Taxonomy of Middle Eocene Diatom Resting Spores and Their Allied Taxa from the Central Arctic Basin

Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

Itsuki Suto,1 Richard W. Jordan2 and Mahito Watanabe3 1Department of Earth and Planetary Sciences, Graduate School of Environmental Studies, Nagoya University, Chikusa, Nagoya 464-8601, Japan 2Department of Earth and Environmental Sciences, Faculty of Science, Yamagata University, Kojirakawa-machi 1-4-12, Yamagata 990-8560, Japan 3Institute of Geology and Geoinformation, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), Central 7, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567, Japan email: [email protected] email: [email protected] email: [email protected]

ABSTRACT: In the late summer of 2004, Integrated Ocean Drilling Program (IODP) Expedition 302, also called the Arctic Coring Ex- pedition (ACEX), successfully drilled the first deep boreholes on the Lomonosov Ridge in the central Arctic Ocean. The well preserved fossil diatoms used here are from biosiliceous Unit 2 in Holes 2A and 4A of middle Eocene age. In the lower part of Unit 2, resting spores occurred abundantly with other fossil diatoms. 25 diatom resting spore taxa and five allied vegetative cell taxa are described in this study of ACEX samples. Moreover 11 diatom taxa which did not occur in these sediments are also described for comparison with the Eocene Arctic resting spores. Their biostratigraphic ranges are also indicated. 10 of the resting spore species which occur in the ACEX samples had already appeared during the late Cretaceous while the rest of them appeared in Eocene. 21 of 25 (84%) resting spore taxa became extinct during the middle Eocene to early Oligocene. Most resting spore taxa described in this study do not belong to Chaetoceros resting spores because they lack a single ring of puncta on the hypovalve mantle that characterizes the resting spores of Chaetoceros and became extinct before Oligocene, therefore it is clear that Chaetoceros did not flourish in the middle Eocene in the Arctic Ocean. Other diatom genera that produced resting spores such as Pterotheca and Pseudopyxilla, might have prospered before the Eocene/Oligocene boundary, although their vegetative cells are unknown so far. Since some Chaetoceros resting spore taxa are reported in this study, most coastal regions experienced regular seasonal environmental change, which benefitted genera such as Pterotheca, Pseudopyxilla and Odontotropis, but also there might have been some patchy coastal upwelling regions with nutrient depletion and sporadic supplies where Chaetoceros may have survived. The abundant dinoflagellate cysts preserved in middle Eocene ACEX cores provide evidence of stable conditions before the Eocene/Oligocene boundary. The resting spore ecology of most resting spore taxa before the Eocene may have been similar to that of dinoflagellate cysts rather than that of Chaetoceros resting spores after the Oligocene.

INTRODUCTION ate and boreal waters, but are also found in polar and tropical regions (e.g. Schrader 1978, Leventer 1991), especially in Fossil diatoms have been reported in many oceanic sediment upwelling areas (Hargraves 1984) and reported from ancient cores, especially those of the DSDP (Deep-Sea Drilling Project) sediments, extending back to the Cretaceous (Hanna 1927b, and ODP (Ocean Drilling Program), as biostratigraphic mark- Ross and Sims 1974). Fossil diatom resting spores have been ers in various geological epochs, particularly Miocene (e.g. used as paleoclimatic, especially upwelling, indicators. Suto Yanagisawa and Akiba 1998). Although extensive studies of (2006a) proposed that the increase in diversity and abundance fossil Arctic diatoms in diatomites (e.g. Strelnikova 1974, of Chaetoceros resting spores from the late Eocene to early Barron 1985, Medlin and Priddle 1990, Tapia and Harwood Oligocene in the Norwegian Sea indicated a change from a sta- 2002) have been reported, these studies only documented the ble environment with regular seasonal supply of nutrients to an late Cretaceous or Holocene and Pleistocene diatoms, and since unstable one with depletion and sporadic supply. He also men- then there have been few papers on Eocene Arctic diatoms. tioned that Chaetoceros might have established itself as the Moreover, the taxonomy of fossil diatom resting spores has main primary producer in the Oligocene Norwegian Sea, re- been neglected. placing dinoflagellates and/or nannoplankton which had been the main producers till the late Eocene because their diversities Some coastal planktonic diatoms survive unfavorable environ- decreased across the boundary (Falkowski et al. 2004). mental conditions as resting spores. The model of Gran (1912) proposed that resting spores were benthic resting stages, and subsequent studies showed that they are formed in response to In the late summer of 2004, Integrated Ocean Drilling Program nutrient depletion, darkness and low temperature (e.g. Kuwata (IODP) Expedition 302, also known as the Arctic Coring Expe- et al. 1993, Oku and Kamatani 1995, 1997, 1999, McQuoid and dition (ACEX), successfully drilled the first deep boreholes in Hobson 1996). Resting spores having thick silicified valves and the central Arctic Ocean, penetrating a ~430m-thick package of lacking areolae are preserved frequently as fossils in nearshore sediment on the Lomonosov Ridge (Backman et al. 2005a, b, sediments. The occurrences of fossil diatom resting spores are Moran et al. 2006) (Text-figure 1). The well preserved Eocene concentrated in coastal waters and are most common in temper- fossil diatoms used here are from biosiliceous Unit 2 in Holes micropaleontology, vol. 55, nos. 2-3, pp. 259-312, text-figures 1-9, plates 1-13, 2009 259 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

cies is separated from Peripteropsis norwegica Suto (2005b) by Pterotheca cf. aculeifera Grunow sensu HAJÓS and STRADNER 1975, lacking branched thin and wide processes. p. 933, pl. 28, figs. 1, 2 nec pl. 12, fig. 6. Pterotheca carinifera Grunow in VAN HEURCK sensu MCCOLLUM Stratigraphic and geographic distributions: 1975, p. 535, pl. 10, fig. 4 nec pl. 16, figs. 6, 7. This species oc- Pterotheca danica (Grunow) FORTI 1909, p. 13. – GOMBOS 1983, p. curred in middle Eocene sediments from IODP Leg 302 Sites 570, pl. 3, fig. 9. – GOMBOS and CIESIELSKI 1983, p. 603, pl. 13, 2A and 4A in the central Arctic Ocean. figs. 1-3, 9. – BARRON et al. 1984, p. 156, pl. 8, fig. 10. – BALDAUF 1985, p. 464, pl. 12, figs. 8, 9. – HARWOOD 1988, p. 86, fig. 18.12. – Remarks: This species does not appear to belong to the fossil DESIKACHARY and SREELATHA 1989, p. 218, pl. 100, figs. 1, 2, resting spore morpho-genus Peripteropsis of extant 5. Chaetoceros because of the absence of a ring of puncta on the Pterotheca major JOUSÉ 1955, p. 101, text-fig. 1; pl. 6, fig. 2. – GOMBOS 1983, p. 570. – GOMBOS and CIESIELSKI 1983, p. 603, hypovalve margin. pl. 13, figs. 6-8. – HARWOOD 1988, p. 86, fig. 18.16. Pterotheca spada TEMPÈRE et BRUN sensu GOMBOS and Porotheca danica (Grunow) Fenner 1994 CIESIELSKI 1983, p. 603, pl. 13, figs. 4, 5. Plate 7, figures 1-28 Pterotheca (Grunow) FORTI sensu HARGRAVES 1984, p. 71, figs. 14-16. Porotheca danica (Grunow) FENNER 1994, p. 114, pl. 4, figs. 16, 17; Pterotheca carinifera (Grunow in Van Heurck) FORTI sensu HAR- pl. 15, figs. 1-6. WOOD 1988, p. 86, fig. 18.6. Basionym: Stephanogonia (Pterotheca?) danica GRUNOW in VAN Stephanogonia novazelandica Grunow sensu DESIKACHARY and HEURCK 1880-1885, pl. 83 bis., figs. 7, 8. SREELATHA 1989, p. 228, pl. 100, figs. 3, 4. Pyxilla? carinifera Grunow sensu HOMANN 1991, p. 139, pl. 55, fig. 6 References: Stephanogonia danica GRUNOW 1866, p. 146. – CLEVE- nec figs. 1-5, 8. EULER 1951, Handl. 2: 1, p. 110, figs. 232a, b. – HOMANN 1991, p. Pterotheca carinifera Grunow sensu HARWOOD and BOHATY 2000, 141, pl. 55, figs. 7, 9-16. p. 93, pl. 3, fig. t; pl. 9, fig. o. Synonymy: Pyxilla carinifera var. russica PANTOCSEK 1905, Bd. 3, pl. 35, fig. 491; Bd. 3, pl. 29, fig. 423. Pterotheca danica GRUNOW, HANNA 1927a, p. 119, pl. 20, fig. 11. – Emended description: Epivalve convex, cylindrical with a high PROSCHKINA-LAVRENKO 1949, p. 203, pl. 75, fig. 9. – HAJÓS mantle, diameter 13-45µm, transapical axis 30-65µm. The cen- 1976, p. 829, pl. 16, figs. 12-15. – GOMBOS 1977, p. 596, pl. 23, fig. tral part of epivalve face protracted forming a hollow tube with 5. – LEE 1993, p. 42, pl. 3, fig. 4. – DELL’AGNESE and CLARK a flat top. Epivalve surface generally structured by seven to 1994, fig. 9.11.

TEXT-FIGURE 8 Geographic and stratigraphic distribution of Trochosira spinosa Kitton.

1-25. Trochosira spinosa 15 Fur Formation, Denmark (Fenner 1994); 1-17. Reported as Trochosira spinosa. 16 ODP Hole 908A (Scherer and Koç1996); 1 Mors, Denmark (Kitton 1871); 17 DSDP Site 338 (This study). 2 Mors Formation, Denmark (Van Heurck 1880-1885); 18, 19. Reported as Trochosira spinosus. 3 Lower course of the Anadyr River, Russia (Sheshu- 18 Jutland, Denmark (Sims 1988); kova-Poretskaya 1967); 19 Cape Roberts Project, Antarctica (Scherer et al. 4 DSDP Site 173 (Schrader 1973a); 2000). 5 west Kazakhstan (Glezer et al. 1974); 20. Reported as Trochosira spinosa? 20 McMurdo Sound, Antarctica (Harwood and Bohaty 6 DSDP Site 337 (Schrader and Fenner 1976); 2000). 7 DSDP Site 338 (Schrader and Fenner 1976); 21, 22. Reported as Trochosira ornata. 21 Jutland, Denmark (Van Heurck 1880-1885); 8 DSDP Site 339 (Schrader and Fenner 1976) 22 Fur Formation, Denmark (Fenner 1994). 9 DSDP Site 343 (Schrader and Fenner 1976); 23. Reported as Sceletonema ornatum. 10 DSDP Site 338 (Dzinoridze et al. 1978); 23 eastern slopes of Ural Mountains, USSR (Jousé 11 DSDP Site 339 (Dzinoridze et al. 1978); 1955). 12 DSDP Site 340 (Dzinoridze et al. 1978); 24. Reported as Sceletonema spinosum. 24 eastern slopes of Ural Mountains, USSR (Jousé 13 Hawthorn Formation, South Carolina (Abbott and 1955). Andrews 1979); 25. Reported as Trochosira coronata. 14 Mors and Fur Formations, Denmark (Homann 1991); 25 ODP Hole 913B (Scherer and Koç 1996).

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TEXT-FIGURE 8 Legend on opposite page. eight radial hyaline ridges from the edge between the mantle Comparison: This species is very similar to Kentrodiscus and the valve face to the elevated central top. Radial hyaline blandus Long, Fuge et Smith (1946) of Nikolaev et al. (2001, p. ridges with arranged knobs and short spines on it, and smaller 25, pl. 36, figs. 1-5), which was found in late Cretaceous marine anastomosing hyaline ridges present between these ridges. deposits in the Marca Shale Member, California. Both species Mantle hyaline, perforated by small pores and small hyaline have a cylindrical highly vaulted valve shape with a flat top pos- anastomosing ribs. The pore which is present on the top of the sessing a slit in the central part. In Nikolaev et al. (2001), the central raised platform (Fenner 1994) was not observed in this specimens are illustrated with a nearly flat hypovalve covered study. Hypovalve is featureless, with a raised rim and concave with numerous short strong spines. The genus Kentrodiscus central area, occasionally with a slightly central elevation (see Pantocsek (1903), which contains some species from the late figure 14 in Hargraves 1984), although frustule was not ob- Cretaceous, for example, K. fossilis Pantocsek (1903), K. served in this study. aculeatus Hanna (1927b), K. andersoni Hanna (1927b) and K. armatus Hajós in Hajós and Stradner (1975), is characterized by Type level and locality: Lower Eocene, Mors Formation in having valves protracted to form a hollow tube with a flat top Jutland, Denmark (Grunow in Van Heurck 1880-1885). with numerous strong spines on the epi- and hypovalve faces. Kentrodiscus blandus lacks spines on the epivalve surface, but Type specimen: Depository not designated. has radially arranged hyaline ridges which run from the edge

275 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

between the mantle, therefore K. blandus may belong to the ge- Comparison: This species is easily distinguished from Poro- nus Porotheca although the hypovalve structure of Po. danica theca danica by its more slender valve and its possession of is unknown. hyaline ridges lacking knobs and spines. This species also resembles Pterotheca spada (= Pt. subulata) and Pseudopyxilla This species is also similar to Pseudopyxilla carinifera in that capreolus in possessing a hollow tube on its epivalve, but is the valve shape forms a hollow tube with radially arranged identified from the former by its nearly flat hypovalve and from hyaline ridges running from the flat top to mantle edge, but it the latter by lacking a dichotomous branching hyaline process at differs from the latter by its larger valve size and the possession the distal end of the hollow tube. of hyaline ridges with knobs and spines on it. Pterotheca pokrovskajae Jousé sensu Harwood (1988, p. 86, figs. 12.9-10, Stratigraphic and geographic distributions: This species occurs 18.19-23) may be distinguished from Po. danica by the lack of from the late Cretaceous to the late Miocene (Text-figure 3). abundant pores on its valve. This species was not observed in this study.

Stratigraphic and geographic distributions: This species was Remarks: This species is characterized by its hyaline cylindrical frequently found in late Cretaceous to early Miocene sediments to conical valve, therefore this species was transferred to the ge- (Text-figure 3). This species was found in late Cretaceous and nus Pseudopyxilla in this study. When Fenner (1994) erected early Paleocene sediments from Seymour Island, Antarctic the genus Porotheca, she mentioned that it is characterized by Peninsula (Harwood 1988), from late Cretaceous DSDP Site cylindrical to conical valves with a central elevation with a 275 sediments at the southeast margin of Campbell Plateau near pore-like opening on top. It is unknown whether or not Ps. New Zealand (Hajós and Stradner 1975), and from the Alpha carinifera possesses such a pore-like opening, however its Ridge, Arctic Ocean (Dell’Agnese and Sreelatha 1989). With stratigraphic and geographic distributions resemble closely regards to Eocene sediments, this species has been reported those of Po. danica, therefore Ps. carinifera may belong to the from all parts of the world including the IODP Expedition 302, genus Porotheca and be a variety of Po. danica. central Arctic Ocean, however it was also found in the Southern Hemisphere in Oligocene sediments and from the high latitude The specimens of Pterotheca carinifera in Harwood (1988, p. Pacific Ocean in early Miocene deposits. 86, fig. 18.6), Harwood and Bohaty (2000, p. 93, pl. 3, fig. t; pl. 9, fig. o) and McCollum (1975, p. 535, pl. 16, figs. 6, 7 nec pl. Etymology: Not designated. – but presumably refers to Den- 10, fig. 4), and of Pyxilla? carinifera in Homann (1991, p. 139, mark. pl. 55, figs. 6, 8 nec figs. 1-5) are identified as Porotheca danica because their large valves with hyaline ridges are covered with Pseudopyxilla carinifera (Grunow in Van Heurck) Suto, Jordan et knobs and spines. The specimen of Pterotheca carinifera in Lee Watanabe comb. nov. (1993, p. 42, pl. 3, fig. 10 nec pl. 1, fig. 19; pl. 2, fig. 17) is Pterotheca subulata. Basionym: Pyxilla ? carinifera GRUNOW in VAN HEURCK 1880-1885, pl. 83, fig. 5, 6. – HOMANN 1991, p. 139, pl. 55, figs. 1-5, Etymology: The Latin carinifera means “coarse keel”. nec figs. 6, 8. Synonymy: Pterotheca carinifera (GRUNOW in VAN HEURCK) Pseudopyxilla dubia (Grunow in Van Heurck) Forti 1909 FORTI 1909, p. 13. – DESIKACHARY and SREELATHA 1989, p. Plate 8, figures 1-21 218, pl. 142, fig. 10. Pterotheca carinifera GRUNOW, HANNA 1927a, p. 119, pl. 20, figs. Pseudopyxilla dubia (Grunow) FORTI 1909, pl. 1, figs. 1-3. – HAJÓS 9, 10. – PROSCHKINA-LAVRENKO 1949, p. 203, pl. 75, figs. 7a, b; 1968, p. 136, pl. 38, figs. 2, 3. – HANNA 1970, p. 191, figs. 66, 68. – pl. 77, fig. 1; pl. 98, fig. 8. – SHESHUKOVA-PORETSKAYA 1967, SCHRADER and FENNER 1976, pl. 44, figs. 13, 14. – FENNER p. 270. – GOMBOS 1976, p. 596, pl. 23, figs. 1, 2. 1978, p. 526, pl. 14, fig. 9; pl. 17, figs. 1-6. – GOMBOS and Pyxilla (Rhizosolenia?) carinifera Grunow sensu CLEVE-EULER CIESIELSKI 1983, p. 603. – GOMBOS 1984, p. 500, pl. 2, figs. 1951, Handl. 2: 1, p. 93, fig. VI-p. 10-12. – FENNER 1994, p. 115, pl. 9, fig. 12. – HARWOOD and Pterotheca carinifera var. curvirostris JOUSÉ 1955, p. 99, pl. 2, fig. 7. – BOHATY 2000, pl. 4, fig. d. HARWOOD 1988, p. 86, fig. 18.7. Pseudopyxilla dubia Grunow – PROSCHKINA-LAVRENKO 1949, p. Pterotheca carinifera GRUNOW in VAN HEURCK – MCCOLLUM 200, pl. 73, fig. 13; pl. 98, figs. 1a, b. 1975, p. 535, pl. 16, figs. 6, 7 nec pl. 10, fig. 4. Pseudopyxilla dubia (Grunow in Van heurck) FORTI – BARRON Pterotheca carinifera (Grunow) FORTI – SCHRADER and FENNER 1975, p. 152, pl. 11, fig. 13. – HARWOOD 1988, p. 85, figs. 17.23, 24. 1976, p. 994, pl. 9, fig. 6; pl. 43, fig. 12. – LEE 1993, p. 42, pl. 1, fig. 19; pl. 2, fig. 17 nec pl. 3, fig. 10. – FENNER 1994, p. 116. Basionym: Pyxilla? dubia Grunow in VAN HEURCK 1880-1885, pl. Pterotheca minor HARWOOD 1988, p. 86, figs. 12.12, 13. – HAR- 83, figs. 7, 8. WOOD and BOHATY 2000, p. 93, pl. 3, figs. r, s. References: Pyxilla dubia Grunow in VAN HEURCK 1880-1885, pl. Description: Epivalve convex, cylindrical with a high mantle, 83, fig. 12. – HASEGAWA 1977, p. 87, pl. 21, fig. 4. – DESI- diameter 7-22µm, transapical axis 10-70µm. The central part of KACHARY and SREELATHA 1989, p. 219, pl. 93, figs. 3-6, 15. Pyxilla dubia Grunow – HANNA 1927a, p. 119, pl. 20, fig. 13. epivalve face protracted to form a hollow tube with a flat top. Pyxilla (Rhizosolenia?) dubia Grunow in CLEVE-EULER 1951, Handl. Epivalve surface generally structured by four radial hyaline 2: 1, p. 93, figs. VI-n. ridges from the edge between the mantle and the valve face to Pyxilla (Pyxilla) dubia Grunow ex VAN HEURCK sensu KANAYA the elevated central top, hyaline between radial hyaline ridges. 1957, p. 114, pl. 8, fig. 10. Mantle distinct and hyaline. Hypovalve nearly flat and feature- Rhizosolenia dubia (Grunow) HOMANN 1991, p. 69, figs. 1-8, 11-13. less (see pl. 55, figure 2 in Homann 1991), although frustule Synonymy: Rhizosolenia americana Ehrenberg sensu EHRENBERG 1854, pl. 18, figs. 98a, h, i nec figs. 98b-g. was not observed in this study. Pseudopyxilla americana (Ehrenberg) FORTI sensu HAJÓS and STRADNER 1975, p. 933, pl. 12, fig. 3. Type level and locality: Lower Eocene, Jutland, Denmark. Pyxilla ? baltica Grunow in VAN HEURCK 1880-1885, pl. 83, figs. 1, 2. Type specimen: Depository not given. Pyxilla baltica Grunow in VAN HEURCK 1880-1885, pl. 83 bis., fig. 4.

