Hostname: page-component-78c5997874-fbnjt Total loading time: 0 Render date: 2024-11-19T05:36:31.511Z Has data issue: false hasContentIssue false
  • English
  • Français

A new approach using high-resolution computed tomography to test the buoyant properties of chambered cephalopod shells

Published online by Cambridge University Press:  23 February 2015

Robert Lemanis ,
Stefan Zachow ,
Florian Fusseis  and
René Hoffmann
Robert Lemanis
Affiliation:
Institute of Geology Mineralogy, and Geophysics, Ruhr Universität Bochum, Bochum 44801, Germany. E-mail: [email protected], [email protected]
Stefan Zachow
Affiliation:
Department of Scientific Visualization and Data Analysis, Zuse Institute, Berlin 14195, Germany. E-mail: [email protected]
Florian Fusseis
Affiliation:
School of Geosciences, University of Edinburgh, Edinburgh, U.K. E-mail: [email protected]
René Hoffmann
Affiliation:
Institute of Geology Mineralogy, and Geophysics, Ruhr Universität Bochum, Bochum 44801, Germany. E-mail: [email protected], [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

The chambered shell of modern cephalopods functions as a buoyancy apparatus, allowing the animal to enter the water column without expending a large amount of energy to overcome its own weight. Indeed, the chambered shell is largely considered a key adaptation that allowed the earliest cephalopods to leave the ocean floor and enter the water column. It has been argued by some, however, that the iconic chambered shell of Paleozoic and Mesozoic ammonoids did not provide a sufficiently buoyant force to compensate for the weight of the entire animal, thus restricting ammonoids to a largely benthic lifestyle reminiscent of some octopods. Here we develop a technique using high-resolution computed tomography to quantify the buoyant properties of chambered shells without reducing the shell to ideal spirals or eliminating inherent biological variability by using mathematical models that characterize past work in this area. This technique has been tested on Nautilus pompilius and is now extended to the extant deep-sea squid Spirula spirula and the Jurassic ammonite Cadoceras sp. hatchling. Cadoceras is found to have possessed near-neutral to positive buoyancy if hatched when the shell possessed between three and five chambers. However, we show that the animal could also overcome degrees of negative buoyancy through swimming, similar to the paralarvae of modern squids. These calculations challenge past inferences of benthic life habits based solely on calculations of negative buoyancy. The calculated buoyancy of Cadoceras supports the possibility of planktonic dispersal of ammonite hatchlings. This information is essential to understanding ammonoid ecology as well as biotic interactions and has implications for the interpretation of geochemical data gained from the isotopic analysis of the shell.

Type
Articles
Information
Paleobiology , Volume 41 , Issue 2 , March 2015 , pp. 313 - 329
Copyright
Copyright © 2015 The Paleontological Society. All rights reserved. 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Literature Cited

Abel, R. L., Laurini, C. R., and Richter, M.. 2012. A palaeobiologist’s guide to “virtual”micro-CT preparation. Palaeontologia Electronica 15:6T.Google Scholar
Arnold, J. M., Landman, N. H., and Mutvei, H.. 2010. Development of the embryonic shell of Nautilus. Pp. 373–400in W. Bruce Saunders and Neil H. Landman, eds. Springer Netherlands.Google Scholar
