The early Palaeozoic order Ascocerida is a group of morphologically unique and rare cephalopods known from the Ordovician and Silurian rocks of Avalonia, Baltica, Laurentia and Perunica. The limited Estonian record of Silurian ascocerids is complemented with a specimen from the Pähkla locality (Island of Saaremaa; Paadla Regional Stage, Ludlow Series) representing the stratigraphically oldest known occurrence of ascocerids in the Silurian of Estonia. The strata that were formerly exposed in Pähkla are likely correlated to the Hemse Group of the Island of Gotland (Sweden) having a remarkable record of ascocerids. The appearance of Silurian ascocerids in Estonia is confined to a time interval when the group had the highest species diversity and the widest geographic dispersion, reaching also outside Baltica for the first time.
Ault, C. H. & Carr, D. D. 1978. Thick high-purity limestone and dolomite in Carroll County, Indiana. Proceedings of Indiana Academy of Sciences, 87, 282–291.
Barrande, J. 1855. Sur les Ascoceras. Prototype des Nautilides. Bulletin de la Societé Géologique de France, 2, 157–177.
Barrande, J. 1865. Système silurien du centre de la Bohême, I.ère partie: Recherches Paléontologiques, Vol. II, Céphalopodes, pls 1–107.
Barrande, J. 1867. Système silurien du centre de la Bohême 2, Céphalopodes, texte, pt. 1. 1–712.
Barrande, J. 1877. Système silurien du centre de la Bohême, I.ère partie: Recherches Paléontologiques, Vol. II, Classe de Mollusques, Ordre des Céphalopodes, pp. 743–1505.
Billings, E. 1857. New species of fossils from Silurian rocks of Canada. Report for the Years 1853–1856, Geological Survey of Canada, 245–345.
Billings, E. 1865. Palæozoic fossils: Vol. 1, containing descriptions and figures of new or little known species of organic remains from the Silurian rocks. 1861–1865. Geological Survey of Canada, Special Report, 1–426.
Billings, E. 1866. Catalogues of the Silurian Fossils of the Island of Anticosti: with Descriptions of Some New Genera and Species. Geological Survey of Canada; Dawson Brothers, Montreal; Bailliere, London, 93 pp.
http://dx.doi.org/10.4095/216072
Blake, J. F. 1882. A Monograph of the British Fossil Cephalopods, Part 1. Introduction and Silurian Species. London, 1–248.
Dzik, J. 1984. Phylogeny of the Nautiloidea. Palaeontologia Polonica, 45, 3–203.
Flower, R. H. 1941. Development of the Mixochoanites. Journal of Paleontology, 15, 523–548.
Flower, R. H. 1952. New Ordovician cephalopods from eastern North America. Journal of Paleontology, 26, 24–59.
Flower, R. H. 1963. New Ordovician Ascoceratida. Journal of Paleontology, 37, 69–85.
Foerste, A. F. 1928. Some hitherto unfigured Ordovician cephalopods from Anticosti Island. Transactions of the Royal Society of Canada, 3rd Series, 22, 223–234.
Foerste, A. F. 1929. Cephalopods of the Red River Formation of Southern Manitoba. Denison University Bulletin, Journal of the Scientific Laboratories, 24, 129–235.
Foerste, A. F. 1930. Port Byron and other Silurian cephalopods. Denison University Bulletin, Journal of the Scientific Laboratories, 23, 1–110.
Foerste, A. F. & Savage, T. E. 1927. Ordovician and Silurian cephalopods of the Hudson Bay area. Journal of the Scientific Laboratories, Denison University Bulletin, 22, 1–107.
Frey, R. C. 1985. A well-preserved specimen of Schuchertoceras (Cephalopoda, Ascocerida) from the Upper Ordovician (basal Richmondian) of Southwest Ohio. Journal of Paleontology, 59, 1506–1511.
