On the basis of detailed SEM-EDS study and computer tomography scanning, the single specimen of the enigmatic Martsaphyton moxi from the Aseri Stage (Darriwilian; Middle Ordovician) of Estonia, was identified as a member of the phylum Cnidaria and subphylum Medusozoa, with unspecified (incertae sedis) class placement. Our results confirm a number of similarities in the morphology and chemical composition with previously described Sphenothallus Hall 1847 and Torellella Holm 1893, also interpreted as cnidarians. All three show tubiculous morphology, lamellar skeleton structure and calcium phosphatic composition. The new species differs from the previously described members in its unique root-like appendages, widened apertural chamber and lack of a laterally thickened skeleton wall.
The element analysis revealed an unexpected chemical composition – high content of silica, iron, aluminium, potassium and sodium – of the rock matrix surrounding the specimen, which suggests possible involvement of material of volcanic origin in the sediment.
Adler, L. & Jarms, G. 2009. New insights into reproductive traits of scyphozoans: special methods of propagation in Sanderia malayensis Goette, 1886 (Pelagiidae, Semaeostomeae) enable establishing a new classication of asexual reproduction in the class Scyphozoa. Marine Biology, 156, 1411–1420.
https://doi.org/10.1007/s00227-009-1181-6
Ford, R. C., Van Iten, H. & Clark, G. R. 2016. Microstructure and composition of the periderm of conulariids. Journal of Paleontology, 90, 389–399.
https://doi.org/10.1017/jpa.2016.63
Hall, J. 1847. Palaeontology of New York. Volume I. Containing Descriptions of the Organic Remains of the Lower Division of the New York System. C. Van Benthuysen, Albany, 338 pp.
Hatschek, B. 1888. Lehrbuch der Zoologie. Eine morphologische Ubersicht der Thierreiches zur Einfuhrung in das Stadium der Wissenschaft. Erste Liefrung.Fischer, Jena, iv + 304 pp.
https://doi.org/10.5962/bhl.title.1381
Hints, L. 1997. Aseri Stage. In Geology and Mineral Resources of Estonia (Raukas, A. & Teedumäe, A., eds), pp. 66–67. Estonian Academy Publishers, Tallinn.
Holm, G. 1893. Sveriges kambrisk-siluriska Hyolithidae och Conularidae. Sveriges Geologiska Undersökning, Afhandlingar och Uppsatser, C112, 1–172.
Jaansoon-Orviku, K. 1927. Beiträge zur Kenntnis der Aseri- und der Tallinna-Stufe in Eesti. I. Tartu Ülikooli Geoloogia Instituudi Toimetused, 5, 1–40.
Klaamann, E. & Nestor, H. 1976. Kui valitses Neptunus [When Neptune was ruling]. Horisont, 3, 4–9 [in Estonian].
Kozłowski, R. 1968. Nouvelles observations sur les Conulaires. Acta Palaeontologica Polonica, 13, 497–531.
Luha, A. 1967. Maismaa asustamine organismidega [Inhabiting terrestrial environments with organisms]. Eesti Loodus, 11, 656–662 [in Estonian].
Männik, P. & Viira, V. 1990. Conodonts. In Field Meeting Estonia 1990. An Excursion Guidebook (Kaljo, D. & Nestor, H., eds), pp. 84–90. Estonian Academy of Sciences, Tallinn.
Männil, R. 1990. The Ordovician of Estonia. In Field Meeting Estonia 1990. An Excursion Guidebook (Kaljo, D. & Nestor, H., eds), pp. 11–20. Estonian Academy of Sciences, Tallinn.
Meidla, T., Ainsaar, L. & Hints, O. 2014. The Ordovician System in Estonia. In 4th Annual Meeting of IGCP 591, Estonia, 10–19 June 2014. Abstracts and Field Guide (Bauert, H., Hints, O., Meidla, T. & Männik, P., eds), p. 118. University of Tartu, Tartu.
Nestor, H., Soesoo, A., Linna, A., Hints, A. & Nõlvak, J. 2007. The Ordovician in Estonia and Southern Finland, GeoGuide Baltoscandia. Tallinn, 32 pp.
Öpik, A. 1927. Beiträge zur Kenntnis der Kukruse-(C2) Stufe in Eesti. II. Acta et Commentationes Universitatis Tartuensis, 12(3), 1–33.