276 Micropaleontology, vol. 55, nos. 2-3, 2009

TEXT-FIGURE 9 Generalized biostratigraphic ranges of diatom resting spore morpho-species from the early to middle Eocene cores in the central Arctic Ocean and their allied species. Black and gray lines mean the occurrences from sediments in the Northern and Southern Hemispheres, respectively. Star symbols mean that the specimens may be vegetative cells. Species enclosed with squares were not observed in the IODP Expedition 302 samples. The biostratigraphic data of genera Goniothecium and Odontotropis are modified after Suto et al. (2008 and submitted).

Pseudopyxilla baltica (Grunow) FORTI 1909, pl. 1, figs. 8, 9. – Pseudopyxilla rossica (?) – SCHRADER and FENNER 1976, p. 994, pl. PROSCHKINA-LAVRENKO 1949, p. 201, pl. 98, figs. 6a-c. – 12, figs. 19, 20; pl. 44, figs. 2, 4 nec pl. 44, fig. 5. SCHRADER and FENNER 1976, p. 994, pl. 44, figs. 3, 6, 9. Pyxilla hungarica PANTOCSEK 1905, Bd. 3, pl. 26, fig. 392. Pseudopyxilla baltica (?)(Grunow) FORTI – HARWOOD and Pseudopyxilla hungarica (Pantocsek) FORTI 1909, p. 14. – HAR- MARUYAMA 1992, p. 705, pl. 2, figs. 9, 10. WOOD 1988, p. 85, figs. 17.26, 27. Pyxilla russica PANTOCSEK 1905, Bd. 3, pl. 19, fig. 277. – Pyxilla vasta PANTOCSEK 1905, Bd. 3, pl. 40, fig. 551. DESIKACHARY and SREELATHA 1989, p. 220, pl. 93, fig. 12. Pseudopyxilla tempereana FORTI 1909, p. 15, pl. 1, fig. 11. – Pseudopyxilla russica (Pantocsek) Forti sensu HANNA 1927b, p. 27, PROSCHKINA-LAVRENKO 1949, p. 200, pl. 98, fig. 2. – GLEZER pl. 4, fig. 4. – PROSCHKINA-LAVRENKO 1949, p. 200, pl. 97, fig. et al. 1974, pl. 53, fig. 11. – FENNER 1991. p. 139, pl. 9, fig. 3. – 7; pl. 75, fig. 3. – HAJÓS and STRADNER 1975, p. 933, pl. 12, figs. FENNER 1994, p. 115. 1, 2; pl. 27, fig. 9. – FENNER 1994, p. 115. – NIKOLAEV et al. 2001, Pseudopyxilla peragallorum FORTI 1909, p. 16, pl. 1, fig. 10. – p. 24, pl. 35, figs. 1, 2. PROSCHKINA-LAVRENKO 1949, p. 200, pl. 97, fig. 6. Pseudopyxilla rossica (Pantocsek) FORTI 1909, p. 14, pl. 1, fig. 13. – Pseudopyxilla obliquepileata FORTI 1909, p. 17, pl. 1, fig. 12. – SHESHUKOVA-PORETSKAYA 1967, p. 261, pl. 39, figs. 1a, b. – PROSCHKINA-LAVRENKO 1949, p. 200, pl. 98, figs. 3a-b. STRELNIKOVA 1974, p. 111, pl. 56, figs. 6-8. – SCHRADER and Pyxilla (Rhizosolenia?) antiqua CLEVE-EULER 1951, Handl. 2: 1, p. FENNER 1976, p. 994, pl. 12, figs. 19, 20; pl. 44, figs. 2, 4, nec pl. 44, 93, figs. 167, VI-o. fig. 5. – HARWOOD 1988, p. 86, figs. 17.28, 29. – HOMANN 1991, Pseudopyxilla sp. of FENNER 1978, p. 526, pl. 17, fig. 7. – FENNER p. 134, pl. 54, fig. 12. 1991, p. 139, pl. 9, fig. 4. – NIKOLAEV et al. 2001, p. 24, pl. 35, fig. 3.

277 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

Rhizosolenia setigera Brightwell sensu HOMANN 1991, p. 71, pl. 35, Stratigraphic and geographic distributions: This species is cos- figs. 9, 10. mopolitan and a long-ranged species from the late Cretaceous through to the Pliocene (Text-figure 4). Description: Frustule heterovalvate. In valve view, valve circular, convex in the middle. Valve surface hyaline or covered with Remarks: Several species which possess highly cylindrical and numerous dense and minute puncta. In girdle view, valve con- convex valves that are hyaline or covered with numerous dense vex, cylindrical with a high mantle, 5-70µm in diameter. Height puncta have been described as Ps. baltica, Ps. dubia, Ps. of valve is variable, nearly 1 to 7 times its diameter. Mantle dis- hungarica, Ps. obliquepileata, Ps. peragallorum, Ps. russica tinct and all surface hyaline or hyaline near the top or bottom of (sometimes misspelled rossica) and Ps. tempereana. These spe- mantle with numerous puncta on lower area. Opposite valve cies may be separated by the presence or absence of puncta on circular, convex in the middle, sometimes preserved with a del- the valve mantle and by differences in the height of the holotype icate crown which are covered with dense and minute puncta. specimens. Another confusion may have been caused by the dif- Valve surface hyaline or covered with numerous dense and ficulty in identifying specimens which are preserved in the sedi- minute puncta. In girdle view, valve convex, cylindrical with a ments as separated valves (such as only one valve or an opposite high mantle. Height of valve is variable, nearly 1 to 7 times its valve with/without a crown). However several forms with/with- diameter. Mantle distinct, entire surface hyaline or hyaline near out puncta were observed in middle Eocene IODP Leg 302 sam- the top or bottom of mantle with numerous puncta on lower ples (at one site) and most of the stratigraphic and geographic area. It is unknown which of the valves is the epivalve or distributions of these species are cosmopolitan and long-ranged hypovalve in this study. indicating little differences between them (Text-figure 4). Therefore we assumed that these species belong to a single or Type level and locality: Lower Eocene, Jutland, Denmark. are varieties of one species. Type specimen: Depository not designated. According to Homann (1991), the resting spore type “Pseudo- Comparison: This species is very similar to other Pseudo- pyxilla” belongs to species related to the genus Rhizosolenia, pyxilla species like Ps. aculeata and Ps. directa in having cylin- because Homann (1991) found that the vegetative cells look like drical and conical valves, and Ps. americana, Ps. capreolus and Rhizosolenia and are very different from resting spores. Thus Ps. jouseae in having cylindrical valves, but is differentiated most relationships between these different frustule types remain from the former two species by its lower convex valve, and unknown. Therefore the resting spore morpho-genus Pseudo- from the latter three species by the absence of a branching pro- pyxilla is here maintained. The Rhizosolenia-like vegetative cess on the valve top. valves are also illustrated in Proschkina-Lavrenko (1949). Moreover, Marino et al. (1991) also hypothesized that the fossil species Pyxilla dubia has a closer affinity to the genus Chaetoceros than to the genus Rhizosolenia based on the origi-

PLATE 1 Anaulus arcticus sp. nov. All figures are transmitted light micrographs (LM). Scale bar = 10µm, which applies to all figures.

1,2 Holotype. IODP Site 302-2A-61X-2, 2-3cm. Girdle 18,19 IODP Site 302-2A-59X-CC, 0-1cm. Girdle view of view of paired valves. paired valves. 3,4 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 20,21 IODP Site 302-2A-59X-CC, 0-1cm. Girdle view of paired valves. paired valves. 5,6 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of 22,23 IODP Site 302-2A-59X-CC, 0-1cm. Girdle view of paired valves. paired valves. 7,8 IODP Site 302-2A-55X-CC. Girdle view of paired 24,25 IODP Site 302-2A-59X-CC, 0-1cm. Girdle view of valves. paired valves. 9,10 IODP Site 302-2A-61X-2, 2-3cm. Girdle view of 26,27 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of paired valves. frustule. 11,12 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 28,29 IODP Site 302-2A-59X-CC, 0-1cm. Girdle view of paired valves. frustule. 13-15 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of 30,31 IODP Site 302-2A-61X-2, 2-3cm. Girdle view of frustule. frustule connected to hypovalve of opposite valve. 16,17 IODP Site 302-2A-61X-2, 2-3cm. Girdle view of paired valves.

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micropaleontology, vol. 55, nos. 2-3, 2009 279 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

nal drawing of Forti (1909). Sometimes valves are preserved ameter, cylindrical with a high mantle, conical at one end, and with a delicate crown covered with dense puncta (see Van extending into a long tapered spine. The tapered spine bifur- Heurck 1880-1885, Desikachary and Sreelatha 1989). From cated at the end (see pl. 8, fig. 30). Height of valve is variable, their illustrations, the crown on some spore valves may repre- nearly 1 to 4 times its diameter not including the conical area sent preserved vegetative cells. with long tapered spine. Mantle distinct, covered with numerous wrinkles. Opposite valve (perhaps hypovalve) circular, con- Etymology: The Latin dubia means “uncertain”. vex (see pl. 8, figs. 26, 27).

Pseudopyxilla jouseae Hajós in Hajós and Stradner 1975 Type level and locality: Upper Cretaceous. DSDP Site 275 (lat. Plate 8, figures 22-31 50° 26.34’ S, 176° 18.99’ E) in 2,837 m water depth on the eastern edge of the Campbell Plateau to the southwest of the Bounty Pseudopyxilla jouseae HAJÓS in HAJÓS and STRADNER 1975, p. 933, pl. 12, figs. 4, 5. Islands, South Pacific; in sample 1-1, 118-120cm. Synonym: Pterotheca sp. (aff. carinifera Grunow) of JOUSÉ 1951, p. 59, pl. 4, fig. 4. Type specimen: Deposited in the collections of the Hungarian Geological Survey, Budapest; holotype (figs. 4, 5), no. 2799/1. Emended description: Frustule heterovalvate. In valve view, valve circular. Valve surface hyaline, covered with numerous Comparison: This species is characterized by a conical and cy- wrinkles and nearly straight ridges from the top of the conical lindrical valve covered with wrinkles, and a long tapered and bi- area to the mantle margin. In girdle view, valve 5-20µm in di- furcating spine.

PLATE 2 Anaulus arcticus sp. nov.

Figures 1-35 are LM and figs. 36-47 are SEM, respectively. The scale bar in fig. 1 is 10µm and it also applies to figs. 2-35. The scale bars in figs. 36-47 are 10µm.

1 IODP Site 302-2A-59X-CC, 0-1cm. Valve view. 37 IODP Site 302-4A-5X-1, 2-3cm. Valve view of epivalve. 2,3 IODP Site 302-2A-59X-CC, 0-1cm. Valve view. 38 IODP Site 302-4A-5X-1, 2-3cm. Valve view of 4-6 IODP Site 302-2A-59X-CC, 0-1cm. Frustule in valve epivalve. view. 39 IODP Site 302-4A-5X-1, 2-3cm. Inner valve view of 7,8 IODP Site 302-2A-59X-CC, 0-1cm. Valve view. epivalve. 9,10 IODP Site 302-2A-61X-2, 2-3cm. Valve view. 40 IODP Site 302-4A-5X-1, 2-3cm. Inner valve view of 11,12 IODP Site 302-2A-61X-2, 2-3cm. Valve view. epivalve. 13,14 IODP Site 302-2A-61X-2, 2-3cm. Valve view. 41 IODP Site 302-4A-5X-1, 2-3cm. Inner valve view of epivalve 15,16 IODP Site 302-2A-61X-2, 2-3cm. Valve view. 42 IODP Site 302-4A-5X-1, 2-3cm. Oblique valve view 17,18 IODP Site 302-2A-61X-2, 2-3cm. Valve view. of hypovalve. 19,20 IODP Site 302-4A-4X-1, 0-3cm. Valve view. 43 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of epivalve. 21,22 IODP Site 302-4A-6X-2, 2-3cm. Valve view. 44 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of 23,24 IODP Site 302-4A-7X-1, 2-3cm. Valve view. hypovalve. 25-27 IODP Site 302-4A-5X-1, 2-3cm. Valve view. 45 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of hypovalve. 28,29 IODP Site 302-4A-5X-1, 2-3cm. Valve view. 46 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of 30,31 IODP Site 302-4A-4X-1, 0-3cm. Valve view. paired valves. 32,33 IODP Site 302-4A-4X-1, 0-3cm. Valve view. 47 IODP Site 302-4A-5X-1, 2-3cm. Oblique girdle view 34,35 IODP Site 302-4A-4X-1, 0-3cm. Valve view. of frustule. 36 IODP Site 302-4A-5X-1, 2-3cm. Valve view of epivalve.

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micropaleontology, vol. 55, nos. 2-3, 2009 281 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

Stratigraphic and geographic distributions: Hajós and Stradner pl. 57, figs. 1-16, 23-26 nec figs. 17-22 – GOMBOS 1977, p. 596, pl. (1975) reported this species from the late Cretaceous cores of 23, figs. 1, 2. – SCHRADER and FENNER 1976, p. 994, pl. 43, figs. 1-4. – FENNER 1978, p. 527, pl. 17, figs. 8-21. – DZINORIDZE et al. DSDP Site 275 and this species was observed in middle Eocene 1978, pl. 9, fig. 6. – GOMBOS 1983, p. 570. – GOMBOS and cores of IODP Leg 302 in this study (Text-figure 4). CIESIELSKI 1983, p. 603. – GOMBOS 1984, p. 500. – SANFILIPPO and FOURTANIER 2003, pl. 3, fig. 7. – TSOY 2003, pl. 1, fig. 7. Etymology: This species was named in honor of Dr. A. P. Jousé. Pterotheca aculeifera Grunow in VAN HEURCK 1896, p. 430, fig. 151. – HAJÓS 1976, p. 829, pl. 16, figs. 6-8. – SCHERER and KOÇ 1996, Pterotheca aculeifera Grunow in Van Heurck 1880-1885 (= Pterot- p. 86, pl. 8, fig. 11. – TAPIA and HARWOOD 2002, p. 328. heca crucifera Hanna 1927b) Pterotheca aculeifera (Grunow) VAN HEURCK – BALDAUF 1985, p. Plate 9, figures 1-47 464, pl. 10, figs. 13, 14. – FENNER 1994, p. 116, pl. 4, fig. 8. Pterotheca aculeifera (Grunow in VAN HEURCK) VAN HEURCK – Basionym: Pterotheca (Pyxilla ??) aculeifera GRUNOW in VAN HARWOOD 1988, p. 86, figs. 18.3, 4. – DESIKACHARY and HEURCK 1880-1885, pl. 83 bis, fig. 5. SREELATHA 1989, p. 218, pl. 93, fig. 11. References: Pterotheca aculeifera GRUNOW, VAN HEURCK 1896, Pterotheca aculeifera (Grunow) GRUNOW em. HOMANN 1991, p. p. 430, fig. 151. |PROSCHKINA-LAVRENKO 1949, p. 202, pl. 75, 135, pl. 35, figs. 15-18. – HARWOOD and BOHATY 2000, p. 93, pl. fig. 4b nec fig. 4a. – SHESHUKOVA-PORETSKAYA 1967, p. 266. – 1, fig. l; pl. 9, fig. p. GLEZER et al. 1974, pl. 12, fig. 5. – STRELNIKOVA 1974, p. 114,

PLATE 3 Figures 1-22, 24-36, 38, 39, 41-52 are LM and figs. 23, 37, 40 and 53 are SEM, respectively. The scale bars in figs. 1 and 2, and 24 and 25 are 10µm and those also apply to figs. 3-22 and 41-52, and 26-33, respectively. The scale bars in figs. 23, 37, 38 and 39, 40 and 53 are 10µm, respectively.

1-23. Resting spore sp. C. 28 DSDP Leg 38, Site 338-29-1, 130-131cm. Valve 1,2 IODP Site 302-2A-54X-CC. Girdle view of frustule. view. 3,4 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of 29,30 IODP Site 302-2A-54X-CC. Girdle view. frustule. 31-33 IODP Site 302-2A-61X-2, 2-3cm. Girdle view. 5,6 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of frustule. 34-36 IODP Site 302-4A-5X-1, 2-3cm. Girdle view. 7,8 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of 37 IODP Site 302-4A-5X-1, 2-3cm. Girdle view. frustule. 38-40. Liradiscus ? sp. A. 9,10 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 38,39 IODP Site 302-2A-59X-2, 122-123cm. Valve view. frustule. 40 IODP Site 302-2A-59X-2, 122-123cm. Valve view. 11,12 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of 41-53. Peripteropsis ? sp. A. frustule. 41,42 IODP Site 302-2A-52X-2, 2-3cm. Girdle view of 13,14 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of frustule. frustule. 43,44 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of 15,16 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of frustule. frustule. 45,46 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 17,18 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of frustule. frustule. 47,48 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 19,20 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of frustule. frustule. 49,50 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of 21,22 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of frustule. frustule. 51,52 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 23 IODP Site 302-4A-5X-1, 2-3cm. Girdle view. frustule. 24-37. Costopyxis trochlea (Hanna) Strelnikova in Glezer et al. 53 IODP Site 302-4A-5X-1, 2-3cm. Oblique girdle view 24,25 DSDP Leg 38, Site 338-29-1, 130-131cm. Girdle of frustule. view of frustule. 26,27 DSDP Leg 38, Site 338-29-1, 130-131cm. Girdle view.