Frýda, J. & Manda, Š. 2013. A long-lasting steady period of isotopically heavy carbon in the late Silurian ocean: evolution of the δ13C record and its significance for an integrated δ13C, graptolite and conodont stratigraphy. Bulletin of Geosciences, 88, 463–482.
http://dx.doi.org/10.3140/bull.geosci.1436
Furnish, W. M. & Glenister, B. F. 1964. Nautiloidea – Tarphycerida. In Treatise on Invertebrate Paleontology. Part K. Mollusca 3. Endoceratoidea, Actinoceratoidea, Nautiloidea, Bactritoidea (Moore, R. C., ed.), pp. 343–367. Geological Society of America, New York, and the University of Kansas Press, Lawrence, Kansas, USA.
Hauer, F. R. 1847. Neue Cephalopoden aus den rothen Marmor von Aussee. Haidenger’s Naturwissenschaftliche-Abhandlungen, 1, 257–277.
Hints, O. 2008. The Silurian System of Estonia. In The Seventh Baltic Stratigraphical Conference, Abstracts and Field Guide (Hints, O., Ainsaar, L., Männik, P. & Meidla, T., eds), pp. 113–114. Geological Society of Estonia, Tallinn.
Holland, C. 1999. The nautiloid cephalopod order Ascocerida in the British Silurian. Palaeontology, 42, 683–689.
Hyatt, A. 1883. Genera of fossil cephalopods. Proceedings of the Boston Society of Natural History, 22, 253–338.
Kaljo, D. 1970. Mollusks. In The Silurian of Estonia (Kaljo, D., ed.), pp. 150–153. Valgus, Tallinn [in Russian].
Kesling, R. V. 1961. A new species of Billingsites, an ascoceratid Cephalopod, from the Upper Ordovician Ogontz Formation of Michigan. Contribution From the Museum of Paleontology, The University of Michigan, 17, 77–121.
Klaamann, E. 1970. The Paadla Stage. In The Silurian of Estonia (Kaljo, D., ed.), pp. 276–286. Valgus, Tallinn [in Russian].
Kõrts, A. 1991. Distribution of calcareous algae, oncolites and stromatolites in Wenlock–Ludlow boundary beds in Estonia. Proceedings of the Estonian Academy of Sciences, Geology, 40, 43–49.
Kříž, J. 1991. The Silurian of the Prague Basin (Bohemia) – tectonic, eustatic and volcanic controls on facies and faunal development. In The Murchison Symposium. Proceedings of an International Conference on The Silurian System (Bassett, M. G., Lane, P. D. & Edwards, D., eds), Special Papers in Palaeontology, 44, 179–203.
Kříž, J. 1992. Silurian field excursions: Prague Basin (Barrandian) Bohemia. National Museum of Wales, Geological Series, 13, 1–111.
Kříž, J. 1999. Bivalvia dominated communities of Bohemian type from the Silurian and Lower Devonian carbonate facies. In Final Report, Project Ecostratigraphy. Paleocommunities: A Case Study from the Silurian and Lower Devonian (Boucot, A. J. & Lawson, J. D., eds), pp. 225–248. Cambridge University Press, Cambridge.
Kříž, J., Jaeger, H., Paris, F. & Schönlaub, H. P. 1986. Přídolí – the fourth subdivision of the Silurian. Jahrbuch den Geologischen Bundesanstalt, 129, 291–360.
Kříž, J., Dufka, P., Jaeger, H. & Schönlaub, H. P. 1993. The Wenlock/Ludlow boundary in the Prague Basin (Bohemia). Jahrbuch der Geologischen Bundesanstalt, 136, 809–839.
Kříž, J., Degardin, J. M., Ferretti, A., Hansch, W., Gutiérrez Marco, J. C., Paris, F., Piçarra d’Almeida, J. M., Robardet, M., Schönlaub, H. P. & Serpagli, E. 2003. Silurian stratigraphy and paleogeography of north Gondwanan and Perunican Europe. In Silurian Lands and Seas – Paleogeography Outside of Laurentia (Landing, E. & Johnson, M. E., eds), New York State Museum Bulletin, 493, 105–178.
Kröger, B. 2007. Concentrations of juvenile and small adult cephalopods in the Hirnantian cherts (Late Ordovician) of Porkuni, Estonia. Acta Palaeontologica Polonica, 52, 591–608.
