DOCSLIB.ORG

The Hydrostatics of Paleozoic Ectocochleate Cephalopods

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Hydrostatics of Paleozoic Ectocochleate Cephalopods Palaeontologia Electronica palaeo-electronica.org The hydrostatics of Paleozoic ectocochleate cephalopods (Nautiloidea and Endoceratoidea) with implications for modes of life and early colonization of the pelagic zone David J. Peterman, Christopher C. Barton, and Margaret M. Yacobucci ABSTRACT Understanding the hydrostatic properties of ectocochleate cephalopods is essen- tial to study the functional morphology of their shells. The conditions for neutral buoy- ancy, static orientation of the living animal, and their hydrostatic stability are key factors to determine the physical relationships and constraints on cephalopod life habits and paleoecology. The hydrostatics of early orthoconic and cyrtoconic Paleozoic cephalo- pods were investigated by digitally reconstructing morphotypes within Nautiloidea and Endoceratoidea. Morphotypes were chosen from several traditional orders and include endogastric cyrtocones (Ellesmerocerida and Discosorida), exogastric cyrtocones (Oncocerida), and longi-orthocones (Orthocerida and Endocerida). The extant nautilid, Nautilus pompilius, was also modeled as a reference for the hydrostatics of the Paleo- zoic cephalopods. All cyrtocone models have similar hydrostatic stability to the Nautilus and only the ellesmerocerid was found to be negatively buoyant. The hydrostatics of the neutrally buoyant cyrtocones suggests that they behaved as relatively poor-swim- ming demersal or nekto-benthic predators. This mode of life aligns with the largely ner- itic distribution of individuals belonging to these clades in the Paleozoic. In contrast, the orthocones studied were all capable of neutral buoyancy, much more stable than the Nautilus model, and all had vertical syn vivo orientations in a static setting. The hydro- static properties of these morphotypes and their largely pelagic distribution support their role as vertical migrants. However, adapically distributed cameral deposits and endosiphuncular deposits would reduce stability, easing deviation from a vertical orien- tation. These adaptations, along with dorsal color patterns on some species, suggest that active locomotion in orthocones may have been more important than previously thought. David J. Peterman. Department of Earth and Environmental Sciences, Wright State University, Dayton, Ohio, United States of America. [email protected] Peterman, David J., Barton, Christopher C., and Yacobucci, Margaret M. 2019. The hydrostatics of Paleozoic ectocochleate cephalopods (Nautiloidea and Endoceratoidea) with implications for modes of life and early colonization of the pelagic zone. Palaeontologia Electronica 22.2.24A 1-29. https://doi.org/10.26879/884 palaeo-electronica.org/content/2019/2521-cephalopod-hydrostatics Copyright: May 2019 Paleontological Society. This is an open access article distributed under the terms of Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0), which permits users to copy and redistribute the material in any medium or format, provided it is not used for commercial purposes and the original author and source are credited, with indications if any changes are made. creativecommons.org/licenses/by-nc-sa/4.0/ PETERMAN, BARTON, & YACOBUCCI: CEPHALOPOD HYDROSTATICS Christopher C. Barton. Department of Earth and Environmental Sciences, Wright State University, Dayton, Ohio, United States of America. [email protected] Margaret M. Yacobucci. Department of Geology, Bowling Green State University, Bowling Green, Ohio, United States of America. [email protected] Keywords: cephalopod; Ordovician; buoyancy; orientation; paleoecology; digital models Submission: 3 May 2018. Acceptance: 11 April 2019. INTRODUCTION Okamoto, 1996). This belief is largely due to the difficulty of computing accurate volumes and the Paleozoic ectocochleate cephalopods include total mass distribution. The stability indices derived diverse and paleoecologically important higher by previous authors are proportionate to the results taxa, two of which are the focus of this