Chitinozoans have been known to science for nearly a century. Due to their biostratigraphic utility, chitinozoans were intensively studied from the 1960s to the 1980s, and they have an important place in Ordovician stratigraphy nowadays, alongside graptolites and conodonts. However, identifying chitinozoans is often complicated due to poorly illustrated and documented type specimens. During the last decades, descriptions of new species have decreased significantly, whereas open nomenclature has been adopted widely. The affinity of chitinozoans has been discussed in several recent papers, but further exceptional specimens and the application of up-to-date study techniques are needed to understand their biological functioning. The Ordovician chitinozoan biozonal schemes were mostly established in the 1990s. With much more data subsequently reported, many biozones currently need revision, and possibly new useful zones could be established. Herein we discuss how to tackle the problems in chitinozoan research by building an open-access database and restudying the poorly documented type materials using advanced techniques. This would foster progress and facilitate studies in systematics, evolution, biostratigraphy, palaeogeography and the biological affinity of chitinozoans.
Achab, A. 1989. Ordovician chitinozoan zonation of Quebec and western Newfoundland. Journal of Paleontology, 63(1), 14–24.
https://doi.org/10.1017/S0022336000040907
Achab, A. and Maletz, J. 2021. The age of the Euconochitina symmetrica Zone and implication for Lower Ordovician chitinozoan and graptolite zonations of Laurentia. Review of Palaeobotany and Palynology, 295, 104508.
https://doi.org/10.1016/j.revpalbo.2021.104508
Achab, A. and Paris, F. 2007. The Ordovician chitinozoan biodiversification and its leading factors. Palaeogeography, Palaeoclimatology, Palaeoecology, 245(1–2), 5–19.
https://doi.org/10.1016/j.palaeo.2006.02.030
Achab, A., Asselin, E. and Liang, B. 2000. A structured database and image acquisition system in support of palynological studies: CHITINOS. Review of Palaeobotany and Palynology, 113(1–3), 15–26.
https://doi.org/10.1016/S0034-6667(00)00049-X
Alroy, J. 2001. A multispecies overkill simulation of the end-Pleistocene megafaunal mass extinction. Science, 292(5523), 1893–1896.
https://doi.org/10.1126/science.1059342
Alroy, J., Aberhan, M., Bottjer, D. J., Foote, M., Fursich, F. T., Harries, P. J. et al. 2008. Phanerozoic trends in the global diversity of marine invertebrates. Science, 321(5885), 97–100.
https://doi.org/10.1126/science.1156963
Amberg, C. E., Vandenbroucke, T. R. A., Molyneux, S. G. and Servais, T. 2017. Chitinozoans from the upper Tremadocian (Lower Ordovician) Watch Hill Formation of the Lake District, northern England. Palynology, 41(sup1), 23–30.
https://doi.org/10.1080/01916122.2017.1348721
Combaz, A. and Peniguel, G. 1972. Étude palynostratigraphique de l’Ordovicien dans quelques sondages du Bassin de Canning (Australie Occidentale) (Ordovician palynostratigraphic study in some boreholes of the Canning Basin (Western Australia)). Bulletin du Centre de Recherches Pau – SNPA, 6, 121–167.
Cooper, R. A. and Sadler, P. M. 2012. The Ordovician Period. In The Geologic Time Scale 2012 (Gradstein, F. M., Ogg, J. G., Schmitz, M. and Ogg, G. eds). Elsevier, Amsterdam, 489–523.
https://doi.org/10.1016/B978-0-444-59425-9.00020-2
Eisenack, A. 1931. Neue Mikrofossilien des baltischen Silurs. I (New microfossils of the Baltic Silurian. I). Paläontologische Zeitschrift, 13(1–2), 74–118.
https://doi.org/10.1007/BF03043326
Fan, J. X., Shen, S. Z., Erwin, D. H., Sadler, P. M., MacLeod, N., Cheng, Q. M. et al. 2020. A high-resolution summary of Cambrian to Early Triassic marine invertebrate biodiversity. Science, 367(6475), 272–277.
