Ebridianos Fósiles

EBRIDIANOS FÓSILES EN LA LITERATURA CIENTÍFICA

RECOPILACIÓN DE DESCRIPCIONES E IMÁGENES (desde el año 1973 al año 2009)

Saunders, A.D., Larsen, H.C., and Wise, S.W., Jr. (Eds.), 1998

Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 152

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13. SILICEOUS SPONGE SPICULES, SILICOFLAGELLATES, AND EBRIDIANS FROM HOLE 918D,

CONTINENTAL RISE OF THE GREENLAND MARGIN1

L. Kirk Lurvey,2,3 Kevin McCartney,2 and Wuchang Wei4

ABSTRACT

Sediments recovered from Hole 918D on the continental rise of the Greenland Margin were found to contain siliceoussponge spicules, silicoflagellates, and ebridians. An extreme fossil-barren interval occurred in lower Miocene and upperMiocene sediments of the core, with sponge spicules occurring in the middle Miocene. Though generally rare, the sponge spi-cules were morphologically diverse, with monaxons being the most abundant. Other morphologies and an undescribed spiculetype were found. Representatives of several silicoflagellate genera were found in a narrow horizon of the upper Pliocene. Thesilicoflagellates were of a variety of ages, showing that this layer has been reworked. This interval also included two largeebridians, Triskelion gorgon and Adonnadonna primadonna, that have not been previously described from the North Atlantic.

INTRODUCTION

Ocean Drilling Program (ODP) Leg 152 recovered sediment sam-ples from six sites off the Greenland coast in order to study the riftvolcanism and history of glaciation of the area. These sites were on anorthwest-southeast transect across the East Greenland Margin, ap-proximately 130 km from the Greenland coast near the center of aseaward-dipping reflector sequence (SDRS) (Fig. 1).

A diverse assemblage of siliceous sponge spicules were found inmiddle Miocene sediments from Site 918D. The spicules were notgenerally abundant but were well preserved. The assemblage wasdominated by monaxons with other spicule morphologies represent-ing a fraction of total spicule abundance. The abundance and diversi-ty of sponge spicules at Hole 918D are tabulated in this study (Table1).

Sponge spicules from deep ocean sediments have been studied in-frequently. The results of this study can be compared to those of Mc-Cartney (1987, 1990), Ahlbach and McCartney (1992) and Zolnik etal., (1992); see McCartney (1990) for a tabulation of other spongespicule literature from deep ocean studies. These studies show a gen-erally similar diversity, with monaxons being the predominant spi-cule group. Palmer (1988) and Ivanik (1983) found abundant tetrax-onal and triaxonal spicules and used their relative abundances tomake paleobathymetric interpretations, but these spicule types werenot abundant in this study.

METHODS

Raw samples were processed by disaggregating the sedimentsamples in 100-mL beakers after which H2O2 and 10% HCl solutionswere added. The beakers were then heated for 3–4 hr on a hot plate.The remaining solutions were placed in test tubes and centrifuged anddecanted three times. Smear slides were made from the remainingsediments using Canada balsam and 22 mm × 50 mm coverslips.

Investigations were made using an Olympus BH-2 light micro-scope with a 20× objective. The entire coverslip was examined andabsolute counts of specimens were recorded. In the event that nospecimens were found on half of the coverslip, the rest was not inves-tigated. In the narrow horizon where silicoflagellates and ebridianswere present, extra slides were made and examined to increase spec-imen counts. The abundance of specimens was recorded in absolutecounts, with pieces representing over half of the specimen, or enoughto allow identification, counted as one.

SITE SUMMARY

Site 918D (63°5.572′N, 38°38.334′W; water depth 1868.2 m) wasdrilled on the upper continental rise and has a thick Quaternary sec-tion. The site was selected to determine the age and subsidence his-tory of the SDRS, the oceanographic history of the Irminger Basin,and the history of glaciation in southern Greenland. The core fromHole 918D provides the most complete sedimentary record recoveredin the North Atlantic.

Sponge spicules were found to be sparse in an 80-m interval of themiddle Miocene and rare or absent elsewhere in the core. The spongespicule-bearing interval is in lithologic Unit II, which is a silt withvarying amounts of nannofossils and clay. The sponge spicules werealways present in this interval but their numbers never exceeded 31specimens in a slide.

Silicoflagellates and ebridians were only found in two samples;all but one of the observed specimens came from Sample 152-918D-13R-1, 93−94 cm. This sample is from lithologic Subunit ID, whichis a silt with dropstones.

SPONGE SPICULES

Sponges have an internal skeleton of spicules that may be of cal-careous or siliceous composition. Various spicule shapes and sizeshave been used to classify poriferans taxonomically (Ehrenberg,1854). However, a single living sponge may contain a variety of spi-cule types. A descriptive terminology has been used to classifysponge spicules in recent literature (Bukry, 1978; Palmer, 1988; Ahl-bach and McCartney, 1992), and is used in this study. Various typesof sponge spicules are described here including monaxons, whichhave a skeletal element with a single axis; polyaxons, which havemany equal-sized rays radiating from a single central point; and tri-axons, which are spicules with three axes.

1Saunders, A.D., Larsen, H.C., and Wise, S.W., Jr. (Eds.), 1998. Proc. ODP, Sci.

Results,152: College Station, TX (Ocean Drilling Program).2 Micropaleontology Undergraduate Research Laboratory, University of

Maine at Presque Isle, Presque Isle, ME 04769, U.S.A. Correspondence author:

[email protected] of Geology, University of Maine, Orono, ME 04469, U.S.A.4Scripps Institution of Oceanography, University of California at San Diego, La

Jolla, CA 92093-0215, U.S.A.

L.K. LURVEY, K. MCCARTNEY, W. WEI

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Genus BACHMANNOCENA Locker, 1974; emend. Bukry, 1987

Bachmannocena apiculata (Schulz)(Pl. 3, Figs. 3, 4)

Bachmannocena apiculata (Schulz), Bukry, 1987, p. 403−404

Remarks. This silicoflagellate is common in sediments of the Eocene andOligocene and suggests that the sediments in Sample 152-918D-13R-1, 92−

94 cm have been reworked.

Genus CORBISEMA Hanna, 1928

Corbisema hastata hastata (Lemmermann)(Pl. 3, Figs. 5, 6)

Dictyocha triacantha hastata Lemmermann, 1901, p. 259, pl. 10, figs. 16, 17Corbisema hastata hastata (Lemmermann), Bukry, 1976, p. 892, pl. 4, figs.

9−16

Remarks. The two specimens of this taxon were distinctly arrowheadshaped and were slightly asymmetrical.

Corbisema triacantha (Lemmermann)(Pl. 3, Fig. 2)

Corbisema apiculata (Lemmermann), Ling, 1972, p. 153, pl. 24, fig. 1

Remarks. The two specimens found of this taxon were slightly larger thantypical C. triacantha.

Genus DICTYOCHA Ehrenberg, 1837

Dictyocha messanensis Haeckel(Pl. 3, Fig. 10)

Dictyocha messanensis Haeckel, in Peters (1860), p. 799−800

Remarks. This taxon has considerable variability in the shape of its basalring, the robustness of the skeletal elements, and in the presence or absence ofan apical spine. Locker and Martini (1986) and other workers divided this tax-on into several subspecies and forms, but these distinctions were difficult toapply consistently, thus, this taxon was not subdivided in this study.

Genus DISTEPHANUS Stohr, 1880

Distephanus crux (Ehrenberg)(Pl. 3, Figs. 7−9)

Distephanus crux crux (Ehrenberg), Bukry, 1976 [Leg 36], p. 895

Remarks. This was the most abundant silicoflagellate found in the studywith a total count of 12. Several of these were variants with longer spines thanusual for the species. A lone member of this species, shown on Plate 3, Fig. 9,was found in Sample 152-918D-39R-2, 95−96 cm.; this was the only sili-coflagellate in this study not found in Sample 152-918D-13R-1, 92−94 cm.

Genus NAVICULOPSIS Frenguelli, 1940

Naviculopsis constricta (Schulz)(Pl. 3, Fig. 1)

Naviculopsis constricta (Schulz), McCartney and Wise, 1987, p. 807, pl. 5,figs. 5−8

EBRIDIANS

Several representatives of ebridians were also found in Sample152-918D-13R-1, 92−94 cm. No ebridians were found elsewhere inthe study.

Genus ADONNADONNA Gombos, 1982

Adonnadonna primadonna (Gombos)(Pl. 4, Fig. 1)

Adonnadonna primadonna Gombos, 1982, p.446

Remarks. This very unusual and large ebridian is similar and is probablyclosely related to Triskelion gorgon. Both have enormous size and exception-al surface ornamentation. For further remarks see those with Triskelion gor-gon.

Genus AMMODOCHIUM Hovasse, 1932

Ammodochium rectangulare (Schulz)(Pl. 4, Fig. 6)

Ammodochium rectangulare (Schulz), Ling, 1971, p. 694

Genus CRANIOPSIS Hovasse ex Frenguelli, 1940

Craniopsis octo Hovasse ex Frenguelli, 1940

Craniopsis octo Hovasse ex Frenguelli, 1940, p. 92, figs. 31 a−c

Genus EBRIOPSIS Hovasse, 1932

Ebriopsis antiqua antiqua (Schulz)

Ebriopsis antiqua Schulz, 1928 (in part), p. 273–274, fig. 696Ebriopsis antiqua antiqua (Schulz), Ling, 1977, p. 215, pl. 17–18

Genus TRISKELION Gombos, 1982

Triskelion gorgon Gombos(Pl. 4, Figs. 2−4)

Triskelion gorgon Gombos, 1982, p. 446−447

Remarks. This problematic fossil has previously been found by Gombos(1982) in the middle Eocene of the southwest Atlantic Ocean and by McCart-ney and Wise (1990) in Oligocene sediments from the Weddell Sea near Ant-arctica. The occurrence in reworked sediments off Greenland suggests thatthis taxon is far more widely distributed, both geologically and geographical-ly, than its sparse literature would indicate.