study: Nau- of the current study in the sense that larger values tiloidea and Endoceratoidea. Understanding the represent larger restoring moments to the equilib- hydrostatic properties of their conches is essential rium condition. Stability values quantify the resis- to better understand their modes of life, especially tance to wave action or ease/difficulty in modifying during their initial liberation from the benthos and syn vivo orientation via active locomotion. A stabil- colonization of the pelagic zone during the Early ity index of zero represents a scenario where the Ordovician. The goals of the present work were to centers of buoyancy and gravity coincide, and 1) create highly accurate, three-dimensional digital there is no preferred orientation (similar to an models of a range of early Paleozoic cephalopod object in zero gravity). Larger stability values will morphotypes; 2) use these models to calculate key result in larger restoring moments acting to return hydrostatic properties, including the conditions the object to its static equilibrium condition. How- necessary to achieve neutral buoyancy, the static ever, no studies have tested the magnitude of orientation and stability of the shell during life; and hydrodynamic restoration for cephalopods with dif- 3) interpret these hydrostatic properties in the con- ferent stability indices. Therefore, stability indices text of these cephalopods’ paleoecology. in the current study are relative to each other and Ectocochleate cephalopod conches consist of the extant ectocochleate analogue, Nautilus a body chamber inhabited by the living animal and pompilius. a phragmocone divided by septa into a series of While there is much variability in shell mor- progressively larger chambers (camerae) through- phology throughout the evolutionary history of out ontogeny. The phragmocone functions as an these cephalopods, only early Paleozoic cyrto- apparatus to regulate weight and buoyancy. This cones and orthocones (curved and straight structure becomes a passive gas float if cameral conches, respectively; Figure 1) were investigated liquid is removed and replaced with gas. This here. The hydrostatics of the extant nautilid, Nauti- decrease in mass allows the phragmocone to be lus pompilius, was used as a reference for these positively buoyant and compensates for the nega- Paleozoic cephalopods. Specific taxa were chosen tive buoyancy of the soft body and mineralized that best represent the putative nautiloid clades shell, which are denser than seawater. Neutral Ellesmerocerida, Orthocerida, Oncocerida, and buoyancy is achieved when the total mass of the Discosorida and the endoceratoid clade, organism is equal to the mass of the displaced Endocerida. Although there are varying degrees of seawater (following Archimedes’ principle). The disparity, common morphotypes that have wide- static orientation of an object occurs when the cen- reaching implications for other taxa were selected ters of buoyancy and gravity are aligned vertically, for study. while the object's stability is dependent upon their degree of separation (Okamoto, 1996; Wester- Ordovician Biodiversification mann, 1998). Hydrostatic stability is quantified by The Great Ordovician Biodiversification Event the stability index (the distance between the cen- marked a drastic morphological and taxonomic ters of buoyancy and gravity normalized by the diversification of many marine organisms (Frey et cube root of the organismal volume). Earlier stud- al., 2004). Consequently, the nautiloids rapidly ies have assumed the center of gravity to coincide diversified and expanded their habitat from shal- with the center of the body chamber (Trueman, low, low latitude paleoenvironments to nearly all 1941; Raup, 1967; Raup and Chamberlain, 1967; 2 PALAEO-ELECTRONICA.ORG FIGURE 1. Depiction of general terms used within this study. Orthocones refer to straight shelled cephalopods, whereas cyrtocones are slightly curved. Long and short varieties of these shells are referred to by the prefixes longi- and brevi-, respectively. Exogastric and endogastric shells have a convex and concave venter, respectively (ventral