Bandel, K. 1982. Morphologie und Bildung der frühontogenetischen Gehäuse bei conchiferen Mollusken. Facies 7(1): 1–197.Google Scholar
Bandel, K., and Boletzky, S.. 1979. A comparative study of the structure, development, and morphological relationships of chambered cephalopod shells. Veliger 21:313–354.Google Scholar
Bartol, I. K., Krueger, P. S., Stewart, W. J., and Thompson, J. T.. 2009. Pulsed jet dynamics of squid hatchlings at intermediate Reynolds numbers. Journal of Experimental Biology 212:1506–1518.CrossRefGoogle ScholarPubMed
Boletzky, S. 2002. Yolk sac morphology in cephalopod embryos. In H. Summesberger, K. Histon, and H. E. A. Daurer, eds. Cephalopods—present and past. Abhandlungen der Geologischen Bundesanstalt 57:57–68.Google Scholar
Bruun, A. F. 1943. The biology of Spirula spirula (L.). Dana Report 24:1–48.Google Scholar
Calow, S. 1987. Fact and theory—an overview. Pp. 351–365in P. R. Boyle, ed. Cephalopod life cycles, Vol. II. Comparative reviews. Academic Press, London.Google Scholar
Chamberlain, J. A. 1976. Flow patterns and drag coefficient of cephalopod shells. Palaeontology 19:539–563.Google Scholar
Chamberlain, J. A 1981. Hydromechanical design of fossil cephalopods. In M. R. House, and J. R. Senior, eds. The Ammonoidea. Systematics Association Special Volume 18:289–336. Academic Press, New York.Google Scholar
Chamberlain, J. A 1993. Locomotion in ancient seas: constraint and opportunity in cephalopod adaptive design. Geobios 26:49–61.Google Scholar
Chamberlain, J. A 2010. Locomotion of Nautilus. Pp. 489–525 in Saunders and Landman 2010.CrossRefGoogle Scholar
Chun, C. 1915. Die Cephalopoden: Myopsida, Octopoda. Pp. 405–522. in Wissenschaftliche Ergebnisse Der Deutschen Tiefsee-Expedition, “Valdivia” 1898–1899, Vol. 18. Gustav Fischer, Jena.Google Scholar
Crick, R. E. 1988. Buoyancy regulation and macroevolution in nautiloid cephalopods. Senckenbergiana Lethaea 69:2.Google Scholar
Cunningham, J. A., Rahman, I. A., Lautenschlager, S., Rayfield, E. J., and Donoghue, P. C. J.. 2014. A virtual world of paleontology. Trends in Ecology and Evolution 29:6.Google Scholar
Currie, E. D. 1957. The mode of life of certain goniatites. Transactions of the Geological Society of Glasgow 22:169–186.Google Scholar
Daniel, T. L., Helmuth, B. S., Saunders, W. B., and Ward, P. D.. 1997. Septal complexity in ammonoid cephalopods increased mechanical risk and limited depth. Paleobiology 23:470–481.Google Scholar
Davis, R. A. 2010. Nautilus studies—the first twenty-two centuries. Pp. 3–21 in Saunders and Landman 2010.Google Scholar
De Baets, K., Klug, C., Korn, D., and Landman, N. H.. 2012. Early evolutionary trends in ammonoid embryonic development. Evolution 66:1788–1806.Google Scholar
Delanoy, G., Magnin, A., Selebran, M., and Selebran, J.. 1991. Moutoniceras nodosum d’Orbigny, 1850 (Ammonoidea, Ancyloceratina) une très grande ammonite heteromorphe du Barremien inferieur. Revue de Paleobiologie 10:229–245.Google Scholar
Denton, E. J., and Gilpin-Brown, J. B.. 1966. On the buoyancy of the pearly Nautilus. Journal of the Marine Biological Association of the United Kingdom 46:723–759.Google Scholar
Denton, E. J., and Gilpin-Brown, J. B.. 1973. Floatation mechanisms in modern and fossil cephalopods. Advances in Marine Biology 11:197–268.Google Scholar
Derham, W. 1726. Philosophical experiments and observations of the late eminent Dr. Robert Hooke, S.R.S. and Geom. Prof. Gresh., and other eminent virtuoso’s in his time. W. Derham, London.Google Scholar