DISCUSSION

This study documents primarily the occurrence of sponge spiculesin Hole 918D. Sample 152-918D-13R-1, 93−94 cm, which lackedsponge spicules, was unusual in that it contained nearly all of the sil-icoflagellates and ebridians found in the study. The silicoflagellatesand ebridians found in this sample were diverse, but include only onetaxon, the silicoflagellate Dictyocha messanensis that is typicallyfound in lower Pliocene sediments. The other taxa are reworked.

Most of the reworked taxa are of geologically long-ranging spe-cies, making the age of the source material difficult to determine pre-cisely. The presence of the ebridian Triskelion gorgon in the sample,however, indicates an age of middle Eocene to early Oligocene. Allof the silicoflagellates found in this sample, except for the singlespecimen of Dictyocha messanensis, could be of the same age.

The core description (Larsen, Saunders, Clift, et al., 1994) indi-cates that the sediment of Sample 152-918D-13R-1, 93−94 cm wasmoderately disturbed. This is part of lithologic Unit ID, which con-sists of well-lithified quartz silt with clay and dark-gray compact sed-iment with isolated dropstones scattered throughout. The core de-scription does not mention turbidites in this interval, although turbid-ites of two types are found in lithologic Unit IB, which occurred at71.1–236.0 mbsf.

Several other studies of the Greenland transect also found rework-ing during the Pliocene or Pleistocene. Pliocene sediments at Site 919included several foraminifers that were reworked (Israelson and

SILICEOUS SPONGE SPICULES, SILICOFLAGELLATES, EBRIDIANS

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Spezzaferri, this volume), and Wei (this volume) found Cretaceousnannofossils associated with dropstones in Pleistocene sediments,which he suggests were ice-rafted detritus.

The reworked fossils of Sample 152-918D-13R-1, 93−94 cm,might also be deposited as a result of ice-rafting, but it is more diffi-cult to explain by this mechanism the concentration of typically un-common and giant specimens such as Triskelion gorgon. Raftingshould widely disperse the reworked specimens, and it would takeunusual amounts of ice-rafting to deposit such a large concentrationof silicoflagellates and ebridians in this sample. We believe that theconcentration of siliceous microfossils in this sample can better beexplained by a turbidity current.

CONCLUSIONS

The core from Hole 918D contained siliceous sponge spicules,silicoflagellates, and ebridians. The sponge spicules were found inthe middle Miocene sediments, but were generally low in absoluteabundance. The lower Miocene was largely barren, as was the upperMiocene and lower Pliocene. However, in the lower Pliocene theredid occur an unusual presence of silicoflagellates and ebridians inSample 152-918D-13R-1, 93−94 cm. The core description indicatesthe sample was moderately reworked. This study found unusuallylarge microfossils, including Triskelion gorgon, which suggests a tur-bidity current.

ACKNOWLEDGMENTS

We are grateful to Earl Oman for his slide preparation, help, andinterest. We wish to thank Dr. Stuart Gelder for his assistance andtechnical advice. Sherwood W. Wise, Jr., and Andrew M. Gombos,Jr., provided valuable constructive comments on the manuscript. Wethank the Ocean Drilling Program for providing the samples and theopportunity to conduct this study. Photographic material was contrib-uted by the University of Maine at Presque Isle. This project, com-pleted as an independent undergraduate research project, is Micro-paleontology Undergraduate Research Lab publication No. 4.

REFERENCES

Ahlbach, W.J., and McCartney, K., 1992. Siliceous sponge spicules from Site748. In Wise, S.W., Jr., Schlich, R., et al., Proc. ODP, Sci. Results, 120:College Station, TX (Ocean Drilling Program), 833−837.

Bukry, D., 1976. Cenozoic silicoflagellate and coccolith stratigraphy, SouthAtlantic Ocean, Deep Sea Drilling Project Leg 36. In Hollister, C.D.,Craddock, C., et al., Init. Repts. DSDP, 35: Washington (U.S. Govt. Print-ing Office), 885−917.

————, 1978. Cenozoic coccolith, silicoflagellate, and diatom stratigra-phy, Deep Sea Drilling Project Leg 44. In Bensen, W.E., Sheridan, R.E.,et al., Init. Repts. DSDP, 44: Washington (U.S. Govt. Printing Office),807−863.

————, 1979. Cenozoic coccolith and silicoflagellate stratigraphy, North-ern Mid-Atlantic Ridge and Reykjanes Ridge, Deep Sea Drilling ProjectLeg 49. In Luyendyk, B.P., Cann J.R., et al., Init. Repts. DSDP, 49: Wash-ington (U.S. Govt. Printing Office), 551−582.

————, 1987. Eocene siliceous and calcareous phytoplankton, Deep SeaDrilling Project Leg 95. In Poag, C.W., Watts, A.B., et al., Init. Repts.DSDP, 95: Washington (U.S. Govt. Printing Office), 395−415.

Ehrenberg, C.G., 1854. Mikrogeologie: Das Erden und Felsen schaffendeWirken des unsichtbar kleines selbständigen Lebens auf der Erde:Leipzig (Leopold Voss).

Frenguelli, J., 1940. Consideraciones sobre los silicoflagelados fósiles. Rev.Mus. La Plata, Secc. Geol., 2:37−112.

Gombos, A.M., Jr., 1982. Three new and unusual genera of ebridians fromthe Southwest Atlantic Ocean. J. Paleontol., 56:444−448.

Hartman, W.D., 1982. Form and distribution of silica in sponges. In Simp-son, T.L., and Volcani, B.E. (Eds.), Silicon and Siliceous Structures inBiological Systems: New York (Springer-Verlag), 453−491.

Ivanik, M.M., 1983. Paleogene and Neogene sponge spicules from Sites 511,512, and 513 in the South Atlantic. In Ludwig, W.J., Krasheninnikov, V.A., et al., Init. Repts. DSDP, 71 (Pt. 2): Washington (U.S. Govt. PrintingOffice), 933−950.

Larsen, H.C., Saunders, A.D., Clift, P.D., et al., 1994. Proc. ODP, Init.Repts., 152: College Station, TX (Ocean Drilling Program).

Lemmermann, E., 1901. Silicoflagellatae. Ber. Dtsch. Bot. Ges., 19:247−271.Ling, H.Y., 1971. Silicoflagellates and ebridians from the Shinzan diatoma-

ceous mudstone member of the Onnagawa Formation (Miocene), North-east Japan. In Farinacci, A. (Ed.), Proc. 2nd Planktonic Conf. Roma.Rome (Ed. Technosci.), 689−703.

————, 1972. Upper Cretaceous and Cenozoic silicoflagellates and ebrid-ians. Bull Am. Paleontol., 62:135−229.

————, 1977. Late Cenozoic silicoflagellates and ebridians from the east-ern North Pacific region. In Saito, T., and Ujiie, H. (Eds.), Proc. First Int.Congr. Pacific Neogene Stratigraphy, 1:205−233.

Locker, S., and Martini, E., 1986. Silicoflagellates and some sponge spiculesfrom the southwest Pacific, DSDP Leg 90. In Kennett, J.P., von derBorch, C.C., et al., Init. Repts. DSDP, 90: Washington (U.S. Govt. Print-ing Office), 887−924.

McCartney, K., 1987. Siliceous sponge spicules from Deep Sea DrillingProject Leg 93. In van Hinte, J.E., Wise, S.W., Jr., et al., Init. Repts.DSDP, 93 (Pt. 2): Washington (U.S. Govt. Printing Office), 815−824.

————, 1990. Siliceous sponge spicules from Ocean Drilling ProgramLeg 113. In Barker, P.F., Kennett, J.P., et al., Proc. ODP, Sci. Results, 113:College Station, TX (Ocean Drilling Program), 963−970.

McCartney, K., and Wise, S.W., Jr., 1987. Silicoflagellates and ebridiansfrom the New Jersey Transect, Deep Sea Drilling Project Leg 93, Sites604 and 605. In van Hinte, J.E., Wise, S.W., Jr., et al., Init. Repts. DSDP,93 (Pt. 2): Washington (U.S. Govt. Printing Office), 801−814.

————, 1990. Cenozoic silicoflagellates and ebridians from ODP Leg113: biostratigraphy and notes on morphologic variability. In Barker, P.F.,Kennett, J.P., et al., Proc. ODP, Sci. Results, 113: College Station, TX(Ocean Drilling Program), 729−760.

Palmer, A., 1988. Paleoenvironmental significance of siliceous sponge spi-cules from Sites 627 and 628, Little Bahama Bank, Ocean Drilling Pro-gram Leg 101. In Austin, J.A., Jr., Schlager, W., et al., Proc. ODP, Sci.Results, 101: College Station, TX (Ocean Drilling Program), 159−168.

Peters, W., 1860. Kurzen Auszug aus einer Abhandlung des Hrn. Dr. ErnstHaeckel über neue, ledende Radiolarien des Mittelmeeres und legte diedazu gehörigen Abbildungen vor. Mber. Verh. K. Preuss. Akad. Wiss.Berlin, 794−817.

Schulz, P., 1928. Beiträge zur Kenntnis fossiler und rezenter Silicoflagel-laten. Bot. Arch., 21:225−292.

Zolnik, R., McCartney, K., and White, L.D., 1992. Siliceous sponge spiculesfrom Site 795. In Pisciotto, K.A., Ingle, J.C., Jr., von Breymann, M.T.,Barron, J., et al., Proc. ODP, Sci. Results, 127/128 (Pt. 1): College Sta-tion, TX (Ocean Drilling Program), 541−544.

Date of initial receipt: 14 August 1995

Date of acceptance: 12 June 1996

Ms 152SR-216

SILICEOUS SPONGE SPICULES, SILICOFLAGELLATES, EBRIDIANS

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Plate 4. Ebridians (570×; scale bar = 35 µm). 1. Adonnadonna primadonna Gombos; Sample 152-918D-13R-1, 93−94 cm. 2−4. Triskelion gorgon Gombos;

Sample 152-918D-13R-1, 93−94 cm. 5. Unknown ebridian, Sample 152-918D-13R-1, 93−94 cm. 6. Ammodochium rectangulare (Schulz), lorica; Sample 152-

918D-13R-1, 93−94 cm.

Tracking Environmental Change

Using Lake Sediments

Volume 3:

Terrestrial, Algal,

and Siliceous Indicators

Edited by

John P. SmolDepartment of Biology,

Queen’s University

H. John B. BirksBotanical Institute,University of Bergen

and

William M. LastDepartment of Geological Sciences,

University of Manitoba

KLUWER ACADEMIC PUBLISHERS

NEW YORK, BOSTON, DORDRECHT, LONDON, MOSCOW

10. EBRIDIANS

ATTE KORHOLA ([email protected])Department of Ecology and Systematics

Division of Hydrobiology

University of Helsinki

P. O. Box 17 (Arkadiankatu 7)

FIN00014 Helsinki, Finland

JOHN P. SMOL ([email protected])Paleoecological Environmental Assessment

and Research Lab (PEARL)

Department of Biology

116 Barrie St., Queen’s University

Kingston

Ontario K7L 3N6 Canada

Keywords: Ebridians, Ebria tripartita, sediment, Baltic Sea, palaeoecology, eutrophication, dissolution

Introduction

Ebridians are a group of microscopic, heterotrophic, primarily marine plankton, characterized by a siliceous internal skeleton that is frequently preserved in sedimentary deposits.They are cosmopolitan, mainly neritic, but can also be found in estuaries, shallow embayments, and semienclosed seas such as the Baltic Sea and the Black Sea (Ernisse &McCartney, 1993; Korhola & Grönlund, 1999). Ebridians have a modern diversity of onlya few species, and are not particularly significant components of modern marine plankton.However, in contrast to the diatoms, where perhaps 90% of the described species areliving, most of the described ebridian taxa are fossil forms. Indeed, ebridian research isessentially palaeontologic, and they are widely used in stratigraphy in palaeoceanographyand in palaeobiologic studies.

As such, the connection of ebridians to a volume on palaeolimnological methods andindicators may be a bit tenuous, but they are occasionally recorded in freshwater (likelyfrom allochthonous sources) and brackish profiles, and so this short chapter attempts toprovide a brief overview of this group which may be of use to the palaeolimnologist.Our primary aim is to attract attention to these organisms, whose remains are foundregularly in the sediment record, but are often overlooked. In addition, we explore thepotential usefulness and indicator value of the group in future palaeoecological studies.

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J. P. Smol, H. J. B. Birks & W. M. Last (eds. ), 2001. Tracking Environmental Change Using Lake Sediments.

Volume 3: Terrestrial, Algal, and Siliceous Indicators. Kluwer Academic Publishers, Dordrecht, The Netherlands.

226 ATTE KORHOLA & JOHN P. SMOL

We focus in particular on one species, Ebria tripartita (Schumann) Lemmermann, and oneenvironment, namely the brackishwater Baltic Sea, where this species has been studiedquite intensively during recent years. Ernisse & McCartney (1995) provide a more detailedsummary of these indicators, and Loeblich et al. (1968) provide an annotated index ofebridian taxa.

Morphology, taxonomy and preservation in the sediments

Ebridians do not appear in the fossil record before the Cenozoic, but their fossils havebeen found in particularly large numbers in Cenozoic sedimentary rocks that are rich invarious other siliceous remains (Tappan, 1980). After a phase of rapid diversification inthe Paleocene, during which at least eight ebridian genera evolved, they suffered massiveextinctions by the close of the Miocene. Although they have a relatively diverse fossilhistory, ebridians are relatively rare in the sediments of modern seas. Only three (possiblyfour) species, assigned to two genera (Ebria and Hermesinum), are known to exist today(Taylor, 1990). The ecological characteristics of the few living ebridians are poorly known,and so they have played a relatively small role in modern research.

Ebridians commonly range from 10 to in length and from 20 to in width(Lipps, 1979). Their cells are more or less spherical, colourless, and contain a single nucleusand two flagella of different lengths (Lipps, 1979; Tikkanen, 1986). Some ebridian taxaproduce cystlike features at one end of the skeleton that may have served as a protective enclosure during periods of environmental stress (Ernisse & McCartney, 1995). Ebridians arepreserved in bottom deposits because of their internal siliceous skeleton, which consists of aframework of solid rods, in thickness (Preisig, 1994). In Ebria tripartita, the systemof rods comprises three stems, which branch in a regular manner from an initial branchingpoint, thus forming a triadial, basketlike symmetry (Figs. 1 and 2). In Hermesinum foursuch branches are found. The rods are usually angular and possess many small spines andnodules, as shown by electron microscopy (Fig. 2B). The average length of the siliceousskeleton of E. tripartita is and the average width is (Tikkanen, 1986). Thesiliceous skeleton of ebridians is highly resistant both against mechanical abrasion andchemical dissolution.

The taxonomic status of ebridians is presently rather uncertain (Preisig, 1994). On onehand, they resemble silicoflagellates, but have a skeleton of solid tubular rods rather thanhollow ones. On the other hand, the structure of their nuclei as well as their endoskeleton hassome common features with some dinoflagellates (Loeblich, 1982; Lipps, 1979; Locker& Martini, 1986). Indeed, the evolutionary relations among ebridians, silicoflagellates,and endoskeletal dinoflagellates are in many respects unclear. Today, the ebridians are,nevertheless, often regarded as a separate taxonomic unit (Ebriophyceae/Ebriida) withuncertain phylogenetic affinities (Taylor, 1990; Preisig, 1994).

In the older literature, there have been erroneous identifications concerning these taxa.Most common mistakes include the assignment of the species with other dinoflagellates,silicoflagellates or even Radiolaria. It is perhaps because of these identification problems that these taxa have rarely been recognized and have only been used in a fewpalaeolimnological studies.

EBRIDIANS 227

Methodological aspects

The chemical treatment of subsamples follows the standard methodology developed fordiatom sample preparation (Battarbee, 1986 and Battarbee et al., this volume). Naphrax®

or Hyrax® or comparable media can be used as mountants. Counting is performed under alight microscope at 1000× magnification. The frequencies of ebridians can be determined

(Westman, 1999), which can then be based on the sum of total diatoms/siliceous fossils +ebridians. In general, ebridians tend to be rather rare, occurring in low absolute frequenciesin an average microfossil preparation (Ernisse & McCartney, 1995). Moreover, their remainsare often fragmented (Korhola & Grönlund, 1999). The preservation of the main part ofthe central skeleton (a complete driadial system of rods) can be used as the criterion for theenumeration of one species.

Brief history of use of ebridians in palaeoecological research

Ebridian research has developed episodically, with an initial phase of interest in the nineteenth century, a quiet interval between about 1910 and 1950, and a second, mostly geologicphase of development since then, in conjunction with renewed interest in subjects such asplate tectonics and palaeoceanography after WWII. Most extensive and reliable data aboutthe biostratigraphic ranges of ancient ebridian species have been generated during theDeep Sea Drilling Project (DSDP, 1968 to 1983) and the Ocean Drilling Project (ODP,1985 to present). For example, Locker & Martini (1989) established nine ebridian zonesthat span the interval from the Early Miocene to the early Quaternary, and demonstratedthat these organisms might have some value as biostratigraphic markers and environmentalindicators. The work dealing with ancient ebridians (i. e., preQuaternary biostratigraphy)is referenced and discussed in more detail in Ernisse & McCartney (1995), whereas here

relative to diatoms (Korhola & Grönlund, 1999) or the total siliceous microfossil assemblage

228 AITE KORHOLA & JOHN P. SMOL

we discuss the few living ebridians and their applicability to more recent environmentaland palaeolimnological problems.

Little is known about the presentday ecological preferences of the ebridians, which, ofcourse, hinders palaeoecological interpretations. According to Lipps (1979), they are veryabundant in nutrientrich, cool marine waters at high latitudes. It seems that from the twomain living species, Hermesinun adiraticum is a stenohaline organism that thrives in warmwaters, whereas E. tripartita has a wider tolerance to temperature and salinity variations(Rhodes & Gibson, 1981). The latter is the only ebridian species alive in the Baltic Seatoday, and intact remains of E. tripartita, are frequently found in sediments representingthe ancient history of the Baltic basin, such as the Eemian Baltic Sea about 120 000 yrs BP(Brander, 1937; Niemelä & Tynni, 1979; Eriksson et al., 1980; Grönlund, 1991).

In the Baltic Sea, increased abundances of this taxon are regularly noted in the uppermostparts of sediment cores and are commonly interpreted as indicating nutrient enrichmentand/or upwelling (e. g., Miller & Risberg, 1990; Grönlund, 1991, 1993; Saxon & Miller,1993; Andrén, 1995). For example, Miller & Risberg (1990) noted increased abundances ofEbria tripartita in surface sediments of a core from the northwestern Baltic, and related thischange to the acceleration of eutrophication during the last ca. 20 years. Similarly, Korhola& Gronlund (1999) observed in the Gotland basin core a slight increase in the abundance ofE. tripartita towards the core surface. This increase was also tentatively interpreted as beingrelated to the progressive eutrophication of the basin. Numerous studies (e. g., Rosenberg,

EBRIDIANS 229

1984; Elmgren, 1989; Baltic Marine Environment Protection Commission, 1990) point toa marked increase in nutrients in the Baltic Sea during the last 200 years.

However, in the sediment core from Töölö Bay (Fig. 3), central Helsinki (Finland), theabundances of E. tripartita were particularly low during the most pronounced eutrophication stage, as inferred from diatoms (Korhola & Blom, 1996; Korhola & Grönlund, 1999).One explanation could be that, despite the species’ general preference for nutrientrichwaters, it might be less competitive in hypereutrophic waters, especially if the eutrophication is associated with heavy blooms of other planktonic algae (Korhola & Grönlund,1999). On the other hand, studies of recent blooms in Long Island Sound USA (Ernisse &McCartney, 1993) and the Baltic Sea (Kononen & Niemi, 1984) have observed significantyeartoyear fluctuations in the absolute abundance of ebridians, which do not seem to berelated to changes in either salinity or trophic status.

