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doi:10.2204/iodp.proc.342.206.2018

Methods and materials

At Site U1411 (41°37′5.94″N, 48°59′59.94″W), three holes were drilled on the seafloor of the southeast Newfoundland Ridge at 3299 m water depth (see the “Site U1411” chapter [Norris et al., 2014]; Fig. F1). We took 39 sediment samples of ~20 cm³ volume from the working halves of Cores 342-U1411B-16X through 28X (Table T1). All the core sediments consist of two lithologic units: silty clay with nannofossils at 140–235 m core composite depth below seafloor (CCSF) and nannofossil chalks with foraminifers at 235–266 m CCSF (lithostratigraphic Units II and III, respectively). The sediments are pinkish to white in color. Using planktonic biostratigraphy, the core sediments are dated to be ~37.9–33.4 Ma, late Eocene to early Oligocene, and correlate to nannofossil Zones NP18–NP21 of Martini (1971) and foraminiferal Zones E14–O1 of Wade et al. (2011). The paleodepth at 34 Ma is estimated to be around 3000 m.

For extracting ostracod specimens, we washed samples using a sieve with 32 µm openings. Ostracod specimens were picked from fractions >150 µm using a fine brush under a binocular microscope. The specimens were observed and their photos were taken with a JSM-6500F scanning electron microscope (SEM) (JEOL Ltd.) (Pl. P1, P2, P3, P4, P5) and an optical microscope in order to identify them to the species level and describe morphological characteristics.

For illustrating the internal structures of the new species, the specimens were immersed in tap water in a Petri dish and observed under transmitted light on a VHX-2000 digital microscope (Keyence, Ltd.). Images of the internal structures were also captured. Using the focus stacking system equipped with the digital microscope, deep-focus images of the internal structures were made (Pl. P6). Image outlines were drawn to identify shapes of marginal pore canals and vestibulum (Fig. F2). Valve length and valve height of the specimens were measured using the digital microscope (Table T1, T2; Fig. F3). The SEM and the digital microscopes are hosted at the Center for Advanced Marine Core Research at Kochi University (Japan).

For systematic descriptions, higher taxonomy followed Brandão et al. (2017). The general terminology of the morphology followed Sylvester-Bradley and Benson (1971) and Horne et al. (2002). The terminology for characteristics of Krithe and trachyleberids followed Coles et al. (1994) and Yasuhara et al. (2015), respectively. According to Athersuch et al. (1989), carapace size is classified as follows:

• Small: <500 µm long
• Medium: 500–650 µm long
• Large: >650 µm long

All the specimens were registered and deposited at the National Museum of Nature and Science (NMNS) (Tsukuba, Japan) and the Scripps Institution of Oceanography (SIO) (University of California, San Diego), which are Micropaleontological Reference Centers for the International Ocean Discovery Program (Table T1). The catalog numbers at NMNS and SIO have prefixes of MPC and SIO-BIC, respectively.

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