Diener, C. 1912. Lebensweise und Verbreitung der Ammoniten. Neues Jahrbuch für Mineralogie, Geologie und Paläontologie 192:67–89.Google Scholar
Dietl, G. 1978. Die heteromorphen Ammoniten des Dogger (Stratigraphie, Taxonomie, Phylogenie, Ökologie). Stuttgarter Beiträge zur Naturkunde B 33:1–97.Google Scholar
Drushchits, V. V., Doguzhayeva, L. A., and Lominadze, T. A.. 1977. Internal structural features of the shell of middle Callovian ammonites. Paleontological Journal 1977(3): 16–29.Google Scholar
Ebel, K. 1983. Berechnungen zur schwebefähigkeit von ammoniten. Neues Jahrbuch für Geologie und Paläontologie, Monatshefte 1983:614–640.Google Scholar
Ebel, K 1990. Swimming abilities of ammonites and limitations. Palaeontologische Zeitschrift 64:25–38.Google Scholar
Ebel, K 1992. Mode of life and soft body shape of heteromorph ammonites. Lethaia 25:179–193.Google Scholar
Ebel, K 1999. Hydrostatics of fossil ectocochleate cephalopods and its significance for the reconstruction of their lifestyle. Paläontologische Zeitschrift 73:277–288.Google Scholar
Engeser, T. 1996. The position of the Ammonoidea within the Cephalopoda. Pp. 3–19 in Landman et al. 1996b.Google Scholar
Engeser, T., and Keupp, H.. 2002. Phylogeny of the aptychi-possessing Neoammonoidea (Aptychophora nov., Cephalopoda). Lethaia 35:79–96.Google Scholar
Frech, F. 1915. Loses und geschlossenes Gehäuse der tetrabranchiaten Cephalopoden. Centralblatt für Mineralogie, Geologie und Paläontologie 16:593–606.Google Scholar
Greenwald, L., and Ward, P. D.. 2010. Buoyancy in Nautilus. Pp. 547–560 in Saunders and Landman 2010.Google Scholar
Harries, P. J., Kauffman, E. G., and Hansen, T. A.. 1996. Models for biotic survival following mass extinction. In M. B. Hart, ed. Biotic recovery from mass extinction events. Geological Society of London Special Publication 102:41–60.Google Scholar
Hassan, M. A., Westermann, G. E. G., Hewitt, R. A., and Dokainish, M. A.. 2002. Finite-element analysis of simulated ammonoid septa (extinct Cephalopoda): septal and sutural complexities do not reduce strength. Paleobiology 28:113–126.Google Scholar
Haury, L., and Weihs, D.. 1976. Energetically efficient swimming behavior of negatively buoyant zooplankton. Limnology and Oceanography 21:797–803.Google Scholar
Heptonstall, W. B. 1970. Buoyancy control in ammonoids. Lethaia 3:317–328.Google Scholar
Hewitt, R. A., Westermann, G. E. G., and Checa, A.. 1993. Growth rates of ammonites estimated from aptychi. Geobios Mémoire Special (Villeurbanne) 15:203–208.Google Scholar
Higashiura, K., and Okamoto, T.. 2012. Life orientation of heteromorph ammonites under the negatively buoyant condition: a case study on the Eubostrychoceras muramotoi Matsumoto. Fossils (Kaseki) 92:19–30.Google Scholar
Hoffmann, R., and Zachow, S.. 2011. Non-invasive approach to shed new light on the buoyancy business of chambered cephalopods (Mollusca). IAMG 2011 Publication. doi: 10.5242.iamg.2011.0163.Google Scholar
Hoffmann, R., Schultz, J. A., Schellhorn, R., Rybacki, E., Keupp, H., Gerden, S. R., Lemanis, R., and Zachow, S.. 2014. Non-invasive imaging methods applied to neo- and paleo-ontological cephalopod research. Biogeosciences 11:2721–2739.Google Scholar
House, M. R. 1965. A study in the Tornoceratidae: the succession of Tronoceras and related genera in the North American Devonian. Philosophical Transactions of the Royal Society of London B 250:79–130.Google Scholar