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micropaleontology, vol. 55, nos. 2-3, 2009 283 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

2A and 4A of IODP Expedition 302 (Moran et al. 2006). In the vaulted with 3 or 5 slightly inflated undulations in girdle view. lower part of Unit 2, resting spores occurred abundantly with Epivalve surface covered with randomly scattered fine pores. other fossil diatoms. Each end is slightly raised with one strong short curved spine. One rimoportula near the center of the epivalve. Mantle of In this paper, we have attempted to provide taxonomic notes on epivalve distinct with rows of dense pores. Hypovalve rectangu- the fossil resting spore taxa from middle Eocene Arctic core lar with marginal ridge in girdle view. There are two types of materials, with a synonymy list, microscope observations and marginal ridge, one at the absolute margin between hypovalve several key references for each taxon. Our main goal is to iden- and mantle, the others close to the inner part of the margin. In- tify the main diatoms and resting spore assemblages in order to ternal marginal ridge area flat or slightly undulated. No apply diatom biostratigraphy to the stratigraphic sequence of rimoportula on the hypovalve. Mantle of hypovalve distinct the material from the central Arctic Ocean. The detailed strati- with fine pores near the valve area, hyaline around opposite graphic data and paleoceanographic and paleoecological impli- part. Paired valves formed by two types of hypovalves com- cations of the Eocene Arctic Ocean were presented by Stickley pletely connected by marginal ridges. et al. (2008) for Holes 2A and 4A. However, the taxonomy of some of the other diatoms except for resting spore taxa from the Type level and locality: Middle Eocene, IODP Expedition ACEX cores will be described in subsequent papers. 302-4A, 11X-CC, Arctic Ocean. MATERIAL AND METHODS Holotype here designated: Slide MPC-04958 (Micro- IODP Expedition 302 (or ACEX), recently obtained Recent to paleontology Collection, National Science Museum, Tokyo, Cretaceous marine sedimentary records from Holes 2A and 4A England Finder N31-4; illustrated in Plate 1, Figs. 1, 2). (~87°52.00’N; 136°10.64’E; 1288m water depth; Text-figure 1), on the Lomonosov Ridge in the central Arctic Ocean. Comparison: It is difficult to distinguish our new species from Biostratigraphy and magnetostratigraphy were used to con- A. mediterraneus var. mediterraneus Grunow in Van Heurck struct an age model, with dinocysts providing the bulk of the (1880-1885) and A. americanus Hustedt (1955), however, A Neogene biostratigraphic data, and diatom, ebridian and arcticus has random scattered pores on its epivalve. This spe- silicoflagellate data being used to date the Eocene (Backman et cies differs from A. mediterraneus var. intermedia Grunow in al. 2005a). Van Heurck (1880-1885) by its round apex, and from A. minutus Grunow in Van Heurck (1880-1885) and A. sibiricus The expanded late early to middle Eocene sediment sequences Strelnikova (1974) by its rounded valve in girdle view. of Holes 302-2A and 302-4A typically comprise abundant fossils of dinoflagellate and chrysophyte cysts, diatoms, ebridians, and silicoflagellates. Biosilica is not present before the late Stratigraphic and geographic distributions: This species oc- early Eocene interval (~320m) and above the interval (205m~). curred abundantly in middle Eocene sediments from IODP Leg In these Eocene sediments, a lot of fossil resting spore valves 302 Sites 2A and 4A in the central Arctic Ocean (Text-figure 2). were preserved with other diatom frustules. Barron (1985) and Dell’Agnese and Clark (1994) also reported this species as A. sibiricus from the late Cretaceous Alpha In this study, samples of a nearly complete section of Tertiary Ridge, Arctic Ocean. On the other hand, Harwood (1988) and sediments of DSDP Leg 38 Site 338 (67° 47.11’ N, 05° 23.26’ Barron and Mahood (1993) also reported this species as A. E; water depth 400.8m; Text-figure 1) are also used to compare sibiricus and A. sp A. from the early Paleocene to the late Creta- some resting spore taxa in the Norwegian Sea with those in the ceous Antarctic Ocean, and as A. sp. from the early Oligocene Arctic Ocean. These samples contain well-preserved diatoms of Antarctic Ocean, respectively. According to Hustedt (1930) and middle Eocene, Oligocene and early to middle Miocene. Abbott and Andrews (1979), the similar species A. mediterraneus was a littoral form inhabiting warm waters, such as the Processed strewn slides were prepared following the method of south coast of England and the Mediterranean, therefore our Suto (2003). Diatom frustules were mounted in pleurax for LM new species may have lived in warm and littoral environments. observations and coated with gold for SEM observation. Identi- fication and photodocumentation of resting spores were made Remarks: Harwood (1988) mentioned that the occurrence of A at x400 using an Olympus BM40 light microscope and Olym- arcticus (= their specimens of A. sibiricus)andHemiaulus pus DP-12 digital camera. SEM examinations were carried out elegans in resting spore and vegetative cell diatom assemblages, using a JEOL JSM-5800 LV scanning electron microscope at respectively, from the Arctic Ocean (Kitchell et al. 1986), and the National Science Museum of Japan. suggests that A. arcticus is a resting spore of H. elegans.

RESULTS Anaulus mediterraneus var. intermedia Grunow in Van Heurck Anaulus arcticus Suto, Jordan et Watanabe sp. nov. (1880-1885, pl. 102, fig. 9) and in Wornardt (1967, p. 68, fig. Plate 1, figures 1-31; Plate 2, figures 1-47 134) is characterized by its constricted valve center and tapered valve apex, but this variety illustrated in Hustedt (1930, p. 892, Synonymy: Anaulus sibiricus STRELNIKOVA sensu BARRON 1985, fig. 535), Proschkina-Lavrenko (1949, p. 212, pl. 99, fig. 13) p. 141, pl. 10.2, fig. 10. – HARWOOD 1988, p. 79, figs. 9.12-14. – and Abbott and Andrews (1979, p. 233, pl. 1, fig. 14) may be a DELL’AGNESE and CLARK 1994, fig. 3.3. Anaulus sp. A in HARWOOD 1988, p. 79, figs. 9.16, 17. new variety of this species because their valves are not con- Anaulus sp. in BARRON and MAHOOD 1993, p. 38, pl. 4, fig. 7. stricted and have a slightly lanceolated apex. Hustedt (1955) indicated that A. americanus differs from A. mediterraneus by its Description: Frustule heterovalvate. Valve broadly linear with smaller size and finer structure but A. americanus might be only large, cuneate, bluntly rounded apices, apical axis 10-35µm, a variety of A. mediterraneus. transapical axis 6-14µm. Valve divided into 3 or 5 equal parts by 2 or 4 transverse internal septa. Epivalve rectangular, Etymology: The Latin word arcticus means “Arctic”.

260 Micropaleontology, vol. 55, nos. 2-3, 2009

TEXT-FIGURE 1 Location map of Integrated Ocean Drilling Program (IODP) Expedition (or the Arctic Coring Expedition, ACEX) Leg 302 in the Arctic Ocean.

Costopyxis trochlea (Hanna) Strelnikova in Glezer et al. 1988 Trochosira trochlea HANNA sensu DZINORIDZE et al. 1978, pl. 4, figs. 12, 13. – FENNER 1985, p. 741, fig. 12.10. – FENNER 1991, pl. Plate 3, figures 24-37 11, fig. 15. Pterotheca gracillima FENNER 1978, p. 527, pl. 12, figs. 5, 6. – Costopyxis trochlea (Hanna) STRELNIKOVA in GLEZER et al. 1988, BARRON et al. 1984, p. 156, pl. 8, fig. 11. p. 51, pl. 32, figs. 17, 18. – SCHERER and KOÇ 1996, p. 86, pl. 8, figs. Pterotheca sp. of FENNER 1978, p. 527, pl. 12, fig. 3. 8-10. – GLADENKOV 1998, pl. 1, figs. 11a, b. – TSOY 2003, pl. 2, Pterotheca sp. 4 of FENNER 1978, p. 527, pl. 12, fig. 4. fig. 12. Pterotheca sp. of BARRON et al. 1984, p. 156, pl. 8, fig. 12. Basionym: Trochosira trochlea HANNA 1927a, p. 123, pl. 21, figs. 8, 9. Trochosira aff. gracillima (Fenner) FENNER 1991, p. 141, pl. 11, figs. Synonymy: Pterotheca sp. (1) of SCHRADER and FENNER 1976, p. 22, 25. 994, pl. 35, fig. 15. Stephanopyxis ornata SCHULZ sensu HARWOOD and MARUYAMA Pterotheca sp. (3) of SCHRADER and FENNER 1976, p. 994, pl. 35, 1992, p. 706, pl. 2, fig. 6. figs. 17, 18. Trochosira gracillima (Fenner) Fenner. – FENNER 1994, p. 122. Pterotheca sp. (4) of SCHRADER and FENNER 1976, p. 994, pl. 35, fig. 19.

261 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

Genus et species indet. C of HARWOOD and BOHATY 2000, p. 94, pl. base of the mantle there is a ring of relatively large pedal “seg- 5, fig. p. ments” (Fenner 1985).

Description: Frustule isovalvate, 4-8µm in diameter, pervalvar Type level and locality: Lower Miocene, locality 894, Phoenix axis 6-13µm without spine. Valves circular in valve view, Canyon, 7 miles north of Coalinga, Fresno County, California highly cylindrical with a convex upper part in girdle view. One (basionym species Trochosira trochlea Hanna 1927a). Middle or sometimes two (Plate 3, figures 29, 30) long bifurcate spines Eocene, planktonic foraminiferal zone P10/P11 (synonym spe- on top of the center. Valve face covered with very finely cies Pterotheca gracillima Fenner 1978). punctate (20-22 puncta in 10µm) which are of constantly equal size on the whole valve and are arranged in straight radial dou- Type specimen: Sample no. 3050, deposited in the Museum of ble- to triple-rows. A ring of short hyaline ridges at the transi- California Academy of Sciences (basionym species Trochosira tion between convex and cylindrical mantle of the valve. At the trochlea Hanna 1927a). Deposited in the sample collections of

TEXT-FIGURE 2 (opposite page) Geographic and stratigraphic distribution of Anaulus arcticus Suto, Jordan et Watanabe, Costopyxis trochlea (Hanna) Strelnikova in Glezer et al., Leptoscaphos punctatus (Grove et Sturt) Schrader and Leptoscaphos levigatus (Sheshukova-Poretskaya) Suto, Jordan et Watanabe. a-f. Anaulus arcticus 10-14. Reported as Pterotheca gracillima or Trochosira a IODP Site 302-2A and 4A (This study). gracillima. 10 DSDP Site 356 (Fenner 1978); b-d. Reported as Anaulus sibiricus. b Alpha Ridge, Arctic Ocean (Barron 1985); 11 DSDP Site 338 (Fenner 1978); c Seymour Island, Antarctic Peninsula (Harwood 12 Kellogg Shale, California (Barron et al. 1984); 1988); 13 DSDP Hole 700B (Fenner 1991); d Alpha Ridge, Arctic Ocean (Dell’Agnese and Clark 1994). 14 Fur Formation, Denmark (Fenner 1994). e, f. Reported as Anaulus sp. 15-17. Reported as Pterotheca sp. e Seymour Island, Antarctic Peninsula (Harwood 15 DSDP Site 338 (Schrader and Fenner 1976); 1988); 16 DSDP Site 356 (Fenner 1978); f ODP Hole 739C (Barron and Mahood 1993). 17 Kellogg Shale, California (Barron et al. 1984). 1-20. Costopyxis trochlea 18, 19. Reported as Stephanopyxis ornata. 1-4. Reported as Costopyxis trochlea. 18 ODP Hole 748B (Harwood and Maruyama 1992); 1 Kamchatka, Russia (Glezer et al. 1988); 19 ODP Hole 749B (Harwood and Maruyama 1992). 2 ODP Hole 913B (Scherer and Koç 1996); 20. Reported as Genus et species indet. C. 3 Kamenka Formation, Bering Island (Gladenkov 20 McMurdo Sound, Antarctica (Harwood and Bohaty 1998); 2000). A-C. Leptoscaphos levigatus 4 IODP Site 302-2A and 4A (This study). A Rekinnik Inlet, eastern side of Penzhina Bay, 5-9. Reported as Trochosira trochlea. Kamchatka, Russia (Sheshukova-Poretskaya 1967); 5 the lower Miocene shales, north of Coalinga, Califor- B Anadyr River, Russia (Sheshukova-Poretskaya nia (Hanna 1927a); 1967); 6 DSDP Site 338 (Dzinoridze et al. 1978); C IODP Site 302-2A and 4A (This study). 7 DSDP Site 340 (Dzinoridze et al. 1978); D-F. Leptoscaphos punctatus 8 Kellogg Shale, California (Fenner 1985); D Oamaru, New Zealand (Schrader 1969); 9 DSDP Site 208 (Fenner 1991). E Oamaru, New Zealand (Desikachary and Sreelatha 1989); F IODP Site 302-2A and 4A (This study).

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TEXT-FIGURE 2 Legend on opposite page.

DSDP samples of Dr. H.-J. Schrader, School of Oceanography, ments of ODP Hole 700B in the southwest Atlantic (Fenner Oregon State University, Corvallis, Oregon (synonym species 1991). This species mainly occurred from the early Eocene to Pterotheca gracillima Fenner 1978). late Oligocene sediments all around the world (Text-figure 2). Fenner (1978) described the species Pterotheca gracillima (p. Comparison: The only similar form observed in the literature is 527, pl. 12, figs. 5, 6 in Fenner 1978) from the middle to late the upper Cretaceous Costopyxis schulzii (Steinecke) Glezer, Eocene cores of DSDP Site 356 at the southwestern edge of the but this species is distinguished from C. trochlea by its much Sao Paulo Plateau, western South Atlantic. The youngest speci- larger size and coarser areolation with many small scattered mens are reported from early Miocene sediments in California spines on the valve surface besides the two subcentral long (Hanna 1927a). spines. Remarks: This species was formerly observed and named as Stratigraphic and geographic distributions: The oldest occur- Pterotheca gracillima (e.g. Fenner 1978, Barron et al. 1984) rence of this species is from the early to late Paleocene sedi- and Pt. sp. 1, 3 and 4 (Schrader and Fenner 1976), Stephano-

263 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

TEXT-FIGURE 3 (opposite page) Geographic and stratigraphic distribution of Porotheca danica Grunow in Van Heurck and Pseudopyxilla carinifera (Grunow in Van Heurck) Suto, Jordan et Watanabe.

1-28. Porotheca danica 22. Reported as Stephanogonia novazealandica. 22 Oamaru, New Zealand (Desikachary and Sreelatha 1-2. Reported as Porotheca danica. 1989). 1 Fur Formation, Denmark (Fenner 1994); 23. Reported as Pterotheca cf. aculeifera. 2 IODP Site 302-2A and 4A (This study). 23 DSDP Site 275 (Hajós and Stradner 1975). 3-16. Reported as Pterotheca danica. 24-26. Reported as Pterotheca carinifera. 3 Mors Formation, Denmark (Van Heurck 1880-1881); 24 DSDP Site 274 (McCollum 1975); 4 the early Miocene shales north of Coalinga, Fresno 25 Seymour Island, Antarctic Peninsula (Harwood County, California (Hanna 1927); 1988); 5 DSDP Site 275 (Hajós and Stradner 1975); 26 McMurdo Sound, Antarctica (Harwood and Bohaty 6 DSDP Holes 280A, 281A and 283 (Hajós 1976); 2000). 27. Reported as Pyxilla? carinifera. 7 DSDP Site 328 (Gombos 1977); 27 Fur Formations, Denmark (Homann 1991). 8 DSDP Hole 512 (Gombos 1983); 28. Reported as Pterotheca spada. 9 DSDP Site 511 (Gombos and Ciesielski 1983); 28 DSDP Site 511 (Gombos and Ciesielski 1983). 10 Kellogg Shale, northern California (Barron et al. a-l. Pseudopyxilla carinifera 1984); a-f. Reported as Pterotheca carinifera. 11 DSDP Hole 552A and Site 553 (Baldauf 1985); a early Miocene shales north of Coalinga, California (Hanna 1927a); 12 Seymour Island, Antarctic Peninsula (Harwood 1988); b DSDP Site 274 (McCollum 1975); 13 Oamaru, New Zealand (Desikachary and Sreelatha c DSDP Site 338 (Schrader and Fenner 1976); d. DSDP 1989); Site 348 (Schrader and Fenner 1976); 14 Yeonil Group in the Pohang Basin, Korea (Lee 1993); e Oamaru, New Zealand (Desikachary and Sreelatha 1989); 15 Alpha Ridge, Arctic Ocean (Dell’Agnese and Clark 1994); f Yeonil Group in the Pohang Basin, Korea (Lee 1993). 16 McMurdo Sound, Antarctica (Harwood and Bohaty g, h. Reported as Pyxilla carinifera. 2000). g Jutland, Denmark (Van Heurck 1880-1881); 17-18. Reported as Pterotheca major. h Fur and Mors Formations (Homann 1991). 17 eastern slope of Ural Mountains, USSR (Jousé 1955); i, j. Reported as Pterotheca carinifera var. curvirostris. 18 DSDP Hole 512 (Gombos 1983); i eastern slope of Ural Mountains, USSR (Jousé 1955); 19 DSDP Site 511 (Gombos and Ciesielski 1983); j Seymour Island, Antarctic Peninsula (Harwood 1988). 20 Seymour Island, Antarctic Peninsula (Harwood 1988). k, l. Reported as Pterotheca minor. k Seymour Island, Antarctic Peninsula (Harwood Stephanogonia danica 21. Reported as . 1988); 21 Fur Formations, Denmark (Homann 1991). l McMurdo Sound, Antarctica (Harwood and Bohaty 2000).

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TEXT-FIGURE 3 Legend on opposite page. pyxis ornata (sensu Harwood and Maruyama 1992) and Genus Dispinodiscus ? sp. A et species indet. C (Harwood and Bohaty 2000), but these taxa Plate 4, figures 40-45 all bear the same characteristics as C. trochlea. Specimens of this species may not be resting spores, but actually vegetative Description: Frustule heterovalvate, apical axis 8-10µm, cells. pervalvar axis 4-6µm without bristles. In girdle view, epivalve hyaline, slightly vaulted with strong bristle near each apex and This species was described as a species of the genus Trochosira its center, with distinct mantle. Mantle of epivalve hyaline. by Hanna (1927a) because it possesses one long spine at the Hypovalve vaulted in central area or nearly flat, with a strong valve center. Later, Trochosira trochlea was transferred to the bristle at the center, with distinct mantle. Mantle of hypovalve genus Costopyxis by Strelnikova in Glezer et al. (1988), be- hyaline with a single ring of puncta at its base (see Plate 4, fig- cause it has much coarser areolation with strong hyaline ridges ure 40). than other Trochosira species. Comparison: This species is characterized by its hyaline epi- Etymology: The Latin costo-pyxis and trochlea means “box and hypovalves with strong bristles at the valve center and near with ribs” and “pulley”, respectively. each apex.

265 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

TEXT-FIGURE 4 Geographic and stratigraphic distribution of Pseudopyxilla dubia (Grunow in Van Heurck) Forti and Pseudopyxilla jouseae Hajós in Hajós and Stradner.