direction towards the right for both cyrtocones). Each figure is modified from Teichert et al. (1964). marine paleoenvironments around the globe Endocerida consist of mostly straight orthoconic (Kröger and Zhang, 2009). In the earliest Ordovi- conchs that can be much larger than the elles- cian (beginning of the Tremadocian stage) only a merocerids. In the case of the endocerids, it is single nautiloid clade, the Ellesmerocerida, common for species to reach several meters in existed. Their conches can be characterized as length, making them the largest swimming organ- generally small (<10 cm), slightly curved, endogas- isms in the Ordovician (Teichert and Kummel, tric (that is, coiling toward the venter) cyrtocones 1960). One striking difference between the ortho- with close septal spacing, and fewer small longi- cerids and endocerids, aside from size, is the much conic forms (Furnish and Glenister, 1964). The larger siphuncle with common mineralized endosi- appearance of Ellesmerocerida in the Late Cam- phuncular deposits within the cones of Endocerida brian marked the first cephalopods with siphuncu- (Teichert, 1964a). Cameral deposits are commonly lar characteristics that would have increased the found within Orthocerida (and many other nauti- transport capacity of cameral liquid, allowing loids), and their hydrostatic attributes were investi- replacement with gases
Load more

Recommended publications
  • Early Paleozoic Life & Extinctions (Part 1)
    NJU Course Extinctions: Past, Present & Future Prof. Norman MacLeod School of Earth Sciences & Engineering, Nanjing University Extinctions: Past, Present & Future Extinctions: Past, Present & Future Course Syllabus (Revised) Section Week Title Introduction 1 Course Introduction, Intro. To Extinction Introduction 2 History of Extinction Studies Introduction 3 Evolution, Fossils, Time & Extinction Precambrian Extinctions 4 Origin of Life & Precambrian Extionctions Paleozoic Extinctions 5 Early Paleozoic World & Extinctions Paleozoic Extinctions 6 Middle Paleozoic World & Extinctions Paleozoic Extinctions 7 Late Paleozoic World & Extinctions Assessment 8 Mid-Term Examination Mesozoic Extinctions 9 Triassic-Jurassic World & Extinctions Mesozoic Extinctions 10 Labor Day Holiday Cenozoic Extinctions 11 Cretaceous World & Extinctions Cenozoic Extinctions 12 Paleogene World & Extinctions Cenozoic Extinctions 13 Neogene World & Extinctions Modern Extinctions 14 Quaternary World & Extinctions Modern Extinctions 15 Modern World: Floras, Faunas & Environment Modern Extinctions 16 Modern World: Habitats & Organisms Assessment 17 Final Examination Early Paleozoic World, Life & Extinctions Norman MacLeod School of Earth Sciences & Engineering, Nanjing University Early Paleozoic World, Life & Extinctions Objectives Understand the structure of the early Paleozoic world in terms of timescales, geography, environ- ments, and organisms. Understand the structure of early Paleozoic extinction events. Understand the major Paleozoic extinction drivers. Understand
    [Show full text]
  • 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
    [Show full text]
  • Cambrian Cephalopods
    BULLETIN 40 Cambrian Cephalopods BY ROUSSEAU H. FLOWER 1954 STATE BUREAU OF MINES AND MINERAL RESOURCES NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY CAMPUS STATION SOCORRO, NEW MEXICO NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY E. J. Workman, President STATE BUREAU OF MINES AND MINERAL RESOURCES Eugene Callaghan, Director THE REGENTS MEMBERS Ex OFFICIO The Honorable Edwin L. Mechem ...................... Governor of New Mexico Tom Wiley ......................................... Superintendent of Public Instruction APPOINTED MEMBERS Robert W. Botts ...................................................................... Albuquerque Holm 0. Bursum, Jr. ....................................................................... Socorro Thomas M. Cramer ........................................................................ Carlsbad Frank C. DiLuzio ..................................................................... Los Alamos A. A. Kemnitz ................................................................................... Hobbs Contents Page ABSTRACT ...................................................................................................... 1 FOREWORD ................................................................................................... 2 ACKNOWLEDGMENTS ............................................................................. 3 PREVIOUS REPORTS OF CAMBRIAN CEPHALOPODS ................ 4 ADEQUATELY KNOWN CAMBRIAN CEPHALOPODS, with a revision of the Plectronoceratidae ..........................................................7
