Late Triassic to Early Jurassic radiolarian, conodont and ammonite assemblages from the Tavuscayiri block, Mersin Mélange, southern Turkey: Time constraints for the T / J boundary and sedimentary evolution of the southern margin of the northern Neotethys Author Tekin, Kagan Author Krystyn, Leopold Author Okuyucu, Cengiz Author Bedi, Yavuz Author Sayit, Kaan text Geodiversitas 2020 2020-11-26 42 27 493 537 journal article 10.5252/geodiversitas2020v42a27 20141273-3452-4388-b6a8-aab9193c87fe 1638-9395 4447758 urn:lsid:zoobank.org:pub:1A437774-B5BE-49F2-8DEF-D46F2790484A Canoptum cephalobulbosum Tekin , n. sp. ( Fig. 11 K-O) urn:lsid:zoobank.org:act: E28BC50B-39C6-4959-B646-EB90ABB2B414 HOLOTYPE . — Sample Orbuk-15, HU.JMB.0145 ( Fig. 11K ). PARATYPES . — HU.JMB.0146 ( Fig. 11L ), HU.JMB.0147 ( Fig.11M ), HU.JMB.0148 ( Fig. 11N ), HU.JMB.0149 ( Fig. 11O ). TYPE LOCALITY . — Orbuklukeli section, Mersin Mélange, NW of Mersin city, southern Turkey . ETYMOLOGY. — Due to its very bulbose cephalis. OCCURRENCE. — Upper Triassic, Rhaetian, Orbuklukeli section, Mersin Mélange, NW of Mersin city, southern Turkey . DIMENSIONS (based on five specimens, in µm). — Maximum length of test: 144-160 ( holotype : 144, average: 151.4); Maximum width of test: 80-96 ( holotype : 96, average: 90.4). DESCRIPTION Test mainly conical with three to four post-abdominal segments, increasing in width until second post-abdominal segment, then last two post-abdominal segments decreasing in width. Cephalis knob-like, bulbous, poreless without horn. Collar stricture mainly poreless and marked by a shallow depression. Test increasing in width slowly until the second post-abdominal segment and subtrapezoidal to hoop-shaped in outline while last two segments decreasing in width, and inverse subtrapezoidal to hoop-shaped in outline. Thorax mainly covered by veneer of microgranular silica but sometimes including some subcircular scattered pores. In some specimens ( Fig. 11K, O ), small nodes are also visible at the surface of thorax. Abdomen and post-abdominal segments with small, numerous, circular to subcircular pores. In some specimens ( Fig. 11K, M ), where veneer of microgranular silica is not prominent, two rows of pores are visible just below and above the circumferential strictures. REMARKS This species differs from Canoptum rhaeticum ( Kozur & Mostler 1981: 103-104 , pl. 20, figs 1-4) by having a very bulbous cephalis, shorter and slimmer test composed of less segments.