1-44. Pseudopyxilla dubia 23-25. Reported as Pyxilla baltica and Pseudopyxilla baltica. 23 Mors Formation, Denmark (Van Heurck 1880-1881); 1-18. Reported as Pyxilla dubia and Pseudopyxilla dubia. 1 Jutland, Denmark (Van Heurck 1880-1881); 24 DSDP Site 338 (Schrader and Fenner 1976); 2 Deposit in Monterey, California (Van Heurck 25 ODP Hole 747A (Harwood and Maruyama 1992). 1880-1881); 26. Reported as Pseudopyxilla hungarica. 3 6 miles northwest of Newman, California (Hanna 26 Seymour Island, Antarctic Peninsula (Harwood 1927a); 1988). 4 Mors Formation, Denmark (Cleve-Euler 1951); 27-37. Reported as Pyxilla russica (or P. rossica)and Pseudopyxilla russica (or Ps. rossica). 5 Kellogg and “Sidney” shales, California (Kanaya 27 Moreno Gulch, California (Hanna 1927b); 1957); 28 North and South Sakhalin, Russia (Sheshukova- 6 Szurdokpüspöki diatomite stop, Hungary (Hajós Poretskaya 1967); 29. Western Siberia (Strelnikova 1968); 1974); 7 St. Paul Island, Bering Sea, Alaska (Hanna 1970); 30 DSDP Site 275 (Hajós and Stradner 1975); 8 Sisquoc Formation, California (Barron 1975); 31 DSDP Site 338 (Schrader and Fenner 1976); 9 DSDP Site 338 (Schrader and Fenner 1976); 32 DSDP Site 348 (Schrader and Fenner 1976); 10 Nakayama Formation, Sado Island, Japan (Hasegawa 33 Seymour Island, Antarctic Peninsula (Harwood 1977); 1988); 11 DSDP Site 356 (Fenner 1978); 34 Oamaru, New Zealand (Desikachary and Sreelatha 12 DSDP Hole 511 (Gombos and Ciesielski 1983); 1989); 13 DSDP Hole 524 (Gombos 1984); 35 Fur Formation, Denmark (Homann 1991); 14 Seymour Island, Antarctic Peninsula (Harwood 36 Fur Formation, Denmark (Fenner 1994); 1988); 37 Moreno Gulch, California (Nikolaev et al. 2001). 15 Oamaru, New Zealand (Desikachary and Sreelatha 38. Reported as Rhizosolenia setigera. 1989); 38 Mors Formation, Denmark (Homann 1991). 16 Fur Formation, Denmark (Fenner 1994); 39-41. Reported as Pseudopyxilla tempereana. 17 McMurdo Sound, Antarctica (Harwood and Bohaty 39 Western Siberia (Glezer et al. 1974); 2000); 40 ODP Hole 700B (Fenner 1991); 18 IODP Site 302-2A and 4A (This study). 41 Fur Formation, Denmark (Fenner 1994). 19. Reported as Rhizosolenia dubia. 42-44. Reported as Pseudopyxilla sp. 19 Mors and Fur Formations, Denmark (Homann 1991). 42 DSDP Site 356 (Fenner 1978); 20, 21. Reported as Rhizosolenia americana and Pseudopyxilla 43 ODP Hole 700B (Fenner 1991); americana. 20 Richmond, Virginia, USA (Ehrenberg 1854); 44 Moreno Gulch, California (Nikolaev et al. 2001). 21 DSDP Site 275 (Hajós and Stradner 1975). a, b. Pseudopyxilla jouseae a DSDP Site 275 (Hajós and Stradner 1975); 22. Reported as Pyxilla (Rhizosolenia?) antiqua. 22 Mors Formation, Denmark (Cleve-Euler 1951). b IODP Site 302-2A and 4A (This study).

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TEXT-FIGURE 4 Legend on opposite page.

Stratigraphic and geographic distributions: This species oc- Stratigraphic occurrence: This species was recognized abun- curred rarely in middle Eocene sediments only from IODP Leg dantly in middle Eocene sediments from the Lomonosov Ridge, 302 Site 4A-6X-2, 2-3cm in the central Arctic Ocean. Arctic Ocean in this study.

Remarks: This species may belong to the fossil resting spore Goniothecium decoratum Brun morpho-genus Dispinodiscus of extant Chaetoceros because of Emended description: See Suto, Jordan and Watanabe (2008). the presence of a ring of puncta on the hypovalve margin. This species looks like a Dispinodiscus species (see Suto 2004b), but is distinguished from them by its central bristles on the epi- and Stratigraphic occurrence: This species was not observed in the hypovalves. IODP Leg 302 samples.

Goniothecium danicum Grunow in Cleve et Möller emend. Suto in Goniothecium rogersii Ehrenberg Suto, Jordan et Watanabe 2008 Emended description: See Sims and Mahood (1998) and Suto, Emended description: See Suto, Jordan and Watanabe (2008). Jordan and Watanabe (2008).

267 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

Stratigraphic occurrence: This species was not observed in the lowly truncated. Valve surface covered with numerous scat- Arctic Coring Expedition sediments. tered fine puncta. Mantle distinct with scattered fine puncta.

Leptoscaphos levigatus (Sheshukova-Poretskaya) Suto, Jordan et Type level and locality: the upper Middle Miocene to lower Up- Watanabe comb. nov. per Miocene, Etolon suite, Rekinnik Inlet, Kamchatka, Russia. Plate 5, figures 1-28 Type specimen: Deposited in the collection of the Chair of Basionym: Biddulphia levigata SHESHUKOVA-PORETSKAYA Lower Plants, St.-Petersburg University, St.-Petersburg, Russia, 1967, p. 218, pl. 35, figs. 4a, b ; pl. 36, figs. 3a, b. exhibit no. 1154.

Description: Frustule heterovalvate, apical axis 25-70µm, Comparison: This species resembles L. punctatus in valve pervalvar axis 7-10µm. Valve elongate, narrowly elliptical, or shape but is differentiated from the latter by its nearly hyaline narrowly lanceolate with rounded corners, sides subuniformly valve. Sheshukova-Poretskaya (1967) mentioned that this spe- curved. One valve slightly convex, the other nearly flat and cies is similar to spores of modern Antarctic neritic Biddulphia

TEXT-FIGURE 5 (opposite page) Geographic and stratigraphic distribution of Pterotheca aculeifera (Grunow) Forti.

1-35. Pterotheca aculeifera 19 Fur Formation, Denmark (Fenner 1994); 1-27. Reported as Pterotheca aculeifera. 20 ODP Hole 913B (Scherer and Koç 1996); 1 Jutland and Mors, Denmark (Van Heurck 1880- 21 McMurdo Sound, Antarctica (Harwood and Bohaty 1881); 2000); 2 Mors, Denmark (Van Heurck 1896); 22 Slidre Fjord Section, Canada (Tapia and Harwood 3 Kellogg and “Sidney” shales, California (Kanaya 2002); 1957); 23 Horton River Section, Canada (Tapia and Harwood 4 Lower course of the Anadyr River, Russia 2002) (Sheshukova-Poretskaya 1967); 24 ODP Hole 1128C (Sanfilippo and Fourtanier 2003); 5 Western Siberia (Glezer et al. 1974); 25 Kronotskii Bay, east Kamchatka, Russia (Tsoy 2003); 6 Western Siberia (Strelnikova 1974); 26 DSDP Site 338 (This study); 7 DSDP Site 328 (Gombos 1977); 27 IODP Site 302-2A and 4A (This study). 8 DSDP Site 283 (Hajós 1976); 28-31. Reported as Pterotheca crucifera. 9 DSDP Site 338 (Schrader and Fenner 1976); 28 Moreno Gulch, California (Hanna 1927); 10 DSDP Site 356 (Fenner 1978); 29 DSDP Site 275 (Hajós and Stradner 1975); 11 DSDP Site 340 (Dzinoridze et al. 1978); 30 Seymour Island, Antarctic Peninsula (Harwood 1988); 12 DSDP Holes 512 and 512A (Gombos 1983); 31 Moreno Gulch, California (Nikolaev et al. 2001). 13 DSDP Site 511 (Gombos and Ciesielski 1983); 32-34. Reported as Pterotheca sp. 14 DSDP Site 524 (Gombos 1984); 32 DSDP Hole 327A and Site 328 (Gombos 1977); 15 DSDP Hole 553A (Baldauf 1985); 33 ODP Hole 700B (Fenner 1991); 16 Seymour Island, Antarctic Peninsula (Harwood 34 McMurdo Sound, Antarctica (Harwood and Bohaty 1988); 2000). 17 Oamaru, New Zealand (Desikachary and Sreelatha 35. Reported as Pseudopyxilla americana. 1989); 35 Alpha Ridge, Arctic Ocean (Dell’Agnese and Clark 1994). 18 Mors and Fur Formations, Denmark (Homann 1991);

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TEXT-FIGURE 5 Legend on opposite page. striata Karsten, but differs from it by the asymmetry of the Remarks: Specimens of this species may be resting spores of L. frustule, narrower valves, and random distribution of the punctatus or a related species because of the similarities in areolae. valve size and shape, and the possession of much less puncta on the valve surface. Stratigraphic and geographic distributions: Sheshukova- Etymology: The Latin word levigatus means “smooth”. Poretskaya (1967) observed this species from the lower course of the Anadyr River, the late Eocene to Oligocene opoka silt Leptoscaphos punctatus (Grove et Sturt) Schrader 1969 stones, and from Etolon suite Rekinnik Inlet, Kamchatka, Rus- Plate 6, figures 1-33 sia. According to the last Russian Stratigraphic Schemes for the Cenozoic of Kamchatka and Sakhalin, the age of the Etolon Leptoscaphos punctatus (GROVE et STURT) SCHRADER 1969, p. 15, suite is the late middle Miocene to early late Miocene. This spe- pl. 9, figs. 4a-b. – DESIKACHARY and SREELATHA 1989, p. 110, pl. 75, figs. 9, 10. cies was observed abundantly in middle Eocene sediments from Basionym: Stoschia (?) punctata GROVE et STURT 1887, p. 145, pl. IODP Leg 302 Sites 2A and 4A in the central Arctic Ocean in 14, fig. 52. this study (Text-figure 2).

269 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

Description: Chain-forming (Plate 6, Figs. 32, 33). Frustule Comparison: This species bears a close resemblance to L. isovalvate, apical axis 25-52µm, pervalvar axis 5-13µm. Valve levigatus but differs from it by having a valve covered with elongate, narrowly elliptical, or narrowly lanceolate with coarser puncta. rounded corners, sides subuniformly curved. Valve surface slightly convex, with numerous scattered coarse puncta, some Stratigraphic and geographic distributions: Schrader (1969) interrupted by widely transverse hyaline unequal interspaces ir- collected this species from the late Eocene Totara Limestone, regularly arranged. Rimoportula near the edge of mantle on the Oamaru, New Zealand. This species was observed abundantly valve central area. Mantle distinct with scattered equally spaced in middle Eocene sediments from IODP Leg 302 Sites 2A and and clearly separated puncta. 4A in the central Arctic Ocean in this study (Text-figure 2).

Remarks: Specimens of this species may be vegetative cells of Type level and locality: Not designated. L. levigatus.

Type specimen: Depository not designated. Etymology: The Latin word punctatus means “punctate”.

TEXT-FIGURE 6 Geographic and stratigraphic distribution of Pterotheca evermanii Hanna, Pterotheca harrensis (Fenner) Suto, Jordan et Watanabe, Pterotheca kittoniana Grunow in Van Heurck, Pt. kittoniana var. minuta Fenner, Pt. kittoniana var. kamtschatica Gaponov, Pt. minuta (Fenner) Suto, Jordan et Watanabe and Pt. reticulata Sheshukova-Poretskaya.

1-9. Pterotheca evermanii f DSDP Site 214 (Fenner 1991); 1 upper Moreno Shale, California (Hanna 1927); g DSDP Hole 524A (Fenner 1991); 2 Western Siberia (Glezer et al. 1974); h Mors and Fur Formations, Denmark (Homann 1991); 3 Western Siberia (Strelnikova 1974); i Fur Formation, Denmark (Fenner 1994). 4 Seymour Island, Antarctic Peninsula (Harwood j. Reported as Pterotheca aculeifera. 1988); j Western Siberia (Strelnikova 1974). 5 ODP Hole 700B (Fenner 1991); k. Pterotheca kittoniana var. minuta 6 Mors and Fur Formations, Denmark (Homann 1991); k Fur Formation, Denmark (Fenner 1994). 7 Fur Formation, Denmark (Fenner 1994); A-D. Pterotheca minuta A Reported as Pterotheca minuta. A. IODP Site 302-2A 8 Moreno Gulch, California (Nikolaev et al. 2001); and 4A (This study). 9 IODP Site 302-2A and 4A (This study). B Reported as Pseudopyxilla minuta. B. Fur Formation, 10, 11. Pterotheca harrensis Denmark (Fenner 1994). 10 IODP Site 302-2A and 4A (This study). C Reported as Hemiaulus kittonii. C. Mors, Denmark (Van Heurck 1880-1881). 11 Reported as Pseudopyxilla harrensis. Fur Formation, Denmark (Fenner 1994). D Reported as Pterotheca tuffata. D. Fur Formation, a, b. Pterotheca kittoniana var. kamtschatica Denmark (Fenner 1994). a Kronotsk area, Kamchatka, Russia (Sheshukova- E-I. Pterotheca reticulata Poretskaya 1967); E Rekinniki Bay, eastern side of Penzhina Bay, Kamchatka, Russia and Nituy, Gurovka, and Gornaya b Western Siberia (Glezer et al. 1974). rivers, South Sakhalin, Russia (Sheshukova- c-j. Pterotheca kittoniana var. kittoniana Poretskaya 1967); c-g. Reported as Pterotheca kittoniana. F DSDP Site 348 (Schrader and Fenner 1976); c Jutland and Mors, Denmark (Van Heurck 1880- G DSDP Site 348 (Dzinoridze et al. 1978); 1881); H Szurdokpüspöki diatomite stop, Hungary (Hajós d Seymour Island, Antarctic Peninsula (Harwood 1986); 1988); I DSDP Site 338 (This study). e ODP Hole 702B (Fenner 1991);

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TEXT-FIGURE 6 Legend on opposite page.

Liradiscus ? sp. A Remarks: It is unknown whether or not this species belongs to Plate 3, figures 38-40 the fossil resting spore morpho-genus Liradiscus of extant Chaetoceros because its frustule was not observed and we could Description: Frustule not observed. Valve elliptical to oval in not confirm the presence or absence of a single ring of puncta on valve view, apical axis 20-28µm, pervalvar axis 8-9µm. Valve the hypovalve. hyaline, nearly flat, entire surface covered with net-like veins. Odontotropis arctica sp. A Comparison: This species is similar to Liradiscus species, especially L. pacificus (Suto 2004a) in possessing net-like veins, but Description: See Suto, Watanabe and Jordan (submitted). differs from L. pacificus by having a nearly flat valve. Type level and locality: See Suto, Watanabe and Jordan (sub- Stratigraphic and geographic distributions: This species was mitted). observed in middle Eocene sediments only from IODP Leg 302 Site 2A-59X-2, 122-123 in the central Arctic Ocean in this Stratigraphic occurrence: This species is preserved abundantly study. in middle Eocene sediments from the Lomonosov Ridge.

271 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

Odontotropis arctica sp. A var. 1 Suto in Suto, Watanabe et Jordan submitted Description: See Suto, Watanabe and Jordan (submitted). Stratigraphic occurrence: This species did not occur in Description: See Suto, Watanabe and Jordan (submitted). Lomonosov Ridge sediments.

Type level and locality: See Suto, Watanabe and Jordan (sub- Odontotropis danicus Debes in Hustedt 1930 mitted). Description: See Suto, Watanabe and Jordan (submitted). Stratigraphic occurrence: This species occurred abundantly in middle Eocene sediments from the Lomonosov Ridge. Stratigraphic occurrence: This species was preserved abundantly in middle Eocene sediments from the central Arctic Odontotropis? carinata Grunow 1884 Ocean in this study.

Basionym: Odontotropis ? carinata GRUNOW 1884, p. 59 (with no il- Odontotropis galeonis Hanna 1927b lustration). Description: See Suto, Watanabe and Jordan (submitted). Stratigraphic occurrence: In this study, this species was preserved abundantly in middle Eocene sediments from the Stratigraphic occurrence: This species was not observed in this Lomonosov Ridge. study.

Odontotropis cristata Grunow 1884 Odontotropis birostrata Pantocsek 1903

Basionym: Biddulphia ? cristata GRUNOW in VAN HEURCK 1880- Basionym: Odontotropis birostrata PANTOCSEK 1903, Bd. 2, pl. 17, 1885, pl. 102, fig. 4. fig. 286, Bd. 3, pl. 14, fig. 214.

TEXT-FIGURE 7 (opposite page) Geographic and stratigraphic distribution of Trochosira coronata Schrader and Fenner, Trochosira mirabilis Kitton and Trochosira polychaeta (Strelnikova) Sims.

1-9. Trochosira coronata f-i. Reported as Trochosira cf. or aff. mirabilis. f Mors and Fur Formations, Denmark (Homann 1991); 1-6. Reported as Trochosira coronata. 1 DSDP Site 338 (Schrader and Fenner 1976); g ODP Hole 698A (Fenner 1991); 2 DSDP Site 339 (Schrader and Fenner 1976); h ODP Hole 700B (Fenner 1991); 3 DSDP Site 340 (Schrader and Fenner 1976); i ODP Hole 702B (Fenner 1991). 4 DSDP Site 338 (Sims 1988); A-H. Trochosira polychaeta 5 Fur Formation, Denmark (Fenner 1994); A, B. Reported as Trochosira polychaeta. A Alpha Ridge, Arctic Ocean (Sims 1988); 6 IODP Site 302-2A and 4A (This study). B IODP Site 302-2A and 4A (This study). 7-9. Reported as Trochosira mirabilis 7 DSDP Site 338 (Dzinoridze et al. 1978); C-E. Reported as Sceletonema polychaetum. C Western Siberia (Strelnikova 1971); 8 DSDP Site 339 (Dzinoridze et al. 1978); D Western Siberia (Strelnikova 1974); 9 DSDP Site 340 (Dzinoridze et al. 1978). E Alpha Ridge, Arctic Ocean (Barron 1985). a-i. Trochosira mirabilis F. Reported as Pyrgodiscus triangulatus. a-e. Reported as Trochosira mirabilis. F DSDP Site 275 (Hajós and Stradner 1975). a Mors, Denmark (Kitton 1871); G, H. Reported as Trochosiropsis polychaeta. b Mors Formation, Denmark (Van Heurck 1880-1885); G Slidre Fjord Section, Canada (Tapia and Harwood c ‘Kamishev’, eastern slopes of the Ural mountains, 2002); USSR (Sims 1988); H Horton River Section, Canada (Tapia and Harwood d Mors and Fur Formations, Denmark (Homann 1991); 2002). e Fur Formation, Denmark (Fenner 1994).

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TEXT-FIGURE 7 Legend on opposite page.