In recent years, there has been an increased interest in modern (extant) forms foundas fossils in the surface sediment of the shallow seas. Westman (2000) studied four longsediment cores, five short cores, and more than 20 surfacesediment samples representingthe years 1993 and 1997 for subfossil ebridians in die Baltic Sea proper. He was unable todistinguish any systematic trend in the abundance of E. tripartita during the most recentcenturies, although a slight increase in the relative abundance of this taxon was observedin all subsurface cores. All variation in the ebridian data seemed to be confined to periods


when there were also major changes in diatom assemblages—a situation that seems tohold true in other cases as well (e. g., Korhola & Grönlund, 1999). This prompted Westman(1999) to conclude that the changes in the abundance of E. tripartita are "most probablyattributable to alterations in the species composition of primary production in the Baltic, andhence represent only a secondary effect of environmental change". As E. tripartita mainlyfeeds on diatoms (Ernisse & McCartney, 1993), changes in its relative frequency couldsimply result from changes in the composition of the diatom flora and/or the contributionof the diatom flora to total primary production (Westman, 1999). This feature is illustratedin Figure 4, where the abundances of E. tripartita in the surfacesediments of the BalticSea proper sampled in 1993 and 1997 are contrasted against the major differences indiatom assemblages, as revealed by cluster analysis (Westman, 1999). As the abundanceof E. tripartita in the sediments seems to be reflected in major differencies in the diatomassemblage, it may be assumed that the distribution of the species in the sediments ispredominantly controlled by differencies in the composition of the diatom assemblage.

In an ongoing study dealing with the eutrophication history of the shallow Baltic Seainlets, ebridians have been identified together with diatoms in 45 sampling stations alongthe coastal area of southern Finland (Weckström & Korhola, in press). Only a few remains

EBRIDIANS 231

of E. tripartita were found, with their absolute numbers ranging between 0–12 per 500diatom frustules in sediment samples. A preliminary principal components analysis (PCA)performed on the measured water chemistry and ebridian data suggests that the ebridiandistributions and abundances in this data set are correlated with the PCA axis 1 consistingof salinty and ionic concentration (Fig. 5). This axis explained 46. 6% of the variance in theenvironmental and ebridian data. It thus seems that ebridians in these shallow embaymentsprefer sites of relatively high salinity (>4psu), conductivity and, to some extent,concentrations. Further studies will focus on the relationships of ebridians in these shallowcoastal waters to various diatom species and assemblages.

Indicator value and future research priorities

At present, contradictory data regarding the indicator value of ebridians exist, which aremost obviously related to the rudimentary ecological data available for these organisms.


As shown by the examples discussed in this chapter, ebridians clearly show stratigraphicchanges in sediment profiles, yet the ecological interpretations of these changes are stillspeculative. Clearly, more systematic studies on the distribution of these organisms along arange of various ecological gradients are needed in order to achieve a more comprehensiveunderstanding of the palaeolimnological significance of the group.

Future studies should focus on the collection of modern surfacesediment data sets alonga wide range of environments and ecological conditions in different marine systems. Someresults indicate that the observed patterns in the frequency distributions of ebridians may bepartly due to the selective preservation of their siliceous skeletons (Korhola & Grönlund,1999). Thus, the questions dealing with the preservation and taphonomy of these organismsshould be researched more fully. The taxonomy of ebridians is in many respects vague;thus in order for ebridians to become more useful indicators, detailed taxonomic studiesusing both light and electron microscopy are needed. Moreover, if ebridians are stronglyaffected by grazing pressure, as suggested by Westman (1999), then the question of whichfood web changes might affect ebridians would be an interesting research question.

Summary

Ebridians are a group of microscopic, heterotrophic marine plankters. Their siliceousendoskeletons are preserved in sedimentary deposits, and so they can be studied usingthe same techniques developed for other siliceous indicators, such as diatoms. They areprimarily marine, and so are not frequently encountered by palaeolimnologists, but theymay be common in brackish waters, such as the Baltic Sea, estuaries, and some lacustrineenvironments that may have had an influx of marine material. Only a few species areknown to exist today. Relatively little is known about the ecological optima and tolerances oftaxa, which currently hampers palaeoecological interpretations. However, ongoing researchsuggests they have some potential in palaeoenvironmental studies.

Acknowledgements

The study was funded by the Academy of Finland Grant 101 7383 to AK. We thankKaarina Weckström for counting the ebridian remains from the surfacesediments of theGulf of Finland.

References

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Baltic Marine Environment Protection Commission, Helsinki Commission, 1990. Second PeriodicAssessment of the State of the Marine Environment of the Baltic Sea, 1984–1988; BackgroundDocument. Baltic Sea Environment Proceedings 35 B, 432 pp.

Brander, G., 1937. Zur Deutung der intramoränen Tonablagerungen an der Mga. unweit vonLeningrad. Bull. Comm. Géol. Fin. 119: 93–113.

Edler, L., G. Hällfors & Å. Niemi, 1984. A preliminary checklist of the phytoplankton of the BalticSea. Acta Bot. Fenn. 128, 26 pp.

EBRIDIANS 233

Elmgren, R., 1989. Man’s impact on the ecosystem od the Baltic Sea: Energy flows today and at theturn of the century. Ambio 6: 326–332.

Eriksson, B., T. Grönlund & R. Kujansuu, 1980. Interglasiaalikerrostuma Evijärvellä Pohjanmaalla(English summary: An interglacial deposit at Evijärvi in the Pohjanmaa region). Geologi 32:65–71.

Ernisse, J. & K. McCartney, 1993. Ebridians. In Lipps, J. H. (ed. ) Fossil Prokaryotes and Protists.Blackwell Scientific Publication Inc., Boston: 131–140.

Ernisse, J. & McCartney, 1995. Ebridians and endoskeleton dinoflagellates. In Blome, C. D., P. Whalen& K. Reedet (eds. ) Siliceous Microfossils. Paleontology Society Short Courses in Paleontology8: 177–185.

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Kononen, K. & Å. Niemi, 1984. Long term variation of the phytoplankton composition at the entranceto the Gulf of Finland. Ophelia suppl. 3: 101–110.

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D.A. Barnum, J.F. Elder, D. Stephens & M. Friend (eds), The Salton Sea.

© 2002 Kluwer Academic Publishers. Printed in the Netherlands.

217

Skeletal development in Hermesinum adriaticum Zacharias, aflagellate from the Salton Sea, California

M. A. TiffanyDepartment of Biology, San Diego State University, U.S.A.

Key words: Ebriidians, phytoplankton, salt lake

Abstract

Hermesinum adriaticum is a rarely reported unicellular biflagellated organism with a solid siliceous skeleton. Live

specimens were not observed but many skeletons were found in sediments and, in small numbers, in cyanobacterial

mats and the water column of the Salton Sea, a salt lake in California, U.S.A. Stages of the developing skeleton

were studied with scanning electron microscopy, and the progression from small tetraxial daughter skeletons to

complete asymmetrical adult skeletons is presented. Some variability in the adult skeletons is illustrated.

Introduction

Ebriidians are a rare group of marine heterotrophic

flagellates of uncertain classification. Corliss (1994)

has tentatively placed them in his phylum Opalozoa,

and Taylor (1990) put them as possibly related to the

dinoflagellates. Ebriidians have two dissimilar flagella

and solid internal siliceous skeletons in contrast to the

external hollow skeletons of silicoflagellates. There

are two extant genera validly described, Ebria Borgert

andHermesinum Zacharias, of these Ebria is the more

commonly reported in plankton surveys.

Presently, H.adriaticum Zacharias and H. platense

Frenguelli are the only two known extant species in the

genus. Others have been recorded as fossils, mostly

from the Miocene (Tappan, 1980). The type of H. ad-

riaticum was from the Adriatic Sea (Zacharias, 1906).

Occasional blooms of H. adriaticum have been recor-

ded from the southern Mediterranean near the Nile

River (Halim, 1960), the Black Sea (Bodeanu, 1969),

the Pettaquamscutt River in Rhode Island (Hargraves

& Miller, 1974), the lower Chesapeake Bay (Rhodes

& Gibson 1981) and Lake Rogoznica, a salt lake near

the eastern Adriatic coast (Vilicic et al., 1996/97). The

greatest abundance of H.adriaticum found to date was

in the Salton Sea, California in 1955 (Carpelan, 1961)

at 450 cells/ml, although it was misidentified as “a

silicoflagellate, possibly Dictyocha sp.?”. For a pho-

tograph of a living cell of H. adriaticum, see Rhodes

& Gibson (1981).

Figure 1. Diagram showing the terminology for parts of the Her-

mesinum adriaticum skeleton (after Deflandre, 1952).

Reproduction of the ebriidian cell has been little

studied, and only asexual division is known (Tappan,

1980). Formation of the skeleton of the daughter cell is

thought to begin before nuclear division and be nearly

complete before cellular division. Rarely, double skel-

etons are formed by the accidental fusion of the daugh-

ter with the original skeleton (Hovasse, 1932). Skeletal

parts are named using the traditional nomenclature of

sponge spicules as proposed by Deflandre (1952) and

are shown in Figure 1.

218

Study area

The Salton Sea is a saline lake in Imperial County,

California that is below sea level and receives inflows

from agricultural and municipal wastewaters. It began

as a freshwater lake formed as a result of an acci-

dental diversion of the Colorado River in 1905. Due

to the lack of an outflow and the evaporation rates

in its desert environment, the salinity rose gradually.

When Carpelan (1961) reported high densities of H.

adriaticum in 1955–1956, the lake had a salinity close

to that of seawater. Presently it has a salinity of ap-

proximately 43 g l−1. Scanning electron microscope

images of adult skeletons of H.adriaticum from the

Salton Sea, taken by A. R. Loeblich from 1967 to

1969, have previously been published (Tappan, 1980).