    [Show full text]
  • Part I. Revision of Buttsoceras. Part II. Notes on the Michelinoceratida
    MEMOIR 10 PART I Revision of Buttsoceras PART II Notes on the Michelinoceratida By ROUSSEAU H. FLOWER 1 9 6 2 STATE BUREAU OF MINES AND MINERAL RESOURCES NEW MEXICO INSTITUTE OF MINING AND TECHNOLOGY CAMPUS STATION SOCORRO, NEW MEXICO NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY E. J. Workman, President STATE BUREAU OF MINES AND MINERAL RESOURCES Alvin J. Thompson, Director THE REGENTS MEMBERS Ex OFFICIO The Honorable Edwin L. Mechem ........................................ Governor of New Mexico Tom Wiley .......................................................... Superintendent of Public Instruction APPOINTED MEMBERS William G. Abbott ............................................................................................... Hobbs Holm 0. Bursum, Jr. ......................................................................................... Socorro Thomas M. Cramer ......................................................................................... Carlsbad Frank C. DiLuzio ...................................................................................... Albuquerque Eva M. Larrazolo (Mrs. Paul F.) ............................................................... Albuquerque Published October I2, 1962 For Sale by the New Mexico Bureau of Mines & Mineral Resources Campus Station, Socorro, N. Mex.—Price $2.00 Contents PART I REVISION OF BUTTSOCERAS Page ABSTRACT ....................................................................................................................... INTRODUCTION .............................................................................................................................
    [Show full text]
  • First Record of Non-Mineralized Cephalopod Jaws and Arm Hooks
    Klug et al. Swiss J Palaeontol (2020) 139:9 https://doi.org/10.1186/s13358-020-00210-y Swiss Journal of Palaeontology RESEARCH ARTICLE Open Access First record of non-mineralized cephalopod jaws and arm hooks from the latest Cretaceous of Eurytania, Greece Christian Klug1* , Donald Davesne2,3, Dirk Fuchs4 and Thodoris Argyriou5 Abstract Due to the lower fossilization potential of chitin, non-mineralized cephalopod jaws and arm hooks are much more rarely preserved as fossils than the calcitic lower jaws of ammonites or the calcitized jaw apparatuses of nautilids. Here, we report such non-mineralized fossil jaws and arm hooks from pelagic marly limestones of continental Greece. Two of the specimens lie on the same slab and are assigned to the Ammonitina; they represent upper jaws of the aptychus type, which is corroborated by fnds of aptychi. Additionally, one intermediate type and one anaptychus type are documented here. The morphology of all ammonite jaws suggest a desmoceratoid afnity. The other jaws are identifed as coleoid jaws. They share the overall U-shape and proportions of the outer and inner lamellae with Jurassic lower jaws of Trachyteuthis (Teudopseina). We also document the frst belemnoid arm hooks from the Tethyan Maastrichtian. The fossils described here document the presence of a typical Mesozoic cephalopod assemblage until the end of the Cretaceous in the eastern Tethys. Keywords: Cephalopoda, Ammonoidea, Desmoceratoidea, Coleoidea, Maastrichtian, Taphonomy Introduction as jaws, arm hooks, and radulae are occasionally found Fossil cephalopods are mainly known from preserved (Matern 1931; Mapes 1987; Fuchs 2006a; Landman et al. mineralized parts such as aragonitic phragmocones 2010; Kruta et al.
