Geology and Fossils Craigleith Area Ontario
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Nautiloid Shell Morphology
MEMOIR 13 Nautiloid Shell Morphology By ROUSSEAU H. FLOWER STATEBUREAUOFMINESANDMINERALRESOURCES NEWMEXICOINSTITUTEOFMININGANDTECHNOLOGY CAMPUSSTATION SOCORRO, NEWMEXICO MEMOIR 13 Nautiloid Shell Morphology By ROUSSEAU H. FLOIVER 1964 STATEBUREAUOFMINESANDMINERALRESOURCES NEWMEXICOINSTITUTEOFMININGANDTECHNOLOGY CAMPUSSTATION SOCORRO, NEWMEXICO NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY E. J. Workman, President STATE BUREAU OF MINES AND MINERAL RESOURCES Alvin J. Thompson, Director THE REGENTS MEMBERS EXOFFICIO THEHONORABLEJACKM.CAMPBELL ................................ Governor of New Mexico LEONARDDELAY() ................................................... Superintendent of Public Instruction APPOINTEDMEMBERS WILLIAM G. ABBOTT ................................ ................................ ............................... Hobbs EUGENE L. COULSON, M.D ................................................................. Socorro THOMASM.CRAMER ................................ ................................ ................... Carlsbad EVA M. LARRAZOLO (Mrs. Paul F.) ................................................. Albuquerque RICHARDM.ZIMMERLY ................................ ................................ ....... Socorro Published February 1 o, 1964 For Sale by the New Mexico Bureau of Mines & Mineral Resources Campus Station, Socorro, N. Mex.—Price $2.50 Contents Page ABSTRACT ....................................................................................................................................................... 1 INTRODUCTION -
Holochoanites Are Endoceroids Rousseau H
HOLOCHOANITES ARE ENDOCEROIDS ROUSSEAU H. FLOWER, New York State Museum Albany 1, N. Y. INTRODUCTION The Holochoanites may be defined as those cephalopods in which the septal necks are so elongated that they extend from the septum of which they are a part and a prolongation, apicad to the next septum, or even farther. Hyatt (1884) first regarded the Holochoanoidea as one of two major divisions of the Nautiloidea. Later (1900) he replaced his other division, the Ellipochoanoidea, by four divisions the Orthochaonites, Cyrtochoanites, Schistochoanites and Mixochoanites, and changed the name Holochoanoidea to Holochoanites for uniformity. In the mean- time, further study caused him to modify the contents of the holochoanitic division materially. Some genera originally placed in this group, such as Trocholites, proved upon further study to possess ellipochoanitic septal necks. The genus Aturia, while properly holochoanitic, was removed, because it was recognized that it represented a development of elongated septal necks in Tertiary time, which was obviously quite unrelated to that of other holochoanitic cephalopods, few of which survived the close of the Ordovician. Miller and Thompson (1937) showed that the elongation of the septal necks in Aturia was a secondary feature and the ellipochoanitic ancestry was indicated by the retention of connecting rings. It was believed that the Holochaonites proper contain cephalopods in which the long necks were primitive, and no connecting rings were developed. Unfortunately Hyatt does not seem to have committed himself on his ideas concerning the relationship of the Holochoanites with other cephalopods. It is not clear whether this was because of his preoccupation with the phyletic sig- nificance of early stages and the controversy that developed about the origin of the Ammonoidea and their relationship to the Nautiloidea, or whether he was as much perplexed by the problem as have been those of us who have come after him in the study of cephalopods. -