House, M. R 1985. The ammonoid time-scale and ammonoid evolution. Geological Society of London Memoirs 10:273–283.Google Scholar
House, M. R 1996. Juvenile goniatites survival strategies following Devonian extinction events. In M. B. Hart, ed. Biotic recovery from mass extinction events. Geological Society of London Special Publication. 102:163–185.Google Scholar
Jacobs, D. K. 1992. Shape, drag, and power in ammonoid swimming. Paleobiology 18:203–220.Google Scholar
Jacobs, D. K., and Chamberlain, J.. 1996. Buoyancy and hydrodynamics in ammonoids. Pp. 169–224 in Landman et al. 1996b.Google Scholar
Jacobs, D. K., and Landman, N. H.. 1993. Nautilus—a poor model for the function and behavior of ammonoids. Lethaia 26:101–111.Google Scholar
Klinger, H. C. 1981. Speculations on buoyancy control and ecology in some heteromorph ammonites. In M. R. House and J. R. Senior, eds. The Ammonoidea. Systematics Association Special Volume 18: 337–355. Academic Press, New York.Google Scholar
Klug, C., and Korn, D.. 2004. The origin of ammonoid locomotion. Acta Palaeontologica Polonica 49:235–242.Google Scholar
Korn, D., Hopkins, M. J., and Walton, S. A.. 2013. Extinction space—a method for the quantification and classification of changes in morphospace across extinction boundaries. Evolution 67:2795–2810.Google ScholarPubMed
Kröger, B. 2001. Comments on Ebel’s benthic-crawler hypothesis for ammonoids and extinct nautiloids. Paläontologische Zeitschrift 75:123–125.CrossRefGoogle Scholar
Kröger, B 2002. On the efficiency of the buoyancy apparatus in ammonoids: evidences from sublethal shell injuries. Lethaia 35:61–70.Google Scholar
Kröger, B., Vinther, J., and Fuchs, D.. 2011. Cephalopod origin and evolution: a congruent picture emerging from fossils, development and molecules. Bioessays 33:602–613.Google Scholar
Kruta, I., Landman, N., Rouget, I., Cecca, F., and Tafforeau, P.. 2011. The role of ammonites in the Mesozoic marine food web revealed by jaw preservation. Science 331:70–72.Google Scholar
Kruta, I., Landman, N. H., and Cochran, J. K.. 2014. A new approach for the determination of ammonite and nautilid habitats. PLoS ONE 9:e87479.Google Scholar
Kulicki, C., and Wierzbowski, H.. 1983. The Jurassic juvenile ammonites of the Jagua Formation, Cuba. Acta Palaeontologica Polonica 28(3–4), 369–384.Google Scholar
LaBarbera, M. 2008. Hydrodynamics. Pp. 322–326in D. E. G. Briggs, and P. R. Crowther, eds. Palaeobiology II. Blackwell Science, Oxford.Google Scholar
Landman, N. H., Tanabe, K., and Shigeta, Y.. 1996a. Ammonoid embryonic development. Pp. 343–405 in Landman et al. 1996b.Google Scholar
Landman, N. H., Tanabe, K., and Davis, R. A. eds. 1996b. Ammonoid paleobiology. Plenum, New York.Google Scholar
Lehmann, W. M. 1932. Stereo-Röntgenaufnahmen als Hilfsmittel bei der Untersuchung von Versteinerungen. Natur und Museum 62:323–330.Google Scholar
Longridge, L. M., Smith, P. L., Rawlings, G., and Klaptocz, V.. 2009. The impact of asymmetries in the elements of the phragmocone of Early Jurassic ammonites. Palaeontologia Electronica 12:15.Google Scholar
Lukeneder, A., Harzhauser, M., Muelleffer, S. S., and Piller, W. E.. 2010. Ontogeny and habitat change in Mesozoic cephalopods revealed by stable isotopes (δ18O, δ13C). Earth and Planetary Science Letters 296:103–114.Google Scholar