    [Show full text]
  • On Growth and Form of Irregular Coiled-Shell of a Terrestrial Snail: Plectostoma Concinnum (Fulton, 1901) (Mollusca: Caenogastropoda: Diplommatinidae)
    On growth and form of irregular coiled-shell of a terrestrial snail: Plectostoma concinnum (Fulton, 1901) (Mollusca: Caenogastropoda: Diplommatinidae) Thor-Seng Liew1,2,3 , Annebelle C.M. Kok1,2 , Menno Schilthuizen1,2,3 and Severine Urdy2,4,5 1 Institute Biology Leiden, Leiden University, Leiden, The Netherlands 2 Naturalis Biodiversity Center, Leiden, The Netherlands 3 Institute for Tropical Biology and Conservation, Universiti Malaysia Sabah, Jalan UMS, Kota Kinabalu, Sabah, Malaysia 4 Centrum Wiskunde & Informatica, Science Park, Amsterdam, The Netherlands 5 University of California San Francisco (UCSF), Anatomy Department, Genentech Hall, San Francisco, CA, United States ABSTRACT The molluscan shell can be viewed as a petrified representation of the organism’s on- togeny and thus can be used as a record of changes in form during growth. However, little empirical data is available on the actual growth and form of shells, as these are hard to quantify and examine simultaneously. To address these issues, we studied the growth and form of a land snail that has an irregularly coiled and heavily ornamented shell–Plectostoma concinnum. The growth data were collected in a natural growth experiment and the actual form changes of the aperture during shell ontogeny were quantified. We used an ontogeny axis that allows data of growth and form to be ana- lysed simultaneously. Then, we examined the association between the growth and the form during three diVerent whorl growing phases, namely, the regular coiled spire Submitted 14 March 2014 phase, the transitional constriction phase, and the distortedly-coiled tuba phase. In Accepted 25 April 2014 addition, we also explored the association between growth rate and the switching Published 15 May 2014 between whorl growing mode and rib growing mode.
    [Show full text]
  • Cephalopoda: Chiroteuthidae) Paralarvae in the Gulf of California, Mexico
    Lat. Am. J. Aquat. Res., 46(2): 280-288, 2018 Planctoteuthis paralarvae in the Gulf of California 280 1 DOI: 10.3856/vol46-issue2-fulltext-4 Research Article First record and description of Planctoteuthis (Cephalopoda: Chiroteuthidae) paralarvae in the Gulf of California, Mexico Roxana De Silva-Dávila1, Raymundo Avendaño-Ibarra1, Richard E. Young2 Frederick G. Hochberg3 & Martín E. Hernández-Rivas1 1Instituto Politécnico Nacional, CICIMAR, La Paz, B.C.S., México 2Department of Oceanography, University of Hawaii, Honolulu, USA 3Department of Invertebrate Zoology, Santa Barbara Museum of Natural History Santa Barbara, CA, USA Corresponding author: Roxana De Silva-Dávila ([email protected]) ABSTRACT. We report for the first time the presence of doratopsis stages of Planctoteuthis sp. 1 (Cephalopoda: Chiroteuthidae) in the Gulf of California, Mexico, including a description of the morphological characters obtained from three of the five best-preserved specimens. The specimens were obtained from zooplankton samples collected in oblique Bongo net tows during June 2014 in the southern Gulf of California, Mexico. Chromatophore patterns on the head, chambered brachial pillar, and buccal mass, plus the presence of a structure, possibly a photophore, at the base of the eyes covered by thick, golden reflective tissue are different from those of the doratopsis stages of Planctoteuthis danae and Planctoteuthis lippula known from the Pacific Ocean. These differences suggest Planctoteuthis sp. 1 belongs to Planctoteuthis oligobessa, the only other species known from the Pacific Ocean or an unknown species. Systematic sampling covering a poorly sampled entrance zone of the Gulf of California was important in the collection of the specimens. Keywords: Paralarvae, Planctoteuthis, doratopsis, description, Gulf of California.