Description: Frustule isovalvate, apical axis 10-32µm, Description: See Suto, Watanabe and Jordan (submitted). transapical axis 5-12µm not including the thin and wide processes. Valve narrowly to broadly elliptical in valve view. Stratigraphic occurrence: This species occurred in middle Epivalve hyaline, slightly convex in the center, with numerous Eocene sediments from the Lomonosov Ridge in this study. thin and wide processes, with distinct valve mantle. Epivalve mantle hyaline, high. Hypovalve hyaline, vaulted with one Odontotropis hyalina Witt 1886 (= Odontotropis klavsenii Debes) hump, with numerous thin and wide processes, with distinct valve mantle. Mantle of hypovalve hyaline. The thin and wide Description: See Suto, Watanabe and Jordan (submitted). processes hyaline, flat around the margins of the epi- and hypovalves, slender processes becoming at their tips and curved Stratigraphic occurrence: This species occurred in middle near their apices. Eocene sediments from the Lomonosov Ridge in this study. Comparison: This species is characterized by its numerous thin Peripteropsis ? sp. A and wide processes around the margins of the epi- and Plate 3, figures 41-52 hypovalves, slender processes becoming at their tips. This spe-

273 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

TEXT-FIGURE 8 Geographic and stratigraphic distribution of Trochosira spinosa Kitton.

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277 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

PLATE 1 Anaulus arcticus sp. nov. All figures are transmitted light micrographs (LM). Scale bar = 10µm, which applies to all figures.

278 Itsuki Suto, Richard W. Jordan and Mahito Watanabe Plate 1

micropaleontology, vol. 55, nos. 2-3, 2009 279 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

PLATE 2 Anaulus arcticus sp. nov.

Figures 1-35 are LM and figs. 36-47 are SEM, respectively. The scale bar in fig. 1 is 10µm and it also applies to figs. 2-35. The scale bars in figs. 36-47 are 10µm.

280 Itsuki Suto, Richard W. Jordan and Mahito Watanabe Plate 2

micropaleontology, vol. 55, nos. 2-3, 2009 281 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

282 Itsuki Suto, Richard W. Jordan and Mahito Watanabe Plate 3

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Synonymy: Pyxilla ?? aculeifera Grunow in VAN HEURCK (Simple type; see Plate 9, Figs. 44-47). Apex crowned with a 1880-1885, pl. 83, figs. 13, 14. huge spine (sometimes two, double spiny type; see Plate 9, Figs. Pterotheca crucifera HANNA 1927b, p. 30, pl. 4, fig. 5. – PROSCHKINA-LAVRENKO 1949, p. 202, pl. 98, fig. 7. – HAJÓS 41-43) apparently square in shape and with sharp keels on each and STRADNER 1975, p. 934, pl. 12, figs. 8, 9, 22; pl. 27, fig. 7; pl. corner. Keels extending down over the conical portion for a 28, fig. 3. – HARWOOD 1988, p. 86, fig. 18.5. – NIKOLAEV et al. short distance, two heavy sides, wing-like projections are devel- 2001, p. 26, pl. 39, figs. 8, 9. oped near the top of the spine and connected with each other. Pyxilla (Rhizosolenia?) aculeifera Grunow sensu CLEVE-EULER Mantle of epivalve distinct and hyaline. Hypovalve slightly 1951, Handl. 2: 1, p. 93, figs. 168a-d, VI-r. convex and hyaline. Mantle of hypovalve distinct and hyaline. Pyxilla (Pterotheca) aculeifera (Grunow ex Van Heurck) sensu KANAYA 1957, p. 109, pl. 8, figs. 1, 2. Type level and locality: Lower Eocene, Jutland, Denmark. Pterotheca uralica JOUSÉ sensu STRELNIKOVA 1974, p. 115, pl. 57, figs. 27-30a, b. – FENNER 1978, p. 527, pl. 17, fig. 22. Pterotheca sp. 2 in MCCOLLUM 1975, p. 535, pl. 10, fig. 10. Type specimen: Depository not designated. Pterotheca sp. A in GOMBOS 1977, p. 526, pl. 23, figs. 3, 4. – HAR- WOOD and BOHATY 2000, p. 93, pl. 9, figs. l-n. Comparison: This species is very similar to Pt. kittoniana by Pterotheca sp. 1 in FENNER 1991, p. 139, pl. 2, fig. 10. having siliceous ridges extending from the margin to the apex Pseudopyxilla americana sensu DELL’AGNESE and CLARK 1994, but is distinguished from the latter by its huge spines with fig. 4.6. wing-like projections on the valve apex. This species also resembles Pt. evermanii as both possess a branching process on Description: Frustule heterovalvate, apical axis 4-15µm, their valve tops, but can easily be separated from the latter by its pervalvar axis of epivalve 8-17µm not including the spine. In strongly inflated rather than conical valve shape and its valve valve view, valve shape circular. In girdle view, epivalve surface with siliceous ridges. strongly convex or inflated with about 10 coarse, weak or strong siliceous ridges extending from the margin to the apex, Stratigraphic and geographic distributions: The first occur- interspaces hyaline, sometimes these ridges not developed rence of this species is unknown, but the oldest is known from

PLATE 4 Figures 1-38, 40-45 are LM and fig. 39 is SEM, respectively. The scale bars in figs. 1 and 2 is 10µm and it also applies to figures 3-38 and 40-45. The scale bar in fig. 39 is 10µm.

1-39. Resting spore sp. D 23,24 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 1,2 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of frustule. frustule. 25,26 IODP Site 302-2A-54X-CC. Girdle view of frustule. 3,4 IODP Site 302-2A-52X-2, 2-3cm. Girdle view of frustule. 27,28 IODP Site 302-4A-5X-1, 2-3cm. Valve view of hypovalve. 5,6 IODP Site 302-2A-52X-2, 2-3cm. Girdle view of frustule. 29,30 ODP Site 302-2A-52X-2, 2-3cm. Valve view of hypovalve. 7,8 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of frustule. 31,32 IODP Site 302-4A-7X-1, 2-3cm. Valve view of hypovalve. 9,10 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of frustule. 33,34 IODP Site 302-2A-52X-2, 2-3cm. Valve view of hypovalve. 11,12 IODP Site 302-2A-59X-2, 122-123cm. Girdle view of frustule. 35,36 IODP Site 302-2A-54X-CC. Epivalve view of frustule. 13,14 IODP Site 302-2A-59X-CC, 0-1cm. Girdle view of epivalve. 37,38 IODP Site 302-4A-6X-2, 2-3cm. Hypovalve view of frustule. 39. IODP Site 302-4A-5X-1, 2-3cm. Girdle 15,16 IODP Site 302-2A-52X-2, 2-3cm. Girdle view of view of frustule. frustule. 40-45. Dispinodiscus ? sp. A 17,18 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 40,41 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of frustule. frustule. 19,20 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 42,43 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of frustule. frustule. 21,22 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 44,45 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of frustule. frustule.

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the late Cretaceous (Text-figure 6). The reported last occur- FENNER 1994, p. 116, pl. 4, fig. 9. – NIKOLAEV et al. 2001, p. 26, pl. rences of this species are in the early Oligocene from sediments 39, figs. 6, 7. Synonymy: Pterotheca sp. in JOUSÉ 1963, fig. 113. of DSDP Site 511 (Gombos and Ciesielski 1983) and ODP hole Pseudopyxilla sp. in HARWOOD 1988, p.86, fig. 17.25. 1128C (Sanfilippo and Fourtanier 2003). Description: Frustule heterovalvate, diameter 5-20µm, trans- Remarks: The fossil closest in appearance to this diatom was apical axis of epivalve 6-20µm excluding the spines. In valve described by Hanna (1927b, p. 30, pl. 4, fig. 5) from the view, valve shape circular. In girdle view, epivalve highly cy- Moreno Shale in California, upper Cretaceous, as Pterotheca lindrical, hyaline. Epivalve surface thick and heavy with one or crucifera Hanna. He discriminated the species from Pt. two huge spines on the top, at the upper end of which there are aculeifera because it has a “shorter valve” and “much heavier several irregular branches. Length of each valve varies consid- radiating ridges”. However, Pt. crucifera is identified as Pt. erably in proportion to diameter and the arrangement of the aculeifera in this study, because their valve shapes and sizes are branched spine is not uniform, although in all the specimens ob- dependent on the capacities of their vegetative valves. served so far the branching portion is about the same distance from the tip of the spine; the spine is bent slightly away from the Pterotheca aculeifera in Proschkina-Lavrenko (1949, p. 202, axis. Mantle of epivalve distinct, high and hyaline. Hypovalve pl. 75, fig. 4a), Jousé (1963, figs. 111, 114) and Strelnikova slightly convex or nearly flat and hyaline. Mantle of hypovalve Pt. kittoniana (1974, p. 114, pl. 57, figs. 17-22) belong to be- not distinct and hyaline. Diameter of holotype, 20µm. cause they lack a branching process on their valve tops and siliceous ridges on their valve surfaces. Pterotheca cf. aculeifera Type level and locality: Upper Cretaceous (Maastrichtian), up- in Hajós and Stradner (1975, p. 933, pl. 12, fig. 6) and per Moreno Shale in the upper half of a 200 foot thick Pterotheca sp. cf. P. crucifera in Harwood (1988, p. 86, figs. diatomaceous shale near the top of the formation in Moreno 12.14, 15) look like a species in the genus Monocladia Suto, but Gulch, Panoche Hills, northwestern Fresno County, California. the first occurrence of the genus Monocladia is reported from latest Oligocene in the Atlantic Ocean (Suto 2005c). Therefore, Type specimen: Deposited in the collections of the Museum of these specimens might be Pterotheca spp. Other specimens of the California Academy of Sciences, San Francisco, California; Pterotheca cf. aculeifera in Hajós and Stradner (1975, p. 933, holotype (Fig. 6 of Hanna 1927b), no. 2031. pl. 28, figs. 1, 2) are identical to Porotheca danica because of their valve shapes. Comparison: This species closely resembles Pt. aculeifera by possessing a branching process on the valve top, but can be eas- Etymology: The Latin aculeifera means “rough spines” ily identified from the latter by its conical rather than inflated valve shape and its valve surface which lacks siliceous ridges. Pterotheca evermanii Hanna 1927b Plate 8, figures 32-50 Stratigraphic and geographic distributions: The occurrence reports of this species are few, however the oldest ones are re- Pterotheca evermanii HANNA 1927b, p. 31, pl. 4, fig. 6. – ported from the late Cretaceous sediments in the Moreno Shale, PROSCHKINA-LAVRENKO 1949, p. 203, pl. 98, fig. 9. – GLEZER et al. 1974, pl. 12, fig. 4. – STRELNIKOVA 1974, p. 112, pl. 56, figs. California (Hanna 1927b) and in West Siberia (Strelnikova 12-15. – HARWOOD 1988, p. 86, fig. 18.13, 14. – FENNER 1991, p. 1974) (Text-figure 6). The youngest one is from the middle 139, pl. 2, fig. 13. – HOMANN 1991, p. 137, pl. 53, figs. 21-23. – Eocene core of IODP Expedition 302.

PLATE 5 Leptoscaphos levigatus (Sheshukova-Poretskaya) Suto, Jordan et Watanabe Figures 1-18 are LM and figs. 19-28 are SEM. The scale bar in fig. 1 is 10µm and it also applies to figs. 2-18. The scale bars in figs. 19-28 are 10µm.

1,2 IODP Site 302-2A-59X-CC, 0-1cm. Valve view. 17,18 IODP Site 302-2A-52X-2, 2-3cm. Valve view. 3-5 IODP Site 302-2A-59X-2, 122-123cm. Valve view of 19 Enlargement of Fig. 20. frustule. 20 IODP Site 302-2A-59X-2, 122-123cm. Girdle view 6-8 IODP Site 302-4A-6X-2, 2-3cm. Valve view of of frustule. frustule. 21 IODP Site 302-2A-59X-2, 122-123cm. Inner valve 9,10 IODP Site 302-2A-59X-2, 122-123cm.Valve view. view. 11,12 IODP Site 302-2A-59X-2, 122-123cm. Valve view. 22-24 Enlargement of Fig. 21. 13,14. IODP Site 302-2A-59X-2, 122-123cm. Valve view. 25 IODP Site 302-2A-59X-2, 122-123cm. Valve view. 15,16 IODP Site 302-2A-59X-2, 122-123cm. Girdle view 26-28 Enlargement of Fig. 25. of frustule.

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Pterotheca harrensis (Fenner) Suto, Jordan et Watanabe comb. Etymology: This species is named after the Harre borehole, nov. Denmark. Plate 8, figures 51, 52 Pterotheca kittoniana Grunow in Van Heurck 1880-1885 var. Basionym: Pseudopyxilla harrensis FENNER 1994, p. 115, pl. 4, figs. kittoniana 1-3. Pterotheca (Pyxilla ??) kittoniana Grunow in VAN HEURCK 1880-1885, pl. 83 bis., figs. 9-11. Original description: The small valves are highly convex with a Pterotheca kittoniana Grunow in Van Heurck – HARWOOD 1988, p. 86, figs. 18.1, 2. – FENNER 1991, p. 139, pl. 8, fig. 7. – FENNER basal incision. In this furrow, small oval depressions form a 1994, p. 116, pl. 11, figs. 3-6. basal circle. The two valves are connected by a hyaline, Synonymy: Pyxilla ?? kittoniana Grunow in VAN HEURCK 1880-1885, structureless high mantle. pl. 83, figs. 10, 11. Pterotheca kittoniana (Grunow) GRUNOW – HOMANN 1991, p. 138, pl. 53, figs. 19, 20, 26, 27. Type level and locality: Lower Eocene, the Fur Formation re- Pterotheca kittoniana var. kamtschatica GAPONOV, PROSCHKINA- covered from the Harre borehole. LAVRENKO 1949, p. 202, pl. 75, figs. 5a, b. Pterotheca aculeifera GRUNOW, PROSCHKINA-LAVRENKO 1949, Type specimen: Deposited in the collections of the Hustedt Col- p. 202, pl. 75, fig. 4a nec fig. 4b. – JOUSÉ 1963, figs. 111, 114. – STRELNIKOVA 1974, p. 114, pl. 57, figs. 17-22 nec figs. 1-16, lection, Bremerhaven; holotype (pl. 4, fig. 3 of Fenner (1994)), 23-26. sample K 134, 200.31 - 200.40m. Description: Frustule heterovalvate, apical axis 6-32µm, Comparison: This species differs in its shape from all other pervalvar axis of epivalve 8-30µm. In valve view, valve shape Pterotheca species. circular. In girdle view, epivalve strongly convex or inflated with coarse, strong siliceous ridges extending from the margin Stratigraphic and geographic distributions: This species was to the apex as connecting spines, interspaces hyaline and with reported from the early Eocene sediments of the Fur Formation, one long central spine. Mantle of epivalve distinct and hyaline. Denmark (Text-figure 6). Only one specimen was observed in Hypovalve slightly convex and hyaline with one long central the middle Eocene cores of IODP Leg 302-4A-4X-1, 0-3cm in spine and marginal spines. In valve view, spines rise from the this study. center and there are hyaline bifurcating ribs that radiate somewhat irregularly from the center towards the margin. Mantle of Remarks: The valve of this species is not cylindrical which hypovalve distinct and hyaline. Two frustules connected by sili- characterizes Pseudopyxilla, and lacks a single ring of puncta at ceous ridges and central spines of each epivalve. the base of its hypovalve which characterizes fossil Chaeto- ceros resting spore morpho-species. This species is character- Type level and locality: Lower Eocene, Jutland, Denmark. ized by its round valve shape and therefore Pseudopyxilla harrensis is transferred to Pterotheca harrensis in this study. Type specimen: Depository not designated.

PLATE 6 Leptoscaphos punctatus (Grove et Sturt) Schrader Figures 1-25 are LM and figs. 26-33 are SEM, respectively. The scale bar in fig. 1 is 10µm and it also applies to figs. 2-25. The scale bars in figs. 26-33 are 10µm.

1, 2 IODP Site 302-2A-59X-2, 122-123cm. Valve view. 22,23 IODP Site 302-2A-59X-CC, 0-1cm. Valve view. 3,4 IODP Site 302-2A-61X-2, 2-3cm. Valve view. 24,25 IODP Site 302-2A-54X-CC. Valve view. 5,6 IODP Site 302-2A-52X-2, 2-3cm. Valve view. 26 IODP Site 302-2A-59X-2, 122-123cm. Valve view. 7,8 IODP Site 302-2A-52X-2, 2-3cm. Valve view. 27, 28 Enlargement of Fig. 26. 9,10 IODP Site 302-2A-52X-2, 2-3cm. Valve view. 29 IODP Site 302-2A-59X-2, 122-123cm. Inner valve view. 11-13 IODP Site 302-4A-6X-2, 2-3cm. Valve view of frustule. 30,31 Enlargement of Fig. 29. 14,15 IODP Site 302-2A-59X-CC, 0-1cm. Valve view. 32 IODP Site 302-2A-59X-2, 122-123cm. Girdle view of frustule. 16,17 IODP Site 302-2A-53X-CC. Valve view. 33 Enlargement of Fig. 32. 18,19 IODP Site 302-2A-53X-CC. Valve view. 20,21 IODP Site 302-2A-59X-2, 122-123cm. Valve view.

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Comparison: This species is very similar to Pt. aculeifera by erected by Ehrenberg (1854) and several species have been de- having siliceous ridges extending from the margin to the apex scribed such as C. californicum Ehrenberg (1854), C. conicum but is distinguished by lacking huge spines with wing-like pro- Greville (1865), C. jordanii Hanna (1927b), C. morenoensis jections on the valve apex. This species is distinguished from Long, Fuge et Smith (1946), C. dubium Lohman (1948), C. the variety Pt. kittoniana var. minuta Fenner by its larger size. ellipticum Lohman (1948), C. pacificum Kolbe (1954) and C. simplex Hajós in Hajós and Stradner (1975). All of these species Stratigraphic and geographic distributions: This species has possess hyaline bifurcating ribs on their valve surface, but most been reported from Cretaceous sediments in western Siberia of them possess distinct mantles and vaulted valves except for (Strelnikova 1974), from Paleocene sediments in the Seymour C. jordanii and C. simplex. Since the hypovalve of Pt. Island, Antarctic and from early Eocene deposits in Denmark, kittoniana is nearly flat, Pt. kittoniana is separated from the ge- but was not recognized in IODP Expedition 302 sediments in nus Cladogramma. C. jordanii and C. simplex may belong to this study (Text-figure 6). the genus Pterotheca as mentioned by Fenner (1994), but it is still not clear. Remarks: Pterotheca kittoniana (Grunow) Forti sensu Hajós (1986, pl. 48, figs. 11-13), collected from the Miocene sedi- Etymology: This species is named in honor of Dr. F. Kitton. ments of the Szurdokpüspöki diatomite stop in Hungary, belongs to Syndendrium akibae Suto because of its strongly Pterotheca kittoniana var. kamtschatica Gapanov 1927 domed valve with several repeated, dichotomous, branching hyaline processes (Suto 2003). Pterotheca kittoniana var. kamtschatica GAPANOV 1927 sensu SHESHUKOVA-PORETSKAYA 1967, p. 268, pl. 39, figs 3a-f. – Fenner (1994) mentioned that epi- and hypovalves have been GLEZER et al. 1974, pl. 47, figs. 9a-c. assigned even to different genera Cladogramma Ehrenberg and Pterotheca Grunow, because these two valves are so different Remarks: Pterotheca kittoniana var. kamtschatica Gaponov and the hypovalve possesses hyaline bifurcating ribs that radi- sensu Proschkina-Lavrenko (1949, p. 202, pl. 75, figs. 5a, b) ate somewhat irregularly from the center towards the margin. and Fenner (1978, p. 527, pl. 9, figs. 2, 5), and Pt. kittoniana Therefore, Fenner (1994) also indicated that C. simplex Hajós Grunow sensu Jousé (1977, pl. 33, fig. 13) may belong to in Hajós and Stradner (1975, p. 928, pl. 4, figs. 7, 8, pl. 28, fig. Pterotheca reticulata because these specimens possess 5) is a synonym of Pt. kittoniana. The genus Cladogramma was anastomosing hyaline rims on their valve surface, but it is un-

PLATE 7 Porotheca danica (Grunow) Fenner Figures 1-21 are LM and figs. 22-27 are SEM. The scale bar in figs. 1 and 2 is 10µm and it also applies to figs. 3-21. The scale bars in figs. 22, 27 and 28 are 10µm and the scale bar in fig. 22 applies to figs. 23-26.

