Skip to main content Accessibility help
×
Home

Skeletal microstructure and mode of attachment in Palaeacis species (Anthozoa: Tabulata) from the Mississippian and Pennsylvanian of northeastern Oklahoma and northwestern Arkansas

  • Gregory E. Webb (a1)

Abstract

Three species of the Paleozoic coral Palaeacis are described from northeastern Oklahoma and northwestern Arkansas. Included are the Chesterian species P. carinata Girty and P. snideri n. nom., a replacement name for the junior homonym P. cuneata Snider, and the Desmoinesian? species P. erecta n. sp. Coralla of each species exhibit two types of microstructure that characterize two skeletal zones. The outer skeletal zone is composed of numerous parallel trabeculae, mostly between 0.2 and 0.3 mm in diameter, that lie perpendicular to, and have their accretionary surfaces on, the exterior surface of the corallum. Trabeculae are closely spaced laterally and are not organized into rows except uncommonly on the distal portion of some coralla. Where trabeculae coalesce into parallel rows, ornamentation on the corallum exterior consists of parallel ridges or rows of small nodes. Where trabeculae are irregularly arranged, external ornamentation consists of irregularly disposed nodes. The inner skeletal zone consists of radially fibrous stereoplasm arranged into discrete septal spines that coalesce into irregularly developed septal ridges in each calice. In P. erecta, septal spines merge into continuous layers of fibro-normal stereoplasm in some places. On the basis of microstructure, corallum morphology, and external ornamentation P. carinata and P. snideri can be allied with P. axinoides Smyth and P. robusta Webb. Palaeacis erecta falls within the same group on the basis of microstructure and ornament, but has a unique corallum morphology.

Two distinct types of skeletal attachment occur in these Palaeacis species. Palaeacis carinata and P. snideri exhibit an encrusting attachment surface that results in a prostrate growth habit wherein smaller substrates were entirely engulfed, producing free-living coralla. Palaeacis erecta exhibits a small, circular attachment surface and an erect growth habit wherein most skeletal accretion occurs perpendicular to, and away from, the substrate. The substrate is not engulfed and the corallum remains attached and sessile throughout astogeny. Palaeacis erecta is, to date, the only Palaeacis species known to possess this erect, sessile growth form.

Copyright

References

Hide All
Bassler, R. S. 1950. Faunal lists and descriptions of Paleozoic corals. Geological Society of America Memoir 44, 315 p.
Chudinova, I. I. 1976. Pervaya nakhodka Palaeacis (Tabulata) kirgone verkhoyan'ya. Paleontologicheski Zhurnal, 1976(3):3035.
Conkin, J. E., Bratcher, T. M., and Conkin, B. M. 1978. Palaeacis obtusa (Meek and Worthen), 1860, emended: its morphology, ontogeny, and stratigraphic significance. University of Louisville Studies in Paleontology and Stratigraphy, 7, 27 p.
Girty, G. H. 1910. New genera and species of Carboniferous fossils from the Fayetteville shale of Arkansas. New York Academy of Science Annals, 20:189238.
Huffman, G. G. 1958. Geology of the flanks of the Ozark Uplift. Oklahoma Geological Survey Bulletin 77, 281 p.
ICZN. 1985. International Code of Zoological Nomenclature. International Trust for Zoological Nomenclature (with the British Museum, Natural History, London) and University of California Press, Berkeley, 3rd ed., 338 p.
Jeffords, R. M. 1955. Mississippian corals from New Mexico and a related Pennsylvanian species. University of Kansas Paleontological Contributions, Coelenterata 3, 12 p.
McGugan, A. 1983. First record and a new species of Palaeacis Haime, 1857 from the Mississippian of western Canada. Journal of Paleontology, 57:4247.
Meek, F. B., and Worthen, A. H. 1860. Descriptions of new Carboniferous fossils from Illinois and other western states. Proceedings of the Academy of Sciences of Philadelphia, 1860:447448.
Milne-Edwards, H. 1857. Histoire naturelle des coralliaires ou polypes proprement dits. Atlas. Roret, Paris, 11 p.
Milne-Edwards, H., and Haime, J. 1850. A monograph of the British fossil corals. First part: introduction. Palaeontographical Society Monograph, London, 71 p.
Moore, R. C., and Jeffords, R. M. 1945. Descriptions of Lower Pennsylvanian corals from Texas and adjacent states. University of Texas Publication, 4401:63208.
Nudds, J. R. 1983. The Carboniferous coral Palaeacis in Ireland. Palaeontology, 26:211225.
Pilcher, R. C. 1975. Intraspecific variation in Palaeacis, a Carboniferous tabulate coral. Geological Society of America Abstracts with Programs, 7:226.
Plusquellec, Y., Lafuste, J., and Webb, G. E. 1990. Organisation de type tétracoralliaire des rides septales de Palaeacis (Cnidaria, Carbonifère). Lethaia, 23:385397.
Roemer, C. F. 1883. Lethaea geognostica, Theil 1: Lethaea palaeozoica, Part 2. Schweizerbart, Stuttgart, p. 113544.
Sando, W. J. 1969. Revision of some of Girty's invertebrate fossils from the Fayetteville Shale (Mississippian) of Arkansas and Oklahoma—corals. U.S. Geological Survey Professional Paper, 606-B:914.
Smyth, L. B. 1929. On the structure of Palaeacis . Scientific Proceedings of the Royal Dublin Society, 19:125138.
Snider, L. C. 1915. The paleontology of the Chester Group in Oklahoma. Oklahoma Geological Survey Bulletin, 24:67122.
Sutherland, P. K., and Manger, W. L. (eds.). 1977. Mississippian–Pennsylvanian boundary in northeastern Oklahoma and northwestern Arkansas. Oklahoma Geological Survey Guidebook, 18, 185 p.
Tourneur, F. J., Lafuste, J. G., and Plusquellec, Y. 1991. Trachypsammia Gerth 1921: morphology, microstructure and systematic affinities. Abstracts VI. International Symposium on Fossil Cnidaria including Archaeocyatha and Porifera:89.
Webb, G. E. 1989. Skeletal structure and microstructure in Visean Palaeacis from Queensland. Memoir of the Association of Australasian Palaeontologists, 8:199206.
Webb, G. E. 1990. Lower Carboniferous coral fauna of the Rockhampton Group, east-central Queensland. Memoir of the Association of Australasian Palaeontologists, 10:1167.

Related content

Powered by UNSILO

Skeletal microstructure and mode of attachment in Palaeacis species (Anthozoa: Tabulata) from the Mississippian and Pennsylvanian of northeastern Oklahoma and northwestern Arkansas

  • Gregory E. Webb (a1)

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed.