Hostname: page-component-cd9895bd7-8ctnn Total loading time: 0 Render date: 2024-12-20T05:51:37.507Z Has data issue: false hasContentIssue false
  • English
  • Français

Independent testing of a paleobiological hypothesis: the optical design of two Ordovician pelagic trilobites reveals their relative paleobathymetry

Published online by Cambridge University Press:  20 May 2016

Tim McCormick  and
Richard A. Fortey
Tim McCormick
Affiliation:
Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom. E-mail: timm@nhm.ac.uk and raf@nhm.ac.uk
Richard A. Fortey
Affiliation:
Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom. E-mail: timm@nhm.ac.uk and raf@nhm.ac.uk
Get access Rights & Permissions [Opens in a new window]

Abstract

Evidence that can be used to interpret the life habits of extinct organisms usually takes three forms: functional analysis, analogy with living organisms, and geological evidence. Independent quantitative tests for habit are rarely available. A theory of optimum eye design originally derived for living aquatic arthropods provides quantitative data that are used to test previous suppositions about the life habits of two Ordovician pelagic trilobites: that the telephinid trilobite Carolinites was epipelagic while the cyclopygid Pricyclopyge was mesopelagic. Optimum compound eye design theory uses measured lens diameters and interommatidial angles to determine the “eye parameter” (p), which can be used to gauge approximate optimum level of illumination for the eyes of these trilobites. The eye parameter provides an independent test for their relative paleobathymetry. Values of the eye parameter measured in the dorso-ventral direction across two eyes of Carolinites killaryensis utahensis were found to have medians of 2.13 and 3.24. Values measured in the antero-posterior direction have medians of 3.17 and 4.86 for the two eyes. Values measured in the dorso-ventral direction across two eyes of Pricyclopyge binodosa have medians of 4.23 and 4.98, while values measured in the antero-posterior direction have medians of 7.06 and 8.31. Eye parameters are higher in Pricyclopyge than in Carolinites, the difference statistically significant at p = 0.05. The eyes of Pricyclopyge are optimally designed for lower levels of illumination than are those of Carolinites. This accords with the previous interpretations of the former trilobite as mesopelagic and the latter as epipelagic.

Type
Articles
Information
Paleobiology , Volume 24 , Issue 2 , Spring 1998 , pp. 235 - 253
Copyright
Copyright © The Paleontological Society 

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

Clarkson, E. N. K. 1966. Schizochroal eyes and vision in some phacopid trilobites. Palaeontology 9: 464–487.Google Scholar
Clarkson, E. N. K. 1975. The evolution of the eye in trilobites. Fossils and Strata 4: 7–31.Google Scholar
Clarkson, E. N. K. 1979. The visual system of trilobites. Palaeontology 22: 1–22.Google Scholar
Cocks, L. R. M. and Fortey, R. A. 1990. Lower Palaeozoic facies and faunas around Gondwana. Pp. 183–200. Audley-Charles, M. G., Hallam, A.Gondwana and Tethys Geological Society of London Special Publication No. 37. London.Google Scholar
Fordyce, D. and Cronin, T. W. 1989. Comparison of fossilized schizochroal compound eyes of phacopid trilobites with eyes of modern marine crustaceans and other arthropods. Journal of Crustacean Biology 9: 554–569.Google Scholar
Fordyce, D. 1993. Trilobite vision: a comparison of schizochroal and holochroal eyes with the compound eyes of modern arthropods. Paleobiology 19: 288–303.Google Scholar
Fortey, R. A. 1974. A new pelagic trilobite from the Ordovician of Spitsbergen western Ireland and Utah. Palaeontology 17: 11–124.Google Scholar
Fortey, R. A. 1975a. The Ordovician trilobites of Spitsbergen. II. Asaphidae, Nileidae, Raphiophoridae and Telephinidae of the Valhallfonna Formation Norsk Polarinstitutt Skrifter. 162: 1–207.Google Scholar
Fortey, R. A. 1975b. Early Ordovician trilobite communities. Fossils and Strata 4: 339–360.Google Scholar
Fortey, R. A. 1985. Pelagic trilobites as an example of deducing the life habits of extinct arthropods. Transactions of the Royal Society of Edinburgh: Earth Sciences 76: 219–230.Google Scholar
Fortey, R. Aamd R. M. Owens 1987. The Arenig Series in South Wales: stratigraphy and palaeontology. I. The Arenig Series in South Wales Bulletin of the British Museum (Natural History) Geology. 41: 69–307.Google Scholar
Fortey, R. A. 1990. Trilobites. Pp. 121–142. McNamara, K. J.Evolutionary trends Belhaven, London.Google Scholar
Grant, R. E. 1975. Methods and conclusions in functional analysis: a reply. Lethaia 8: 31–34.Google Scholar
Horridge, G. A. 1977. Insects which turn and look. Endeavour (new series) 1: 7–17.Google Scholar
Kirk, N. H. 1969. Some thoughts on the ecology, mode of life, and evolution of the Graptolithina. Proceedings of the Geological Society of London 1659: 273–292.Google Scholar
Kirk, N. H. 1972. Some thoughts on the construction of the rhabdosome in the Graptolithina, with special reference to extrathecal tissue and its bearing on the theory of automobility. University College of Wales Department of Geology Publications. 1: 1–21.Google Scholar
Kirk, N. H. 1975. More thoughts on the construction and functioning of the rhabdosome in the Graptoloidea in the light of their ultrastructure. University College of Wales Department of Geology Publications. 7: 1–24.Google Scholar
Marek, L. 1961. The trilobite family Cyclopygidae Raymond in the Ordovician of Bohemia. Rozpravy Ústredního ústavu geologického 28: 1–83.Google Scholar
Marshall, N. B. 1979. Developments in deep-sea biology. Blandford, Poole, England.Google Scholar
McNamara, K. J. 1980. Evolutionary trends and their functional significance in chasmopine trilobites. Lethaia 13: 61–78.Google Scholar
Purnell, M. A. 1995. Microwear in conodont elements and macrophagy in the first vertebrates. Nature 374: 798–800.Google Scholar
Rickards, R. B. 1975. Palaeoecology of the Graptolithina an extinct class of the phylum Hemichordata. Biological Reviews 50: 397–436.Google Scholar
Rudwick, M. J. S. 1961. The feeding mechanism of the Permian brachiopod Prorichthofenia. Palaeontology 3: 450–471.Google Scholar
Shergold, J. H. and Laurie, J. R. 1996. Early Ordovician trilobite taxonomy and biostratigraphy of the Emanuel Formation Canning Basin Western Australia Part 1. Palaeontographica A 240: 65–103.Google Scholar
Snyder, A. W. 1977. Acuity of compound eyes: physical limitations and design. Journal of Comparative Physiology A 116: 161–182.Google Scholar
Snyder, A. W., Stavenga, G., and Laughlin, S. B. 1977. Spatial information capacity of compound eyes. Journal of Comparative Physiology A 116: 183–207.Google Scholar
Stockton, W. L. and Cowen, R. 1976. Stereoscopic vision in one eye: paleophysiology of the schizochroal eye of trilobites. Paleobiology 2: 304–315.Google Scholar