1,2 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of 20,21 IODP Site 302-2A-59X-CC, 0-1cm. Valve view of epivalve. epivalve. 3,4 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of 22 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of epivalve. epivalve. 5,6 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 23 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of epivalve. epivalve. 7-9 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of 24 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of epivalve. epivalve. 10,11 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 25 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of epivalve. epivalve. 12,13 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 26 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of epivalve. epivalve. 14,15 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 27 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of epivalve. T epivalve. 16,17 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 28 IODP Site 302-2A-59X-CC, 0-1cm. Valve view of epivalve. epivalve. 18,19 IODP Site 302-2A-61X-2, 2-3cm. Girdle view of epivalve.

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known whether or not these specimens belong to Pt. reticulata Pterotheca kittoniana var. minuta Fenner 1994 due to the difference of their stratigraphic ranges between the holotype and typical Pt. reticulata (see Remarks on Pt. Pterotheca kittoniana var. minuta FENNER 1994, p. 117, pl. 11, fig. 13. reticulata). Moreover, this variety found by Baldauf and Barron (1987, p. 7, pl. 10, fig. 14) in late Oligocene dredge samples Original description: The frustule is heterovalvar. One valve is from the Navarine Basin Province, Bering Sea may be identical slightly convex. It has marginal spines and one long central with Pterotheca spp. or Syndendrium spp., but it is not yet clear spine. The other valve has a high mantle with a basal incision whether or not this specimen belongs to one of these genera. and four spines rising from the border between valve face and mantle.

PLATE 8 Figures 1-19, 22-29, 32-48, 51 and 52 are LM and figs. 20, 21, 30, 31, 49 and 50 are SEM. The scale bars in figs. 1 and 2, 32 and 33 are 10µm and it also applies to figs. 3-19 and 22-29, and 34-48. The scale bars in figs. 20, 21, 30, 31, 49-52 are 10µm.

1-21. Pseudopyxilla dubia (Grunow) Forti 30 IODP Site 302-2A-59X-2, 122-123cm. Girdle view 1-3 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of of epivalve. epivalve. 31 IODP Site 302-4A-5X-1, 2-3cm. Pseudopyxilla 4,5 ODP Site 302-4A-7X-1, 2-3cm. Girdle view of jouseae ?orPorotheca danica ?. Girdle view of epivalve. epivalve. 6,7 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of 32-50. Pterotheca evermanni Hanna epivalve. 32,33 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of frustule. 8,9 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of epivalve. 34,35 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of epivalve. 10,11 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of epivalve. 36 IODP Site 302-2A-59X-CC, 0-1cm. Girdle view of epivalve. 12,13 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of frustule. 37,38 IODP Site 302-2A-59X-2, 122-123cm. Girdle view of frustule. 14,15 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of epivalve. 39,40 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of frustule. 16,17 IODP Site 302-2A-59X-2, 122-123cm. Girdle view of epivalve. 41,42 IODP Site 302-2A-55X-CC. Girdle view of epivalve. 18,19 IODP Site 302-2A-57X-CC, 0-1cm. Girdle view of 43,44 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of epivalve. frustule. 20 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of 45,46 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of epivalve. epivalve. 21 Enlargement of Fig. 20. 47,48 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of frustule. 22-31. Pseudopyxilla jouseae Hajós 22,23 IODP Site 302-2A-59X-CC, 0-1cm. Girdle view of 49 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of epivalve. epivalve. 24,25 IODP Site 302-2A-59X-CC, 0-1cm. Girdle view of 50 IODP Site 302-2A-59X-2, 122-123cm. Girdle view epivalve. of epivalve. 26,27 IODP Site 302-2A-59X-2, 122-123cm. Girdle view 51, 52. Pterotheca harrensis (Fenner) Suto, Jordan et Watanabe of epivalve. 51, 52 IODP Site 302-4A-4X-1, 0-3cm. Girdle view. 28,29 IODP Site 302-2A-59X-2, 122-123cm. Girdle view of epivalve.

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Type level and locality: Lowest Eocene, the Moler of Fur For- Basionym: Pseudopyxilla minuta FENNER 1994, p. 115, pl. 4, figs. 5-7. mation, Denmark. Synonymy: Hemiaulus kittonii Grunow in VAN HEURCK 1880-1885, pl. 106, figs. 6-9 (6-8. spore in vegetative cell; 9. vegetative cell). – CLEVE-EULER 1951, Handl. 2: 1, p. 123, figs. 266a-d (a. vegetative Type specimen: Deposited in the Grunow Collection in the cell; b. spore in vegetative cell; c, d: resting spores). Naturhistorisches Museum, Wien. Slide no. NHW 3004 d. Pterotheca tuffata FENNER 1994, p. 117, pl. 4, figs. 11, 12.

Comparison: This variety differs from P. kittoniana var. Emended description: Frustule isovalvate, diameter 3-7µm, kittoniana by its smaller size and different shape (Fenner 1994). transapical axis 5-14µm. Valves circular in valve view. Both valves slightly convex in girdle view. Valve faces covered with Stratigraphic and geographic distributions: The holotype of small knobs and short and long spines. Mantle of valve hyaline, this variety is recognized from the earliest Eocene, but was not high and curved inward in its basal part. observed in this study (Text-figure 6) therefore its stratigraphic range and distribution are unknown. Type level and locality: Lower Eocene, the Moler of Fur Forma- Etymology: The Latin minuta means “small” tion, Denmark.

Pterotheca minuta (Fenner) Suto, Jordan et Watanabe comb. nov. Type specimen: Deposited in the Grunow Collection in the Plate 10, figures 1-30 Naturhistorisches Museum, Wien. Slide NHW 3004 d.

PLATE 9 Figures 1-38 and 41, 42, 44-47 are LM and figs. 39, 40 and 43 are SEM, respectively. The scale bar in figs. 1 and 2 is 10µm and it also applies to figs. 3-38, 41, 42, 46 and 47. The scale bars in figs. 39, 40, 43, and 44 and 45 are 10µm.

1-40. Pterotheca aculeifera Grunow 27,28 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of 1,2 IODP Site 302-4A-9X-CC. Girdle view of frustule. epivalve. 3,4 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of 29,30 IODP Site 302-4A-8X-CC. Girdle view of frustule. frustule. 31,32 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of 5,6 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of frustule. frustule. 33,34 DSDP Leg 38, Site 338-26-5, 80-81cm. Girdle view 7,8 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of of epivalve. frustule. 35,36 DSDP Leg 38, Site 338-27-2, 50-51cm. Girdle view 9,10 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of of frustule. frustule. 37,38 DSDP Leg 38, Site 338-26-5, 80-81cm. Girdle view 11,12 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of of epivalve. epivalve. 39 IODP Site 302-2A-59X-2, 122-123cm. Girdle view 13,14 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of of epivalve. frustule. 40 IODP Site 302-4A-5X-1, 2-3cm. Oblique girdle view 15,16 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of of frustule. frustule. 41-43. Pterotheca aculeifera (Double spiny type) 17,18 IODP Site 302-2A-61X-2, 2-3cm. Girdle view of 41,42 IODP Site 302-2A-59X-CC, 0-1cm. Girdle view of frustule. epivalve. 19,20 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of 43 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of frustule. epivalve. 21,22 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 44-47. Pterotheca aculeifera (Simple type) epivalve. 44,45 DSDP Leg 38, Site 338-27-2, 50-51cm. Girdle view of epivalve. 23,24 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of frustule. 46,47 DSDP Leg 38, Site 338-27-2, 50-51cm. Girdle view of epivalve. 25,26 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of frustule.

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Comparison: This species bears a close resemblance with the Pterotheca tuffata Fenner (1994) is identical to Ps. minuta be- fossil Chaetoceros resting spore morpho-genus Xanthiopyxis in cause the specimens had well-preserved long spines. Van possessing numerous knobs and spines on its valve surface (see Heurck (1880-1885) also illustrated this resting spore with Suto 2005e), but is distinguished from the latter by lacking a well-preserved long spines on the valve surfaces in single ring of puncta at the base of the hypovalve mantle. Hemiaulus-like vegetative cells therefore this spore must possess short and long spines on the valve and so the genus Stratigraphic and geographic distributions: This species oc- Pterotheca including this species may belong to the genus curred in the early Eocene sediment of the Fur Formation, Den- Hemiaulus. mark (Van Heurck 1880-1885, Fenner 1994) and in middle Eocene cores from the central Arctic Ocean in this study Etymology: The Latin minuta means “small”. (Text-figure 6). Pterotheca reticulata Sheshukova-Poretskaya 1967 Plate 10, figures 31-40 Remarks: The valve of this species is not cylindrical which characterizes Pseudopyxilla, and lacks a single ring of puncta at Pterotheca reticulata SHESHUKOVA-PORETSKAYA 1967, p. 229, the base of its hypovalve which characterizes fossil Chaeto- pl. 36, figs. 6a-c; pl. 8, figs. 4a-c. – SCHRADER and FENNER 1976, p. 994, pl. 12, fig. 2 nec pl. 12, figs. 1, 11; pl. 38, figs. 10-12, 14-16; pl. ceros resting spore morpho-species. This species is character- 45, fig. 6. – DZINORIDZE et al. 1978, pl. 20, fig. 15. – HAJÓS 1986, ized by its round valve shape and therefore Pseudopyxilla pl. 16, fig. 11; pl. 48, fig. 10. minuta is transferred to Pterotheca minuta in this study.

PLATE 10 All figures are transmitted light micrographs (LM). Scale bar = 10µm, which applies to all figures.

1-30. Pseudopyxilla minuta Fenner 27,28 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of 1,2 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of frustule. frustule. 29,30 IODP Site 302-2A-61X-2, 2-3cm. Girdle view of 3,4 IODP Site 302-2A-52X-2, 2-3cm. Girdle view of frustule. frustule. 31-40. Pterotheca reticulata Sheshukova-Poretskaya 5,6 IODP Site 302-2A-52X-2, 2-3cm. Girdle view of 31,32 DSDP Leg 38, Site 338-8-1, 140-141cm. Girdle view frustule. of epivalve. 7,8 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 33,34 DSDP Leg 38, Site 338-19-4, 10-11cm. Girdle view frustule. of epivalve. 9,10 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 35,36 DSDP Leg 38, Site 338-21-1, 32-33cm. Girdle view frustule. of epivalve. 11,12 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 37,38 DSDP Leg 38, Site 338-8-3, 10-11cm. Girdle view of frustule. epivalve. 13,14 IODP Site 302-2A-61X-2, 2-3cm. Girdle view of 39,40 DSDP Leg 38, Site 338-9-1, 50-51cm. Girdle view of frustule. epivalve. 15,16 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of 41-44. Resting spore sp. A frustule. 41,42 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of frustule. 17,18 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of frustule. 43,44 IODP Site 302-2A-53X-CC. Girdle view of frustule. 19,20 IODP Site 302-2A-61X-2, 2-3cm. Girdle view of 45-50. Resting spore sp. B frustule. 45, 46 IODP Site 302-2A-54X-CC. Girdle view of frustule. 21,22 IODP Site 302-2A-54X-CC. Girdle view of frustule. 47,48 IODP Site 302-2A-54X-CC. Girdle view of frustule. 23,24 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of 49,50 IODP Site 302-2A-54X-CC. Girdle view of frustule. frustule. 25,26 IODP Site 302-2A-61X-2, 2-3cm. Girdle view of frustule.

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Description: Frustule heterovalvate, diameter 7-18µm, the Nituy, Gurovka and Gornaya Rivers, South Sakhalin transapical axis 18-30µm. In valve view, epivalve inflated and (Sheshukova-Poretskaya 1967) (text-figure 6). The typical cap-shaped, 7-18µm in height, neck developed with a height of specimens of Pt. reticulata occurred in the middle Miocene core 2-4µm. Hypovalve vaulted or cap-shaped or in the form of a deposit of DSDP Site 348 (Schrader and Fenner 1976) and in convex lid 3-5µm high with the same kind of neck as the Miocene sediments of the Szurdokpüspöki diatomite stop in epivalve. Structure of both valves consists of anastomosing Hungary (Hajós 1986). This species also occurred sporadically ridges forming a well developed network on the mantle and in the latest Oligocene to middle Miocene sediments of DSDP valve face. Neck hyaline or with fine striae, parallel to central Leg 38, Site 338 in the Norwegian Sea, although it was not ob- axis, 24-26 striae in 10µm. Around the valve face are quite long served from IODP Leg 302. and coarse processes, surrounded by a hyaline covering which extends to the valve mantle. Remarks: Specimens of Pterotheca reticulata found by Schrader and Fenner (1976, p. 994, pl. 12, figs. 1, 11; pl. 38, Type level and locality: the upper Middle Miocene to lower Up- figs. 10-12, 14-16; pl. 45, fig. 6 nec pl. 12, fig. 2), Harwood per Miocene, Etolon suite sediments in the Rekinniki Bay, east- (1986, p. 86, pl. 6, figs. 20-23) and Scherer et al. (2000, p. 436, ern side of Penzhina Bay, Kamchatka pl. 5, figs. 4, 13) are identical to Syndendrium rugosum because they possess the hyaline valve face with some wrinkles and no Type specimen: Deposited in the collection of the Chair of anastomosing ridges, and with several repeated, dichotomous, Lower Plants, St.-Petersburg University, St.-Petersburg, Rus- branching hyaline processes on the strongly convex or inflated sia, no. 1151-2. epivalve (Suto 2005c).

Comparison: This species closely resembles Syndendrium Specimens of Pterotheca kittoniana var. kamtschatica Gaponov rugosum Suto in possessing long spines on its valve, but differs illustrated by Proschkina-Lavrenko and Sheshukova-Poret- from the latter by possessing a network of anastomosing ridges. skaya (1967, p. 268, pl. 39, figs. 3a-f), Glezer et al. (1974, pl. 47, 9a-c) and Fenner (1978, p. 527, pl. 9, figs. 2, 5), Pt. Stratigraphic and geographic distributions: The holotype was kittoniana in Jousé (1977, pl. 33, fig. 13) and Pt. sp. in Fenner collected from the late middle Miocene to early late Miocene (1994, pl. 12, fig. 8) may belong to Pt. reticulata because of sediments from the Etolon suite in the Rekinniki Bay, eastern their anastomosing ridges on the valve face, however they may side of Penzhina Bay, Kamchatka and was also found in late belong to other taxa because they possess some long spines on Miocene to Pliocene sediments from the Maruyama suite along the valve top. The holotype and typical specimens of Pt.

PLATE 11 Figures 1-35 are LM and figs. 36-38 are SEM, respectively. The scale bar in figs. 1 and 2 is 10µm and it also applies to figs. 3-35. The scale bars in figs. 36-38 are 10µm.

1-38. Stephanogonia sp. A 19-21 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of 1,2 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of epivalve. epivalve. 22-24 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of 3,4 IODP Site 302-2A-59X-2, 122-123cm. Girdle view epivalve. of epivalve. 25,26 IODP Site 302-2A-61X-2, 2-3cm. Girdle view of 5,6 IODP Site 302-2A-58X-CC. Girdle view of epivalve. epivalve. 7,8 IODP Site 302-2A-58X-CC. Girdle view of epivalve. 27,28 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of epivalve. 9,10 IODP Site 302-2A-57X-CC. Girdle view of epivalve. 31,32 IODP Site 302-4A-6X-2, 2-3cm. Girdle view of 11,12 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of epivalve. epivalve. 33-35 IODP Site 302-4A-5X-1, 2-3cm. Valve view of 13,14 IODP Site 302-2A-59X-2, 122-123cm. Girdle view epivalve. of epivalve. 36 IODP Site 302-2A-59X-2, 122-123cm. Girdle view 15,16 IODP Site 302-2A-59X-2, 122-123cm. Girdle view of epivalve. of epivalve. 37 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of 29,30 IODP Site 302-2A-59X-2, 122-123cm. Girdle view epivalve. of epivalve. 38 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of 17,18 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of epivalve. epivalve.

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reticulata occurred in Miocene deposits (see Text-figure 6) with inflated plane, divided into 2 equal parts by 1 transverse in- however, the specimens shown here were all collected from ternal septum. Mantle of epivalve distinct, slightly compressed Eocene deposits. Therefore, they may be separate species. near the top of internal septum. Hypovalve nearly flat to slightly convex in the center in girdle view. Etymology: The Latin reticulata means “netlike”. Comparison: This species is similar to Anaulus arcticus in pos- Resting spore sp. A sessing transverse internal septa, but differs from it by having Plate 10, figures 41-44 only one septum. Description: Frustule heterovalvate, apical axis 23-25µm, pervalvar axis 8-10µm. Epivalve hyaline, vaulted in the center, Stratigraphic and geographic distributions: Not reported from or undulated with five inflations in girdle view. Mantle of fossil material. This species occurred rarely in middle Eocene epivalve hyaline. Hypovalve hyaline, undulated with five infla- sediments from IODP Leg 302 Sites 2A and 4A in the central tions in girdle view. Arctic Ocean.

Comparison: Not reported from fossil material. Remarks: This species not observed in valve view in this study however this species may be a variety of A. arcticus which pos- Stratigraphic and geographic distributions: This species oc- sesses one septum because of the similarities in valve structures. curred rarely middle Eocene sediments from IODP Leg 302 Sites 2A and 4A in the central Arctic Ocean. Resting spore sp. C Plate 3, figures 1-23 Remarks: This species was not observed in valve view in this study. Description: Frustule heterovalvate. Valve elliptical in valve Resting spore sp. B view, apical axis 13-35µm, transapical axis 5-15µm without Plate 10, figures 45-50 sheath. In girdle view, epivalve face vaulted, hyaline, surrounded by a sheath, with distinct mantle. Mantle of epivalve Description: Frustule heterovalvate. Valve square to rectangu- hyaline. Sheath of epivalve ornamented with dense rows of sim- lar in girdle view, apical axis 12-14µm, pervalvar axis ple pores. Hypovalve face slightly vaulted or nearly flat, 14-17µm. Epivalve hyaline, rectangular in girdle view, vaulted hyaline, with distinct mantle. Mantle of hypovalve hyaline.

