigraphic range from one region good graptolite sections are known, the similarity in to another. species and succession of faunas above the initially The biostratigraphic section is by Michael Churkin, somewhat provincial Lower Ordovician faunas is again and the systematic descriptions are largely by Claire remarkable. Despite the cosmopolitan character of Carter, who also did all of the camera lucida drawings graptolites, the lowest Silurian graptolite zones are of the graptolites. relatively unknown outside of Great Britain. The lowest Silurian graptolite zones characterized by the ACKNOWLEDGMENTS association of biserial genera such as the long- The authors are indebted to the collecting zeal of established Ordovician Climacograptus, Glyptograptus, G. D. Eberlein, A. T. Ovenshine, M. A. Lanphere, and and Orthograptus and the appearance of the new Charles Carter, without whose help this report would 1 EARLY SILURIAN GRAPTOLITES FROM
Load more

Recommended publications
  • Download Full Article 4.6MB .Pdf File
    https://doi.org/10.24199/j.mmv.1939.11.02 November 1939 MEM. NAT. Mus. VrcT., XI, 193Q. GRAPTOLITES OF AUSTRALIA: BIBLIOGRAPHY AND HISTORY OF RESEARCH By R. A. Keble, F.G.S. ( Palaeontologist, National 1J1usem·n, JJ:[elboiirne) and Professor TV. N. Benson, B.A., D.Sc. (University of Otago, Dunedin, New Zealcind.) The Australian graptolite fauna is probably the most complete in the world, certainly in regard to its Ordovician components, a fact clearly appreciated by McCoy. He had ready for the press descriptions and figures of most of the species afterwards described in J amcs Hall's J\fonograph published iu 1865, which may be regarded as the basis of systematic graptolite research, when he received from Hall a proof of his fignres. McCoy immediately conceded him priority and adopted his specific names. Had Hall delayed sending his proof, McCoy wonld certainly have pnblisl1ed his figures and descriptions and his name would have been just as pl'ominent in the literature of graptoliies as Hall's. Com­ menting on "Graptolitcs (Didymograpsus) frutieosus (Hall sp.)," l\IcCoy snys, "this is the first Victorian gmptolitc I ever smv, and, as it was then a new species, I had named it in my .MSS. after J\fr. J. A. Panton, who found it iu the soft shalcs of Bcn(Ugo, of ·which goldficld he was then "\Varden, nncl in ·whose hospitable camp I was then able to recognize the true g-cological age of the gold-bearing Rlates of the colony for the first time. �rhe same species was subsequently dis­ covered by Professor Hall in Canada; aud ns he kindly sent me an early proof of his illustration before publication, I of course adopted his name as above" (Prod.
    [Show full text]
  • Systematics in Palaeontology
    Systematics in palaeontology THOMAS NEVILLE GEORGE PRESIDENT'S ANNIVERSARY ADDRESS 1969 CONTENTS Fossils in neontological categories I98 (A) Purpose and method x98 (B) Linnaean taxa . x99 (e) The biospecies . 202 (D) Morphology and evolution 205 The systematics of the lineage 205 (A) Bioserial change 205 (B) The palaeodeme in phyletic series 209 (e) Palaeodemes as facies-controlled phena 2xi Phyletic series . 2~6 (A) Rates of bioserial change 2~6 (B) Character mosaics 218 (c) Differential characters 222 Phylogenetics and systematics 224 (A) Clade and grade 224 (a) Phylogenes and cladogenes 228 (e) Phylogenetic reconstruction 23 I (D) Species and genus 235 (~) The taxonomic hierarchy 238 5 Adansonian methods 240 6 References 243 SUMMARY A 'natural' taxonomic system, inherent in evolutionary change, pulses of biased selection organisms that themselves demonstrate their pressure in expanded and restricted palaeo- 'affinity', is to be recognized perhaps only in demes, and permutations of character-expres- the biospecies. The concept of the biospecies as sion in the evolutionary plexus impose a need a comprehensive taxon is, however, only for a palaeontologically-orientated systematics notional amongst the vast majority of living under which (in evolutionary descent) could organisms, and it is not directly applicable to be subsumed the taxa of the neontological fossils. 'Natural' systems of Linnaean kind rest moment. on assumptions made a priori and are imposed Environmentally controlled morphs, bio- by the systematist. The graded time-sequence facies variants, migrating variation fields, and of the lineage and the clade introduces factors typological segregants are sources of ambiguity into a systematics that cannot well be accommo- in a distinction between phenetic and genetic dated under pre-Darwinian assumptions or be fossil grades.