Marine micro-organisms were likely introduced

accidentally along with marine fish that were stocked

into the Salton Sea, mostly in the 1940s and 1950s.

Many of these fish were from the Gulf of Califor-

nia, some from the Pacific Ocean and coastal Texas.

Most of the organisms in the Sea are of marine ori-

gin,includingH. adriaticum, possibly as a direct result

of these introductions. Migratory birds are a less likely

source of inoculation because the life cycle is not

known to include a cyst form (Tappan, 1980).

H. adriaticum has an optimum temperature of 20–

25 ◦C (Hargraves & Miller, 1974), well within the

range for the Salton Sea of 12–35 ◦C. The salinity

tolerance is unknown, but it has been reported at sa-

linities as low as about 12 g l−1 (Hargraves & Miller

1974) and as high as 38 g l−1 (Vilicic et al., 1996/97).

Materials and methods

A study of diatoms was carried out as part of a larger

bio-inventory of the Salton Sea during 1999. Skeletons

of H. adriaticum were encountered during the SEM

analysis of samples prepared for the determination of

diatom species.

Surface sediment was sampled on January 20,

1999 from mid-lake stations by L. F. R. Levine-

Fricke as part of a study of sediment contaminants

using a modified Birge-Eckman dredge. One of these

samples (GB64-46.2-12099), taken at 33◦ 23′ 23.9′′ N,

115◦ 51′ 57.0′′ W (about 4 km from the eastern shore

in the northern basin) was donated to the author for

study of diatoms and other microfossils. Depth at the

site was 13 m.

Samples of floating cyanobacterial mats were

taken from Varner Harbor at the headquarters of the

Salton Sea State Recreational Area. A mid-lake water

sample was taken by bucket from the surface (ap-

proximately the top 10 cm) from the northern basin

(33◦ 23′ 23.9′′ N, 115◦ 51′ 57.0′′ W) on 4/7/99.

All samples were treated by the Van Stosch method

(Hasle & Syvertsen, 1997) using HNO3 and H2SO4 to

remove organic material, dried on a coverslip, coated

with Au/Pd, and examined with a Hitachi 5200 SEM

using 10 KV accelerating voltage.

Results and discussion

H. adriaticum, previously known to be present in the

Salton Sea, (Carpelan, 1961; Tappan, 1980) was found

in several types of samples in 1998–1999. The largest

numbers were found in the sediment sample. The

sediment sample contained a great many individual

skeletons of H.adriaticum. Both adult and daughter

skeletons were found. The number of skeletons in the

surficial sediments suggests a bloom occurred in the

recent past.

Several adult and daughter skeletons from organ-

isms that may have been alive when collected were

found on SEM stubs of samples of cyanobacterial

mats that had been processed with concentrated acids.

These mats rise to the surface in summer and contain

many entrained benthic diatoms as well as the much

rarer H.adriaticum. H. adriaticum is thought to be

herbivorous on diatoms (Tappan, 1980) or flagellates

(Hargraves & Miller, 1974).

A single adult skeleton was found on a stub pre-

pared from a mid-lake surface water sample. This may

represent resuspension from the sediment or a living

specimen at the time it was collected. No living spe-

cimens of H. adriaticum were observed during this

study.

A complete progression of daughter skeletons was

found in samples from small tetraxial daughter skel-

etons about 10 µm long to adult skeletons 37–54 µm

long (mean=44.4 µm, n=29).

The young skeletons, called trianes, have four rays

called the actines. Three of these are set at about 120◦

apart in a plane, the fourth projects at a 90◦ angle from

that plane (Fig. 2A, B). The fourth actine is topped

by a triangle of silica (Fig. 2B, C). The two anterior

apices of the triangle grow extensions that close to

become the small circular upper window (Fig. 2D–

F). The posterior apex of the triangle lengthens but

219

Figure 2. Stages in the development of and variability in skeletons of Hermesinum adriaticum. (A and B) very young skeletons showing the

primary four-sided symmetry. (C and D) beginning of secondary development of the apices of the original skeleton. (E) small dorsal window

beginning to form and continuation of apical growth with large upper window now fully formed. (F) adult left-handed skeleton with fully

formed opisthoclade and spinose surface. (G) an adult right-handed skeleton showing smoother surface than the individual in F. (H) Error in

skeleton formation with misplaced anterior apex and an extension to dorsal apex instead of an opisthoclade. (I and J) Double anterior apices.

(K) illustration of rugose texture of skeleton at higher magnification. (L) spiny surface of adult skeleton. Scale bar for A–J=10 µm, for K=1 µm,

and for L=5 µm.

normally does not connect further to the skeleton. The

three bottom actines extend during development, the

two anterior ones trifurcating (Fig. 2C). The third,

posterior actine becomes the longer rhabde, forming

the axis of the skeleton. It has three extensions, one

of which becomes the posterior spine and one that

220

will help form the opisthoclade, an arch-like feature.

The anterior extensions extend in a curved manner

and fuse to form the large upper window (Fig. 2E).

The anterior spine is formed at the forward end of this

large window. The posterior extension of one of the

anterior actines fuses with that of the rhabde to make

the opisthoclade in the adult skeleton (Fig. 2E, F). The

posterior extension of the other anterior actine forms

the lateral spine.

The small upper window forms two bridges on

either side to the lower anterior window forming a

sort of siliceous basket in which the nucleus of the

daughter cell will reside (Fig. 2E). At which point

in the skeletal development the nucleus divides and

exactly when the daughter nucleus enters the newly

forming skeleton is not known, but Deflandre (1952)

illustrated a cell undergoing cytokinesis with an in-

complete daughter skeleton, the nuclear ‘basket’ of

silicon not yet formed.

Skeletons of Hermesinum are always asymmetric

with a completed arch only on one side of the skel-

eton. Assuming that Figure 1 illustrates the ‘dorsal’

view of the skeleton (after Hargraves & Miller, 1974),

the right-handed skeleton is defined as one where the

opisthoclade is on the right side of the skeleton. The

illustration of a double skeleton given by Hovasse

(1932) shows fused daughter skeletons that are mirror

images. This suggests that after division one daugh-

ter is left-handed (Fig. 2F) and one is right-handed

(Fig. 2G). This would imply that in a population of

this species equal numbers of left and right-handed

skeletons should be present. Of the 29 adult skeletons

of Hermesinum examined, 15 had the arch on the left

side and 14 on the right, in close agreement with this

hypothesis.

Much variability in the development of the skel-

eton occurs in the ebriidians. The morphology of

several skeletons in this study differed substantially

from the diagram in Figure 1. For example, in Fig-

ure 2H the upper triangle of silica apparently extended

to the posterior apex, forming a bridge; an ‘error’ ob-

served in several specimens. In Figure 2I, there are two

small upper windows instead of one and in Figure 2J

two anterior apices were accidentally formed. In these

samples, no double skeletons were observed but they

are known to be common in the ebriidians (Tappan,

1980). It is not clear what, if any, effect this variability

might have on the cell.

At high magnification, the texture of the skeleton

is evident (Fig. 2K). In contrast to the relative smooth-

ness seen in some silica secreting organisms, such as

silicoflagellates and some diatoms, it is rather rugose.

The skeleton is solid and internal to the cell. This is in

contrast to silicoflagellates that have a hollow external

skeleton. A ridge about 1.5–1.7 µm wide is central

to the main rib which ranged from 2.5 to 4 µm wide.

The apices and other projections are sometimes dec-

orated with an extensive spiny surface (Fig. 2L) that

may merely be a variable feature. It is also possible

that these spines continue developing after the basic

skeleton is completed (compare Fig. 2F, G).

The mechanism of silica deposition in ebriidi-

ans is unknown (Preisig, 1994). More is understood

about diatom frustules (Schmid & Schultz, 1979)

and chrysophycean cysts (Sandgren, 1989) which are

formed with the SDV (silica depositional vesicle).

Transmission electron microscope studies may elu-

cidate the mechanism of skeleton formation in the

asymmetric Hermesinum and determine if a similar

membrane is used to make the daughter skeleton. This

would require fixation of living material. It would

also be of interest to determine the timing and mech-

anism of movement of the newly formed nucleus to

the daughter cell. In addition, study of the cellu-

lar ultrastructure may help to determine the correct

classification of this organism.

Acknowledgements

I would like to thank the staff of LFR Levine-Fricke,

especially Richard Vogl and Ryan Henry, for the sedi-

ment sample; James Watts, Brandon Swan and Kristen

Reifel for obtaining water samples; Joan Dainer for

technical assistance; and Stuart Hurlbert for reviewing

the manuscript. I would like to thank Steven Barlow

for the generous use of the Electron Microscope Fa-

cility at San Diego State University. I also thank two

anonymous reviewers.

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Jour. Korean Earth Science Society, v. 27, no. 1, p. 95−117, February 2006

경북 포항분지 북부 지역의 연일층군(제3기)에서 산출되는

포낭류 화석을 비롯한 소수 규질 미화석군에 대한 연구

고 영 구*

전남대학교 사범대학 과학교육학부, 500-757, 광주광역시 북구 용봉동 300

Minor Siliceous Microfossil Group and Fossil Cysts from the

Yeonil Group (Tertiary) in the Northern Area of the

Pohang Basin, Kyeongbuk Province, Korea

Yeong-Koo Koh*

Department of Science Education, Chonnam National University, Gwangju 500-757, Korea

Abstract: From the Tertiary Yeonil Group distributed in Songra and Cheongha areas, the northern part of the Pohang

Basin, nine archaeomonad species belonging to two genera, and other three types of chryophycean cysts considered as

stomatocysts, five endoskeletal dinoflagellate species belonging to three genera and eighteen ebridian species belonging to

eleven genera were identified. Based on above siliceous microfossil assemblages, the Yeonil Group is corresponded to

Middle Miocene age. The group is correlated with the Calvert Formation (Maryland in USA) and the Hojuji Formation

(in Central Japan) by its archaeomonad cysts. And, the group is correlated with the intervals of Actiniscus elongatus to

Middle Hermesinella conata zones in Southwest Pacific region and of Spongebria miocenica to Middle Hermesinella

schulzii zones in Vøring Plateau, Norwegian Sea, based on the ebridian assemblages of the group. From the

chrysophycean cyst including archaeomonad, endoskeletal dinoflagellate and ebridian assemblages in the Yeonil Group of

the study area, it is inferred that cold water masses dominated during the deposition of the group with occasional warm

water. The upper part of the group might be somewhat colder than the lower one of the group in depositional condition.