PLATE 12 Figures 1-10, 14-31 and 33-35 are LM and figs. 11-13, 32 and 36 are SEM, respectively. The scale bar in figs. 1 and 2, and 14 and 15 are 10µm and those also apply to figs. 3-10, and 16-31 and 33-35, respectively. The scale bars in figs. 11-13 and 36, and 32 are 10µm and 5µm, respectively.

1-12. Stephanogonia sp. B 20,21 IODP Site 302-2A-59X-CC, 0-1cm. Valve view. 1,2 IODP Site 302-2A-61X-2, 2-3cm. Girdle view of 22, 23. Trochosira spinosa Kitton epivalve. 22,23 DSDP Leg 38, Site 338-14-3, 20-21cm. Girdle view 3,4 IODP Site 302-4A-4X-1, 0-3cm. Girdle view of of chained frustules. epivalve. 24, 25. Vallodiscus ? sp. A 5,6 IODP Site 302-2A-53X-CC. Valve view of epivalve. 24, 25 IODP Site 302-2A-53X-CC. Valve view. 7-10 IODP Site 302-2A-61X-2, 2-3cm. Valve view of 26-32. Xanthiopyxis type A (knobbly type) epivalve. 26,27 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of frustule. 11 IODP Site 302-4A-5X-1, 2-3cm. Valve view of epivalve. 28,29 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of frustule. 12 IODP Site 302-4A-5X-1, 2-3cm. Oblique girdle view. 30,31 IODP Site 302-2A-52X-2, 2-3cm. Girdle view of 13-21. Trochosira coronata ? Schrader et Fenner frustule. 13 IODP Site 302-2A-59X-2, 122-123cm. Oblique valve view. 32 IODP Site 302-4A-5X-1, 2-3cm. Oblique valve view. 14,15 IODP Site 302-2A-52X-2, 2-3cm. Valve view. 33-36. Xanthiopyxis sp. B (short spiny type) 33-35 IODP Site 302-4A-5X-1, 2-3cm. Valve view. 16,17 IODP Site 302-2A-52X-2, 2-3cm. Valve view. 36 IODP Site 302-4A-5X-1, 2-3cm. Girdle view of 18,19 IODP Site 302-2A-59X-CC, 0-1cm. Valve view. frustule.

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Comparison: This taxon is characterized by its sheath around strong bristle near each apex, with distinct mantle. Mantle of the margin of the epivalve with dense rows of simple pores. hypovalve hyaline with few scattered areolae. This taxon is very similar to Coronodiscus collarius Suto (2004c) in possessing a sheath with dense rows of simple pores Comparison: This taxon is characterized by having an epivalve but is distinguished from the latter by the absence of a single with two humps covered with numerous straight veins and ring of puncta and sheath on the hypovalve. knobs, and a hypovalve with two strong bristles. This taxon is very similar to the resting spore of extant Chaetoceros debilis Stratigraphic and geographic distributions: This taxon oc- and fossil morpho-species genus Dispinodiscus species (Suto curred in middle Eocene sediments from IODP Leg 302 Sites 2004b), but is clearly separated from them by its absence of a 2A and 4A in the central Arctic Ocean. ring of puncta on the hypovalve margin.

Remarks: This taxon does not appear to belong to the fossil Stratigraphic and geographic distributions: This taxon oc- resting spore morpho-genus Coronodiscus of extant curred abundantly in middle Eocene sediments from IODP Leg Chaetoceros because of the absence of a ring of puncta on the 302 Sites 2A and 4A in the central Arctic Ocean. hypovalve margin. Remarks: This taxon does not belong to the fossil resting spore Resting spore sp. D morpho-genus of Chaetoceros because of the absence of a ring Plate 4, figures 1-39 of puncta on the hypovalve margin. This taxon looks like Hemiaulus tumidicornis (Strelnikova 1971, 1974), but differs Description: Frustule heterovalvate. Valve narrowly elliptical from the latter by its valve covered with knobs. Hemiaulus in valve view, apical axis 6-18µm, transapical axis 4-12µm, tumidicornis sensu Barron (1985) and Dell’Agnese and Clark pervalvar axis 8-18µm without bristles. In girdle view, epivalve (1994) from late Cretaceous sediments of the Alpha Ridge, cen- vaulted with two humps, covered with numerous straight veins tral Arctic Ocean are also similar to this species due to the and knobs, with distinct mantle. Mantle of epivalve distinct, pore-less valve surface, but resting spore sp. D is distinguished hyaline. Hypovalve vaulted in central area or nearly flat, with a from these specimens by its hypovalve with one hump. These

PLATE 13 Figures 1-33, 36-41 and 43-48 are LM and figs. 34, 35 and 42 are SEM. The scale bar in figs. 1 and 2, and 36 and 37 are 10µm and those also apply to figs. 3-33 and 43-48, and 38-41. The scale bars in figs. 34, 35 and 42 are 10µm.

1-35. Trochosira polychaeta (Strelnikova) Sims 32,33 IODP Site 302-2A-55X-CC, 0-1cm. Girdle view of 1-3 IODP Site 302-2A-61X-2, 2-3cm. Valve view. frustule connected to opposite valve. 4,5 IODP Site 302-2A-53X-CC. Valve view. 34 IODP Site 302-2A-59X-2, 122-123cm. Girdle view of connected valves. 6,7 IODP Site 302-2A-53X-CC. Valve view. 35 IODP Site 302-2A-59X-2, 122-123cm. Oblique valve 8-10 IODP Site 302-2A-61X-2, 2-3cm. Valve view. view of frustule. 11,12 IODP Site 302-2A-59X-CC, 0-1cm. Valve view. 36-42. Chaetoceros hypovalve (hyaline type) 36,37 IODP Site 302-4A-5X-1, 2-3cm. Valve view of 13,14 IODP Site 302-2A-59X-CC, 0-1cm. Valve view. hypovalve. 15-17 IODP Site 302-2A-61X-2, 2-3cm. Valve view. 38,39 IODP Site 302-4A-5X-1, 2-3cm. Valve view of 18,19 IODP Site 302-2A-59X-CC, 0-1cm. Valve view. hypovalve. 20,21 IODP Site 302-4A-4X-1, 0-3cm. Valve view. 40,41 IODP Site 302-4A-7X-1, 2-3cm. Valve view of hypovalve. 22,23 IODP Site 302-2A-53X-CC. Valve view. 42 IODP Site 302-4A-5X-1, 2-3cm. Valve view of 24,25 IODP Site 302-2A-59X-CC, 0-1cm. Girdle view of hypovalve. frustule. 43-48. Chaetoceros hypovalve (wrinkled type) 26,27 IODP Site 302-2A-61X-2, 2-3cm. Girdle view of con- 43,44 IODP Site 302-4A-8X-CC, bottom. Valve view of nected valves. hypovalve. 28,29 IODP Site 302-4A-7X-1, 2-3cm. Girdle view of 45,46 IODP Site 302-4A-4X-1, 0-3cm. Valve view of frustule. hypovalve. 30,31 IODP Site 302-2A-59X-CC, 0-1cm. Girdle view of 47,48 IODP Site 302-4A-4X-1, 0-3cm. Valve view of frustule. hypovalve.

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specimens of Hemiaulus taxa may represent vegetative cells Comparison: This species differs from T. mirabilis by possess- and resting spores because of the similarities of their valve ing three or four circular central spines. shapes. Moreover, resting spore sp. D may be the descendant of Hemiaulus tumidicornis sensu Barron (1985) and Dell’Agnese Stratigraphic and geographic distributions: This species oc- and Clark (1994). curred in Eocene DSDP Sites 338-340 cores in the Norwegian Sea (Schrader and Fenner 1976, Dzinoridze et al. 1978, Sims Stephanogonia sp. A 1988) and from the Fur Formation in Denmark (Fenner 1994) Plate 11, figures 1-38 (Text-figure 7). The specimens considered to belong to this species occur in IODP Leg 302 sediments. Description: Valve truncated pyramidal with flat top, swollen in the middle, and with a wide flat circular brim at the base, Remarks: The specimens from IODP Leg 302 in this study may turning up shortly at its edge, valve widest at the base, 12-14µm be dissolved valves of this species with eroded linking spines or in diameter. Valve surface covererd with numerous siliceous separation valves lacking linking spines of T. spinosa (and/or T. ridges extending from the margin of valve and mantle to base of polychaeta) as mentioned by Sims (1988). The specimen of valve top margin and running off to long bristles, interspace Trochosira coronata in Scherer and Koç (1996) is identified as hyaline with a row of puncta near the base of the ridge (see pl. T. spinosa because it links by a ring of solid spines in the valve 11, figs. 36-38). Mantle distinct with puncta equally spaced and central area. clearly separated (see Pl. 11, fig. 36). Frustule not observed. Etymology: The Latin coronata means “crowned”. Comparison: This taxon is very similar to Stephanogonia hanzawae Kanaya (1959, p. 118, pl. 11, figs. 3-7) by its trun- Trochosira mirabilis Kitton 1871 cated pyramidal valve with flat top, but is distinguished from the latter by its long and strong bristles on the valve top. Trochosira mirabilis KITTON 1871, p. 170, pl. 14, figs. 8, 9. – VAN HEURCK 1880-1885, pl. 83 bis, fig. 13. – SCHMIDT 1874-1959, pl. Stratigraphic and geographic distributions: This species oc- 176, fig. 55; pl. 180, fig. 48. – CLEVE-EULER 1951, Handl. 2: 1, p. curred abundantly in middle Eocene sediments from IODP Leg 110, fig. 234a. – SIMS 1988, p. 247, figs. 1-6, 25. – HOMANN 1991, 302 in the central Arctic Ocean. p. 65, pl. 44, figs. 5, 9-13. – FENNER 1994, p. 122, pl. 2, figs. 2-4.

Remarks: This taxon does not belong to the fossil resting spore Synonymy: Trochosira cf. mirabilis Kitton – HOMANN 1991, p. 66, pl. morpho-genus of Chaetoceros because of the absence of a ring 44, figs. 7, 8. of puncta on the hypovalve margin and presence of numerous Trochosira aff. mirabilis Kitton – FENNER 1991, p. 141, pl. 11, figs. areolae on the valve surface and the mantle (see Plate 11, fig. 19, 20. 36). Emended description: See Sims (1988). Stephanogonia sp. B Type level and locality: Lower Eocene, Fur Formation, Den- Plate 12, figures 1-12 mark. Description: Frustule heterovalvate. In valve view, epivalve circular, 13-38µm in diameter, covered with radial siliceous Type specimen: Depository not designated. ridges from the center to margin, interspace of ridges hyaline. Comparison: This species is very similar to T. polychaeta as In girdle view, epivalve high to low cylindrical with vaulted they possess three-faceted rods on the valve center linking the top, slightly swollen at the middle. Epivalve surface covered opposite valves, but this species is easily separated from the lat- with numerous siliceous ridges extending from the valve top to ter by its longer rod up to two times the length of each frustule base and some strong bristles running off from the ridges near and by the presence of numerous long flattened spines at the the vaulted area. Mantle of epivalve distinct with puncta valve margin. This species is also distinguished from T. equally spaced and clearly separated (see Pl. 12, fig. 12). In coronata which is connected by several (2-5) circular central valve view, hypovalve circular and concave inside the frustule linking spines (see Schrader and Fenner 1976, Sims 1988). (see Pl. 12, fig. 12) with sparsely concave areas. In girdle view, hypovalve nearly flat. Stratigraphic and geographic distributions: This species occurred in Paleocene sediments of ODP Holes 698A, 700B and Stratigraphic and geographic distributions: This species oc- 702B in the sub-Antarctic southwest Atlantic Ocean (Fenner curred abundantly in middle Eocene sediments from IODP Leg 1991), in early to middle Eocene Mors and Fur Formations, 302 in the central Arctic Ocean. Denmark (Kitton 1871, Van Heurck 1880-1885, Homann 1991, Trochosira coronata ? Schrader and Fenner 1976 Fenner 1994) and in late Eocene sediments from the eastern Plate 11, figures 13-21 slopes of the Ural Mountains (Sims 1988) (Text-figure 7). Trochosira coronata SCHRADER and FENNER 1976, p. 1003, pl. 29, Remarks: The occurrences of this species changed from the figs. 9-11; pl. 35, figs. 7-13, 20, 21. – SIMS 1988, p. 250, figs. 11-14, Southwestern Atlantic Ocean in the Paleocene to the North At- 27, 28. – FENNER 1994, p. 122. lantic in the Eocene, but the cause of this migration from south Synonym: Trochosira mirabilis sensu DZINORIDZE et al. 1978, pl. 4, in the Paleocene to north in the Eocene is unknown. fig. 14. Etymology: The Latin mirabilis means “curious”. Emended description: See Sims (1988). Trochosira polychaeta (Strelnikova) Sims 1988 Type level and locality: Upper Eocene, DSDP Site Plate 13, figures 1-35 338-28-28-2, 48-50cm, the Norwegian Sea. Trochosira polychaeta (Strelnikova) SIMS 1988, p. 251, figs. 15-21, Type specimen: Depository not designated. 29-34.

304 Micropaleontology, vol. 55, nos. 2-3, 2009

Basionym: Sceletonema polychaetum STRELNIKOVA 1971, p. 42, pl. Comparison: This species differs from others by lacking mar- 1, figs. 3-5. – STRELNIKOVA 1974, p. 54, pl. 3, figs. 3-7. – ginal spines and by possessing numerous subcentral inter- BARRON 1985, p. 141, pl. 10.1, figs. 2-4. Synonymy: Pyrgodiscus triangulatus HAJÓS and STRADNER 1975, p. digitating spines. 928, figs. 11a, b; pl. 18, figs. 5, 6. Trochosiropsis polychaeta (STRELNIKOVA) TAPIA in TAPIA and Stratigraphic and geographic distributions: The occurrences HARWOOD 2002, p. 330, pl. 8, figs. 3, 4. from Eocene to the Oligocene are reported from numerous areas, especially the North Atlantic Ocean (Text-figure 8). This Emended description: See Sims (1988). species also occurred in DSDP Site173 sediments, estimated to be middle to late Miocene in age (Schrader 1973) and from the Type level and locality: Upper Cretaceous (Campanian), West- middle Miocene Hawthorn Formation (Abbott and Andrews ern Siberia. 1979).

Type specimen: Depository not designated. Etymology: The Latin spinosa means “spiny”. Vallodiscus ? sp. A Comparison: This species is very similar to T. mirabilis as it Plate 12, figures 24, 25 possesses three-faceted rods in the valve center linking the opposite valve, but this species is easily separated from the latter Description: Frustule not observed. Valve elliptic in valve by its shorter rod and by the absence of long flattened spines at view, apical axis 36µm, pervalvar axis 10µm. Valve hyaline, the valve margin. convex, with a single ring of straight veins along the valve margin, extending normal to the plane of the valve. Center of Stratigraphic and geographic distributions: The occurrences of epivalve face hyaline. this species in the late Cretaceous are reported from Western Si- beria (Strelnikova 1971, 1974), Alpha Ridge in the Arctic Comparison: This species is similar to Vallodiscus species Ocean (Barron 1985, Sims 1988), Slidre Fjord and Horton (Suto 2005a) in possessing a single ring of straight veins along River Sections in Canada (Tapia and Harwood 2002) and the valve margin, but differs from other Vallodiscus species by DSDP Site 275 in the South Pacific near New Zealand (Hajós its elliptic valve shape. and Stradner 1975)(Text-figure 7). This study is the first to report its occurrence in the middle Eocene. Stratigraphic and geographic distributions: Only one specimen was observed in middle Eocene sediments from IODP Leg 302 Site 2A-59X-2, 122-123 in the central Arctic Ocean in this Remarks: On eroded valves, the central linking mechanism is study. often missing, with little evidence to show that it had ever been present, apart from a few missing cribra (see Plate 13, Figs. 4, 5, Remarks: It is unknown whether or not this species belongs to 22, 23, 35). the fossil resting spore morpho-genus Vallodiscus of extant Chaetoceros because its frustule was not observed and we could Etymology: The Latin poly-chaeta means “many bristles”. not confirm the presence or absence of a single ring of puncta on the hypovalve. Trochosira spinosa Kitton 1871 Plate 12, figures 22-23 Xanthiopyxis type A (knobbly type) of Suto 2004e Plate 12, figures 26-32 Trochosira spinosa KITTON 1871, p. 170, pl. 14, figs. 6, 7. – VAN HEURCK (1880-1885), pl. 83 bis, figs. 14, 15. – CLEVE-EULER Description: Frustule heterovalvate. Valve oval to narrowly or 1951, Handl. 2: 1, p. 110, figs. 234b, c. – SHESHUKOVA-PORET- broadly elliptical in valve view. In girdle view, epivalve face SKAYA 1967, p. 137, pl. 11, figs. 6a, b; pl. 13, figs. 4a, b. – SCHRADER 1973, p. 713, pl. 12, figs. 18, 19. – GLEZER et al. 1974, vaulted, with numerous knobs and short veins. Mantle of pl. 31, figs. 5a, b; pl. 53, fig. 9. – SCHRADER and FENNER 1976, p. epivalve hyaline. Hypovalve slightly vaulted or flat, or vaulted 1003, pl. 12, fig. 18. – DZINORIDZE et al. 1978, pl. 4, fig. 15. – in the center, hyaline or with knobs. Mantle of hypovalve ABBOTT and ANDREWS 1979, p. 255, pl. 6, fig. 19. – HOMANN hyaline, with a single ring of puncta at its base. 1991, p. 67, pl. 17, figs. 6-13. – FENNER 1994, p. 123, pl. 3, fig. 9. – SCHERER and KOÇ 1996, p. 89, pl. 4, figs. 18-20. Comparison: This taxon is characterized by knobs and veins on Trochosira spinosus Kitton sensu SIMS 1988, p. 248, figs. 7-10, 26. – the epivalve and the hyaline mantle of the epivalve. SCHERER et al. 2000, p. 440, pl. 2, figs. 4-6. Trochosira spinosa ? Kitton sensu HARWOOD and BOHATY 2000, p. 94, pl. 4, fig. j. Stratigraphic and geographic distributions: This taxon was observed rarely in middle Eocene sediments from IODP Leg 302 Synonymy: Trochosira ornata GRUNOW in VAN HEURCK Sites 2A and 4A in the central Arctic Ocean in this study. (1880-1885), pl. 83, fig. 15. – FENNER 1994, p. 123, pl. 3, figs. 1, 2, 4. Remarks: The valves of these specimens belong to several Sceletonema ornatum Grunow sensu JOUSÉ 1955, p. 83, pl. 1, fig. 2. Xanthiopyxis species, but it is very difficult to determine which Sceletonema spinosum (Kitton) JOUSÉ 1955, p. 85, pl. 1, figs. 3, 4. one, when their frustules are not observed. Therefore, these Trochosira coronata Schrader and Fenner sensu SCHERER and KOÇ 1996, p. 89, pl. 4, figs. 22, 25. valves must be counted as “Xanthiopyxis type A (knobbly type)”, when only an epivalve or hypovalve is observed during Emended description: See Sims (1988). the counting process (Suto 2004e). Xanthiopyxis type B (short spiny type) of Suto 2004e Type level and locality: Lower Eocene. Mors, Jutland, Den- Plate 12, figures 33-36 mark. Description: Frustule heterovalvate. Valve oval to narrowly or Type specimen: Depository not designated. broadly elliptical in valve view. In girdle view, epivalve face

305 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

vaulted, with numerous short strong spines. Mantle of epivalve genera. Here, it is not possible to determine the nature of the hyaline. Hypovalve slightly vaulted or flat, or vaulted in the resting spores in Hemiaulus and/or Pyxilla, and the proposal center, hyaline or with numerous strong spines. Mantle of that Pterotheca represents such resting spores must be consid- hypovalve hyaline, with a single ring of puncta at its base. ered highly speculative.

