Buttler and Wilson—Ordovician cave-dwelling bryozoans from Kentucky


575


Figure 7. Bioclaustration: (1) NMW 2017.9G.2.2, void with thickened wall overgrown by colony; (2) NMW 2017.9G.1.2, thickened wall grown around tubular structure. Longitudinal sections; scale bars=1mm.


In one specimen from Kentucky growing upwards on the exposed surface, brown deposits are found on the upper surfaces of diaphragms (Fig. 8). These do not have any indications of polypide anatomy similar to those recognized in other lower Paleozoic trepostomes from North America (Boardman, 1999).


Conclusions


Figure 8. NMW 2017.9G.3.2, Longitudinal section growing upwards showing the dark remains of organic material (black arrows) above diaphragms in zooecial chambers (white arrow indicating air bubbles). Longitudinal section; scale bar=1mm.


the category Impedichnia (Tapanila, 2005) because they impe- ded the normal growth of Stigmatella personata.


Organic remains


Remains found within the living chambers of Cincinnatian trepostomes have been interpreted as preserved indications of polypides. These were first identified by Cummings and Gallo- way in 1915, who recognized brown granular material that was present in autozooids, but never in mesopores. The degenerated cells that result from the normal degeneration-regeneration cycles of living bryozoan polypides are known as brown bodies (Boardman, 1999). The fossilized remains of organic material that may have been brown bodies are referred to as brown deposits (Boardman and Cheetham, 1983; Key et al., 2008).


This cave fauna is one of few submarine examples known in the Paleozoic. The distribution of organisms in and outside the caves supports the hypothesis that early cave-dwelling organ- isms were little differentiated from their exposed counterparts (see Taylor and Wilson, 2003). Mesozoic cave and other cavity faunas, in contrast, usually had distinct polarization between cryptic and exposed communities (Palmer and Fürsich, 1974; Palmer and Wilson, 1990; Taylor and Palmer, 1994; Wilson, 1998). This fauna represents a community of large bryozoan colonies bored by two distinct organisms, with symbionts growing on the surface and biofilms developing on the dead parts of the colony.


Acknowledgments


We thank A.J. Valentine-Baars (Amgueddfa Cymru) for pre- paring the thin sections and J. Turner (Amgueddfa Cymru) for assistance with photography. The Luce Fund at The College of Wooster generously provided funds for the fieldwork. M.M. Key Jr., P.N. Wyse Jackson, and A. Ernst provided very helpful reviews.


References


Boardman, R.S., 1999, Indications of polypides in feeding zooids and polymorphs in Lower Paleozoic Trepostomata (Bryozoa): Journal of Paleontology, v. 73, p. 803–815.


Boardman, R.S., and Cheetham, A.H., 1983, Glossary of morphologic terms, in Robison, R.A., ed., Treatise on Invertebrate Paleontology, Pt. G, Bryozoa,


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