Orviku, K. 1940. Lithologie der Tallinna-Serie (Ordovizium, Estland) I. Tartu, 249 pp.
Perlitz, H. G. (ed.). 1927. Loodusuurijate Seltsi 1926 aasta aruanne. Sitzungsberichte der Naturforscher-Gesellschaft bei der Universität Tartu, 1, 34, p. 4 [in Estonian].
Peterson, K. W. 1979. Development of coloniality in Hydrozoa. In Biology and Systematics of Colonial Organisms (Larwood, G. & Rosen, B. R., eds), pp. 105–139. Academic Press, New York.
Rõõmusoks, A. 1970. Stratigrafiya viruskoj serii (ordovik) Severnoj Éstonii [Stratigraphy of the Viruan Series (Middle Ordovician) in Northern Estonia]. Valgus Publishers, Tallinn, 346 pp. [in Russian, with English summary].
Ruppert, E. E., Fox, R. S. & Barnes, R. D. 2004. Invertebrate Zoology: A Functional Evolutionary Approach, Seventh Edition. Brooks/Cole Thompson Learning, Belmont, California, XVII + 962 + I–26 pp.
Schmidt, F. 1874. Über einige neue und wenig bekannte baltisch-silurische Petrefacten. Mémoires de l´Académie Impériale des Sciences de St.-Petersbourg, 21(11), 1–48.
Sturesson, U. & Bauert, H. 1994. Origin and palaeogeographical distribution of the Viruan iron and phosphate ooids in Estonia: evidence from mineralogical and chemical compositions. Sedimentary Geology, 93, 51–72.
https://doi.org/10.1016/0037-0738(94)90028-0
Sutton, M. D. 2008. Tomographic techniques for the study of exceptionally preserved fossils. Proceedings of the Royal Society B, 275, 1587–1593.
https://doi.org/10.1098/rspb.2008.0263
Suyarkova, A. & Koren, T. N. 2009. Advances in the Ordovician graptolite biostratigraphy of the St Petersburg area, Russia. Estonian Journal of Earth Sciences, 58, 3–9.
https://doi.org/10.3176/earth.2009.1.01
Taylor, T. N., Taylor, E. L. & Krings, M. 2009. Paleobotany. The Biology and Evolution of Fossil Plants. Elsevier, 1230 pp.
Torsvik, T. H. & Cocks, L. R. M. 2013. New global palaeogeographical reconstructions for the Early Palaeozoic and their generation. In Early Palaeozoic Biogeography and Palaeogeography (Harper, D. A. T. & Servais, T., eds), Geological Society, London, Memoirs, 38, 5–24.
https://doi.org/10.1144/M38.2
Van Iten, H. 1991. Anatomy, patterns of occurrence, and nature of the conulariid schott. Palaeontology, 34, 939–954.
Van Iten, H. 1992. Microstructure and growth of the conulariid test: implications for conulariid affinities. Palaeontology, 35, 359–372.
Van Iten, H., Cox, R. S. & Mapes, R. H. 1992. New data on the morphology of Sphenothallus Hall: implications for its affinities. Lethaia, 25, 135–144.
https://doi.org/10.1111/j.1502-3931.1992.tb01378.x
Van Iten, H., Leme, J. M., Simões, M. G., and Cournoyer, M. 2019. Clonal colony in the Early Devonian cnidarian Sphenothallus from Brazil. Acta Palaeontologica Polonica, 64, 409–416.
https://doi.org/10.4202/app.00576.2018
Vinn, O. 2006. Possible cnidarian affinities of Torellella (Hyolithelminthes, Upper Cambrian, Estonia). Paläontologische Zeitschrift, 80, 384–389.
https://doi.org/10.1007/BF02990210
Vinn, O. & Kirsimäe, K. 2015. Alleged cnidarian Sphenothallus in the Late Ordovician of Baltica, its mineral composition and microstructure. Acta Palaeontologica Polonica, 60, 1001–1008.
https://doi.org/10.4202/app.00049.2013
Vinn, O., Ernst, A., Wilson, M. A. & Toom, U. 2019. Symbiosis of conulariids with trepostome bryozoans in the Upper Ordovician of Estonia (Baltica). Palaeogeography, Palaeoclimatology, Palaeoecology, 518, 89–96.
https://doi.org/10.1016/j.palaeo.2019.01.018