Ordovician Fauna
II ORDOVICIAN FAUNA By ARTHUR C. McFARLAN THE ORDOVICIAN FAUNA OF KENTUCKY By ARTHUR C. McFARLAN INTRODUCTION HIGH BRIDGE SERIES (M. R. CAMPBELL, 1898) Massive, cliff-forming limestone of Chazy and Stones River age. Three formations are recognized: CAMP NELSON (A. M. Miller, 1905, p. 10). Limestone composed of irregular patches and ramifications of granular rock of the Oregon type distributed through a matrix of dense limestone of the Tyrone type, presumably algal in origin. On weathering the surface becomes honeycombed. Fossils are not common, the more characteristic being Maclurites bigsbyi, Escharopora ramosa, a species of Rhinidictya, and various cephalopods. OREGON—Kentucky River Marble (A. M. Miller, 1905, p. 10). Grey to cream colored, granular, magnesian limestone. TYRONE—Birdseye Limestone of Linney (A. M. Miller, 1905, p. 10). Dense gray, dove, or cream colored limestone, breaking with conchoidal fracture and with small facets of Fig. 25. Map of Kentucky showing outcrop of Ordovician rocks. 50 THE PALEONTOLOGY OF KENTUCKY coarsely crystalline calcite. On weathering the surface becomes white, in which the darker facets are conspicuous, giving rise to the name Birdseye. A bed of bentonite, a greenish clay, occurs near the top. Fossils are few and include such forms as Strophomena incurvata, (see p. 80) Orthis tricenaria, Leperditia fabulites, and the cephalopods Endoceras, Actinoceras, and Cameroceras. LEXINGTON LIMESTONE (M. R. Campbell, 1898) This is the Trenton of Kentucky. As originally defined it included the strata between the Tyrone and Flanagan Chert. As later applied by Miller (1905, p. 18) and Foerste everything up to the base of the Cynthiana is included. -
Bbm:978-1-4615-4837-9/1.Pdf
INDEX Aalenian, 91, 98, 100, 101,395,396,402,423,428 Actinoptena, 497 Aalensis Biozone, 91, 93, 98,100 Actinosepia, 55 Acanthicum Zone (Chronozone), 321, 323, 466, 471, Adamsoceras, 144 472 holmi,144 Acanthoceras, 64, 65, 67, 74 oe/andicum, 144 amphibo/um, 62 Adaptation, 309 bellense, 62 Adaptive, 311 granerosense, 62 radiation, 59, 91,101,102,396,411,412 rhotomagense, 324 Ademic organisms, 407, 408, 412 var. clavatum, 324 AdmirandumlBiruncinatum Zone, 324, 328, 466, var. confusum, 324 476 var. subjlexuosum, 324 Adygeya,47,52,54,55 var. sussexiense, 324 adygensis, 54 aft'. sussexiense, 324 Adygeyidae, 54, 55 Acanthoceratid, -ae, 59, 61,62,63,64,67,68,69,70, Agathiceratidae, 300, 302, 309 71 Agetograptus, 497 Acantholissonia, 521,522,523,524,526,527,528, Aggregate crystal, 233 529 Agoniatites, 23, 26, 27, 37 gerthi, 524, 527 bicanaliculatus, 28, 32, 33, 39 Acanthompha/a, 321; see a/so Pseudowaagenia cf. bicanalicu/atus, 32 Acceleration, 69, 112 costu/atus, 39,40 Accretionary growth, 23, 25, 26, 36, 37, 42 umbona/e, 28 Accumulated elements, 398 cf. umbona/e, 32 Acernaspis, 495, 496 vanuxemi,28, 32, 36 Acetabulum, -la, -Iar (moieity), 204, 205, 207, 208, Agoniatitida, -ina, 23, 27,43 209,214,218 Akrosphaerorthoceras grega/e, 384, 388 Achoanitic, 227, 243, 247, 250; see also Septal neck A/amitocense, 474; see also Aspidoceras Acicular-prismatic layer, 52, 53 AlbertinumlDarwini Zone, 466, 474, 476, 486 Acmonoides (A.), 425 Albian, 62,425,426 Acompsoceras, 64, 65, 74 Aleksin horizon, 507 Acrei (A.), 425 Alispira gracilis, 495, 496 Aerobe/us, -
University of Michigan University Library
