Abstract
In myelodactylids, the coil of the mesostele and the crown with a proxistele coiled in the same plane in the opposite direction result from the two fundamental processes in the evolution of echinoderms, which happened when their free-floating ancestor settled at the bottom and became attached to the ground by the ventral side of the anterior end of the body. The coil of the mesostele emerged due to the tendency of the stem to curve from the ventral to the dorsal side in the larvae, after they became attached, by the ventral side of the preoral lobe, and the growth vector changed from horizontal to vertical. The curvature of the proxistele, together with the crown in the same larval plane but in the opposite direction, from the dorsal side to the ventral, appeared during the paedomorphic delay in the process of elevation (torsion) in the ontogeny of myelodactylids. The coiling of the mesostele and the curvature of the proxistele with the crown in the E‑BC plane determine the conformity of this plane to the larval plane in pentaradiate echinoderms, and the approximate conformity of the E ray to the dorsal side of the larva, and the interray BC to its ventral side. The morphology of myelodactylids shows that their stem in the feeding position stretched along slightly compacted ground, resting on cirri, and the crown extended at a slight acute angle over the stem downstream. In cases of danger, the stem coiled with its lower side inward, so that the crown was protected inside the coil by cirri. The coil of Zuravlicrinus milicinae gen. et sp. nov. from the Silurian of the Urals, and Valimocrinus terentyevi gen. et sp. nov. from the Ordovician of the Leningrad Region, coiled while growing around stems of other crinoids, and could not uncoil. Both genera, as well as Musicrinus Donovan, are known only from stem fragments and are tentatively assigned to myelodactylids. The finding of the genus Eomyelodactylus in China shows its spread far beyond North America. Findings of myelodactylids in Siberia show significant differences from other myelodactylids, allowing them to be assigned to a new genus Imagdacrinus gen .nov.
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REFERENCES
Arendt, Yu.A., Cyrtocrinid Crinoids, Trudy Paleontol. Inst. Akad. Nauk SSSR, 1974, vol. 144, pp. 1–144.
Ausich, W.I., and Copper, P., The Crinoidea of Anticosti Island, Québec (Late Ordovician to Early Silurian), Palaeontographica Canadiana, 2010 vol. 29, pp. 1–157.
Ausich, W.I. and Wilson, M.A., Llandovery (early Silurian) crinoids from Hiiumaa Island, western Estonia, J. Paleont., 2016, vol. 90, no. 6, pp. 1138–1147.
Baumiller, T.K. and Ausich, W.I., Crinoid stalk flexibility: theoretical predictions and fossil stalk postures, Lethaia, 2007, vol. 29, no. 1, pp. 47–59.
Bolton, T.E., Echinodermata of the Ordovician (Pleurocystites, Cremacrinus) and Silurian (Hemicystites, Protaxocrinus, Mcnamaratylus) of the Lake Timiskaming region, Ontario and Quebec, Geological Survey of Canada Bulletin, 1970, vol. 187, pp. 59–66.
Bourseau, J., Ameziane-Cominardi, N., and Roux, M., Un crinoïde pédonculé nouveau (Échinodermes), representant actuel de la famille jurassique des Hemicrinidae: Gymnocrinus richeri nov. sp. des fonds bathyaux de Nouvelle-Calédonie (S.W. Pacifique), Comptes Rendus de l’Académie des Sciences, Série III Sciences de la Vie, 1987, vol. 305, no. 16, pp. 595–599.
Brett, C.E., Terminology and functional morphology of attachment structures in pelmatozoan echinoderms, Lethaia, 1981, vol. 14, pp. 343–370.
Clement, C.R. and Brett, C.E., Echinoderm Faunas of the Decatur Limestone and Ross Formation (Upper Silurian to Lower Devonian) of West-Central Tennessee, Bull. Amer. Paleontol., 2015, no. 388, pp. 1–118.
Donovan, S.K. and Sevastopulo, G.D., Myelodactilid crinoids from the Silurian of the British Isles, Palaeontology. 1989, vol. 32, no. 4, pp. 689–710.
Donovan, S. K., Ristnacrinus and the earliest myelodactylid from the Ashgillian Boda Limestone of Sweden, Geol. För. Stockh. Förhandl., 1985, vol. 106, no. 4, pp. 347–356.
Donovan, S.K., The improbability of a muscular cirroid column, Lethaia, 1989, vol. 22, pp. 307–315.
Donovan, S.K., Problematic aspects of the form and function of the stem in Palaeozoic crinoids, Earth-Sci. Rev., 2016, vol. 154, pp. 174–182.
Donovan, S.K. and Franzén-Bengtson, C., Myelodactylid crinoid columnals from the Lower Visby Beds (Llandoverian) of Gotland, Geol. För. Stockh. Förhandl., 1988, vol. 110, pp. 69–79.
Eckert, J.D. and Brett, C.E., Taxonomy and paleoecology of the Silurian myelodactylid crinoid Crinobrachiatus brachiatus (Hall), Roy. Ontario Mus. Life Sci. Contrib., 1985, vol. 141, pp. 1–15.
Eckert, J.D., The Early Silurian myelodactylid crinoid Eomyelodactylus Foerste, J. Paleontol., 1990, vol. 64, no. 1, pp. 135–141.
Gorzelak, P. and Zamora, S., Understanding form and function of the stem in early flattened echinoderms (pleurocystitids) using a microstructural approach, PeerJ, 2016, vol. 4, e1820.
Gorzelak, P., Głuchowski, E., and Salamon, M.A., Reassessing the improbability of a muscular crinoid stem, Sci. Rep., 2014, vol. 4, Article number: 6049.
Moore, R.C., Ray structures of some inadunate crinoids, The University of Kansas paleontological contributions. Echinodermata, 1962, Article 5, pp. 1–47.