https://doi.org/10.1126/science.aax4953
Hints, O., Antonovitš, L., Bauert, G., Nestor, V., Nõlvak, J. and Tammekänd, M. 2018. CHITDB: a database for documenting and analysing diversification of Ordovician–Silurian chitinozoans in the Baltic region. Lethaia, 51(2), 218–227.
https://doi.org/10.1111/let.12249
Jaglin, J.-C. and Paris, F. 1992. Exemples de tératologie chez les Chitinozoaires du Pridoli de Libye et implications sur la signification biologique du groupe (Examples of teratology in Chitinozoa from Libyan Pridoli and implications for the biological significance of the group). Lethaia, 25(2), 151–164.
https://doi.org/10.1111/j.1502-3931.1992.tb01380.x
Kiessling, W. 2005. Long-term relationships between ecological stability and biodiversity in Phanerozoic reefs. Nature, 433, 410–413.
https://doi.org/10.1038/nature03152
Liang, Y., Servais, T., Tang, P., Liu, J. and Wang, W. H. 2017. Tremadocian (Early Ordovician) chitinozoan biostratigraphy of South China: An update. Review of Palaeobotany and Palynology, 247, 149–163.
https://doi.org/10.1016/j.revpalbo.2017.08.008
Liang, Y., Bernardo, J., Goldman, D., Nõlvak, J., Tang, P., Wang, W. H. et al. 2019. Morphological variation suggests that chitinozoans may be fossils of individual microorganisms rather than metazoan eggs. Proceedings of the Royal Society B, 286(1908), 20191270.
https://doi.org/10.1098/rspb.2019.1270
Liang, Y., Hints, O., Tang, P., Cai, C. Y., Goldman, D., Nõlvak, J. et al. 2020. Fossilized reproductive modes reveal a protistan affinity of Chitinozoa. Geology, 48(12), 1200–1204.
https://doi.org/10.1130/G47865.1
Liang, Y., Nõlvak, J., Xu, H. H., Chen, Y. S. and Hints, O. 2022. Revision of Ordovician chitinozoan Lagenochitina esthonica sensu lato: morphometrics, biostratigraphy and paleobiogeography. Journal of Paleontology, 96(1), 46–60.
https://doi.org/10.1017/jpa.2021.79
Nõlvak, J. and Grahn, Y. 1993. Ordovician chitinozoan zones from Baltoscandia. Review of Palaeobotany and Palynology, 79(3–4), 245–269.
https://doi.org/10.1016/0034-6667(93)90025-P
Nowak, H., Servais, T., Pittet, B., Vaucher, R., Akodad, M., Gaines, R. R. et al. 2016. Palynomorphs of the Fezouata Shale (Lower Ordovician, Morocco): age and environmental constraints of the Fezouata Biota. Palaeogeography, Palaeoclimatology, Palaeoecology, 460, 62–74.
https://doi.org/10.1016/j.palaeo.2016.03.007
Obut, A. M. 1973. О географическом распространении, сравнительной морфологии, экологии, филогении и систематическом положении хитинозоа(On the geographic distribution, comparative morphology, ecology, phylogeny and systematic position of chitinozoans). In Окружающая среда и жизнь вгеологическом прошлом (Environment and Life in the Geological Past) (Zhuravleva, J. T., ed.). Nauka, Novosibirsk, 72–84.
Paris, F. 1990. The Ordovician chitinozoan biozones of the Northern Gondwana domain. Review of Palaeobotany and Palynology, 66(3–4), 181–209.
https://doi.org/10.1016/0034-6667(90)90038-K
Paris, F. 1993. Evolution paléogéographique de l’Europe au Paléozoïque inférieur: le test des chitinozoaires (Paleogeographic evolution of Europe in the Lower Paleozoic: the chitinozoan test). Comptes rendus de l’Académie des Sciences de Paris, Sciences de la Terre et des Planètes, 316, 273–280.