AllM SCANNER TEST CHART#2 Spectra 4 Pi ABCDEFGHIJKLM~~OPORSTUWXYZ~~~~~~~~~~~~~~OP~~~~~~Y~". /?SO123456768 Times Roman 4 PT ABCDEFOHIIKLUNOPQRSTLVWXYZ~~~~~~~~~~~~~~~~~P~P~~~~WX~Y/1601234567%9 6 PT ABCDEFGH1JKLMN0PQRSTUVWXYZabcdefgh1jklmnopqstuvwxyz", /1$0123456789 8 PT ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefgh1jklmnopqrstuvwxyz;:",./?$Ol23456789 10 PT ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz;:",./?$Ol23456789 / Century Schoolbook Bold 4 FT ABCDEFCHIJKLINOPQRSTUVWXYZ~~~~~~~~~~II~~~~~::',.'?M~~~S~~~~~~ 6 PT ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefahiiklmno~arstuvwxvz::'~../?$Ol23456l89 Bodoni Italic (H(I,PfLIII/kI &!>OIPX5?L i UXl/.td,fghc,rhuUn nqyr~ii,t lii /ablZlii(lP ABCDEFGHIJKLMNOPQRSTUVIYXYZ(I~~~~~~~~~~I~~~~~~~~IL~~,, /'SO123456789 A BCDEFGHIJKLMNOPQRSTUVWX YZabcdefghijklmnopyrstuuxyz;:",./?$0123456789 ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefgh~klmnopqrstueu;xyz;:';./?SO Greek and Math Symbols AB~IEI~HIK~MNO~~~PITY~~XVLLP)ISS~B~~~A~UO~~~PPPPX~~~-,5*=+='><><i'E =#"> <kQ)<G White Black Isolated Characters 65432 A4 Page 6543210 MESH HALFTONE WEDGES A4 Page 6543210 665432 CONTBIBUTIONS FEOM THE MUSEUi\d OF PALEONTOLOGY (C&& of ConkibvtiOne from the Yweum of Gedogg) UNIVERSITY OF MICHIGAN THE COLOR PATTERNS OF FOSSIL CEPHALO- PODS AND BRACHIOPODS, WI!I'H NOTES ON GASTEROPODS AND PELECYPODS BY AUG. F. FOERSTE UNIVERSITY OF MICHIGAN ANN ARBOR ROCHESTER INSTITUTE OF TECHNOLOGY, ONE LOME CT W s E38L SEE 9 ~~~~ 2358 zgsp EH2 t 3ms 8 2 3 & sE2Z 53EL B83L BE3 9 2::: 2::: 285 9 gg,Bab EE 2 t s3zr BBE & :/; E 3 5 Z 32EL d SB50 COhTRIBUTIONS FROM THE MUSEUM OF PALEONTOLOGY (Continuationof Contributions from the Museum of Geology) UNIVERSITY OF MICHIGAN Editm: EUGENES. MC~AR~EY The series of contributions from the Museum of Paleontology was inaugurated to provide a medium for the publication of papers based entirely or principally upon the collections in the Museum. When the qhmber of ages issued is sdcient to make a volume, a title-page and a tabf e of contents will be sent to libraries on the mailing list, and also to individuals upon request. -
Middle Early Ordovician, Stairsian) in Eastern New York
Geol. Mag. 145 (4), 2008, pp. 490–520. c 2008 Cambridge University Press 490 doi:10.1017/S0016756808004585 Printed in the United Kingdom Onset of the Ordovician cephalopod radiation – evidence from the Rochdale Formation (middle Early Ordovician, Stairsian) in eastern New York BJORN¨ KROGER*¨ & ED LANDING† ∗Universite´ Lille 1, Laboratoire Geosyst´ emes` (UMR 8157 CNRS), UFR des Sciences de la Terre – batimentˆ SN5, 59655 Villeneuve d’Ascq cedex, France; formerly Museum fur¨ Naturkunde, Humboldt Universitat¨ zu Berlin, Invalidenstrasse 43, D-10115 Berlin, Germany †New York State Museum, Albany, New York 12230, USA (Received 19 February 2007; accepted 19 September 2007; First published online 9 May 2008) Abstract – The Rochdale Formation of eastern New York (= Fort Ann and lower Bascom formations, designations abandoned) is now recognized to record the earliest stages of the Great Ordovician Radiation of cephalopods. The earliest Bassleroceratidae, Tarphyceratidae and endoceridans on the east Laurentian shallow carbonate platform occur in the upper, thrombolite-bearing member of the Rochdale. This fauna demonstrates that the earliest radiation of Ordovician nautiloids took place in the late Tremadocian and is best recorded in tropical platform facies. Revision of this cephalopod fauna based on approximately 190 specimens collected along a 200 km, N–S belt in easternmost New York has provided new information on inter- and intraspecific variation of earlier described species. The ellesmerocerid Vassaroceras and the endocerids Mcqueenoceras and Paraendoceras are emended. New taxa include Bassleroceras champlainense sp.nov.andB. triangulum sp. nov., Mccluskiceras comstockense gen. et sp. nov., Exoclitendoceras rochdalense gen. et sp. nov. and Paraendoceras depressum sp. nov. A rank abundance plot of 146 specimens from a locality in the Lake Champlain lowlands provides information on the community structure of a nautiloid fauna in which the longiconic cyrtoconic Bassleroceras is shown to dominate strongly. -
