A new assemblage of graptolites, rhabdopleuran hemichordates and chitinous hydroids from the late Arenig (Ordovician) of the Banestan area, east-central Iran

Abstract

A rich benthic and planktonic graptolite fauna is associated with encrusting rhabdopleuran hemichordates and chitinous hydrozoans in the late Arenig (Ordovician) part of the Katkoyeh Formation at Banestan, east-central Iran. New taxa described here are the dendroid graptolites Callograptus huckriedei sp. nov. and Dictyonema bitubulata sp. nov. Other dendroid graptolites Dendrograptus sp. cf. D. flexuosus J. Hall, 1865; Acanthograptus divergens Skevington, 1963; and Thallograptus ?succulentus Ruedemann, 1904 are described. The tuboid graptolite Galeograptus sp., the rhabdopleuran hemichordates Rhabdopleura sp. aff. R. primaevus (Kozlowski, 1967) and Kystodendron sp., and the chitinous hydroid Palaeotuba sp. are also described. Graptoloid graptolites described here are Aulograptus? sp., Didymograptus incertus Perner, 1895, Undulograptus formosus (Mu & Lee, 1958), and Yutagraptus sp. cf. Y. mantuanus Riva, 1994. All but two species-level taxa are described from Iran for the first time. The fauna is confirmed as being late Arenig or, less likely, early Llanvirn and thus probably correlates with the early part of the Darriwilian stage. It resembles the Atlantic cold water faunas in lacking isograptids and sinograptids.