In addition, minute chrysopycean cysts considered as stomatocysts suggest the influence of fresh or brackish water during

the deposition of the group.

!"#$%&'( Yeonil Group, cysts, endoskeletal dinoflagellates, ebridians

요 약: 연구지역인 포항분지 북부의 청하와 송라 일대에 분포하는 연일층군에서 2속 5종의 아케오모나드, 이들 외에 3

가지 유형의 스토마토시스트로 생각되는 포낭류 화석, 3속 5종의 내골격 와편모조류 및 11속 18종의 에브리디안 화석

들이 산출되었다. 규질 미화석들의 군집조성에서 연구지역에 분포하는 연일층군의 지질시대는 마이오세 중기에 해당하

며 아케오모나드의 산출에 따르면 미국 메릴랜드의 Calvert층과 일본 중부의 Hojuji층에 대비된다. 내골격 와편모조류와

에브리디안을 이용한 분대에 따르면 연구지역의 연일층군은 남서태평양 해역의 Actiniscus elogatus대에서 Hermesinella

conata대의 중부에, 노르웨이해 연안 Vøring Plateau해역의 Spongebria miocenica대에서 Hermesinella schulzii대의 중부

에 대비된다고 할 수 있다. 연일층군 퇴적환경은 아케오모나드를 비롯한 포낭류 화석, 내골격 와편모조류 및 에브리디

안 군집조성에 따르면, 대체로 한랭수괴가 우세한 환경에서 온난수괴 역시 영향을 미치고 있었으나 두호층의 상부로 가

면서 한랭화가 다소 강화되었던 것으로 생각된다. 그리고 미소 포낭류 화석들의 산출에서 연일층군 퇴적 시, 담수 또는

반염수의 영향을 받았을 가능성이 시사된다.

주요어( 연일층군, 포낭류, 내골격 와편모조류, 에브리디안

(해 설)

*Corresponding author: [email protected]

Tel: 82-62-530-2513

Fax: 82-62-530-2519

경북 포항분지 북부 지역의 연일층군 제!기"에서 산출되는 포낭류 화석을 비롯한 소수 규질 미화석군에 대한 연구

101

이 반원형을 이루는 점에서 A. rectangulare와는 뚜렷

이 구분된다고 하였다. 이 연구에서도 이 견해에 따

라 심하게 굴곡된 신클레이드와 특징적인 전면의 반

원형 창을 가지는 개체들은 A. serotinum으로 분류하

였다. 그리고 A. serotinum 중에서는 상당수의 이중

골격(double skeleten)을 가지는 개체들이 관찰되었다

(Pl. 2, Fig. 5).

Ditripodium latum은 연구지역에서 소수 발견되는

데 용식 등에 의한 것으로 추정되는 파손된 메소클

레이드(mesoclade)를 가지는 개체들이 대부분이다. 2

개의 트리오드(triode)가 엇갈려 결합된 골격구조의

Ebriopsis antiqua는 연구지역에서 다산되는 종들 중

의 하나이다. E. antiqua 개체들 중에서는 골격의 상

부에 로리카를 보유하는 개체와 골격의 클레이드 등

에 불규칙한 돌기(knob) 등이 형성되는 등의 실리카

성분의 부가현상이 진행된 초규질화된 개체들이 관찰

되었다(Pl. 2, Figs. 9, 10). 로리카를 보유하는 개체

들은 하송리 부근의 학전층 하부 시료에서 관찰되는

데, 로리카는 개체의 정부에 접합된 상태로 상부가

다소 축소된 둥근 단지 모양을 하고 있고 그 개구부

(opening)는 다소 넓고 약간 주름진 주변부를 가진다.

E. antiqua에 있어 초규질화는 개체들에 따른 변화가

많아 클레이드에 돌기들만이 관찰되는 형태부터 클레

이드들이 파랑상으로 두터워진 형 및 골격의 상당부

분이 충전된 형태까지 여러 단계들이 관찰된다.

Haplohermesinum은 일반적으로 Ebria로 간주되기도

하였으나 특징적인 트리플렛(triplet) 보유로 재정립된

분류군이다(Locker and Martini, 1989). 연구지역에서

산출되는 Haplohermesinum속으로는 H. hovassei가

극소수 산출된다. 이 종에서도 부분적인 초규질화가

확인된다. Ebrinula(?) sp.는 외형상 Ebriopsis와 유사

하나 신클레이드들을 연결하는 연결주(connective

rod)가 인지되므로 Ebrinula에 속할 가능성이 높다.

이 종류의 개체들은 소수지만 연구지역의 여러 층준

에서 산출된다.

대표적인 4방향 골격형을 지니는 Hermesinella속과

Hermesinum속의 개체들은 연구지역의 학전층과 두호

층에서 Hermesinella fenestrata를 제외하고는 상대적

으로 산출개체수가 많은 편이다. Hermesinella속에서

는 H. conata가 이들 두 속의 개체들 중 가장 대표

적인 다산종으로 풍부히 산출된다. Hermesinum속에

속하는 H. adriaticum, H. obliquum, H. schulzii들은

연구지역에서 빈도는 약간씩 다르지만 대부분 시료에

서 지속적으로 산출한다. 연구지역의 두호층 상부에

서는 이들 Hermesinella속과 Hermesinum속의 개체들

의 산출빈도는 대체로 증가하는 경향을 갖는다.

Table 2. Ebridians from the Yeonil Group in the northern area of Pohang Basin

Formation Hakjeon Formation Duho Formation

Sampling sites

Taxa

HS1 HS2 HS3 HD1 DJ1 DJ2 DJ3 SD1 SD2 SD3 SD4 JR1 JR2 JR3 JR4 JR5 IG1 IG2 IG3

Ammodochium ampulla 12 7 6 1 2 5 15 7 11 23 22 18 3 1 2

Ammodochium danicum 1 1 1 1

Ammodochium cf. A. rectangulare 2 1 2

Ammodochium serotinum 33 29 37 30 11 24 55 39 141 83 195 98 139 8 33 9

Ditripodium latum 6 1 3 1 7 1 1 1

Ebrinula(?) sp. 1 1 1 2 7 5 4 3 1 1 1

Ebriopsis antiqua 19 21 19 17 4 18 27 31 64 63 124 51 120 7 15 4

Haplohermesinum hovassei 1 1 2 1 2 4 3 4 1

Hermesinella conata 12 11 15 7 5 16 11 18 29 9 36 27 37 4 16 11

Hermesinella fenestrata 1 1 2 1 1 1 3 5 2 1 5 2

Hermesinum adriaticum 8 12 13 5 2 8 3 13 4 16 19 3 8 1 3 2

Hermesinum obliquum 5 18 7 4 1 2 3 2 27 7 4 29 1 1

Hermesinum schulzii 9 5 3 2 9 4 18 11 21 14 11 2 4 4

Parathranium tenuipes 1 3 1 3 6 2 5 2 2 6 2 1

Podamphora elgeri 1 2 4

Podamphora sp. 2 2

Pseudammodochium robustum 8 3 2 2 2 5 2 2 7 8 9 8 1 3

Thranium cf. T. crassipes 1 2 1

Total specimens 111 119 117 0 74 25 85 124 139 1 0 313 215 443 237 375 29 84 36


109

Description: Four rayed skeleton with a

rectangular pyramid like plate. Surface of the rays

is smooth or covered weak alveolar structures.

Remarks: The rays of A. tetrasterias in the study

area are highly arched and somewhat irregular in

stretched direction, comparable to those of A.

tetrasterias by Dumitric (1973). The species is

very rare in the Hakjeon and the Duho formations.

Genus Carduifolia Hovasse, 1932

Carduifolia gracilis Hovasse, 1932

Pl. 1, Fig. 19

1932a Carduifolia gracilis n. sp. - Hovasse, p.

127, Fig. 10

1968 Carduifolia gracilis Hovasse. - Loeblich III et

al., p. 150, pl. 49, Figs. 9a-10

1973 Carduifolia gracilis Hovasse. - Dumitric , p.

824, pl. 4, Figs. 21, 26

Description: Four tricostate rayed skeleton. The

rays of the skeleton consist of a slender “X” letter

form arched downward.

Remarks: In southwestern Pacific sediments, C.

gracilis was found in the Middle Miocene

(Dumitric , 1973). The species in the study area is

variable in size and its ray arrangement. C. gracilis

rarely occurs in the Hakjeon and the Duho

formations.

Genus Foliactiniscus Dumitric , 1973

Foliactiniscus mirabilis Dumitric , 1973

Pl. 1, Fig. 21

1973 Foliactiniscus mirabilis n. sp. - Dumitric , p.

823, pl. 1, Figs. 12, 13, 20, pl. 2, Figs. 4, 12, 13

Description: Pentagonal star shaped skeleton with

five highly downward arched rays having alveolar

structures. The skeleton has not central apophyses,

characteristically. The rays of the skeleton are

bilateral in symmetry.

Remarks: In the study area, F. mirabilis has

robust rays arched downward. The species rarely

occur in the Duho Formation.