1355 Evans.Vp
Review of Early to Mid Ordovician orthoconic cephalopods from Iran DAVID H. EVANS, MANSOUREH GHOBADI POUR & LEONID E. POPOV Cephalopods from the late Tremadocian of the Eastern Alborz and the Darriwilian of the Eastern Alborz and Derenjal Mountains consist of relatively poorly preserved, low diversity assemblages of endocerids and orthoceratoids. Bactroceras sp. from the late Tremadocian of the Eastern Alborz is one the earliest occurrences of the genus; similar in age to those from the Montagne Noire, France, and consistent with other high latitude records during the Early Ordovi- cian. Darriwilian taxa consist of an unnamed troedssonellid previously recorded from Sweden, three taxa ascribed to Virgoceras Flower, Sactorthoceras sp. and Gangshanoceras? sp. By comparison with the coeval cephalopod faunas of South China and Baltica, those described here are of very low diversity, but are common to both areas. Darriwilian cephalopod assemblages from other parts of high latitude peri-Gondwana remain poorly known, but consist of eothinoceratids, bathmoceratids, endocerids and orthoceratoids. The Iranian faunas provide a glimpse of the generic composition of part this high latitude assemblage, and indicate clear links with those of South China and Baltica. • Key words: Tremadocian, Darriwilian, Endocerida, Orthocerida, taxonomy, biogeography. EVANS, D.H., GHOBADI POUR,M.&POPOV, L.E. 2013. Review of the Early to Mid Ordovician orthoconic cephalo- pods from Iran. Bulletin of Geosciences 88(1), 21–44 (10 figures). Czech Geological Survey, Prague. -
Part I—New American Wutinoceratidae with Review of Actinoceroid Occurrences in Eastern Hemisphere and Part II—Some Whiterock and Chazy Endoceroids
New Mexico Bureau of Mines & Mineral Resources A DIVISION OF NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY Part I—New American Wutinoceratidae with Review of Actinoceroid Occurrences in Eastern Hemisphere and Part II—Some Whiterock and Chazy Endoceroids by Rousseau H. Flower SOCORRO 1976 11 NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY KENNETH W. FORD, President NEW MEXICO BUREAU OF MINES & MINERAL RESOURCES FRANK E. Kottlowski, Director BOARD OF REGENTS Ex Officio Jerry Apodaca, Governor of New Mexico Leonard DeLayo, Superintendent of Public Instruction Appointed William G. Abbott, President, 1961-1979, Hobbs John M. Kelly, 1975-1981, Roswell Dave Rice, 1972-1977, Carlsbad Steve Torres, 1967-1979, Socorro James R. Woods, 1971-1977, Socorro BUREAU STAFF Full Time WILLIAM E. ARNOLD, Scientific Illustrator NORMA J. MEEKS, Clerk-Typist GEORGE S. AUSTIN, Indust. Minerals Geologist CANDACE H. MERILLAT, Editorial Secretary ROBERT A. BIEBERMAN, Senior Petrol. Geologist NEILA M. PEARSON, Scientific Illustrator LYNN A. BRANDVOLD, Chemist JUDY PERALTA, Seer CORALE BRIERLEY, Chemical Microbiologist MARSHALL A. REITER, Geophysicist JUDY BURLBAW, Editorial Assistant JACQUES R. RENAULT, Geologist PATRICIA E. CANDELARIA, Secretary JAMES M. ROBERTSON, Mining Geologist CHARLES E. CHAPIN, Geologist RONALD J. ROMAN, Chief Research Metallurgist RICHARD R. CHAVEZ, Technician ROBERT SHANTZ, Metallurgist RUBEN A. CRESPIN, Technician JACKIE H. SMITH, Laboratory Assistant THEA ANN DAVIDSON, Geological Technician WILLIAM J. STONE, Hydrogeologist Lois M. DEVLIN, Office Manager DAVID E. TABET, Ass't. Field Geologist Jo DRAKE, Administrative Ass't. & Sec'y. JOSEPH E. TAGGART, JR., Assoc. Mineralogist ROUSSEAU H. FLOWER, Senior Paleontologist SAMUEL THOMPSON III, Petroleum Geologist ROY W. FOSTER, Senior Petrol, Geologist ROBERT H. WEBER, Senior Geologist ROBERT W. -
