New,early ostracods from the Ordovician (Tremadocian) of Iran: systematic,biogeographical and palaeoecological significance

New Tremadocian ostracod material from the Alborz Mountains of Iran confirms the early and widespread occurrence of the Ordovician genus Nanopsis, and the apparently simultaneous first appearance of ostracods in the fossil record at the level of the P. deltifer conodont biozone (485.5 Ma) from China to Argentina. Nanopsis pairidaeza sp. nov. adds to the pool of species diversity for the Early Ordovician, though documented Tremadocian ostracod generic diversity remains low, with only four genera. The presence of Early Ordovician ostracods in Alborz, their occurrence elsewhere in palaeocontinental Gondwana, Baltica and China coupled to their marked absence from the Tremadocian of Laurentia and Siberia, supports the notion of the earliest occurrence of ostracods centred on Gondwana/Baltica.     

Late Ordovician cephalopods,tentaculitides, machaeridians and echinoderms from Kuh-e Faraghan,High Zagros,Iran

Ghavidel-Syooki, M., Evans, D.H., Ghobadi Pour, M., Popov, L.E., Álvaro, J.J., Rakhmonov, U., Klishevich, I.A. & Ehsani, M.D., 15.5.2015. Late Ordovician cephalopods, tentaculitides, machaeridians and echinoderm columnals from Kuh-e Faraghun, High Zagros, Iran. Alcheringa 39, 530–549. ISSN 0311-5518.

Late Ordovician (Katian, uppermost Acanthochitina barbata to Armoricochitina nigerica chitinozoan zones) cephalopods, tentaculitides, machaeridians and echinoderms are documented for the first time from the southern Zagros Ranges. A low-diversity cephalopod fauna includes Geisonocerina dargazense sp. nov., Isorthoceras sp. cf. I. bisignatum (Barrande) and other undetermined orthoceratides. The presence of Late Ordovician tentaculitides in the high- to mid-latitude margins of Gondwana has been documented previously, but no examples have been described in detail. Thus, Costatulites kimi sp. nov., which currently occurs associated with brachiopods characteristic of the Svobodaina havliceki (brachiopod) Association, represents the earliest undoubted record of tentaculitides in Gondwana. Machaeridians constitute a relatively common component of the Late Ordovician benthic faunas from the Mediterranean margin of Gondwana, but no previous records on the Gondwanan Iranian-Arabian segment have been reported. Three echinoderm taxa based on dissociated columnals are documented from the Armoricochitina nigerica chitinozoan Zone, including Sumsaricystis radiatus Stukalina, Ristnacrinus sp. and Rosulicrinus rosulus Stukalina.

Mohammad Ghavidel-Syooki [m_ghavidelsyooki@yahoo.com] Institute of Petroleum Engineering, Technical Faculty of Tehran University, PO Box 11365-4563, Tehran, Iran; David H. Evans [david.evans@naturalengland.org.uk], Natural England, Suite D, Unex House, Bourges Boulevard, Peterborough PE1 1NG, UK; Mansoureh Ghobadi Pour* [mghobadipour@yahoo.co.uk], Department of Geology, Faculty of Sciences, Golestan University, Gorgan, Iran; Leonid E. Popov [leonid.popov@museumwales.ac.uk], Department of Geology, National Museum of Wales, Cathays Park, Cardiff CF10 3NP, UK; J. Javier Álvaro [jj.alvaro@csic.es], Instituto de Geociencias (CSIC-UCM), c/ José Antonio Novais 2, 28040 Madrid, Spain; Utkyr Rakhmonov, Kitab State Geological Reserve, 9 Ipak Yuli Street, Sakhrisabz, Uzbekistan; Inna A. Klishevich, Department of Historical Geology, Geological Faculty, St Petersburg State University, Universitetskaya Naberezhnaya 7/9, 199034 St Petersburg, Russia [inna@IK4848.spb.edu]; Mohammad H. Ehsani [mh_ehsani@hotmail.com], Institute of Petroleum Engineering, Technical Faculty of Tehran University, PO Box 11365-4563, Tehran, Iran. *Also affiliated with Department of Geology, National Museum of Wales, Cathays Park, Cardiff CF10 3NP, UK.     