Manger, W., Stephen, D., and Meeks, L.. 1999. Possible cephalopod reproductive mass mortality reflected by Middle Carboniferous assemblages, Arkansas, southern United States. Pp. 345–364in F. Oloriz and F. Rodriguez-Tovar, eds. Advancing research on living and fossil cephalopods. Kluwer Academic/Plenum, New York.Google Scholar
Mapes, R. H., and Nützel, A.. 2009. Late Palaeozoic mollusc reproduction: cephalopod egg-laying behavior and gastropod larval palaeobiology. Lethaia 42:341–356.Google Scholar
Martins, R. S., Roberts, M. J., Lett, C., Chang, N., Moloney, C.L., Camargo, M. G., and Vidal, E. A. G.. 2013. Modelling transport of chokka squid (Loligo reynaudii) paralarvae off South Africa: reviewing, testing and extending the “westward transport hypothesis”. Fisheries Oceanography 23:116–131.Google Scholar
Matsumoto, T., and Obata, I.. 1962. Notes on Baculites facies. Kaseki 3:57–63.Google Scholar
Meister, C., and Piuz, A.. 2013. Late Cenomanian–Early Turonian ammonites of the southern Tethys margin from Morocco to Oman: biostratigraphy, paleobiogeography and morphology. Cretaceous Research 44:83–103.Google Scholar
Monks, N., and Young, J. R.. 1998. Body position and the functional morphology of Cretaceous Heteromorph ammonites. Palaeontologia Electronica 1:15.Google Scholar
Monnet, C., De Baets, K., and Klug, C.. 2011. Parallel evolution controlled by adaptation and covariation in ammonoid cephalopods. BMC Evolutionary Biology 11:115.Google Scholar
Moreno-Bedmar, J. A., Barragán Manzo, R., Company Sempere, M., and Bulot, L. G.. 2013. Aptian (lower Cretaceous) ammonite biostratigraphy of the Francisco Zarco Dam stratigraphic section (Durango State, northeast Mexico). Journal of South American Earth Sciences 42:150–158.CrossRefGoogle Scholar
Moriya, K., Nishi, H., Kawahata, H., Tanabe, K., and Takayanagi, Y.. 2003. Demersal habitat of Late Cretaceous ammonoids: evidence from oxygen isotopes for the Campanian (Late Cretaceous) northwestern Pacific thermal structure. Geology 31:167–170.Google Scholar
Moseley, H. 1838. On the geometrical forms of turbinated and discoid shells. Philosophical Transactions of the Royal Society of London 128:351–370.Google Scholar
Mutvei, H. 1983. Flexible nacre in the nautiloid Isorthoceras, with remarks on the evolution of cephalopod nacre. Lethaia 16:233–240.Google Scholar
Mutvei, H., and Dunca, E.. 2007. Connecting ring ultrastructure in the Jurassic ammonoid Quenstedtoceras with discussion on mode of life of ammonoids. Pp. 239–256in N. H. Landman, R. A. Davis, and R. H. Mapes, eds. Cephalopods present and past: new insights and fresh perspectives. Springer, Dordrecht.CrossRefGoogle Scholar
Naglik, C., Monnet, C., Goetz, S., Kolb, C., De Baets, K., Tajika, A., and Klug, C.. 2014. Growth trajectories of some major ammonoid sub-clades revealed by serial grinding tomography data. Lethaia. doi: 10.1111/let.12085.Google Scholar
O’dor, R., Wells, J., and Wells, M. J.. 1990. Speed, jet pressure and oxygen consumption relationships in free-swimming Nautilus. Journal of Experimental Biology 154:383–396.Google Scholar
Okamoto, T. 1988. Changes in life orientation during the ontogeny of some heteromorph ammonoids. Palaeontology 31:281–294.Google Scholar
Okamoto, T 1996. Theoretical modeling of ammonoid morphology. Pp. 225–251 in Landman et al. 1996b.Google Scholar
Parent, H., Westermann, G. E. G., and Chamberlain, J. A. Jr. 2014. Ammonite aptychi: functions and role in propulsion. Geobios 47:45–55.Google Scholar
Raup, D. M. 1967. Geometric analysis of shell coiling: coiling in ammonoids. Journal of Paleontology 41:43–65.Google Scholar
Raup, D. M., and Chamberlain, J. A. Jr. 1967. Equations for volume and center of gravity in ammonoid shells. Journal of Paleontology 41:566–574.Google Scholar
Raven, J. A., and Waite, A. M.. 2004. The evolution of silicification in diatoms: inescapable sinking and sinking as escape? New Phytologist 162:45–61.Google Scholar
Rein, S. 1999. On the swimming abilities of Ceratites De Haan and Germanonautilus Mojsisovics from the Upper Muschelkalk (Middle Triassic). Freiberger Forschungsheft 481:39–47.Google Scholar
Reyment, R. A. 1958. Some factors in the distribution of fossil cephalopods. Stockholm Contributions in Geology 1:97–184.Google Scholar
Reyment, R. A 1980. Floating orientations of cephalopod shell models. Palaeontology 23:931–936.Google Scholar
Rieppel, O. 2002. Feeding mechanics in Triassic stem-group sauropterygians: the anatomy of a successful invasion of Mesozoic seas. Zoological Journal of the Linnean Society 135:33–63.Google Scholar
Ritterbush, K. A., and Bottjer, D. J.. 2012. Westermann morphospace displays ammonoid shell shape and hypothetical paleoecology. Paleobiology 38:424–446.Google Scholar
Ritterbush, K. A., Hoffmann, R., Lukeneder, A., and De Baets, K.. 2014. Pelagic palaeoecology: the importance of recent constraints on ammonoid palaeobiology and life history. Journal of Zoology 292:229–241.Google Scholar
Rouget, I., and Neige, P.. 2001. Embryonic ammonoid shell features: intraspecific variation revisited. Palaeontology 44:53–64.Google Scholar
Sato, T., and Tanabe, K.. 1998. Cretaceous plesiosaurs ate ammonites. Nature 394:629–630.Google Scholar
Saunders, W. B., and Landman, N. H., eds. 2010. Nautilus: the biology and paleobiology of a living fossil. Plenum, New York.Google Scholar
Shevyrev, A. A. 2005. Heteromorph ammonoids of the Triassic: a review. Paleontological Journal 39 (Suppl 5):614–628.Google Scholar
Shigeta, Y. 1993. Post-hatching early life history of Cretaceous Ammonoidea. Lethaia 26:133–145.Google Scholar
Staaf, D. J., Gilly, W. F., and Denny, M. W.. 2014. Aperture effects in squid jet propulsion. Journal of Experimental Biology 217:1588–1600.Google Scholar
Stock, S. R. 2008. Microcomputed tomography: methodology and applications. CRC Press, Boca Raton, Fla.Google Scholar
Sutton, M., Rahman, I., and Garwood, R.. 2013. Techniques for virtual palaeontology. Wiley, Chichester, U.K.Google Scholar
Tajika, A., and Wani, R.. 2011. Intraspecific variation of hatchling size in Late Cretaceous ammonoids from Hokkaido, Japan: implication for planktic duration at early ontogenetic stage. Lethaia 44:287–298.Google Scholar
Tajika, A., Naglik, C., Morimoto, N., Pascual-Cebrian, E., Hennhöfer, D., and Klug, C.. 2014. Empirical 3-D model of the conch of the Middle Jurassic ammonite microconch Normannites: its buoyancy, the physical effects of its mature modifications and speculations on their function. Historical Biology (in press).Google Scholar
Tanabe, K. 1975. Functional morphology of Otoscaphites puerculus (Jimbo), an Upper Cretaceous ammonite. Transactions and Proceedings of the Palaeontological Society of Japan, new series 99:109–132.Google Scholar
Tanabe, K 1979. Palaeoecological analysis of ammonoid assemblages in the Turonian Scaphites facies of Hokkaido, Japan. Palaeontology 22:609–630.Google Scholar