NORSK GEOLOGISK TIDSSKRIFT L
-- NORSK GEOLOGISK TIDSSKRIFT UTGITT AV NORSK GEOLOGISK FORENING OSLO MED STATSBIDRAG OG MED BIDRAG FRA NORGES ALMENVITENSKAPELIGE FORSKNINGS RAD REDAKTØR: NIELS-HENR. KOLDERUP BIND 38. h. l, pp. 1-178. A/S John Griegs Boktrykkeri l Bergen 1958 l ____ l NORSK GEOLOGISK TIDSSKRIFT 38 THE MIDDLE ORDOVICIAN OF THE OSLO REGION, NORWAY 10. Nautiloid Cephalopods BY WALTER c. SWEET (The Ohio State University, Columbus, Ohio, U.S. A.) With 21 plates and 20 figures in text CONTENTS :\bstract 4 Introduction and Acknowledgements ................................ 5 The Cephalopod Faunas . .. .. .. 6 Previous Mention . .. 6 Distribution and Stratigraphic Significance ...................... 12 Systematic Paleontology .......................................... 25 Classificati on .................................................. 25 Descriptive Terminology ...................................... 27 Descriptions .................................................. 28 Suborder Ellesmeroceratina Flower, 1950 ....................... 28 Family Baltoceratidae Kobayashi, 1935 ..................... 28 Genus Eobactrites Schindewolf, 1932 ....................... 28 Eobactrites sandbergeri (Barrande) ....................... 28 Family Bathmoceratidae Holm, 1899 ....................... 30 Genus Bathmoceras Barrande, 1865 ...................... 30 Bathmoceras norvegicum Sweet, n. sp.. ................... 32 Suborder Endoceratina Flower, 1950 .......................... 33 Family Endoceratidae Hyatt, 1883 ......................... 33 Genus Dideroceras Flower, 1950 ......................... -
Mollusca: Cephalopoda (Nautiloidea)
9 MOLLUSCA: CEPHALOPODA (NAUTILOIDEA) A. H. King The term Nautiloidea is used here in a broad sense, incorporating the subclasses Endoceratoidea, Actinoceratoidea, Orthoceratoidea and Nautiloidea as perceived by Teichert (1967). Classification at order level is relatively stable; taxonomic complications arise in recognizing the greater diver sity of nautiloids in comparison with ammonoids and reconciling this within a classification at higher level (Holland, 1979, 1987). The scheme adopted below essentially follows Teichert and Moore (in Teichert et al., 1964) to order level, variations from this are noted in the text; the treatment of Cambrian orders follows Chen and Teichert (1983). The enigmatic genera Salterella (=Volborthella) and Vologdinella have been regarded as taxa 'doubtfully classifiable' within the nautiloids and treated as a separate order Volborthellida (Teichert in Teichert et ai, 1964). The present author follows Yochelson (1977, 1981), and assigns these genera to the extinct phylum Agmata. No detailed cladistic analysis has been carried out on nautiloids; comments concerning the mono- or paraphyletic nature of some orders are mainly the author's own views. Order PLECTRONOCER1DA Flower, 1964 F. ELLESMEROCERATIDAE Kobayashi, 1934 (see Fig. 9.1) C. (DOL)-O. (CRD) Mar. F. PLECTRONOCERATIDAE Kobayashi, 1935 Firsh Eburnoceras pissinum Chen and Qi, 1980, upper € . (DOL) Mar. Quadraticephalus Zone, lower Fengshan Formation, Anhui Province, China (Chen and Teichert, 1983). First: Plectronoceras Cambria (Walcott, 1905), Ptychaspis- Lash Oelandoceras sp. Lai, 1965, Baota (= Pagoda) Lime Tsinania Zone, lower Fengshan Formation, Shandong stone Formation, Ningkiang, Shaanxi (=Shensi) Province, Province, China; P. liaoningense Kobayashi, 1935 from China (Lai, 1965). Liaodong Peninsula and P. huaibeiense Chen and Qi 1979, Intervening: TRE-LLO. -
