Advertisement

Paläontologische Zeitschrift

, Volume 65, Issue 1–2, pp 141–151 | Cite as

Trilobite cuticle thickness in relation to palaeoenvironment

  • R. A. Fortey
  • N. V. Wilmot
Article

Abstract

100 thickness measurements from thin sections of cephala or pygidia of early Ordovician trilobites occurring across an onshore to offshore environmental gradient show that progressively greater maximum cuticle thickness was characteristic of increasingly inshore sites. There is a 40-fold difference between the thinnest and thickest cuticles, and exclusively thin cuticles are confined to the offshore Olenid Biofacies. Variability in cuticle thickness increases offshore to onshore. Environmental control is shown to be more influential on cuticle thickness than is the overall length of the trilobite: some comparatively large trilobites having thin cuticles and small trilobites thick cuticles. The environmental factors which might be responsible for the pattern are briefly discussed. The thin cuticles dominating the offshore Olenid Biofacies were probably appropriate for dysaerobic conditions. Thick cuticles in the most inshore biofacies may have offered protection against predators and turbulence, but the additional presence there of trilobites with thinner cuticles is considered to reflect the greater heterogeneity of the epeiric habitat.

Keywords

Cambrian Ordovician Stromatolite Biofacies Cuticle Thickness 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Kurzfassung