EBRIDIANS

Division PYRRHOPHYTA Pascher, 1914

Class EBRIOPHYCEAE Loeblich III, 1970

Order EBRIALES Horniberg et al., 1964

Family Ammodochiaceae Deflandre, 1950

Genus Ammodochium Hovasse, 1932

Ammodochium ampulla Deflandre, 1934

Pl. 2, Fig. 1

1934 Ammodochium ampulla n. sp. - Deflandre, p.

77, Fig. 2

1952 Ammodochium ampulla Deflandre. - p. 128,

Fig. 119

1968 Ammodochium ampulla Deflandre. - Loeblich

III et al., Fig. 14, pl. 48, Fig. 1

1975 Ammodochium ampulla Deflandre. - Perch-

Nielsen, pl. 4, Figs, 17-19, pl. 5, Figs. 23-26

2003 Ammodochium ampulla Deflandre. -

Sanfilippo and Fourtainer, pl. p1, Figs. 23, 24

Description: Rectangular triode skeleton consisting

of an apical ring, an antapical ring, three proclades,

three opisthoclades and three actines. In the

skeleton, proclades and opisthoclades are branched

from actines. The proclades and opisthoclades

consist of upper and lower windows at junctions

between them and apical or antapical ring,

respectively.

Remarks: A. ampulla was initially reported from

the Upper Eocene deposits of New Zealand

(Deflandre, 1934). It also occurred in Oligocene to

Eocene intervals of cores from Southwestern Pacific

(Perch-Nielsen, 1975). The specimens of A. ampulla

from the Yeonil Group have somewhat wider

windows than those of its specimens by Perch-

Nielsen (1975). The species occurs in the Hakjeon

and the Duho formations.

Ammodochium danicum Deflandre, 1951

Pl. 2, Fig. 2

1951 Ammodochium danicum n. sp. - Deflandre, p.

53, Fig. 13

110

고 영 구

Plate 2

Ebridians

Fig. 1. Ammodochium ampulla Deflandre. ×400, Duho Formation, JR3.

Fig. 2. Ammodochium danicum Deflandre. ×600, Duho Formation, SD2.

Fig. 3. Ammodochium cf. A. rectangulare (Schulz) Deflandre. ×400, Hakjeon Formation, HS1.

Fig. 4. Ammodochium serotinum Locker and Martini. ×400, Duho Formation, JR1.

Fig. 5. Ammodochium serotinum Locker and Martini. ×400, double skeleton, Duho Formation, SD2.

Fig. 6. Ditripodium latum Hovasse. ×400, Hakjeon Formation, HS3.

Fig. 7. Ebrinula(?) sp. ×400, Duho Formation, SD2.

Fig. 8. Ebriopsis antiqua (Schulz) Hovasse. ×400, Duho Formation, SD2.

Fig. 9. Ebriopsis antiqua (Schulz) Hovasse. ×400, hypersilicified specimen, Hakjeon Formation, HS3.

Fig. 10. Ebriopsis antiqua (Schulz) Hovasse. ×400, specimen with an encapsulated lorica, Duho Formation, HS2.

Fig. 11. Haplohermesinum hovassei Locker and Martini. ×400, Duho Formation, JR2.

Fig. 12. Hermesinella conata (Deflandre) Locker and Martini. ×400, Duho Formation, JR5.


111

1968 Ammodochium danicum Deflandre. - Loeblich

III et al., p. 144, pl. 48, Figs. 2-9c

1975 Ammodochium danicum curtum Deflandre. -

Perch-Nielsen, p. 880, pl. 5, Figs, 3-4

Description: Small rounded cubic triode skeleton

with an antapical ring curved inward. In the

skeleton, upper windows are located in apical part

but lower ones do not develop.

Remarks: A. danicum specimens from the study

are similar to A. danicum curtum reported by Perch-

Nielsen (1975). But, having outward convex clades,

the specimens of the study area are different from

A. danicum curtum described by Perch-Nielsen

(1975). Therefore, this taxon was classified as A.

danicum in this study. The species is very rare in

the Hakjeon and the Duho formations.

Ammodochium cf. A. rectangulare (Schulz), 1932

Pl. 2, Fig 3

Remarks: The ebridian specimens closely resemble

Ammodochium rectangulare. But they are distinguished

from A. serotinum, having massive proclades and

opisthoclades. And, they have a “T” shaped

synclade and rectangular anterior windows similar to

A. rectangulare described by Locker and Martini

(1986). The specimens of Ammodochium cf. A.

rectangulare are very rare in the Hakjeon and Duho

formations.

Ammodochium serotinum Locker and Martini, 1986

Pl. 2, Figs. 4-5

1986 Ammodochium serotinum n. sp. - Locker and

Martini, p. 943, pl. 2, Figs. 1, 2

Description: Rectangular triode skeleton with

strongly curved synclades, triangular windows in the

tips of proclades and opisthoclades. The skeleton

has semicircular anterior openings between a triode

and surrounding clades.

Remarks: A. serotinum is distinguished by its

more gracile skeleton, the highly arched synclades,

and the above mentioned openings, comparable to

A. rectangulare (Locker and Martini, 1986). The

species are very abundant in the Hakjeon and the

Duho formations.

Family Ditripodiaceae Deflandre, 1951

Genus Ditripodium Hovasse, 1932

Ditripodium latum Hovasse, 1932

Pl. 2, Fig. 6

1932b Ditripodium latum n. sp. - Hovasse, p. 282,

Fig. 6

1968 Ditripodium latum Hovasse. - Loeblich III et

al., p. 153, pl. 37, Fig. 10

1986 Ditripodium latum Hovasse. - Locker and


Description: Baguette type skeleton with large

apical ring, bifurcated short opistoclades, and two

openings including mesoclades.

Remarks: According to Locker and Martini

(1986), the mesoclades of Ditripodium latum tend to

be broken off easily. Most specimens of D. latum

from the study area show broken mesoclades, too.

Plate 2. Continued.

Fig. 13. Hermesinella fenestrata Frenguelli. ×400, Duho Formation, JR2.

Fig. 14. Hermesinum adriaticum Zacharias. ×600, Duho Formation, SD2.

Fig. 15. Hermesium obliquum Locker and Martini. ×600, Duho Formation, JR1.

Fig. 16. Hermesinum schulzii Hovasse. ×400, Duho Formation, JR3.

Fig. 17. Parathranium tenuipes Hovasse. ×400, Duho Formation, SD2.

Fig. 18. Parathranium tenuipes Hovasse. ×400, double skeleton, Duho Formation, SD2.

Fig. 19. Podamphora sp. ×400, Hakjeon Formation, HS2.

Fig. 20. Podamphora elgeri Gemeinhardt. ×400, specimen with an encapsulated lorica, Hakjeon Formation, HS2.

Fig. 21. Pseudammodochium robustum Deflandre. ×400, Hakjeon Formation, HS1.

Fig. 22. Thranium cf. T. crassipes Hovasse. ×400, Hakjeon Formation, HS3.

112

고 영 구

The species rarely occurs in the Hakjeon and the

Duho formations.

Genus Parathrnium Hovasse, 1932

Parathranium tenuipes Hovasse, 1932

Pl. 2, Figs. 17, 18

1932a Thranim tenuipes Hovasse. - p. 123, Fig. 5

1932c Parathranium tenuipes nov. comb. - Hovasse,

p. 464, 465

1968 Parathranium tenuipes Hovasse. - Loeblich

III et al., p. 179, pl. 47, Figs. 16-17

Description: Stool shaped skeleton with an apical

ring and long downward stretched opisthoclades.

The opisthoclades of the skeleton are occasionally

curved outward.

Remarks: The specimens of P. tenuipes from the

study area are different from P. clathratum proposed

by Locker and Martini (1986, 1989) because the

specimens have an upward-convex upper window

and slightly outward curved opisthoclades. The

species is rare in the Hakjeon and the Duho

formations. And, its double skeleton forms are also

encountered in the formations.

Genus Pseudammodochium Hovasse, 1932

Pseudammodochium robustum Deflandre, 1934

Pl. 2, Fig. 21

1934 Pseudammodochium robustum n. sp. -Deflandre,

p. 94, Figs. 39-42

1968 Pseudammodochium robustum Deflandre. -

Loeblich III et al., p. 184, 185, pl. 43, Figs. 16-18b

1989 Pseudammodochium robustum Deflandre. -

Locker and Martini, p. 573, pl. 6, Figs. 6-8

Description: Ellipsoid skeleton with a perforated

surface and an apical opening. The apical opening

is small and placed at the top of the skeleton.

Remarks: For the specimen of Pseudammodochium

robustum from the study area, superficial pores are

more or less larger, relative to those of typical P.

robustum. The species is rare in the Hakjeon and

the Duho formations.

Genus Thranium Hovasse, 1932

Thranium cf. T. crassipes Hovasse, 1932

Pl. 2, Fig. 22

Remarks: This form is similar to Thranium

crassipes in outline. But the form is distinguished

from T. crassipes by straightly stretched opisthoclades

having small inward horns. The form occurs only in

the Hakjeon Formation.

Family Ebriaceae Lemmermann, 1901

Genus Ebrinula Deflandre, 1950

Ebrinula(?) sp.

Pl. 2, Fig. 7

Remarks: E. paradoxa, a unique species of genus

Ebrinula, was initially reported from the Eocene

deposits of Oamaru (Deflandre, 1950). The

specimens of the present form from the study area

are similar to E. paradoxa in the existence of

connective rod connecting anterior synclade with

posterior one. They are rare in the Hakjeon and the

Duho formations.

Family Hermesinaceae Hovasse, 1943

Genus Ebriopsis Hovasse, 1932

Ebriopsis antiqua (Schulz), 1932

Pl. 2, Figs. 8-10

1928 Ebria antiqua Schulz. - p. 273, Figs. 69a-f

1932a Ebriopsis antiqua (Schulz) nov. comb. -

Hovasse, p. 120, Fig. 1

1977 Ebriopsis antiqua antiqua (Schulz). - Ling, p.

215, pl. 3, Figs. 17, 18

1975 Ebriopsis antiqua (Schulz). - Perch-Nielsen,

p. 880, pl. 4, Fig. 15

1986 Ebriopsis cornuta (Ling). - Locker and

Martini, p. 943, 944, pl. 2, Figs. 14-15

Description: Circular lens shaped skeleton

composed of two tripods connected by inward

curved clades with some indentations. The two

tripods are mutually joined in the crossed state of

about sixty degree. The clades of the skeleton are

generally gracile.