Bulletin 90 Tfiakhir PALEONTOLOGY •! 4
^ (/) £ c/) ± CO R ARIES SMITHSONIAN INSTITUTION NOIiniliSNI NVINOSHimS S3IMVy9I Ui C/) ^ Z </> Z . LniliSNI_NVINOSHimS S3 I dVy a n_LI BRAR I ES SMITHSONIAN_INSTITUTIO •'' z _i z _ R ARIES SMITHSONIAN INSTITUTION NOIiniliSNI NVINOSHilWS S3iaVda CO > ^ //v ^ ifliliSNI NVINOSHilWS S3iavyan~LIBRARIES^SMITHS0NIAN~INSTITUTI( IRARIES SMITHSONIAN INSTITUTION NOIifliliSNI NVINOSHillMS S3iavya ^ /^^ - /^^^ ^ iOiliSNl'^NVINOSHilWS S3 I bVy 8 ll'^LI B RAR I ES SMITHSONlAN~'lNSTITUTI( IRARIES SMITHSONIAN INSTITUTION NOIifliliSNI NVINOSHilNS S3iavya g2 ^ z r w 2 g> iniliSNI NVIN0SHill^s'^S3iavaan_LIBRARIES^SMITHS0NIAN INSTITUTIC 3RARIES SMITHSONIAN_INSTITUTION NOIiOiliSNl'^NVINOSHilWS SBIdVya -^ " CO _ O) ? Ui RARIES SMITHSONIAN INSTITUTION NOIiniliSNi NVINOSHillMS SBIMViJa c/j — - — miiiSNi NviNosHiii^JS S3iijvyan libraries Smithsonian institutic RARIES SMITHSONIAN INSTITUTION NOIinillSNI NVINOSHIIWS SHIHVHa millSNI NVINOSHilkNS S3 1 M VM 9 n~L I B RAR I Es'^SMITHSONIAN'iNSTITUTKI . 1 w i» 2: w 2: ,,. CO ^ « RARIES SMITHSONIAN INSTITUTION NOIinillSNI NVINOSHillMS S3 Id VMS iniiiSNi~'NviNOSHims S3iavdan libraries smithsonian"'institutic~ — 2: r- z > I :o ' CO _ (Si ^ t/) RARIES SMITHSONIAN INSTITUTION NOIiniliSNI NVINOSHillMS S3iyvaa iniliSNI_NVIN0SHlllMs'^S3 I HVH a H^LI BRAR I Es'^SMITHSONIAN^INSTITUTIO CO _ = t/j RARIES SMITHSONIAN INSTITUTION N0UniIiSNrNVIN0SHllWS'"S3 I ^ Vb 3 i 1 i'oVi 0, \5n2"S Published i/iontklv hv tlie New York State Education Department ISrLLETIN 373 MAY iqo6 New York State Museum John ]\I. Clarke Director Bulletin 90 TfiAKHir -
The Monster Nautiluses of the Palaeozoic Dr Neale Monks (UK)
The monster nautiluses of the Palaeozoic Dr Neale Monks (UK) he handful of nautilus species today, limited to a few species only ammonites and belemnites did so in found in seas today are found in relatively deep water, but the past. Tsmall, retiring animals that in the past they were quite diverse. Monoplacophorans, like scavenge about at night, foraging Although they look a lot like a limpet, Plectronoceras exile, had shells with for carrion and crustacean moults. their internal anatomy is distinctive, chambers, but no siphuncle. Were However, nautiluses were not with unusual features such as serial the walls that formed the chambers always so insignificant and during repetition of the gills, kidneys and for some other purpose? Did they the first half of the Palaeozoic Era reproductive organs along the body. work like bulkheads, so that the especially, nautiluses were major At least some monoplacophorans had monoplacophoran could build shell predators, occupying the same niches chambered shells. The Late Cambrian that was thin and economical to in Ordovician and Silurian seas as species, Knightoconus antarcticus construct, but just as strong as a sharks do today. was one such species, but, unlike thicker, unchambered shell? Perhaps, cephalopods, the chambers were all but recent work on the genetics The first nautiluses sealed off from one another. Only of the molluscs suggests that Compared to their cousins, the cephalopods have a siphuncle, a cephalopods are more closely related ammonites, the Palaeozoic nautiluses tube-like structure that runs through to scaphopods (tusk shells) than they are relatively unfamiliar animals. the chambers, allowing them to be are to monoplacophorans.