Terminal Cambrian and Early Ordovician (Tremadocian) conodonts from Eastern Alborz,north-central Iran

Hadi Jahangir, Mansoureh Ghobadi Pour, Alireza Ashuri & Arash Amini, December 2015. Terminal Cambrian and Early Ordovician (Tremadocian) conodonts from Eastern Alborz, north-central Iran. Alcheringa ##, ###-###. ISSN 0311-5518.

Uppermost Cambrian (Furongian) and Lower Ordovician (Tremadocian) deposits of eastern Alborz in northern Iran contain several successive low- to moderate-diversity conodont associations including 13 genera and 19 species of euconodonts, paraconodonts and protoconodonts, which define six biozones: 1, the Proconodontus muelleri; 2, Eoconodontus notchpeakensis; 3, Cordylodus andresi; 4, Cordylodus proavus; 5, Paltodus deltifer; and 6, Paroistodus proteus zones. With the exception of Cordylodus andresi, which is otherwise known from Baltoscandia and from the Oaxaquia terrane (Mexico), all index-taxa are geographically widespread, allowing long-range correlation within the Cold Domain or the North Atlantic Province, and in particular with Baltica. Invasion of euconodonts in the Alborz region, defined by the first occurrence of Proconodontus muelleri, coincides closely with a steady rise in sea level and termination of carbonate sedimentation, whereas the transition from the Proconodontus muelleri to Eoconodontus notchpeakensis zones occurs during a highstand interval unlike in Laurentian sequences. The interval corresponding to the Cordylodus andresi and Cordylodus proavus zones, and the transition from the Paltodus deltifer to Paroistodus proteus zones coincided with unstable sea levels and the formation of shoal complexes. The lower boundary of the Floian Stage can be provisionally placed slightly below the first documented occurrence of Acodus sp. cf. A. kechikaensis, somewhat below the second unit of andesitic lava flows in the Simeh-Kuh section.

Hadi Jahangir [jahangir.hadi@gmail.com] and Alireza Ashuri [ashouri2001@yahoo.com] Department of Geology, Faculty of Sciences, Ferdowsi University, Azadi Square, Mashhad 91775-1436, Iran; Mansoureh Ghobadi Pour* [mghobadipour@yahoo.co.uk; m.ghobadipour@gu.ac.ir] and Arash Amini [a.amini@gu.ac.ir], Department of Geology, Faculty of Sciences, Golestan University, Gorgan 49138-15739, Iran. *Also affiliated with Department of Geology, National Museum of Wales, Cathays Park, Cardiff CF10 3NP, UK.     

Ordovician trilobites from Deh-Molla,eastern Alborz,Iran

Ghobadi Pour, M., 21 June 2019. Ordovician trilobites from Deh-Molla, eastern Alborz, Iran. Alcheringa 43, 381–405. ISSN 0311-5518

Seventeen species from 14 genera of Tremadocian and Darriwilian trilobites, plus two taxa recognizable only down to family level, have been documented from the Lower to Middle Ordovician succession of the Deh-Molla area, southeast of Shahrud in northern Iran. Two species, Asaphellus intermedius and Conophrys multituberculatus, are new to science. Unlike previously documented Iranian faunas, the early Tremadocian trilobite assemblage is characterized by proliferation of the olenid Chungkingaspis sinensis, which is also known as the eponymous taxon of the basal Ordovician trilobite biozone in South China. This is the first record of the occurrence of the olenid biofacies in the Ordovician of Iran. Overall, both the Tremadocian and Darriwilian trilobite assemblages show distinct similarity to the contemporaneous faunas of South China down to species level. Trilobite-based correlation with the Ordovician succession of South China confirms the existence of a hiatus at the base of the Ordovician succession in the eastern Alborz and a significant gap, with the upper Tremadocian, Floian and Dapingian parts of the succession completely missing in Deh-Molla.

Mansoureh Ghobadi Pour [mghobadipour@yahoo.co.uk and m.ghobadipour@gu.ac.ir], Department of Geology, Faculty of Sciences, Golestan University, Gorgan 49138-15739, Iran. *Also affiliated with Department of Natural Sciences, Natural Museum of Wales, Cardiff, Cathays Park, Cardiff CF10 3NP, UK.