Die Dicke von 100 Kopf- oder Schwanzschilden frühordovizischer Trilobiten entlang eines Küsten-Schelf-Profiles wurden in Dünnschliffen gemessen. Dabei zeigte sich, daß mit zunehmender Küstennähe die Maximaldicke der Cuticulae zunahm. Die dicksten Cuticulae sind 40mal so dick wie die dünnsten; ausschließlich dünne Cuticulae kommen nur in der küstenfernen Oleniden-Biofazies vor. Die Variationsbreite der Cuticula-Dicke nimmt küstenwärts zu. Die Cuticula-Dicke wird mehr von Umweltfaktoren bestimmt als von der Länge des Trilobiten: Einige verhältnismäßig große Trilobiten besitzen eine dünne Cuticula, und kleine Trilobiten können eine dicke Cuticula haben. Die Milieufaktoren, die das Verteilungsmuster bestimmen, werden kurz diskutiert. Die dünnen Cuticulae, die in der küstenfernen Oleniden-Biofazies dominieren, waren wahrscheinlich eine Anpassung an dysaerobe Verhältnisse. Dicke Cuticulae in der küstennächsten Biofazies boten vermutlich Schutz gegen Räuber und starke Wasserbewegung. Die Tatsache, daß dort auch Trilobiten mit einer dünneren Cuticula vorkommen, läßt sich durch die größere Verschiedenartigkeit des flachen, küstennahen Lebensraums erklären.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Bergström, J. 1973. Organisation, life and systematics of trilobites. - Fossils & Strata2: 1–69, pls. 1-5, Oslo.Google Scholar
  2. Cook, H. E. &Taylor, M. E. 1975. Early Paleozoic continental margin sedimentation, trilobite biofacies and the thermocline, western U.S. - Geology3: 559–562, Boulder, Colo.CrossRefGoogle Scholar
  3. Dalingwater, J. E. 1973. Trilobite cuticle microstructure and composition. - Palaeontology16: 827–839, pls. 107–109, London.Google Scholar
  4. Dalingwater, J. E. &Miller, J. 1977. The laminae and cuticular organisation of the trilobiteAsaplms raniceps. -Palaeontology20: 21–32, pls. 9–10, London.Google Scholar
  5. Evitt, W. R. &Whittington, H. B. 1953. The exoskeleton ofFlexicalymene (Trilobita). -Journal of Paleontology27: 49–55, Tulsa, Oklahoma.Google Scholar
  6. Fortey, R. A. 1974. The Ordovician trilobites of Spitsbergen. I. Olenidae. - Norsk Polarinstitutt Skrifter Nr.160: 1–81, pls. 1–24, Oslo.Google Scholar
  7. — 1975a. Early Ordovician trilobite communities. - Fossils & Strata4: 331–352, Oslo.Google Scholar
  8. — 1975b. The Ordovician trilobites of Spitsbergen. II. Asaphidae, Nileidae, Raphiophondae and Telephinidae of the Valhallfonna Formation. - Norsk Polarinstitutt Skrifter Nr.162: 1–125, pls. 1–41, Oslo.Google Scholar
  9. — 1979. Early Ordovician trilobites from the Catoche Formation (St. George Group), western Newfoundland. -Geological Survey of Canada, Bulletin321: 61–114, Ottawa.Google Scholar
  10. — 1980a. The Ordovician trilobites of Spitsbergen. III. Remaining trilobites of the Valhallfonna Formation.- Norsk Polarinstitutt Skrifter. Nr.171: 1–113, pls. 1–25, Oslo.Google Scholar
  11. — 1980b. Generic longevity in Lower Ordovician trilobites: relation to environment. - Paleobiology6: 24–31, Chicago.Google Scholar
  12. — 1985. Pelagic trilobites as an example of deducing the life habits of extinct arthropods. - Royal Society of Edinburgh, Transactions76: 219–230, Edinburgh.Google Scholar
  13. Fortey, R. ä. &Clarkson, E. N. K. 1976. The function of the glabellar “tubercle” inNileus and other trilobites. - Lethaia9: 101–106, Oslo.CrossRefGoogle Scholar
  14. Henningsmoen, G. 1957. The trilobite family Olenidae. - Norske Videnskaps-Akademi i Oslo, Skrifter. 1. Matematisk-naturvidenskapehg klasse1: 1–303, Oslo.Google Scholar
  15. LUDVIGSEN, R. 1979. Middle Ordovician trilobite biofacies, southern MacKenzie Mountains. - Geological Association of Canada, Special Papers18: 1–37, Waterloo, Ontario.Google Scholar
  16. — 1982. Upper Cambrian and Lower Ordovician trilobite biostratigraphy of the Rabbitkettle Formation, western District of Mackenzie. - Royal Ontario Museum, Life Science Contributions.134: 1–188, 70 figs., Toronto.Google Scholar
  17. Miller, J. 1975. Structure and function of trilobite terrace lines. - Fossils & Strata4: 155–178, Oslo.Google Scholar
  18. — 1976. The sensory fields and life mode ofPhacops rana (Green 1832) (Trilobita). - Royal Society of Edinburgh Transactions69: 337–367, pls. 1–4, Edinburgh.Google Scholar
  19. Mutvei, H. 1981. Exoskeletal structure in the Ordovician trilobiteFlexicalymene. - Lethaia14: 225–234, Oslo.CrossRefGoogle Scholar
  20. Osmölska, H. 1975. Fine morphological characters of some Upper Palaeozoic trilobites. - Fossils & Strata4: 201–207, Oslo.Google Scholar
  21. Palmer, A. R. 1972. Problems of Cambrian biogeography. - 24th International Geological Congress, Section 7: 310–315, Montreal, Quebec.Google Scholar
  22. Shaw, F. C. 1968. Early Middle Ordovician Chazy trilobites of New York. - New York State Museum of Natural History, Memoirs17: 1–114, 24 pls., Albany, N. Y.Google Scholar
  23. Størmer, L. 1930. Scandinavian Trinucleidae, with special reference to Norwegian species and varieties. - Norske Videnskaps-Akademie i Oslo, Skrifter, Matematisk-naturvidenskapelig klasse 1930 (4): 1–111, Oslo.Google Scholar
  24. — 1980. Sculpture and microstructure of the exoskeleton in chasmopinid and phacopid trilobites. -Palaeontology23: 237–271, pls. 25–34, London.Google Scholar
  25. Teigler, D. J. &TOWE, K. M. 1975. Microstructure and composition of the trilobite exoskeleton. -Fossils & Strata4: 137–149, pls. 1–9, Oslo.Google Scholar
  26. Whittington, H. B. 1963. Middle Ordovician trilobites from Lower Head, western Newfoundland. - Museum of Comparative Zoology Harvard University, Bulletin129: 1–118, 36 pls., Cambridge, Massachusetts.Google Scholar
  27. Wilmot, N. V. 1988. Design and function of trilobite exoskeletons.- Unpublished PhD thesis. University of Aston in Birmingham. 207 pp., Birmingham.Google Scholar
  28. Wilmot, N. V. &Fallick, A. E. 1989. Original mineralogy of trilobite exoskeletons. - Palaeontology32: 297–304, London.Google Scholar

Copyright information

© E. Schweizerbart’sche Verlagsbuchhandlung 1991

Authors and Affiliations

  • R. A. Fortey
    • 1
  • N. V. Wilmot
    • 1
  1. 1.Department of PalaeontologyBritish Museum(Natural History)LondonEngland

Personalised recommendations