Tanabe, K 2011. The feeding habits of ammonites. Science 331:37–38.Google Scholar
Tanabe, K., Shigeta, Y., and Mapes, R. H.. 1995. Early life history of Carboniferous ammonoids inferred from analysis of shell hydrostatics and fossil assemblages. Palaios 10:80–86.Google Scholar
Tanabe, K., Landman, N. H., and Kruta, I.. 2012. Microstructure and mineralogy of the outer calcareous layer in the lower jaws of Cretaceous Tetragonitoidea and Desmoceratoidea (Ammonoidea). Lethaia 45:191–199.Google Scholar
Teichert, C. 1967. Major features of cephalopod evolution. Pp. 162–210in C. Teichert and E. L. Yochelson, eds. Essays in paleontology and stratigraphy: R. C. Moore commemorative volume. University of Kansas Press, Lawrence.Google Scholar
Thompson, d’A. W. 1917. On growth and form. Cambridge University Press, Cambridge.Google Scholar
Trueman, A. E. 1941. The ammonite body-chamber, with special reference to the buoyancy and mode of Life of the living ammonite. Quarterly Journal of the Geological Society 96:339–383.Google Scholar
Walton, S. A., Korn, D., and Klug, C.. 2010. Size distribution of the Late Devonian ammonoid Prolobites: indication for possible mass spawning events. Swiss Journal of Geosciences 103:475–494.Google Scholar
Ward, P. D. 1987. The natural history of Nautilus. Allen and Unwin, Boston.Google Scholar
Ward, P. D., and Bandel, K.. 1987. Life history strategies in fossil cephalopods. Pp. 329–350in P. R. Boyle, ed. Cephalopod life cycles, Vol. II. Academic Press, London.Google Scholar
Ward, P. D., and Westermann, G. E. G.. 1976. Sutural inversion in a heteromorph ammonite and its implication for septal formation. Lethaia 9:357–361.Google Scholar
Ward, P. D., and Westermann, G. E. G.. 1977. First occurrence, systematics, and functional morphology of Nipponites (Cretaceous Lytoceratina) from the Americas. Journal of Paleontology 51:367–372.Google Scholar
Ward, P. D., Stone, R., Westermann, G. E. G., and Martin, A.. 1977. Notes on animal weight, cameral fluids, swimming speed, and color polymorphism of the cephalopod Nautilus pompilius in the Fiji Islands. Paleobiology 3:377–388.Google Scholar
Warnke, K., and Keupp, H.. 2005. Spirula—a window to the embryonic development of ammonoids? Morphological and molecular indications for a palaeontological hypothesis. Facies 51:60–65.Google Scholar
Westermann, G. E. G. 1993. On alleged negative buoyancy of ammonoids. Lethaia 26:246–246.Google Scholar
Westermann, G. E. G 1996. Ammonoid life and habitat. Pp. 607–707 in Landman et al. 1996b.Google Scholar
Westermann, G. E. G 1999. Life habits of nautiloids. Pp. 263–298in E. Savazzi, ed. Functional morphology of the invertebrate skeleton. Wiley, Chichester, U.K.Google Scholar
Westermann, G. E. G 2013. Hydrostatics, propulsion and life habits of the Cretaceous ammonoid Baculites. Revue de Paléobiologie 32:249–265.Google Scholar
Westermann, G. E. G., and Tsujita, C. J.. 1999. Life habits of ammonoids. Pp. 299–325in E. Savazzi, ed. Functional morphology of the invertebrate skeleton. Wiley, Chichester, U.K.Google Scholar
Wetzel, W.. 1959. Über Ammoniten-Larven. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen 107:240–252.Google Scholar
Wilga, C. D., and Lauder, G. V.. 2002. Function of the heterocercal tail in sharks: quantitative wake dynamics during steady horizontal swimming and vertical maneuvering. Journal of Experimental Biology 205:2365–2374.Google Scholar
Wright, J. K. 2012. Ammonites. Geology Today 28:186–191.Google Scholar