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 Laxtorum breve Tekin , n. sp. ( Fig. 12 D-J) urn:lsid:zoobank.org:act: AAC22989-AF44-439E-8E99-6493848E6229 Laxtorum sp. – Aita & Spörli 1992 : pl. 5, fig. 12. HOLOTYPE . — Sample Orbuk-32, HU.JMB.0157 ( Fig. 12D ). PARATYPES . — HU.JMB.0158 ( Fig. 12G ), HU.JMB159 ( Fig. 12H ), JMB.0160 ( Fig. 12I ), HU.JMB161 ( Fig. 12J ). TYPE LOCALITY . — Orbuklukeli section, Mersin Mélange, NW of Mersin city, southern Turkey . ETYMOLOGY. — From the Latin brevis-e – short, brief, due its short shell. OCCURRENCE. — Lower Jurassic, lower Sinemurian of Auckland , New Zealand and Orbuklukeli section, Mersin Mélange, NW of Mersin city, southern Turkey . DIMENSIONS (based on seven specimens, in µm). — Length of horn: 84-120 ( holotype : 100, average: 105.7); Maximum length of test: 132-158 ( holotype : 158, average: 141.1); Maximum width of test: 120-168 ( holotype : 125, average: 136.1). DESCRIPTION Test short with three post-abdominal segments. Cephalis hemisphaerical with a long horn. Horn needle-like, subcircular in transversal section, slightly decreasing in width distally and terminated in a sharp end. Rest of the test increasing in width very slowly, and decreasing in width at last segment. Collar, lumbar and following strictures not prominent, not visible at the surface of test. Surface of test covered with thick layer of silica with irregular surface. Test bears circular to subcircular pores of different sizes. REMARKS This species differs from Laxtorum hemingense Whalen & Carter in Carter et al. (1998: 80 , pl. 25, figs 6-8, 13, 14, 24, 25; pl. 27, figs 5, 6, 16, 20) by having a shorter test with very long horn and indistinct circumferential ridges. It can be differentiated from Laxtorum obscurum Tekin , n. sp. by possessing a thin, long horn and longer test with more segments.