Moore, R.C., et al., Order Disparida, in Treatise on Invertebrate Paleontology, Part T. Echinodermata 2, vol. 2. Boulder, Colorado, Lawrence, Kansas: The Geological Society of America and The University of Kansas, 1978, pp. T520–T564.
Motokawa, T., Connective tissue catch in echinoderm, Biological Reviews, 1984, vol. 59, no. 2, pp. 255–270.
Oji, T. and, Amemyia, S., Survival of Crinoid Stalk Fragments and Its Taphonomic Implications, Paleont. Res., 1998, vol. 2, no. 1, pp. 67–70.
Prokop, R.J., Simakocrinus gen. nov. (Crinoidea, col.) from the Bohemian Early and Middle Devonian of the Barrandian area (the Czech Republic), Acta Musei Nationalis Pragae. Series B—Historia Naturalis, 2013, vol. 69, nos. 1–2, pp. 65–68.
Rozhnov, S.V., Crinoids of the superfamily Pisocrinacea. Trudy Paleontol. Inst. Akad. Nauk SSSR, 1981, vol. 192, pp. 1–128.
Rozhnov, S.V., Morphogenesis and evolution of crinoids and other pelmatozoan echinoderms in the early Paleozoic, Paleontol. J., 2002, vol. 36, Suppl. 6, pp. S525–S674.
Rozhnov, S.V., Appearance and evolution of marine benthic communities in the Early Palaeozoic, Paleontol. J., 2006, vol. 40, Suppl. 4, pp. S444–S452.
Rozhnov, S.V., Origin of Echinoderms in the Palaeozoic Evolutionary Fauna: Ecological Aspects, Acta Palaeontol. Sin., 2007, vol. 46, Suppl., pp. 416–421.
Rozhnov, S.V., Development of the trophic structure of Vendian and Early Paleozoic marine communities, Paleontol. J., 2009, vol. 43, no. 11, pp. 1364–1377.
Rozhnov, S.V., The anteroposterior axis in echinoderms and displacement of the mouth in their phylogeny and ontogeny, Biol. Bull., 2012, vol. 39, no. 2, pp. 162–171.
Rozhnov, S.V., Symmetry of echinoderms: from initial bilaterally-asymmetric metamerism to pentaradiality, Nat. Sci., 2014, vol. 6, no. 4, pp. 171–183.
Rozhnov, S.V., Modularity and heterochronies in the evolution of Metazoa: paleontological aspect, Paleontol. J., 2015, vol. 49, no. 14, pp. 1–15.
Rozhnov, S.V., Architectonics of Metazoa as the Basis for the Reconstruction of the Ontogeny and Phylogeny of Extinct Taxa, Paleontol. J., 2018, vol. 52, no. 14, pp. 1672–1678.
Semenov, N.K., Terentiev, S.S., Mirantsev, G.V., et al., A New Hybocrinid Genus (Echinodermata, Crinoidea) from the Middle Ordovician of Ladoga Glint on the Volkhov River, Paleontol. Zhurn., 2021, vol. 55, no. 1, pp. 54–63.
Springer, F., Unusual forms of fossil crinoids, Proc. US Nation. Mus., 1926, vol. 67, no. 2581, pp. 1–137.
Stukalina, G.A., Silurian crinoids of sections of the Gorbiachin and Kureyka rivers, in Razrezy, fauna i flora severo-zapadnoy chasti Tungusskoy sineklizy, Moscow: Nauka, 1982, pp. 111–159. (Silur Sibirskoy platformy, no. 508).
Stukalina, G.A., Silurian crinoids of the Siberian Platform, Trudy Paleontol. Inst. Ross. Akad. Nauk, 2000, vol. 278, pp. 1–109.
Wilkie, I.C., Mutable collagenous tissues: extracellular matrix as mechanoeffector, in Echinoderm Studies, Jangoux, M. and Lawrence, J.M., eds., Rotterdam: Balkema, 1996, pp. 61–102.
Wilkie, I.C., Is muscle involved in the mechanical adaptability of echinoderm mutable collagenous tissue?, J. Exper. Biol., 2002, vol. 205, pp. 159–165.
Yamada, A., Takehana, Y., Tamori, M., and Motokawa, T., Connective Tissues in Echinoderm Animals that can Reversibly Change their Stiffness and their Stiffening Protein Factors, Biophys. J., 2014, vol. 106, no. 2, pp. 733a–734a.
Yeltyschewa, R.S., Ordovician and Silurian crinoids of the Siberian Platform, Trudy VSEGEI, Novaya Seriya, 1960, no. 3 (Biostratigrafiya paleozoya Sibirskoi Platformy. Ordovik i Silur (Biostratigraphy of the Paleozoic of the Siberian Platform. Ordovician and Silurian)), pp. 1–40.
ACKNOWLEDGMENTS
The author is grateful to the staff of the Paleontological Institute, Russian Academy of Sciences: S.V. Bagirov for photography, G.A. Anekeeva for making drawings and comments, and G.A. Mirantsev for valuable remarks. Special thanks to the reviewer V.V. Isayeva, who made important comments.
Funding
This work was supported by the Russian Science Foundation grant no. 19-14-00346. This paper is a contribution to the International Geoscience Program (IGCP) Project 653—The Onset of the Great Ordovician Biodiversification Event.
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Rozhnov, S.V. Two Coils in the Morphology of Myelodactylids (Crinoidea, Disparida): the Morphogenetic Basis of Their Formation and Adaptation Potential. Paleontol. J. 55, 993–1012 (2021). https://doi.org/10.1134/S0031030121090124
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DOI: https://doi.org/10.1134/S0031030121090124