Comparison: These specimens are characterized by short At first, Costopyxis trochlea was introduced as a taxon in the strong spines. vegetative cell genus Trochosira (Hanna 1927b), but was then moved to the resting spore genus Pterotheca (Fenner 1978) and Stratigraphic and geographic distributions: This taxon was ob- finally moved to Costopyxis (Glezer et al. 1988). Costopyxis served rarely in middle Eocene sediments from IODP Leg 302 and Trochosira may be vegetative cells because their valves Sites 2A and 4A in the central Arctic Ocean in this study. possess numerous areolae, although their valves are heavily silicified. Anaulus arcticus looks like a resting spore because this Remarks: These specimens occur abundantly in all of the cores species possesses strong silicified valves and forms paired and onland sections studied. The valves of this taxon are those valves as seen in Goniothecium and Gemellodiscus, but many of several Xanthiopyxis species, but these valves are difficult or scattered pores cover the valve surface and a rimoportula occurs impossible to classify correctly when their frustules are not ob- at the valve center in SEM. Therefore it is not clear whether this served. Therefore these valves must be counted as species may be a vegetative cell or resting spore. Leptoscaphos “Xanthiopyxis type B (short spiny type)”, when only the levigatus may be the resting spore of L. punctatus or a related epivalve or hypovalve is observed during the counting process species, because of the similarities in valve size and shape, and (Suto 2004e). possessing much fewer puncta on the valve surface. The taxo- Hypovalves of fossil resting spores of Chaetoceros nomic implications of Goniothecium and Odontotropis are indi- Plate 13, figures 36-42 (hyaline type); Plate 13, figures 43-48 cated in Suto et al. (2008 and submitted), and these two genera (wrinkled type) do not belong to Chaetoceros resting spores because their large apical axis (2-3 times that of the largest Chaetoceros) are unlike Description: Hypovalve oval to narrowly or broadly elliptical any known recent and fossil Chaetoceros spores. in valve view. In girdle view, valve face slightly vaulted or flat, or vaulted in the center, hyaline or covered with numerous Stephanogonia sp. A and B may be resting spores, but their veg- knobs and short veins. Mantle hyaline. Mantle of hypovalve etative cells are unknown. Resting spore sp. C and sp. D, hyaline, with a single ring of puncta at its base. Liradiscus ? sp. A, Peripteropsis ? sp. A and Vallodiscus ? sp. A may not be Chaetoceros resting spores, because they lack a sin- Remarks: The hypovalves of fossil resting spores of Chaeto- gle ring of puncta on the hypovalve mantle. On the other hand, ceros can be separated into three types; hyaline, knobbly and Dispinodiscus ? sp. A, Xanthiopyxis type A and type B which spiny types. The hyaline type hypovalve lacks processes. The possess this character are fossil resting spores of Chaetoceros. valve surface of the knobbly type one is covered with numerous These resting spore taxa are not named in this study, because the knobs and short spines. The spiny type is covered with lot of genera to which they belong are not yet clear so far. More de- short and long spines. It is impossible to identify which species tailed taxonomic data of these taxa from other oceans and ages the hypovalve belongs to, because many species possess similar are needed for future taxonomic and biostratigraphic studies. hypovalves. Therefore we used these three types when isolated hypovalves were preserved. The possible changes of resting spore strategies before and after the Eocene/Oligocene boundary These three types may belong to Dispinodiscus ?sp.A, Xanthiopyxis sp. A and sp. B., and perhaps to Liradiscus ? sp. A Forty-one diatom taxa including 30 taxa of fossil diatom resting and Vallodiscus ? sp. A if they are the fossil resting spores of spores from Eocene Arctic sediments and 11 of their allied taxa Chaetoceros. have been described in Suto et al. (2008 and submitted) and in this study. Twenty-five out of these 30 taxa are resting spores, while the remaining five taxa may be vegetative cells as indi- DISCUSSION cated above. Text-figure 9 indicates the biostratigraphic ranges The detailed stratigraphic data and paleoceanographic and of these species reported from the northern/southern Hemi- paleoecological implications of the Eocene Arctic Ocean were spheres and described in this study. Although their occurrence presented by Stickley et al. (2008) for Holes 2A and 4A. In this data from the Paleocene are few, 10 resting spore species which study, we present some strategic implications from the resting occurred in the ACEX samples had already appeared from the spore taxonomic data and indicate the taxonomic problems of late Cretaceous, while the others appeared in the Eocene. 21 out some taxa. of 25 (84%) resting spore taxa became extinct during the middle Eocene to early Oligocene. Resting spore or vegetative cell? It has been suggested that Pterotheca represents resting spores Suto (2006) indicated that a major event (named the EO Event) of Pyxilla (e.g. Van Heurck 1896), but in terms of valve struc- that was characterized by the explosive diversification of ture, circular cross-section and the tubed apex, there is a close Chaetoceros resting spores at both the morpho-generic and spe- relationship to the spore of Rhizosolenia setigera Brightwell cific levels, an increase in their abundance, and a decrease in (Hargraves 1976). Pterotheca species probably are the spores their valve size (from 40 to 20µm in average apical axis) oc- of some extinct genus of the Centrales. They may be the spores curred across the Eocene/Oligocene (EO) boundary in the Nor- of species of the genus Hemiaulus Ehrenberg (Jousé 1963). wegian Sea. He also indicated that Chaetoceros might have Gombos and Ciesielski (1983) also indicated that it is possible established itself as the main primary producer in the Oligocene that Pterotheca represents the resting spores of Pyxilla and this Norwegian Sea, replacing dinoflagellates and/or nannoplankton speculation is based on the similarity in valve morphology of which were the main producers till the late Eocene, because the two genera, and the parallel stratigraphic range of the two their diversities decreased across the boundary (Falkowski et al.

306 Micropaleontology, vol. 55, nos. 2-3, 2009

2004). Suto (2006a) mentioned that the possible causes for the TABLE 1 decreased diversities of dinoflagellates and nannoplankton and List of species that occurred in IODP Leg 302 sediments (*) and allied increased diversity of diatoms, especially Chaetoceros,were species from other core materials. associated with changes in coastal conditions from stable to unstable, associated with a regular seasonal environmental *Anaulus articus Suto, Jordan et Watanabe sp. nov. change, such as depletion and sporadic supply of nutrients, to *Costopyxis trochlea (Hanna) Strelnikova in Glezer et al. which Chaetoceros resting spores might be adapted better than 1988 dinoflagellate cysts. *Dispinodiscus ? sp. A *Goniothecium danicum Grunow in Cleve et Möller emend. Most taxa described in this study do not belong to Chaetoceros Suto in Suto, Jordan et Watanabe submitted because they lack a single ring of puncta on the hypovalve mantle that characterizes the resting spores of Chaetoceros, and be- Goniothecium decoratum Brun came extinct before the Oligocene, therefore it is clear that Goniothecium rogersii Ehrenberg Chaetoceros did not flourish in the middle Eocene in the Arctic *Leptoscaphos levigatus (Sheshukova-Poretskaya) Suto, Jor- Ocean. Other diatom genera that produced resting spores such dan et Watanabe comb. nov. as Pterotheca and Pseudopyxilla, might have prospered before *Leptoscaphos punctatus (Grove et Sturt) Schrader 1969 the E/O boundary, although their vegetative cells are still un- *Liradiscus ? sp. A known. Since some Chaetoceros resting spore taxa are recog- *Odontotropis sp. A nized in this study, most coastal regions experienced a regular *Odontotropis sp. B seasonal environmental change, which benefited genera such as Odontotropis cristata Grunow 1884 Pterotheca, Pseudopyxilla and Odontotropis, but also there might have been some patchy coastal upwelling regions with *Odontotropis sp. C nutrient depletion and sporadic supplies where Chaetoceros *Odontotropis danicus Debes in Hustedt 1930 could have survived and evolved. The abundant dinoflagellate Odontotropis galeonis Hanna 1927b cysts preserved in the middle Eocene ACEX core (Moran et al. *Odontotropis sp. C 2006) are evidence of the stable conditions before the E/O *Odontotropis hyalina Witt 1886 (= Odontotropis klavsenii boundary. When the abundance and species richness changes of Debes) resting spores and dinoflagellate cysts in other cores across the *Peripteropsis ? sp. A Eocene/Oligocene boundary are studied and it is shown that *Porotheca danica (Grunow) Fenner 1994 resting spore taxa except Chaetoceros decreased contempora- neously with dinoflagellate cysts before the boundary, it will be Pseudopyxilla carinifera (Grunow in Van Heurck) Suto, Jor- clarified that the resting spore ecology of most resting spore dan et Watanabe comb. nov. taxa before the Eocene may have been similar to that of *Pseudopyxilla dubia (Grunow in Van Heurck) Forti 1909 dinoflagellate cysts rather than Chaetoceros resting spores after *Pseudopyxilla jouseae Hajós in Hajós and Stradner 1975 the Oligocene, or there may be a southward “retreat” of calcare- *Pterotheca aculeifera Grunow in Van Heurck 1880 (= ous microorganisms due to a prominent world-wide cooling Pterotheca crucifera Hanna 1927b) that occurred near the Eocene/Oligocene boundary. *Pterotheca evermanii Hanna 1927b *Pterotheca harrensis (Fenner) Suto, Jordan et Watanabe Problems identifying Pterotheca, Pseudopyxilla and Porotheca comb. nov. The distinction between fossil resting spore genera Pterotheca kittoniana Grunow in Van Heurck 1880-1885 var. Pseudopyxilla Forti, Pterotheca (Grunow) Forti and Porotheca kittoniana Fenner is currently vague. Pterotheca kittoniana var. kamtschatica Gapanov 1927 Pterotheca kittoniana var. minuta Fenner 1994 The name Pseudopyxilla was introduced with a Latin descrip- *Pterotheca minuta (Fenner) Suto, Jordan et Watanabe comb. tion in Forti (1909). This name may have been provisional, and nov. therefore invalidly published (see ICBN 2000 Art. 34.1.b of Greuter et al. 2000). Several species are also included in Forti’s Pterotheca reticulata Sheshukova-Poretskaya 1967 paper, but no generic type was designated. Since this genus was *Resting spore sp. A erected, many species have been described including those *Resting spore sp. B mentioned in this study such as Ps. aculeata Jousé, Ps. *Resting spore sp. C americana (Ehrenberg) Forti, Ps. baltica Forti, Ps. capreolus *Resting spore sp. D Forti and Ps. directa Pantocsek. *Stephanogonia sp. A *Stephanogonia sp. B (Pterotheca sp. A) The name Pterotheca was first introduced by Grunow in Van *Trochosira coronata ? Schrader and Fenner 1976 Heurck (1880-1885) (pl. 83, figs. 5, 6, 9-11), however the name was also not validly published, as no description was provided Trochosira mirabilis Kitton 1871 for the genus, although several species were described (P. *Trochosira polychaeta (Strelnikova) Sims 1988 aculeifera, P. subulata, P. kittoniana and Stephanogonia Trochosira spinosa Kitton 1871 (Pterotheca?) danica). After this genus was introduced, Pt. *Vallodiscus ? sp. A alata Strelnikova, Pt. clavata Strelnikova, Pt. costata Schib- *Xanthiopyxis type A (knobbly type) of Suto 2004e kova, Pt. cretacea Hajós et Stradner, Pt. infundibulum Krotov, *Xanthiopyxis type B (short spiny type) of Suto 2004e Pt. parvula (Hanna) Hajós et Stradner, Pt. pokroskajae Jousé, *Hypovalve of fossil resting spore of Chaetoceros Pt. reticulata Sheshukova-Poretskaya, Pt. sacculifera Fenner, Pt. simplex Strelnikova, Pt. simplex Fenner, Pt. spada Tempère

307 Itsuki Suto et al.: Taxonomy of middle Eocene diatom resting spores and their allied taxa from the central Arctic Basin

et Brun, Pt. spinosa Jousé, Pt. subulata Grunow in Van Heurck, able discussions. Special thanks are given to Professor Kozo Pt. trojana Harwood and Pt. uralica Jousé were added. Takahashi (Kyushu University) and Dr. Jonaotaro Onodera (Kochi University) who provided sieved samples and gave nu- Later, Fenner (1994) separated the genus Porotheca from merous suggestions. We also thanks Dr. Andrey Yu. Gladenkov Pterotheca danica because of its cylindrical valve with a central (Geological Institute, Russian Academy of Sciences) and Mr. elevation with a pore-like opening on top. Fumio Akiba (Diatom Minilab Akiba, Ltd.) for their invaluable discussions and their careful pre-reviews. We also thank Dr. The fossil resting spore genus Pterotheca has been tabulated to- Yoshihiro Tanimura (National Science Museum, Tokyo), who gether with the genus Pseudopyxilla as mentioned above, be- kindly curated the type specimens described in this paper. This cause these have been no observations of their vegetative valves research used samples and data provided by the Integrated as they usually dissolve in the sediments. The distinct differ- Ocean Drilling Program (IODP). IODP is sponsored by the U.S. ences between these genera have not been clarified from these National Science Foundation (NSF) and participating countries papers. Moreover, the vegetative cells of Pterotheca and under the management of the Joint Oceanographic Institutions Pseudopyxilla are still unknown, therefore their generic names (JOI) Inc. must be regarded as morpho-genera for fossil resting spores according to Articles 3.3 and 3.4 of the International Code of Bo- REFERENCES tanical Nomenclature (ICBN; Greuter et al. 2000), as with fossil Chaetoceros resting spores (Suto 2003). We propose that ABBOTT, W. H. and ANDREWS, G. W., 1979. Middle Miocene ma- the differences between these two genera are a vaulted epivalve rine diatoms from the Hawthorn Formation within the Ridgeland in Pterotheca and a cylindrical one in Pseudopyxilla. As the re- Trough, South Carolina and Georgia. Micropaleontology, 25: 225-271. sult, Pterotheca minuta and Pt. harrensis are transferred from Pseudopyxilla in this study. Moreover, Pterotheca carinifera BACKMAN, J., MORAN, K., McINROY, D. B. et al., 2005a. IODP Ex- may belong to Pseudopyxilla or Porotheca because of its cylin- pedition 302, Arctic Coring Expedition (ACEX): A first look at the drical valve, but it did not occur in this study and so the exis- Cenozoic Paleoceanography of the central Arctic Ocean. Scientific tence of the pore-like opening on top could not be clarified. Drilling, 1: 12-17.

We redefine these three genera Porotheca, Pseudopyxilla and ———, 2005b. Proceedings of the Integrated Ocean Drilling Program Pterotheca as below. 302. College Station TX: Integrated Ocean Drilling Program Man- agement International, Inc. Porotheca Fenner 1994 This genus is characterized by having a cylindrical to conical BALDAUF, J. G., 1985. Cenozoic diatom biostratigraphy and valve and a central elevation with a pore-like opening on top. It paleoceanography of the Rockall Plateau region, North Atlantic, Deep Sea Drilling Project Leg 81. In: Roberts, D. G., Schnitker, D. et Proboscia differs from by the lack of a slit-shaped opening at al., Initial Reports of the Deep Sea Drilling Project 81, 439-478. the top and from Rhizosolenia in that the apical rimoportula – if Washington DC: US Government Printing Office. present – has no external part. Species of this genus have resting spores (Fenner 1994). BALDAUF, J. G. and BARRON, J. A., 1987. Oligocene marine diatoms recovered in dredge samples from the Navarin Basin Province, Be- Pseudopyxilla Forti 1909 ring Sea. Washington, DC: U. S. Geological Survey. Bulletin 1765, This genus is characterized by having a cylindrical to conical 17 pp. valve. Frustule heterovalvate. Epivalve cylindrical to conical. Epivalve surface hyaline or covered with numerous wrinkles or BARRON, J. A., 1975. Late Miocene-early Pliocene marine diatoms strong and long process on the top, with no or few areolae. from southern California. Paleontographica B, 151: 97-170. Mantle of epivalve distinct, hyaline with no or numerous puncta ———, 1985. Diatom biostratigraphy of the CESAR 6 core, Alpha and areolae. Hypovalve convex or nearly flat. Hypovalve sur- Ridge. In: Jackson, H. R., Mudie, P. J. and Blasco, S. M., Eds., Initial face hyaline with no or few areolae. Mantle of hypovalve not Geological Report on Cesar: The Canadian Expedition to Study the distinct, hyaline with no puncta and areolae. Alpha Ridge, Arctic Ocean, 137-148. Ottawa: Geological Survey of Canada. Paper 84-22: Pterotheca (Grunow) Forti 1909 This genus is characterized by having a highly vaulted epivalve. BARRON, J. A. and MAHOOD, A. D., 1993. Exceptionally well-pre- Epivalve surface hyaline, with no or few areolae, covered with served early Oligocene diatoms from glacial sediments of Prydz Bay, numerous strongly siliceous straight or anastomosing ridges, East Antarctica. Micropaleontology, 39: 29-45. and/or several spines. Mantle of epivalve distinct, hyaline with BARRON, J. A., BUKRY, D. and POORE, R. Z., 1984. Correlation of no puncta and areolae. Hypovalve convex, less than the height the middle Eocene Kellogg Shale of northern California. of the epivalve. Hypovalve surface hyaline or covered with nu- Micropaleontology, 30: 138-170. merous spines, with no or few areolae. Mantle of hypovalve distinct, hyaline with no puncta and areolae. CLEVE-EULER, A., 1951. Die diatomeen von Schweden und Finnland. Teil 1. Stockholm: Kungl. Svenska Vetenskapsalademiens. ACKNOWLEDGMENTS Handlingar no. 2, 163 pp. We thank the co-chief scientists Dr. Jan Backman (Stockholm DELL’AGNESE, D. J. and CLARK, D. L., 1994. Siliceous microfossils University) and Dr. Kathryn Moran (University of Rhode Is- from the warm late Cretaceous and early Cenozoic Arctic Ocean. land), and the scientific party of IODP Leg 302 ACEX as well Journal of Paleontology, 68: 31-47. as the captain and crew who provided the opportunity for us to sample the sediments on board R/V Oden. We wish to thank Dr. DESIKACHARY, T. V. and SREELATHA, P. M., 1989. Oamaru Dia- Kota Katsuki (Kochi University), Dr. Nalân Koç and Dr. toms. Berlin - Stuttgart,: J. Cramer - Gerbruder Borntraeger Catherine E. Stickley (Norwegian Polar Institute) for invalu- Verlagsbuchhandlung. Bibliotheca Diatomologica, Band 19. 330 pp.

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