Aulacera plummeri (1843)
Ordovician - Indiana
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Stromatoporoid - Aulacera plummeri (1843)
Ordovician - Cincinnatian Series - Maquoketa Group - Dillsboro, Indiana
Measures 9" x 2.5" x 1.5"
Special thanks to Scott Morrison for the images and documentation on his very interesting fossil.
These organisms, looking like weathered fence posts, belong to Aulacera. They are unusual because the knobby surface texture is preserved as well as the pronounced longitudinal ridges. The largest Aulacera found is two metres long but, in life, they may have stood erect and five metres high. This would make these stromatoporoids the tallest organic constructions in the Ordovician seas.
Royal BC Museum - www.livinglandscapes.bc.ca/cbasin/fossils/deep_time.html
I appreciate seeing those photos of the fragmentary tree trunk-like skeletons of cylindrical stromatoporoid sponges from the Late Ordovician of southeastern Indiana. These are probably best assigned to the genus Aulacera of the Family Aulaceratidae (Order Labechiida). I suggest they are from the Ordovician because in other occurrences where good stratigraphic records exist (especially Anticosti Island in Eastern Canada), in North America, Siberia, Novaya Zembla (Arctic Russia), China and Tasmania, they are never found in the Silurian. Indeed they are widely believed to have become extinct during the major Ordovician-Silurian mass-extinction event.
Use of the generic name Aulacera Plummeri 1843 is preferred on grounds of priority over Beatricea Billings 1857. Even Schuchert's (1919) sketch of Plummer's original specimen (from Indiana) shows the prominent spiraling longitudinal ridges that your specimens display and they occur in the type species A. plummeri Galloway & St Jean, 1957 (see illustration in J.J. Galloway's 1957 paper). There are some other species, like A. radiata and A.undulata, that also exhibit the prominent longitudinal ridges. More work needs to be done on the taxonomy of the cylindrical Aulaceras. Paul Copper (Laurentian University, Sudbury, Canada) has the best collections and plans to describe the taxonomy of the Anticosti faunas. In places on Anticosti they form "fossil forests". See also Stearn et al. (1999).
The Treatise, part E (sponge) volume that includes the section on the Class Stromatoporoidea is now being edited and will hopefully be published in a year or so (Webby, in preparation).
Cameron, D. and Copper, P., 1994, "Paleoecology of giant Late Ordovician cylindrical sponges from Anticosti, E Canada", in van Soest, R.W.M., van Kempem, T.M.G. and Braekman, J.-C. (eds.); Sponges in Time and Space; AA Balkema Co., Rotterdam and Brookfield, Vermont, p.13-21.
Galloway, J.J., 1957, Structure and classification of the Stromatoporoidea; Bulletin of American Paleontology, vol. 37 (No.164), 141 p. [see p. 470 and Plate 37, fig. 1a, for illustration of A. plummeri].
Stearn, C.W., Webby, B.D., Nestor, H.and Stock, C.W., 1999, Revised classification and terminology of Palaeozoic stromatoporoids; Acta Palaeontologica Polonica, vol. 44, n. 1, p. 1-70.
Webby, B.D. (Coordinating Author) Porifera (Revised), vol. 4: Hypercalcified Porifera (chiefly Stromatoporoids, Chaetetids, and Archaeocyathids) In Preparation: Winter 2009/Spring 2010.
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