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The clymeniid dilemma: functional implications of the dorsal siphuncle in clymeniid ammonoids

  • William E. Gottobrio (a1) and W. Bruce Saunders (a1)


Clymeniid ammonoids appeared during the Late Devonian (Mid-Famennian) and quickly radiated before becoming extinct at the Devonian/Carboniferous boundary. Outwardly indistinguishable from other ammonoids, clymeniids are distinguished internally by their dorsal siphuncle, contrasted to a ventral siphuncle in almost all other ammonoids. Comparisons of a sample of Clymeniida (n = 22 genera), Goniatitida (n = 33), Prolecanitida (n = 12), and Anarcestida (n = 13) indicate that clymeniids fall within the range of other ammonoids in terms of shell geometry and suture complexity, but their siphuncles average two to three times larger and clymeniid shells are approximately 33% thicker than those of other ammonoids. Although a dorsal siphuncle would be about 50% smaller in surface area and volume than if located in a ventral position, the enlarged clymeniid siphuncle partially and, in some cases, fully compensated for this loss. Hydrostatic simulations of 15 clymeniid genera indicate that their thicker (therefore heavier) shells would have resulted in relatively short body chambers (≈280°) and high aperture orientations (≈90°). In static life-position, these orientations would have placed the dorsal clymeniid siphuncle at or near the bottom of the most recently formed chambers, seemingly an ideal location for draining liquid from the chamber. Migration of the siphuncle to the dorsal side of the shell occurs suddenly during early ontogeny (within the first two or three chambers), and mutation of homeotic gene expression is offered as a possible explanation for the sudden shift. A dorsal siphuncle may have resulted in selection for enlarged siphuncles, but this may have incurred loss of strength against hydrostatic pressure (thereby reducing depth limits) and thus rendered the clade more susceptible to the multiple eustatic and anoxic events that marked the end of the Devonian.



