The Late Devonian (late Famennian) phacopid trilobites represented by Omegops tilabadensis sp. nov. are described and illustrated from the Khoshyeilaq Formation, eastern Alborz Mountains, North Iran. The species formed a monotaxic trilobite association inhabiting a shallow shelf together with diverse brachiopod communities dominated by the athyridides and spiriferides. Constant differences in pygidial morphology between the geographically separated Omegops species from the Middle East, Northwest China (Junggar) and West Europe plus the North African sector of Gondwana may suggest the existence of two geographically isolated Omegops lineages which diverged in pre-Strunian time. The occurrence of conodonts not older than the Bispathodus costatus Zone and the brachiopod Rhipidomella michelini gives a sufficient proof of the Strunian to early Tournaisian age of the uppermost part of the Khoshyeilaq Formation.
Alavi-Naini, M. 2000. Devonian stages of Iran. In Proceedings of the 18th Symposium on Geoscience, Tehran, pp. 80–87 [in Farsi].
Alberti, H. 1972. Ontogenie des Trilobiten Phacops accipitrinus. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, 141, 1‒36.
Ashouri, A. R. 2006. Middle Devonian–Early Carboniferous conodont faunas from the Khoshyeilagh Formation, Alborz Mountains, North Iran. Journal of Sciences, Islamic Republic of Iran, 17, 53‒65.
Bischoff, F. 1957. Die Conodonten-Stratigraphie des rhenoherzynischen Unterkarbons. Abhandlungen Hessisches Landesamt für Bodenforschung, 19, 1‒64.
Bozorgnia, F. 1973. Paleozoic Foraminiferal Biostratigraphy of Central and East Alborz Mountains, Iran. National Iran Oil Company, 185 pp.
Branson, E. R. 1934. Conodonts from the Hannibal Formation of Missouri. University of Missouri Studies, 8, 301‒304.
Brice, D., Lafuste, J., de Lapparent, A. F., Pillet, J. & Yassini, I. 1974. Étude de deux gisements paléozoïques (Silurien et Dévonien) de l’Elbourz oriental (Iran). Annales de la Société Géologique du Nord, 1973, 93, 177–218.
Bronn, H. G. 1825. Über zwei neue Trilobiten. Arten zeitschrift für Mineralogie, Taschenbuch I, 317–321.
Campbell, K. S. W. 1967. Trilobites of the Henryhouse Formation (Silurian) in Oklahoma. Oklahoma Geological Survey Bulletin, 115, 1–68.
Crônier, C. & François, A. 2014. Distribution patterns of Upper Devonian phacopid trilobites: paleobiogeographical and paleoenvironmental significance. Palaeogeography, Palaeoclimatology, Palaeoecology, 404, 12–23.
https://doi.org/10.1016/j.palaeo.2014.03.037
Crônier, C., Budil, P., Fatka, O. & Laibl, L. 2015. Intraspecific bimodal variability in eye lenses of two Devonian trilobites. Paleobiology, 41, 554–569.
https://doi.org/10.1017/pab.2015.29
Domeier, M. 2018. Early Paleozoic tectonics of Asia: towards a full-plate model. Geocsience Frontiers, 9, 789–862.
https://doi.org/10.1016/j.gsf.2017.11.012
Drevermann, F. 1902. Ueber eine Vertretung der Etroeungt-Stufe auf der rechten Rheinseite. Zeitschrift der Deutschen Geologischen Gesellschaft, 54, 480–524.
Farsan, N. M. 1998. Das Etroeungtium (Ober-Devon VI, Strunium) und die letzten Phacopinae (Trilobita) im westlichen Zentral- und West-Afghanistan. Mainzer Naturwissenschaftliches Archiv Beiheft, 21, 17–37.
Feist, R., Yazdi, M. & Becker, T. 2003. Famennian trilobites from the Shotori Range, E‒Iran. Annales de la Société Géologique du Nord, 10 (2nd series), 285–295.
Feist, R., Mahboubi, A. & Girard, C. 2016. New Late Devonian phacopid trilobites from Marhouma, SW Algerian Sahara. Bulletin of Geosciences, 91, 243–259.
https://doi.org/10.3140/bull.geosci.1600
Ghobadi Pour, M., Popov, L. E., Hosseini, M., Adhamian, A. & Yazdi, M. 2013. Late Devonian trilobites and brachiopods from Soh area, Central Iran. Memoirs of the Association of Australasian Palaeontologists, 44, 149–158.
