The Päärdu hardground from the Telychian (Rumba Formation) of western Estonia is sparsely encrusted (0.4% of the studied surface) by possible tabulate corals, sheet-like bryozoans and discoidal echinoderm holdfasts. Both the upper and cryptic sides of the hardground are intensely bioeroded by Trypanites borings. The taxonomic composition of the Päärdu hardground association is rather different from the characteristic Silurian association in being dominated by tabulate corals, while bryozoans and echinoderms played a minor role in the association. The Päärdu hardground is more sparsely encrusted than common for the Late Ordovician and Silurian hardgrounds, but this may be a characteristic feature of the hardgrounds of Baltica. The Päärdu hardground is important among the Silurian hardgrounds because it has unusually low encrustation combined with high bioerosion.
Alvarez, F. & Taylor, P. D. 1987. Epizoan ecology and interactions in the Devonian of Spain. Palaeogeography, Palaeoclimatology, Palaeoecology, 61, 17–31.
http://dx.doi.org/10.1016/0031-0182(87)90039-3
Brett, C. E. & Brookfield, M. E. 1984. Morphology, faunas and genesis of Ordovician hardgrounds from southern Ontario, Canada. Palaeogeography, Palaeoclimatology, Palaeoecology, 46, 233–290.
http://dx.doi.org/10.1016/0031-0182(84)90001-4
Brett, C. E. & Cottrell, J. F. 1982. Substrate specificity in the Devonian tabulate coral Pleurodictyum. Lethaia, 15, 247–262.
http://dx.doi.org/10.1111/j.1502-3931.1982.tb00648.x
Brett, C. E. & Liddell, W. D. 1978. Preservation and paleoecology of a Middle Ordovician hardground community. Paleobiology, 4, 329–348.
Cherns, L. 1980. Hardgrounds in the Lower Leintwardine Beds (Silurian) of the Welsh Borderland. Geological Magazine, 117, 311–326.
http://dx.doi.org/10.1017/S0016756800032556
Cornell, S. R., Brett, C. E. & Sumrall, C. D. 2003. Paleoecology and taphonomy of an edrioasteroid-encrusted hardground association from tentaculitid limestones in the Early Devonian of New York: a Paleozoic rocky peritidal community. PALAIOS, 18, 212–224.
http://dx.doi.org/10.1669/0883-1351(2003)018<0212:PATOAE>2.0.CO;2
Einasto, R. 1964. On the classification and formation of discontinuity surfaces. In Litologiya Paleozojskikh otlozhenij Éstonii [Lithology of Palaeozoic Deposits of Éstonia] (Baukov, S. S., ed.), pp. 121–131. Institute of Geology AN ESSR, Tallinn [in Russian, with English summary].
Franzén, C. 1977. Crinoid holdfasts from the Silurian of Gotland. Lethaia, 10, 219–234.
http://dx.doi.org/10.1111/j.1502-3931.1977.tb00617.x
Halleck, M. S. 1973. Crinoids, hardgrounds, and community succession: the Silurian Laurel–Waldron contact in southern Indiana. Lethaia, 6, 239–252.
http://dx.doi.org/10.1111/j.1502-3931.1973.tb01197.x
Hints, O. 2008. The Silurian system in Estonia. In The Seventh Baltic Stratigraphical Conference. Abstracts and Field Guide (Hints, O., Ainsaar, L., Männik, P. & Meidla, T., eds), p. 46. Geological Society of Estonia, Tallinn.
Kesling, R. V., Hoare, R. D. & Sparks, D. K. 1980. Epizoans of the Middle Devonian brachiopod Paraspirifer bownockeri: their relationships to one another and to their host. Journal of Paleontology, 54, 1141–1154.
Lescinsky, H. L., Edinger, E. & Risk, M. J. 2002. Mollusc shell encrustation and bioerosion rates in a modern epeiric sea: taphonomy experiments in the Java Sea, Indonesia. PALAIOS, 17, 171–191.
http://dx.doi.org/10.1669/0883-1351(2002)017<0171:MSEABR>2.0.CO;2
Melchin, M. J., Cooper, R. A. & Sadler, P. M. 2004. The Silurian Period. In A Geologic Time Scale (Gradstein, F. M., Ogg, J. G. & Smith, A. G., eds), pp. 188–201. Cambridge University Press.
Nestor, H. & Einasto, R. 1977. Model of facies and sedimentology for Paleobaltic epicontinental basin. In Facies and Fauna of the Baltic Silurian (Kaljo, D. L., ed.), pp. 89–121. Institute of Geology AN ESSR, Tallinn [in Russian, with English summary].
Nield, E. W. 1984. The boring of Silurian stromatoporoids towards an understanding of larval behavior in the Trypanites organism. Palaeogeography, Palaeoclimatology, Palaeoecology, 48, 229–243.
http://dx.doi.org/10.1016/0031-0182(84)90046-4
Palmer, T. 1982. Cambrian to Cretaceous changes in hardground communities. Lethaia, 15, 309–323.
http://dx.doi.org/10.1111/j.1502-3931.1982.tb01696.x
Raukas, A. & Teedumäe, A. 1997. Geology and Mineral Resources of Estonia. Estonian Academy Publishers, Tallinn, 436 pp.