    [Show full text]
  • The Great Ordovician Radiation of Marine Life: Examples from South China
    Available online at www.sciencedirect.com Progress in Natural Science 18 (2008) 1–12 Review The great Ordovician radiation of marine life: Examples from South China Renbin Zhan a,*, Jisuo Jin b, Yuandong Zhang a, Wenwei Yuan a a State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China b Department of Earth Sciences, University of Western Ontario, London Ont., Canada N6A 5B7 Received 14 March 2007; received in revised form 23 July 2007; accepted 27 July 2007 Abstract The Ordovician radiation is the earliest and most important biodiversification event in the evolution of the Paleozoic Evolutionary Fauna (PEF), when the basic framework of PEF was established. The radiation underwent a gradual, protracted process spanning more than 40 million years and was marked by several diversity maxima of the PEF. Case studies conducted on the Upper Yangtze Platform (South China Palaeoplate) showed that the Ordovician radiation was characterized by drastic increases in a- and b-diversity in various groups of organisms. During the radiation, brachiopods, trilobites, and graptolites of the PEF became more diverse to dominate over the Cambrian Evolutionary Fauna (CEF) in all marine environments. At either global or regional scales, however, the Ordovician radiation was highly heterogeneous in time and space, and the rate and pattern of radiation exhibited by different major fossil groups were also variable. Ó 2007 National Natural Science Foundation of China and Chinese Academy of Sciences. Published by Elsevier Limited and Science in China Press. All rights reserved. Keywords: Ordovician radiation; Paleozoic Evolutionary Fauna; a-diversity; b-diversity; Upper Yangtze Platform 1.
    [Show full text]
  • MODE of LIFE of GRAPTOLITES Much of the Substance of This Paper
    ACT A PALAEON.TOLOGICA POLONICA Vol. 23 1978 No.4 / .. NANCY HARTSHORNE KIRK MODE OF LIFE OF GRAPTOLITES Abstract. - The probable mode of life of the graptol,ites (crustoids, dendroids and graptoloids) is reconstructed from a, logical interpretation of their rhabdosomal structures. The readaptation of sessile colonial organisms to meet the requirements of a freely-moving existence in the plankton is regarded as the controlling factor in the evolution of the graptoloids. It is suggested that the gradual reduction in the size of the colony in the dicho­ graptids, biserial and uniserial graptoloids may have been a consequence of the undesirability of coloniality in the new environment, and that the graptoloids might have attained individuality, disappea):'ing into the plankton at t e time of their sup- posed extinction. .. Much of the substance of this paper was read to the Symposium on Coloniality at Durham (Systematics Association) in 1976 and should be published shortly. This version contains some new ideas, however, and also many digressions to discuss points of outstanding disagreement. Since the broad outline of my theme will be familiar to graptolitologists, as was not the case for the Systemahcs Association, I trust that the digres­ sions will be of use and interest in themselves, and, placed in parentheses, will not obscure too much my main argument. !tis generally believed that crustoids were encrusting, and the dend­ roids attached benthonic colonies. Their coloniality may have been an adaptation to the benthonic.habit, which could have arisen by failure of asexually budded zooids to separate from the' parent. By forming en­ crusting or tree-like' colonies small, zooids of comparatively simple orga­ nisation would have, been able to establish !hemselves upon the crowded sea floor and avoid being overtropped by competitors.