Kröger, B. 2013. The cephalopods of the Boda Limestone, Late Ordovician, of Dalarna, Sweden. European Journal of Taxonomy, 41, 1–110.
http://dx.doi.org/10.5852/ejt.2013.41
Kuhn, O. 1949. Lehrbuch der Paläozoologie. E. Schweizerbart, Stuttgart, 326 pp.
Lindström, G. 1890. The Ascoceratidae and the Lituitidae of the Upper Silurian formation of Gotland. Kungliga Svenska Vetenskaps-Akademiens Handlingar, 23, 1–54.
Manda, Š. & Kříž, J. 2006. Environmental and biotic changes in subtropical isolated carbonate platforms during the Late Silurian Kozlowskii Event, Prague Basin. GFF, 128, 161–168.
http://dx.doi.org/10.1080/11035890601282161
Manda, Š., Štorch, P., Slavík, L., Frýda, J., Kříž, J. & Tasáryová, Z. 2012. The graptolite, conodont and sedimentary record through the late Ludlow Kozlowskii Event (Silurian) in the shale-dominated succession of Bohemia. Geological Magazine, 149, 507–531.
http://dx.doi.org/10.1017/S0016756811000847
Miller, A. K. 1932. The mixochoanitic cephalopods. University of Iowa Studies, Studies in Natural History, 14, 1–67, 9 pl.
Newell, F. H. 1888. Niagara Cephalopods from Northern Indiana. Proceedings of the Boston Society of Natural History, 23, 466–486.
Percival, I. G. & Wright, A. J. 2005. A new Early Silurian species of Trimerella (Brachiopoda: Craniata) from the Orange district, New South Wales. Linnean Society of New South Wales, 126, 111–120.
Salter, J. W. 1858. On a new genus of Cephalopoda, Tretoceras (Orthoceras bisiphonatum, Sowerby); and on the occurrence of the Genus Ascoceras, Barrande, in Britain. Quarterly Journal of the Geological Society of London, 14, 177–180.
http://dx.doi.org/10.1144/GSL.JGS.1858.014.01-02.24
Schmidt, F. 1858. Untersuchungen über die Silurische Formation von Estland, Nord-Livland und Oesel. Archiv für die Naturkunde Liv-, Ehst- und Kurlands, Ser. 1, 2, 1–248.
Slavík, L., Štorch, P., Manda, Š. & Frýda, J. 2013. Integrated stratigraphy of the Ludfordian in the Prague Synform. GFF, 136, 238–242.
http://dx.doi.org/10.1080/11035897.2013.851733
Štorch, P. 1994. Graptolite biostratigraphy of the lower Silurian (Llandovery and Wenlock) of Bohemia. Geological Journal, 29, 137–165.
http://dx.doi.org/10.1002/gj.3350290204
Štorch, P. 1995a. Upper Silurian (upper Ludlow) graptolites of the N. inexpectatus and N. kozlowskii biozones from Kosov Quarry near Beroun (Barrandian area, Bohemia). Bulletin of the Czech Geological Survey, 70, 65–89.
Štorch, P. 1995b. Biotic crises and post-crisis recoveries recorded by graptolite faunas of the Barrandian area, Czech Republic. Geolines, 3, 59–70.
Štorch, P., Manda, Š. & Loydell, D. K. 2014. The early Ludfordian leintwardinensis graptolite Event and the Gorstian–Ludfordian boundary in Bohemia (Silurian, Czech Republic). Palaeontology, 57, 1003–1043.
http://dx.doi.org/10.1111/pala.12099
Sweet, W. C. 1958. The middle Ordovician of the Oslo region, Norway. 10. Nautiloid cephalopods. Norsk Geologisk Tidsskrift, 38, 1–176.
Watkins, R. 2007. Paleoecology of Silurian reef bivalves, Racine Formation, North America. Lethaia, 29, 171–180.
http://dx.doi.org/10.1111/j.1502-3931.1996.tb01873.x
Whiteaves, J. F. 1884. On some new, imperfectly characterized or previously unrecorded species of fossils from the Guelph formation of Ontario. Geological Survey of Canada, Palaeozoic Fossils, 3, 1–43.
Worthen, A. H. 1890. Description of fossil invertebrates. Geological Survey of Illinois, 8, pt. II, sec. I, 69–154.