Stanley, S. M. 2006. Influence of seawater chemistry on biomineralization throughout Phanerozoic time: paleontological and experimental evidence. Palaeogeography, Palaeoclimatology, Palaeoecology, 232, 214–236.
http://dx.doi.org/10.1016/j.palaeo.2005.12.010
Sullivan, N. B., Brett, C. E., McLaughlin, P. I., Kleffner, M. A. & Cramer, B. D. 2014. Correlation of the Waco Member of the Alger Shale Formation (Silurian; Llandovery; Telychian) in east-central Kentucky and south-central Ohio. GFF, 136, 254–258.
http://dx.doi.org/10.1080/11035897.2013.876657
Sumrall, C. D., Brett, C. E. & McKinney, M. L. 2009. A new agelacrinitid edrioasteroid attached to a large hardground clast from the McKenzie Member of the Mifflintown Member (Silurian) of Pennsylvania. Journal of Paleontology, 83, 794–803.
http://dx.doi.org/10.1666/08-096.1
Tapanila, L., Copper, P. & Edinger, E. 2004. Environmental and substrate control on Paleozoic bioerosion in corals and stromatoporoids, Anticosti Island, Eastern Canada. PALAIOS, 19, 292–306.
http://dx.doi.org/10.1669/0883-1351(2004)019<0292:EASCOP>2.0.CO;2
Taylor, P. D. & Wilson, M. A. 2003. Palaeoecology and evolution of marine hard substrate communities. Earth Science Reviews, 62, 1–103.
http://dx.doi.org/10.1016/S0012-8252(02)00131-9
Thomka, J. R. & Brett, C. E. 2014. Taphonomy of diploporite (Echinodermata) holdfasts from a Silurian hardground, southeastern Indiana, United States: palaeoecologic and stratigraphic significance. Geological Magazine, 151, 649–665.
http://dx.doi.org/10.1017/S001675681300068X
Thomka, J. R. & Brett, C. E. 2015. Paleoecology of pelmatozoan attachment structures from a hardground surface in the middle Silurian Massie Formation, southeastern Indiana. Palaeogeography, Palaeoclimatology, Palaeoecology, 420, 1–12.
http://dx.doi.org/10.1016/j.palaeo.2014.12.001
Vinn, O. 2006. Two new microconchid (Tentaculita Bouček 1964) genera from the Early Palaeozoic of Baltoscandia and England. Neues Jahrbuch für Geologie und Paläontologie, Monatshefte, 2006, 89–100.
Vinn, O. & Toom, U. 2015. Some encrusted hardgrounds from the Ordovician of Estonia (Baltica). Carnets de Géologie, 15, 63–70.
http://dx.doi.org/10.4267/2042/56744
Vinn, O. & Wilson, M. A. 2010. Microconchid-dominated hardground association from the late Pridoli (Silurian) of Saaremaa, Estonia. Palaeontologia Electronica, 13.2.9A.
Vinn, O. & Wilson, M. A. 2012a. Encrustation and bioerosion on late Sheinwoodian (Wenlock, Silurian) stromatoporoids from Saaremaa, Estonia. Carnets de Géologie, CG2012_A07.
Vinn, O. & Wilson, M. A. 2012b. Epi- and endobionts on the late Silurian (early Pridoli) stromatoporoids from Saaremaa Island, Estonia. Annales Societatis Geologorum Poloniae, 82, 195–200.
Vinn, O., Wilson, M. A. & Toom, U. 2015. Bioerosion of inorganic hard substrates in the Ordovician of Estonia (Baltica). PLOS ONE, 10(7), e0134279.
http://dx.doi.org/10.1371/journal.pone.0134279
Wilson, M. A. & Palmer, T. J. 1992. Hardgrounds and hardground faunas. University of Wales, Aberystwyth, Institute of Earth Studies Publications, 9, 1–131.
Wilson, M. A. & Palmer, T. J. 2006. Patterns and processes in the Ordovician Bioerosion Revolution. Ichnos, 13, 109–112.
http://dx.doi.org/10.1080/10420940600850505
Wilson, M. A., Palmer, T. J., Guensburg, T. E., Finton, C. D. & Kaufman, L. E. 1992. The development of an Early Ordovician hardground community in response to rapid sea-floor calcite precipitation. Lethaia, 25, 19–34.
http://dx.doi.org/10.1111/j.1502-3931.1992.tb01789.x
Zatoń, M. & Vinn, O. 2011. Microconchids and the rise of modern encrusting communities. Lethaia, 44, 5–7.
http://dx.doi.org/10.1111/j.1502-3931.2010.00258.x
Zatoń, M., Borszcz, T., Berkowski, B., Rakociński, M., Zapalski, M. K. & Zhuravlev, A. V. 2015. Paleoecology and sedimentary environment of the Late Devonian coral biostrome from the Central Devonian Field, Russia. Palaeogeography, Palaeoclimatology, Palaeoecology, 424, 61–75.
http://dx.doi.org/10.1016/j.palaeo.2015.02.021
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