    [Show full text]
  • 7. Rickards, Wright, Hamedi.Pdf
    Records of the Western AustralIan Museum Supplement No. 58: 103-122 (2000). Late Ordovician and Early Silurian graptolites from southern Iran R.B. Rickardsl, A.J. Wright2 and M.A. HamedP I Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3 EQ, England 1 School of Geosciences, University of Wollongong, Wollongong, N.s.W. 2522, Australia "Department of Geology, Tarbiet Modares University, Tehran, Iran Abstract - Graptolites are described for the first time from the Faraghun mountains (Kuh-e-Faraghun) and the Gahkum mountains (Kuh-e-Gahkum) on the northern edge of the southeast part of the Zagros Mountains, Iran. 38 taxa are recorded, including 4 Ordovician and 34 Silurian species; the latter are the first Silurian graptolites described from Iran. Ashgill (Late Ordovician) graptolite assemblages from Kuh-e-Faraghun include: Persclllptograptlls persculptlls and Orthograptlls amplexicalllis, indicating a persculptlls Biozone age; and Orthograptus amplexicalllis abbreviatlls, indicating the latest Ordovician anceps Biozone. Kuh-e-Faraghun Early Silurian faunas include representatives of the L1andovery leptotheca Biozone; another assemblage, including Monograptlls convollltus and Pselldorthograptlls inopinatlls, indicates the slightly younger L1andovery convollltlls Biozone. Graptolites from Kuh-e-Gahkum comprise a rich Stimlllograptlls sedgwickii assemblage, indicating a slightly higher L1andovery level again (sedgwickii Biozone); a convollltlls Biozone fauna is also probably represented in our collections. INTRODUCTION the Kerman district, East-Central Iran; the fauna Late Ordovician and Early Silurian graptolites, they reported is that described in part from the from two areas in the northern part of the Zagros Katkoyeh Formation by Rickards et al. (1994), now belt (Figures 1, 2, 3), are described for the first time being fully described on the basis of collections from Iran.
    [Show full text]
  • Cortical Fibrils and Secondary Deposits in Periderm of the Hemichordate Rhabdopleura (Graptolithoidea)
    Cortical fibrils and secondary deposits in periderm of the hemichordate Rhabdopleura (Graptolithoidea) PIOTR MIERZEJEWSKI and CYPRIAN KULICKI Mierzejewski, P. and Kulicki, C. 2003. Cortical fibrils and secondary deposits in periderm of the hemichordate Rhabdopleura (Graptolithoidea). Acta Palaeontologica Polonica 48 (1): 99–111. Coenecia of extant hemichordates Rhabdopleura compacta and Rh. normani were investigated using SEM techniques. Cortical fibrils were detected in their fusellar tissue for the first time. The densely packed cortical fibrils form a character− istic band−like construction in fusellar collars, similar to some Ordovician rhabdopleurids. No traces of external second− ary deposits are found in coenecia. Two types of internal secondary deposits in tubes are recognized: (1) membranous de− posits, composed of numerous, tightly packed sheets, similar to the crustoid paracortex and pseudocortex; and (2) fibrillar deposits, devoid(?) of sheets and made of cortical fibrils, arranged in parallel and interpreted as equivalent to graptolite endocortex. There is no significant difference in either the shape or the dimensions of cortical fibrils found in Rhabdopleura and graptolites. The cortical fabric of both rhabdopleuran species studied is composed of long, straight and more or less wavy, unbranched fibrils arranged in parallel; their diameters vary from 220 to 570 µm. The study shows that there is no significant difference between extinct and extant Graptolithoidea (= Pterobranchia) in the histological and ultrastructural pattern of their primary and secondary deposits of the periderm. The nonfusellar periderm of the prosicula is pitted by many depressions similar to pits in the cortical tissue of graptolites. Key words: Rhabdopleura, Pterobranchia, Hemichordata, periderm, sicula, ultrastructure, fibrils. Piotr Mierzejewski [[email protected]], Instytut Paleobiologii PAN, ul.