    [Show full text]
  • Composition and Origin of Jurassic Ammonite Concretions at Gerzen, Germany
    JURASSIC AMMONITE CONCRETIONS COMPOSITION AND ORIGIN OF JURASSIC AMMONITE CONCRETIONS AT GERZEN, GERMANY. By MICHAEL DAVID GERAGHTY, B.Sc. A Thesis Submitted to the School of Graduate Studies in Partial Fulfilment of the Requirements for the Degree Master of Science McMaster University (c) Copyright by Michael David Geraghty, April 1990 MASTER OF SCIENCE (1990) McMaster University (Geology) Hamilton, Ontario TITLE: Composition and Origin of Jurassic Ammonite Concretions at Gerzen, Germany. AUTHOR: Michael David Geraghty, B. Sc. (University of Guelph) SUPERVISOR: Professor G.E.G. Westermann NUMBER OF PAGES: xiii, 154, 17 Figs., 10 Pls. ii ACKNOWLEDGEMENTS I would like to express my sincere gratitude to Dr. Gerd Westermann for allowing me the privilege of studying under his supervision on a most interesting research project. His advice, support and patience were greatly appreciated. I deeply indebted to Mr. Klaus Banike of Gottingen, F. R. Germany for opening his home and his collection of concretions to me and also for his help and friendship. To Erhardt Trute and Family of Gerzen, F.R. Germany, I owe many thanks for their warm hospitality and assistance with my field work. Also Dr. Hans Jahnke of Georg-August University, Gottingen deserves thanks for his assistance and guidance. Jack Whorwood's photographic expertise was invaluable and Len Zwicker did an excellent job of preparing my thin­ sections. Also, Kathie Wright did a great job helping me prepare my figures. Lastly, I would like to thank all those people, they know who they are, from whom I begged and borrowed time, equipment and advice. iii ABSTRACT Study of the ecology of concretion and host sediment fossils from a shell bed in middle Bajocian clays of northwestern Germany indicates a predominantly epifaunal suspension-feeding community living on a firm mud bottom.
    [Show full text]
  • 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.
    [Show full text]
  • 041-2011-Abstracts-BOE-III-Crete.Pdf
    Boreskov Institute of Catalysis of the Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia Institute of Cytology and Genetics of the Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia Borissiak Paleontological Institute of Russian Academy of Sciences, Moscow, Russia III International Conference “Biosphere Origin and Evolution” RETHYMNO, CRETE, GREECE OCTOBER 16-20, 2011 ABSTRACTS Novosibirsk, 2011 © Boreskov Institute of Catalysis, 2011 INTERNATIONAL SCIENTIFIC COMMITTEE Alexei Rozanov, Borissiak Paleontological Institute RAS, Moscow, Russia Co‐Chairman Georgii Zavarzin, Institute of Microbiology RAS, Moscow, Russia Co‐Chairman Vadim Agol Moscow State University, Russia Yury Chernov Severtsov Institute of Ecology and Evolution, Moscow, Russia Institute of Protein Research RAS, Pushchino, Moscow region, Alexander Chetverin Russia David Deamer Biomolecular Engineering, School of Engineering, Santa Cruz, USA V.S. Sobolev Institute of Geology and Mineralogy SB RAS, Nikolay Dobretsov Novosibirsk, Russia Mikhail Fedonkin Geological Institute RAS, Moscow, Russia Siegfried Franck Potsdam Institute for Climate Impact Research, Germany V.I. Vernadskii Institute of Geochemistry and Analytical Chemistry Eric Galimov RAS, Moscow, Russia Mikhail Grachev Limnological Institute SB RAS, Irkutsk, Russia Richard Hoover Nasa Marshall Space Flight Ctr., Huntsville, USA North‐Western Scientific Center RAS, St. Petersburg State Sergey Inge‐Vechtomov University, Russia Trofimuk Institute of Petroleum‐Gas Geology and Geophysics Alexander Kanygin SB RAS, Novosibirsk, Russia Astrospace Centre of Lebedev Physical Institute RAS, Moscow, Nikolay Kardashev Russia Józef Kaźmierczak Institute of Paleobiology PAN, Warsaw, Poland Nikolay Kolchanov Institute of Cytology and Genetics SB RAS, Novosibirsk, Russia Trofimuk Institute of Petroleum‐Gas Geology and Geophysics Alexei Kontorovich SB RAS, Novosibirsk, Russia National Center for Biotechnology Information, National Library Eugene V.
