Hostname: page-component-586b7cd67f-r5fsc Total loading time: 0 Render date: 2024-11-29T07:55:49.911Z Has data issue: false hasContentIssue false
  • English
  • Français

Graptolite ontogeny and the size of the graptolite zooid

Published online by Cambridge University Press:  01 May 2009

Susan Rigby  and
Margaret Sudbury
Susan Rigby
Affiliation:
Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK
Margaret Sudbury
Affiliation:
Thorpe Cottage, Chestnut Avenue, Thornton Dale, Pickering, N. Yorkshire YO18 7RW, UK
Get access Rights & Permissions [Opens in a new window]

Abstract

Two methods of estimating the size of the graptolite zooid are described and discussed. It is possible to size a zooid by reference to cortical bandages or with reference to modem Rhabdopleura and its tubes. These two methods give very different results, with the first suggesting small zooids relative to thecal size and the second suggesting zooids that filled their thecae completely. Comparison is made with the evidence available from rare cases of preserved zooids. When all these observations are considered in the light of the ontogeny of modem pterobranchs, an ontogenetic sequence for the graptolite zooid can be inferred which helps to reconcile the two methods of estimating zooid size. This sequence postulates that most skeletal building occurred early in the life of the zooid, before it developed the capacity to feed or to reproduce, and it implies that only the first of three stages in the zooid's life is recorded in the skeleton. The later stages occurred without normally leaving any trace on the preservable remains of the colony. Finally, there is discussion of the effects which different zooid sizes would have had on some aspects of the functional morphology of a theca and on the hydrodynamic behaviour of the rhabdosome as a whole.

Type
Articles
Information
Geological Magazine , Volume 132 , Issue 4 , July 1995 , pp. 427 - 433
Copyright
Copyright © Cambridge University Press 1995

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

Andres, D., 1980. Feinstrukturen und Verwandtschaftsbeziehungen der Graptolithen. Palaontologische Zeitschrift 54, 129–70.CrossRefGoogle Scholar
Bulman, O. M. B., 1970. Graptolithina with sections on Enteropneusta and Pterobranchia. In Treatise on Invertebrate Paleontology, pt V (2nd edition) (ed. Teichert, C.), pp. 1–161. Boulder, Colorado and Lawrence, Kansas: Geological Survey of America and University of Kansas Press.Google Scholar
Bulman, O. M. B. & Rickards, R. B., 1966. A revision of Wiman's dendroid and tuboid graptolites. Bulletin Geological Institutions, University of Uppsala 43, 1–72.Google Scholar
Crowther, P. R., 1981. The fine structure of graptolite periderm. Special Papers in Palaeontology 26, 1–119.Google Scholar
Crowther, P. R. & Rickards, R. B., 1977. Cortical bandages and the graptolite zooid. Geologica and Palaeontologica 11, 9–16.Google Scholar
Dilly, P. N., 1993. Cephalodiscus graptolitoides sp. nov.: a probable extant graptolite. Journal of the Zoological Society of London 229, 69–78.CrossRefGoogle Scholar
Durman, P. N. & Sennikov, N. V., 1993. A new rhabdopleurid hemichordate from the Middle Cambrian of Siberia. Palaeontology 36, 283–96.Google Scholar
Fortey, R. A. & Bell, A., 1987. Branching geometry and function of multiramous graptoloids. Paleobiology 13, 1–19.CrossRefGoogle Scholar
Fortey, R. A. & Cooper, R. A., 1986. A phylogenetic classification of the graptoloids. Palaeontology 29, 631–54.Google Scholar
Kirk, N. H., 1972. More thoughts on the automobility of the graptolites. Journal of the Geological Society 128, 127–33.CrossRefGoogle Scholar
Kirk, N. H., 1990. Juvenile sessility, vertical automobility, and passive lateral transport as factors in graptoloid evolution. Modern Geology 14, 153–87.Google Scholar
Kozlowski, R., 1949. Les Graptolithes et quelques nouveaux groupes d'animaux du Tremadoc de la Pologne. Palaeontologica Polonica 3, 1–235.Google Scholar
Lester, S. M., 1985. Cephalodiscus sp.; observations of functional morphology, behavior and occurrence in shallow water around Bermuda. Marine Biology 85, 263–8.CrossRefGoogle Scholar
Mitchell, C. E., 1987. Evolution and phylogenetic classification of the Diplograptacea. Palaeontology 17, 353–405.Google Scholar
Mitchell, C. E. & Carle, K. J., 1986. The nematularium of Pseudoclimacograptus scharenbergi (Lapworth) and its secretion. Palaeontology 29, 373–90.Google Scholar
Rickards, R. B., 1975. Palaeoecology of the Graptolithina, an extinct class of the phylum Hemichordata. Biological Reviews of the Cambridge Philosophical Society 50, 397–36.CrossRefGoogle Scholar
Rickards, R. B. & Dumican, L. W., 1984. The fibrillar component of the graptolite periderm. Irish Journal of Earth Sciences 6, 175–203.Google Scholar
Rickards, R. B. & Stait, B. A., 1984. Psigraptus, its classification, evolution and zooid. Alcheringa 8, 101–11.CrossRefGoogle Scholar
Rigby, S., 1993. Population analysis and orientation studies of graptoloids from the Middle Ordovician Utica Shale, Quebec. Palaeontology 36, 267–82.Google Scholar
Rigby, S., 1994 a. Erect tube growth in Rhabdopleura compacta (Hemichordata, Pterobranchia) from off Start Point, Devon. Journal of Zoology 233, 449–55.CrossRefGoogle Scholar
Rigby, S., 1994 b. Shared patterns of skeletal growth in Rhabdopleura (Hemichordata) and graptoloids (Hemichordata). Lethaia 27, 317–24.CrossRefGoogle Scholar
Rigby, S. & Dilly, P. N., 1993. Growth rates of pterobranchs and the lifespan of graptolites. Paleobiology 19, 459–75.CrossRefGoogle Scholar
Stebbing, A. R. D., 1970. Aspects of the reproduction and life cycle of Rhabdopleura compacta (Hemichordata). Marine Biology 5, 205–12.CrossRefGoogle Scholar
Sudbury, M., 1991. The dimensions of the graptolite zooid. Geological Magazine 128, 381–4.CrossRefGoogle Scholar
Towe, K. M. & Urbanek, A., 1972. Collagen like structures in Ordovician graptolite periderm. Nature 237, 443–5.CrossRefGoogle Scholar
Vogel, S., 1981. Life in moving fluids: the physical biology of flow. Boston, Massachusetts: Willard Grant Press, 361 pp.Google Scholar