    [Show full text]
  • Revised Sequence Stratigraphy of the Ordovician of Baltoscandia …………………………………………… 20 Druzhinina, O
    Baltic Stratigraphical Association Department of Geology, Faculty of Geography and Earth Sciences, University of Latvia Natural History Museum of Latvia THE EIGHTH BALTIC STRATIGRAPHICAL CONFERENCE ABSTRACTS Edited by E. Lukševičs, Ģ. Stinkulis and J. Vasiļkova Rīga, 2011 The Eigth Baltic Stratigraphical Conference 28 August – 1 September 2011, Latvia Abstracts Edited by E. Lukševičs, Ģ. Stinkulis and J. Vasiļkova Scientific Committee: Organisers: Prof. Algimantas Grigelis (Vilnius) Baltic Stratigraphical Association Dr. Olle Hints (Tallinn) Department of Geology, University of Latvia Dr. Alexander Ivanov (St. Petersburg) Natural History Museum of Latvia Prof. Leszek Marks (Warsaw) Northern Vidzeme Geopark Prof. Tõnu Meidla (Tartu) Dr. Jonas Satkūnas (Vilnius) Prof. Valdis Segliņš (Riga) Prof. Vitālijs Zelčs (Chairman, Riga) Recommended reference to this publication Ceriņa, A. 2011. Plant macrofossil assemblages from the Eemian-Weichselian deposits of Latvia and problems of their interpretation. In: Lukševičs, E., Stinkulis, Ģ. and Vasiļkova, J. (eds). The Eighth Baltic Stratigraphical Conference. Abstracts. University of Latvia, Riga. P. 18. The Conference has special sessions of IGCP Project No 591 “The Early to Middle Palaeozoic Revolution” and IGCP Project No 596 “Climate change and biodiversity patterns in the Mid-Palaeozoic (Early Devonian to Late Carboniferous)”. See more information at http://igcl591.org. Electronic version can be downloaded at www.geo.lu.lv/8bsc Hard copies can be obtained from: Department of Geology, Faculty of Geography and Earth Sciences, University of Latvia Raiņa Boulevard 19, Riga LV-1586, Latvia E-mail: [email protected] ISBN 978-9984-45-383-5 Riga, 2011 2 Preface Baltic co-operation in regional stratigraphy is active since the foundation of the Baltic Regional Stratigraphical Commission (BRSC) in 1969 (Grigelis, this volume).
    [Show full text]
  • Lab 8: Graptolites and Trace Fossils
    Geos 223 Introductory Paleontology Spring 2006 Lab 8: Graptolites and Trace Fossils Name: Section: AIMS: This lab will introduce you to graptolites (Part A), and to a branch of paleontology known as ichnology (the study of trace fossils; Part B). By the end of Part A this lab you should be familiar with the basic anatomy of graptolites, and have an appreciation for how graptolites are used in the biostratigraphic zonation of the Lower Paleozoic. By the end of Part B of this lab you should be familiar with the basic ethological groups of trace fossils, and have an appreciation for how trace fossils can provide important paleoecological and paleoenvironmental information. PART A: GRAPTOLITES. Graptolites (Class Graptolithina) are an extinct group of colonial hemichordate deuterostomes, similar in morphology and life habit to the modern colonial pterobranch hemichordate Rhabdopleura. The graptolite colony consisted of many clonal zooids, each occupying a theca in the communal skeleton (the rhabdosome). The thecae formed in rows along branches of the rhabdosome called stipes. The rhabdosome was made of a non-mineralized, organic, non-chitinous protein called periderm. Graptolite colonies were either erect fan-like structures growing from the seafloor (most dendroid graptolites, ranging from the Middle Cambrian to the Late Carboniferous) or free-floating in the plankton (the commoner graptoloid graptolites, probably descended from dendroid ancestors and ranging from the Early Ordovician to the Early Devonian). Graptoloid graptolites are very important biostratigraphic zone fossils in Lower Paleozoic strata. 1 DENDROID GRAPTOLITES: A1: Dictyonema. Dendroid graptolite colonies formed fan-like structures with thecae-bearing stipes held apart by horizontal struts (dissepiments).