Hairapetian, V., Ghobadi Pour, M., Popov, L. E., Männik, P. & Miller, C. G. 2017. Silurian stratigraphy of Central Iran – an update. Acta Geologica Polonica, 67, 201−233.
https://doi.org/10.1515/agp-2017-0014
Hawle, I. & Corda, A. J. C. 1847. Prodom einer Monographie der böhmischen Trilobiten. Abhandlungen der Königlischen Böhemischen Gesellschaft der Wissenschaften, 5, 1–176.
Kaesler, R. L. (ed.). 1997. Treatise on Invertebrate Paleontology. Part O. Arthropoda 1. Trilobita, Revised. Volume 1: Introduction, Order Agnostida, Order Redlichiida. Geological Society of America, Boulder, and University of Kansas, Lawrence, xxiv + 530 pp.
Léveillé, C. 1835. Aperçu géologique de quelques localités très riches en coquilles sur les frontières de la France et de Belgique. Mémoires de la Société Géologique de la France, 2, 29–40.
McKellar, R. C. & Chatterton, B. D. 2009. Early and Middle Devonian Phacopidae (Trilobita) of southern Morocco. Palaeontographica Canadiana, 28, 1–110.
Mistiaen, B., Gholamalian, H., Gourvennec, R., Plusquellec, Y., Bigey, F., Brice, D., Feist, M., Feist, R., Ghobadi Pour, M., Kebria-ee, M., Milhau, B., Nicollin, J. P., Rohart, J. C., Vachard, D. & Yazdi, M. 2000. Preliminary data on the Upper Devonian (Frasnian, Famennian) and Permian fauna and flora from the Chariseh area (Esfahan Province, Central Iran). Annales de la Société Géologique du Nord, 8 (2eme serie), 93–102.
Morris, S. F. 1988. A Review of British Trilobites, Including a Synoptic Revision of Salter’s Monograph. Monograph of the Palaeontographical Society, London, 316 pp.
Morzadec, P. 2002. Trilobites Asteropyginae dévoniens d’Iran Devonian Asteropygines trilobites from Iran. Geobios, 35, 411–427.
https://doi.org/10.1016/S0016-6995(02)00037-2
Phillips, J. 1841. Figures and Descriptions of the Palaeozoic Fossils of Cornwall, Devon, and West Somerset. Longman, London, 231 pp.
Richter, R. & Richter, E. 1933. Die letzten Phacopidae. Bulletin du Musée Royal d’Histoire Naturelle de Belgique, 9(21), 1–19.
Richter, R. & Richter, E. 1943. Trilobiten aus dem Devon von Marokko mit einem Anhang über Arten des Rheinlandes. Senckenbergiana, 26(1/3), 116–199.
Salter, I. W. 1864. A monograph of the British trilobites. Palaeontographical Society London, 16, 1–80.
Shahrabi, M. 1990. Geological Quadrangle Map of Iran No H4: Gorgan. Geological Survey of Iran.
Struve, W. 1970. Beiträge zur Kenntnis der Phacopina (Trilobita), 7. Phacops-Arten aus dem rheinischen Devon 1. Senckenbergiana Lethaea, 51, 133–189.
Struve, W. 1976. Beiträge zur Kenntnis der Phacopina (Trilobita), 9: Phacops (Omegops) n. sg. (Trilobita; Ober-Devon). Senckenbergiana Lethaea, 56, 429–451.
Tolokonnikova, Z., Ernst, A. & Yarahmadzahi, H. 2011. Frasnian bryozoans (Late Devonian) from the Khoshyeilagh Section, Alborz Mountains (Northern Iran). Paläontologische Zeitschrift, 85, 393–405.
Torsvik, T. H. & Cocks, L. R. M. 2017. Earth History and Palaeogeography. Cambridge University Press, 317 pp.
https://doi.org/10.1017/9781316225523
Weber, V. N. 1937. Trilobites of the Carboniferous and Permian System of the U.S.S.R. 1. Carboniferous trilobites. Palaeontology of U.S.S.R. Monographs, 71(1), 1–160.
Wendt, J., Kaufmann, B., Belka, Z., Farsan, N. M. & Karimi Bavandpur, A. 2005. Devonian/Lower Carboniferous stratigraphy, facies patterns and palaeogeography of Iran Part II. Northern and central Iran. Acta Geologica Polonica, 55, 31–97.
Yuan, J.-L. & Xiang, L.-W. 1998. Trilobite fauna at the Devonian–Carboniferous boundary in South China (S. Guizhou and N. Guangxi). Bulletin National Museum of Natural Science (Special Publication), 8, 1–281.
Ziegler, W. & Sandberg, C. A. 1984. Palmatolepis-based revision of upper part of standard Late Devonian conodont zonation. Geological Society of America Special Paper, 196, 179–194.