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Averof, M., and Patel, N. H. 1997. Crustacean appendage evolution associated with changes in Hox gene expression. Nature 288:682686.
Becker, R. T. 1993. Anoxia, eustatic changes, and Upper Devonian to lowermost Carboniferous global ammonoid diversity. In House, M. R., ed. The Ammonoidea: environment, ecology, and evolutionary change. Systematics Association Special Volume 47:115163. Clarendon, Oxford.
Becker, R. T., and House, M. R. 1994. Kellwasser Events and goniatite successions in the Devonian of the Montagne Noire with comments on possible causations. Courier Forschungsinstitut Senckenberg 169:4577.
Bogoslovsky, B. I. 1962. Systematic section, Devonian Ammonoidea. Pp. 334347in Ruzhencev, 1962.
Bogoslovsky, B. I. 1969. Devonskie Ammonoidei. I. Agoniatity. Akademiya Nauk SSSR, Paleontologicheskogo Instituta, Trudy 124:1341.
Bogoslovsky, B. I. 1971. Devonskie Ammonoidei. II. Goniatity. Akademiya Nauk SSSR, Paleontologicheskogo Instituta, Trudy 127:1228.
Bogoslovsky, B. I. 1976. Early ontogeny and origin of clymeniid ammonoids. Paleontological Journal 1976:150158. (Translated by the American Geological Institute.)
Bogoslovsky, B. I. 1981. Devonskie Ammonoidei. III. Klimeny. Akademiya Nauk SSSR, Paleontologicheskogo Instituta, Trudy 191:1122.
Chamberlain, J. A. Jr., and Moore, W. A. Jr. 1982. Rupture strength and flow rate of Nautilus siphuncular tube. Paleobiology 8:408425.
Czarnocki, J. 1989. Klimenie Gór Świętokrzyskich. Wyndawnictwa Geologiczne, Warsaw.
Denton, E., and Gilpin-Brown, J. 1966. On the buoyancy of the pearly Nautilus. Journal of the Marine Biological Association of the United Kingdom 46:723759.
Doguzhaeva, L. 1988. Siphuncular tube and septal necks in ammonoid evolution. Pp. 291301in Wiedmann, J. and Kullmann, J., eds. Cephalopods present and past. E. Schweizerbart, Stuttgart.
House, M. R. 1980. On the origin, classification and evolution of the early Ammonoidea. In House, M. R. and Senior, J. R., eds. The Ammonoidea: the evolution, classification, mode of life, and geological usefulness of a major fossil group. Systematics Association Special Volume 18:336. Academic Press, New York.
House, M. R. 1985. Correlation of mid-Paleozoic ammonoid evolutionary events with global sedimentary perturbations. Nature 313:1722.
House, M. R. 1996. Juvenile goniatite survival strategies following Devonian extinction events. In Hart, M. B., ed. Biotic recovery from mass extinction events. Geological Society of London Special Publication 102:163185.
Jacobs, D. K. 1996. Chambered cephalopod shells, buoyancy, structure, and decoupling: history and red herrings. Palaios 11:610614.
JMP. 2002. Version 5. Statistics and graphics guide. SAS Institute, Cary, N.C. (
Korn, D. 1992. Relationship between shell form, septal construction and suture line in clymeniid cephalopods (Ammonoidea; Upper Devonian). Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 185:115130.
Korn, D., and Klug, C. 2002. Ammoneae Devonicae. Pp. 1375in Riegraf, W., ed. Fossilium Catalogus, Animalia I. Backhuys, Leiden.
Korn, D., and Klug, C. 2003. Morphological pathways in the evolution of Early and Middle Devonian ammonoids. Paleobiology 29:329348.
Kullmann, J., Korn, D., and Peterson, M. S. 2001. GONIAT database system, Version 3.0. Tübingen.
Lee, P. N., Callaerts, P., de Couet, H. G., and Martindale, M. Q. 2003. Cephalopod Hox genes and the origin of morphological novelties. Nature 424:10611065.
Marshall, C. R., Orrs, H. A., and Patel, N. H. 1999. Morphological innovation and developmental genetics. Proceedings of the National Academy of Sciences USA 96:99959996.
Miller, A. K., and Unklesbay, A. G. 1943. The siphuncle of late Paleozoic ammonoids. Journal of Paleontology 17:125.
Miller, A. K., Furnish, W. M., and Schindewolf, O. H. 1957. Paleozoic Ammonoidea. Pp. L11L79in Arkell, W. J. et al. Mollusca 4, Cephalopoda, Ammonoidea. Part L ofMoore, R. C., ed. Treatise on invertebrate paleontology. Geological Society of America, New York, and University of Kansas, Lawrence.
Nikolaeva, S. V., and Bogoslovsky, B. I.In press. Late Devonian ammonoids of the South Urals and Middle Asia. Paleontologicheskogo Instituta, Trudy. [In Russian.]
Raup, D. M. 1967. Geometric analysis of shell coiling: coiling in ammonoids. Journal of Paleontology 41:4365.
Raup, D. M., and Chamberlain, J. A. 1967. Equations for volume and center of gravity in ammonoid shells. Journal of Paleontology 41:566574.
Ruzhencev, V. E. 1962. Superorder Ammonoidea. Pp. 243424in Orlov, Yu. A., ed. Fundamentals of paleontology, Vol. 5. Mollusca-Cephalopoda 1. Akademiya Nauk SSSR, Moscow. (Translated by the Israel Program for Scientific Translations, Jerusalem, 1974.)
Saunders, W. B. 1995. The ammonoid suture problem: relationships between shell and septum thickness and suture complexity in Paleozoic ammonoids. Paleobiology 21:343355.
Saunders, W. B., and Shapiro, E. A. 1986. Calculation and simulation of ammonoid hydrostatics. Paleobiology 12:6479.
Saunders, W. B., and Work, D. M. 1997. Evolution of shell morphology and suture complexity in Paleozoic prolecanitids, the rootstock of Mesozoic ammonoids. Paleobiology 23:301325.
Saunders, W. B., Work, D. M., and Nikolaeva, S. V. 1999. Evolution of complexity in Paleozoic ammonoid sutures. Science 286:760763.
Saunders, W. B., Work, D. M., and Nikolaeva, S. V. 2004. The evolutionary history of shell geometry in Paleozoic ammonoids. Paleobiology 30:1943.
Sokal, R. R., and Rohlf, F. J. 1995. Biometry: the principles and practice of statistics in biological research, 3d ed.W. H. Freeman, New York.
Swan, A. R. H., and Saunders, W. B. 1987. Function and shape in late Paleozoic (mid-Carboniferous) ammonoids. Paleobiology 13:297311.
Tanabe, K., and Landman, N. H. 1996. Septal neck-siphuncular complex of ammonoids. In Landman, N. H., Tanabe, K., and Davis, R. A., eds. Ammonoid paleobiology. Topics in Geobiology 13:129165. Plenum, New York.
Tanabe, K., Mapes, R. H., Sasaki, T., and Landman, N. H. 2000. Soft-part anatomy of the siphuncle in Permian prolecanitid ammonoids. Lethaia 33:8391.
Ward, P. D. 1987. The natural history of Nautilus. Allen and Unwin, Boston.
Westermann, G. E. G. 1971. Form, structure, and function of shell and siphuncle in coiled Mesozoic ammonoids. Life Sciences Contributions Royal Ontario Museum 78:139.


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