    [Show full text]
  • Bulletin of the Geological Society of Denmark, Vol. 35/3-4, Pp. 203-207
    Graptolite Taxonomy and Classification MU EN-ZHI Mu En-zhi: Graptolite Taxonomy and Classification. Bull. geol. Soc. Denmark, vol. 35, pp. 203--207, Co­ penhagen, July 1st, 1987. https://doi.org/10.37570/bgsd-1986-35-21 Graptolithina comprises chiefly six orders. Among them Graptoloidea and a part of Dendroidea known as Graptodendroids are planktonic in mode of life. Graptoloidea consists of three suborders namely Axono­ lipa, Axonocrypta and Axonophora. The families Dendrograptidae-Anisograptidae-Tetragraptidae and Didymograptidae-Isograptidae-Cardiograptidae-Diplograptidae-Monograptidae represent anagenetic grades. Some important evolutionary trends took place once again, representing cladogenetic divergen­ ces. All other families or subfamilies are offshoots of various grades. The suborder Axonocrypta is dis­ cussed in detail. Mu En-zhi, Nanjing Institute of Geology and Palaeontology, Academia Sinica, Chimingssu, Nanjing, China, August20th, 1986. General Consideration tinae, tri-radiate Anisograptinae and biradiate Adelograptinae) is derived from the floating Dic­ Graptolithina, a class of Hemichordata, com­ tyonema due to the loss of dissepiments (Mu, prises chiefly six orders known as Dendroidea, 1974), while the reclined Psigraptidae Lin (1981) Graptoloidea, Tuboidea, Camaroidea, Stolonoi­ with isolated autothecae is an offshoot. Recently dea and Crustoidea (Kozlowski, 1949, 1966; Bul­ Zhao & Zhang (1985) proposed a new family man, 1970). The thecae in Dendroidea and Grap­ Muenzhigraptidae with biform autothecae rep­ toloidea are regularly arranged in stipes, al­ resenting the direct ancestor of Psigraptidae. though Dendroidea has three kinds of thecae Graptoloidea first appeared in the late Xin­ (autotheca, bitheca and stolotheca), while Grap­ changian (X3) due to the loss of bithecae from toloidea has only one. In the graptoloid thecae, Adelograptinae and flourished in early Ning­ the proximal portion (protheca) and the distal kuoan (N1), marking another new stage in grap­ portion (metatheca) are homologous with the tolite history.
    [Show full text]
  • Late Ludfordian and Early Pridoli Monograptids from the Polish Lowland
    LATE LUDFORDIAN AND EARLY PRIDOLI MONOGRAPTIDS FROM THE POLISH LOWLAND ADAM URBANEK Urbanek, A. 1997. Late Ludfordian and early Pfidoli monograptids from the Polish Low­ land. In: A. Urbanek and L. Teller (eds), Silur ian Graptolite Faunas in the East European Platform: Stratigraphy and Evolution. - Palaeontologia Polonica 56, 87-23 1. Graptolites etched from the Mielnik-I wellcore (EPoland) reveal the main features of the development of monograptid faunas within the late Ludfordian-early Pi'idoli interval. Fifteen species and subspecies are described and Monog raptus (Slovinog raptus) subgen. n. as well as Neocolonograptu s gen. n. are erected. Morphology of many species has been described adequately for the first time and their systematic position corrected. Four grap­ tolite zones of the late Ludfordian are distinguished. The late Ludfordian fauna, which appears after the kozlowskii Event, is composed mainly of immigrants dominated by hooded monograptids. They reappear as a result of the Lazarus effect. Some of them initiated the lobate-spinose phyletic line terminating with Mon ograptus (Uncinatograptus) spineus, a highly characteristic index species. The lobate and the lobate-spinose types are accompanied by bilobate forms (Pse udomonoclimac is latilobu s). The graptolite sequence indicates that the appeara nce of the early Pfidoli fauna was preceded by a biotic crisis, namely the spineus Event. Therefore this fauna is made up of a few holdovers and some new elements which developed from Pristiograptus dubiu s stem lineage (Neocolonograptus gen. n., Istrograpt us Tsegelnjuk). This early assemblage, com­ posed of bilobate forms, was later enriched by hooded monograptid s, reappearing after the spineus Event.