Paris, F. 1996. Chitinozoan biostratigraphy and palaeoecology. In Palynology: principles and applications (Jansonius, J. and McGregor, D. C., eds). American Association of Stratigraphic Palynologists Foundation, 2, 531–552.
Paris, F. and Nõlvak, J. 1999. Biological interpretation and paleobiodiversity of a cryptic fossil group: the “chitinozoan animal”. Geobios, 32(2), 315–324.
https://doi.org/10.1016/S0016-6995(99)80045-X
Paris, F., Grahn, Y., Nestor, V. and Lakova, I. 1999. A revised chitinozoan classification. Journal of Paleontology, 73(4), 549–570.
https://doi.org/10.1017/S0022336000032388
Servais, T., Achab, A. and Asselin, E. 2013. Eighty years of chitinozoan research: From Alfred Eisenack to Florentin Paris. Review of Palaeobotany and Palynology, 197, 205–217.
https://doi.org/10.1016/j.revpalbo.2013.05.008
Shen, C., Aldridge, R. J., Williams, M., Vandenbroucke, T. R. A. and Zhang, X. G. 2013. Earliest chitinozoans discovered in the Cambrian Duyun fauna of China. Geology, 41(2), 191–194.
https://doi.org/10.1130/G33763.1
Taugourdeau, P. 1981. Les diverses attributions systématiques proposées pour les Chitinozoaires (The various systematic attributions proposed for the Chitinozoa). Cahiers de Micropaléontologie, 1, 17–28.
Taugourdeau, P. and de Jekhowsky, B. 1960. Répartition et description des chitinozoaires Siluro–Dévoniens de quelques sondages de la C.R.E.P.S., de la C.F.P.A. et de la S.N. Repal au Sahara (Distribution and description of Siluro–Devonian chitinozoans from some surveys of C.R.E.P.S., C.F.P.A. and S.N. Repal in the Sahara). Revue de I’Institut Français du Pétrole et Annales des Combustibles Liquides, 15(9), 1199–1260.
Verniers, J., Paris, F., Asselin, E., Van Grootel, G., Achab, A., Nestor, V. et al. 2002. CHITREF: a database with all published chitinozoan references (1930–2001) and a list of all chitinozoan species. In Abstract Volume of Palaeozoic Palynology in the Third Millenium: New Directions in Acritarch, Chitinozoan and Miospore Research. International Meeting and Workshops of the Commission Internationale de Microflore du Paléozoïque, Lille, France (Raevskaya, E. and Servais, T. eds), 14.
Vodička, J., Muir, L. A., Botting, J. P., Špillar, V. and Fatka, O. 2022. Palaeobiological significance of chitinozoan clusters with parallel vesicles. Marine Micropaleontology, 172, 102109.
https://doi.org/10.1016/j.marmicro.2022.102109
Wagner, P. J., Kosnik, M. A. and Lidgard, S. 2006. Abundance distributions imply elevated complexity of post-Paleozoic marine ecosystems. Science, 314, 1289–1292.
https://doi.org/10.1126/science.1133795
Wang, W. H., Feng, H. Z., Vandenbroucke, T. R. A., Li, L. X. and Verniers, J. 2013. Chitinozoans from the Tremadocian graptolite shales of the Jiangnan Slope in South China. Review of Palaeobotany and Palynology, 198, 45–61.
https://doi.org/10.1016/j.revpalbo.2012.02.003
Webby, B. D., Cooper, R. A., Bergström, S. M., Paris, F., Droser, M. L. and Percival, I. G. 2004. Stratigraphic framework and time slices. In The Great Ordovician Biodiversification Event (Webby, B. D., Droser, M. L., Paris, F. and Percival, I. G., eds). Columbia University Press, New York, 41–47.
https://doi.org/10.7312/webb12678-003
Zhang, M. and Chen, X. H. 2009. Early Ordovician chitinozoans from the Fenghsiang and Hunghuayuan formations in Chenjiahe of Yichang, Hubei. Journal of Stratigraphy, 4, 425–431 (in Chinese, with English abstract).