    [Show full text]
  • An Eocene Orthocone from Antarctica Shows Convergent Evolution of Internally Shelled Cephalopods
    RESEARCH ARTICLE An Eocene orthocone from Antarctica shows convergent evolution of internally shelled cephalopods Larisa A. Doguzhaeva1*, Stefan Bengtson1, Marcelo A. Reguero2, Thomas MoÈrs1 1 Department of Palaeobiology, Swedish Museum of Natural History, Stockholm, Sweden, 2 Division Paleontologia de Vertebrados, Museo de La Plata, Paseo del Bosque s/n, B1900FWA, La Plata, Argentina * [email protected] a1111111111 a1111111111 a1111111111 a1111111111 Abstract a1111111111 Background The Subclass Coleoidea (Class Cephalopoda) accommodates the diverse present-day OPEN ACCESS internally shelled cephalopod mollusks (Spirula, Sepia and octopuses, squids, Vampyro- teuthis) and also extinct internally shelled cephalopods. Recent Spirula represents a unique Citation: Doguzhaeva LA, Bengtson S, Reguero MA, MoÈrs T (2017) An Eocene orthocone from coleoid retaining shell structures, a narrow marginal siphuncle and globular protoconch that Antarctica shows convergent evolution of internally signify the ancestry of the subclass Coleoidea from the Paleozoic subclass Bactritoidea. shelled cephalopods. PLoS ONE 12(3): e0172169. This hypothesis has been recently supported by newly recorded diverse bactritoid-like doi:10.1371/journal.pone.0172169 coleoids from the Carboniferous of the USA, but prior to this study no fossil cephalopod Editor: Geerat J. Vermeij, University of California, indicative of an endochochleate branch with an origin independent from subclass Bactritoi- UNITED STATES dea has been reported. Received: October 10, 2016 Accepted: January 31, 2017 Methodology/Principal findings Published: March 1, 2017 Two orthoconic conchs were recovered from the Early Eocene of Seymour Island at the tip Copyright: © 2017 Doguzhaeva et al. This is an of the Antarctic Peninsula, Antarctica. They have loosely mineralized organic-rich chitin- open access article distributed under the terms of compatible microlaminated shell walls and broadly expanded central siphuncles.
    [Show full text]
  • 1540 Evans.Vp
    An early Silurian (Aeronian) cephalopod fauna from Kopet-Dagh, north-eastern Iran: including the earliest records of non-orthocerid cephalopods from the Silurian of Northern Gondwana DAVID H. EVANS, MANSOUREH GHOBADI POUR, LEONID E. POPOV & HADI JAHANGIR The cephalopod fauna from the Aeronian Qarebil Limestone of north-eastern Iran comprises the first comprehensive re- cord of early Silurian cephalopods from peri-Gondwana. Although consisting of relatively few taxa, the assemblage in- cludes members of the orders Oncocerida, Discosorida, Barrandeocerida and Orthocerida. Coeval records of several of these taxa are from low palaeolatitude locations that include Laurentia, Siberia, Baltica and Avalonia, and are otherwise unknown from peri-Gondwana until later in the Silurian. The cephalopod assemblage occurs in cephalopod limestones that currently represent the oldest record of such limestones in the Silurian of the peri-Gondwana margin. The appear- ance of these cephalopods, together with the development of cephalopod limestones may be attributed to the relatively low latitudinal position of central Iran and Kopet-Dagh compared with that of the west Mediterranean sector during the Aeronian. This, combined with the continued post-glacial warming after the Hirnantian glaciation, facilitated the initia- tion of carbonate deposition and conditions suitable for the development of the cephalopod limestones whilst permitting the migration of cephalopod taxa, many of which were previously restricted to lower latitudes. • Key words: Llandovery, Aeronian, Cephalopoda, palaebiogeography, peri-Gondwana. EVANS, D.H., GHOBADI POUR, M., POPOV,L.E.&JAHANGIR, H. 2015. An Early Silurian (Aeronian) cephalopod fauna from Kopet-Dagh, north-eastern Iran: including the earliest records of non-orthocerid cephalopods from the Silurian of Northern Gondwana.
    [Show full text]