    [Show full text]
  • Greenhouse−Icehouse Transition in the Late Ordovician Marks a Step Change in Extinction Regime in the Marine Plankton
    Greenhouse−icehouse transition in the Late Ordovician marks a step change in extinction regime in the marine plankton James S. Cramptona,b, Roger A. Coopera,1, Peter M. Sadlerc, and Michael Footed aDepartment of Paleontology, GNS Science, Lower Hutt 5040, New Zealand; bSchool of Geography, Environment and Earth Science, Victoria University of Wellington, Wellington 6140, New Zealand; cDepartment of Earth Sciences, University of California, Riverside, CA 92521; and dDepartment of the Geophysical Sciences, University of Chicago, Chicago, IL 60637 Edited by Andrew H. Knoll, Harvard University, Cambridge, MA, and approved December 22, 2015 (received for review September 25, 2015) Two distinct regimes of extinction dynamic are present in the major commonly are inferred to be good approximations of their true marine zooplankton group, the graptolites, during the Ordovician ranges in time, and empirical graptoloid range data have been and Silurian periods (486−418 Ma). In conditions of “background” used as examples of, or tests for, macroevolutionary rates (3, 4, extinction, which dominated in the Ordovician, taxonomic evolu- 11–13). Like most of the marine macroplankton, their evolu- tionary rates were relatively low and the probability of extinction tionary dynamics are interpreted to have depended closely on was highest among newly evolved species (“background extinction those of the microphytoplankton and bacterioplankton (13–16), mode”). A sharp change in extinction regime in the Late Ordovician the primary producers in the food web and which, in the modern marked the onset of repeated severe spikes in the extinction rate oceans, are sensitive indicators of oceanic circulation, nutrient curve; evolutionary turnover increased greatly in the Silurian, and flux, and global climate (1, 17); in addition, they depended on the extinction mode changed to include extinction that was inde- physical properties of the water mass such as temperature and pendent of species age (“high-extinction mode”).
    [Show full text]
  • Geologic History a – 1 1. a Whalebone That Originally Contained 200 Grams of Radioactive Carbon-14 Now Contains 25 Grams of C
    Geologic History A – B1 Base your answers to questions 7 and 8 on the graph 1. A whalebone that originally contained 200 grams of below, which shows the generalized rate of decay of radioactive carbon-14 now contains 25 grams of carbon- radioactive isotopes over 5 half-lives. 14. How many carbon-14 half-lives have passed since this whale was alive? (1) 1 (2) 2 (3) 3 (4) 4 2. The diagram below represents a sample of a radioactive isotope. Which diagram best represents the percentage of this radioactive isotope sample that will remain after 2 half- lives? 7. If the original mass of a radioactive isotope was 24 grams, how many grams would remain after 3 half-lives? (1)12 (2)24 (3)3 (4)6 3. The table below shows information about the 8. Which radioactive isotope takes the greatest amount radioactive decay of carbon-14. of time to undergo the change shown on the graph? (1) carbon-14 (3) uranium-238 (2) potassium-40 (4) rubidium-87 ~~~~~~~~~~~~~~~ 9. An igneous rock contains 10 grams of radioactive potassium-40 and a total of 10 grams of its decay products. During which geologic time interval was this rock most likely formed? What is the amount of carbon-14 remaining after 28,500 (1) Middle Archean years? (2) Late Archean (3) Middle Proterozoic (4) Late Proterozoic 10. Which geologic event occurred in New York State at approximately the same time that eurypterids were 4. How old is a fossil that has radioactively decayed becoming extinct? through 4 half-lives of carbon-14? (1) the opening of the Atlantic Ocean (1) 5,700 years (3) 22,800 years (2) the uplift of the Appalachian Mountains (2) 17,100 years (4) 28,500 years (3) the formation of the Catskill Delta (4) the intrusion of the Palisades Sill 5.
    [Show full text]