113

Remarks: In the study area, E. antiqua shows

several varieties as specimens with thickly developed

clades, hypersilicified forms, specimens with small

spines at the apex and/or antapex in their skeletons,

and lorica bearing forms. Lorica in the loricate

forms shows a gently tapered jarred shape with a

wide opening. The opening is surrounded by a thin

wrinkled rim. In this study, specimens with

irregularly indented clades were aligned to E.

antiqua. The species is consistent and abundant in

the Hakjeon and the Duho formations in occurrence.

Genus Haplohermesinum Hovasse, 1943

Haplohermesinum hovassei Locker and Martini,

1989

Pl. 2, Fig. 11

1989, Haplohermesinum hovassei n. sp. - Locker

and Martini, p. 571, pl. 7, Figs. 11-12

Description: Circular lens shaped skeleton with a

characteristic “Y” formed triplet composed of two

synclades, a proclade, and an opisthoclade. Of the

synclades of the skeleton, short two are straight and

other one is round.

Remarks: Comparing with the specimen of H.

hovassei by Locker and Martini (1989), the one in

the study area shows more massive and shorter

straight synclades. The species rarely occurs in the

Hakjeon and the Duho formations.

Genus Hermesinella Deflandre, 1934

Hermesinella conata (Deflandre), 1986

Pl. 2, Fig. 12

1951 Hermesinum conatum Deflandre. - p. 44, 46,

68, Fig. 141

1986 Hermesinella conata (Deflandre) nov. comb.

- Locker and Martini, p. 944, pl. 2, Figs. 9-10

Description: Small rounded triaene skeleton with

strongly curved synclades. A small upper window is

located in the anterior plate of the skeleton. The

opisthoclades of the skeleton are mutually different

in length.

Remarks: The specimen of H. conata from the

study area are well coincided with that of Locker

and Martini (1986), comparatively. The specimens in

the study area are somewhat variable in opisthocladian

arrangement and skeletal outline. H. conata frequently

occurs in the Hakjeon and Duho formations.

Hermesinella fenestrata Frenguelli, 1951

Pl. 2, Fig. 13

1951 Hermesinella fenestrata n. sp. - Frenguelli, p.

279, Fig. 5a

1968 Hermesinella fenestrata Frenguelli. - Loeblich

III et al., p. 164, pl. 51, Fig. 9

1986 Hermesinella fenestrata Frenguelli. - Locker

and Martini, p. 944, pl. 2, Fig. 13

Description: Small circular triaene skeleton with

robust and rugose clades highly arched. Clades in

the anterior part of the skeleton make a triangular

plate with a small circular window in its centre.

Remarks: The specimen in the study area is

nearly circular in outline and smooth junction

between a rhabde and clades, comparable to that of

Hermesinella conata of Locker and Martini (1986).

H. fenestrata is distributed in the Middle Miocene

to the lower part of the Upper Miocene in

southwestern Pacific (Locker and Martini, 1986).

The species rarely occurs in the Hakjeon and the

Duho formations.

Genus Hermesinum Zacharias, 1906

Hermesinum adriaticum Zacharias, 1906

Pl. 2, Fig. 14

1906 Hermesinum adriaticum n. sp. - Zacharias, p.

394, Figs. a-d

1968 Hermesinum adriaticum Zacharias. - Loeblich

III et al., p. 168-169, pl. 40, Figs. 9a-10

1986 Hermesinum adriaticum Zacharias. - Locker


2002 Hermesinum adriaticum Zacharias. - Tiffany,

p. 218-220, Figs. 1-2

Description: Kite type triaene skeleton with two

spines in apical and antapical parts. In the anterior

part of the skeleton, a small window is located in

114

고 영 구

the centre of the “T” formed structure consisted of

clades.

Remarks: Hermesinum adriaticum is the one of

very rare ebridian species survived until the present

(Ernissee and McCartney, 1993). The H. adriaticum

from the study area is commonly smooth in a

rhabde and clades, comparable to that of Locker

and Martini (1986, 1989) and Tiffany (2002). In

addition, the species includes a remarkably long

apical spine. But its basal spine is relatively

indistinct. And, its opisthoclades are frequently

corroded and reduced. Smaller triaenes considered as

larvae stages of the species are sometimes found in

this study. H. adriaticum consistently occurs in the


Hermesinum obliquum Locker and Martini, 1986

Pl. 2, Fig. 15

1986 Hermesinum obliquum n. sp. - Locker and


Description: Triaene skeleton with a asymmetrical

long spine on apical ring and two tapered

opisthoclades tilted downward. The opisthoclades of

the skeleton do not consist of windows.

Remarks: Hermesinum obliquum includes originally

flat upper synclades and asymmetrical apical spine

(Locker and Martini, 1986). The species in the

study area has occasionally curved synclades or two

mutually different apical spines in length. H.

obliquum shows consistent occurrences in the


Hermesinum schulzii Hovasse, 1932

Pl. 2, Fig. 16

1932a Hermesinum schulzii n. sp. - Hovasse, p. 125

1968 Hermesinum schulzii Hovasse. - Loeblich III

et al., p. 174, pl. 41, Figs. 10-20

1995 Hermesinum schulzii Hovasse. - Ernissee and

McCartney, p. 181. Fig. 3(14)

Description: Ovoid triaene skeleton with strongly

curved clades. In the posterior part of the skeleton,

clades trifurcated from an actine make a distinct

triplet with a small window. The posterior triplet of

the skeleton shows “Y” letter form and highly

arched connection to rhabde.

Remarks: The H. schulzii from the study area

shows a distinct triplet with obvious indentations

and outward arched opisthoclades. Its large upper

window in anterior part is somewhat ovoid. The

species consistently occurs in the Hakjeon and the

Duho formations.

Genus Podamphora Gemeinhardt, 1931

Podamphora elgeri Gemeinhardt, 1931

Pl. 2, Fig. 20

1931 Podamphora elgeri n. sp. - Gemeinhardt, p.

107, pl. 10, Fig. 19

1968 Podamphora elgeri Gemeinhardt. - Loeblich

III et al., p. 182, pl. 44, Fig. 4

1989 Podamphora elgeri Gemeinhardt. - Locker


1995 Podamphora elgeri Gemeinhardt. - Ernissee

and McCartney, p. 181, Fig. 3(15)

Description: Triaene skeleton with a jar shaped

lorica at the apex and indented clades highly

curved. The lorica of the skeleton with a short neck

is covered by irregular reticulations.

Remarks: In most cases, Podamphora elgeri is

characterized by a jar shaped lorica at its apex

(Gemeinhardt, 1931). The specimen of P. elgeri in

the study area also has the lorica. It may serve a

kind of protective role during environmental stress

(Ernissee and McCartney, 1995). But Tappan (1980)

suggested that the loricae in ebridians would be not

cyst. The species is restricted in the lower part of

the Hakjeon Formation in occurrence.

Podamphora sp.

Pl. 2, Fig. 19

Remarks: This ebridian specimen from the study

area resembles Podamphora gracile in morphology.

But the specimen has a rather wide opisthocladian

basket and smooth clades without indentations,

comparable to P. gracile. Apical ring is probably


115

reduced in the specimen. They occur in only the

lower part of the Hakjeon Formation.

사 사

이 논문은 2004년도 전남대학교 연구년교수연구비

지원에 의하여 연구되었습니다. 이에 감사드립니다.

논문 내용을 자상하게 검토해 주시고 좋은 의견을

제시해 주신 윤혜수 교수님, 김종헌 교수님 그리고

익명의 심사위원님께 깊이 감사드립니다.

참고문헌

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이영길, 유환수, 고영구, 1991, 포항일대 연일층군의 생층서

와 고환경. 한국고생물학회지, 7(1), 32-62.

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에서 산출된 포자화분 화석군의 고생태. 한국지구과학

회지, 16(3), 215-221.

Adam, D. P. and Mahood, A. D., 1981, Chrysophyte cysts

as potential environmental indicators. Geological Soci-

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Bachmann, A., 1964, Part II Silicoflagellide und Archae-

omonadaceae. In Ichikawa, W., et al., Fossil diatoms,

pollen grains and spores, silicoflagellates and archae-

omonads in the Miocene Hojuji diatomaceous mud-

stone, Noto Peninsula, Central Japan, Science Report of

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Bak, Y., Lee, J. D. and Yun, H., 1996, Middle Miocene

Radiolarians from the Duho Formation in the Pohang

Basin, Korea. Journal of the Paleontological Society of

Korea, 12(2), 225-261.

Bak, Y., Lee, J. D. and Yun, H., 1997, Radiolarian faunas

from the Hagjeon Formation (Middle Miocene) in the

southern Pohang Basin, Korea. Journal of the Paleonto-

logical Society of Korea, 13(2), 137-154.

Bong, P. Y., 1985, Palynology and Stratigraphy of the Neo-

gene Strata in the Pohang Sedimentary Basin. Ph. D.

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Deflandre, G., 1933, Seconde note sur les Archaeomonad-

cées. Bulletin de la Société Botanique de France, 76(5-6),

346-355.

Deflandre, G. 1934, Nomenclature du squelette des Ébri-

acées et description de quelques formes nouvelles.

Annales de Protistologie, 4, 75-96.

Deflandre, G. 1936, Les flagellés fossiles. Aperçu

biologique et paléontologique, Role géologique, Paris,

Hermann & Cie, Actualités Scientifiques et Industri-

elles, 335, 98 p.

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tions de ce genre avec le Ammodochidae. Comptes

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Deflandre, G., 1951, Recherches sur les Ébridiéns, Paléobi-

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la France et de la Belgique, 85, 1-84.

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Dumitric , P., 1968, Consideratii micropaleontologice asu-

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geofizic , geografie, Seria Geologie, 13(1), 227-241.

Dumitric , P., 1973, Cenozoic endoskeletal dinoflagellates

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21 of the DSDP. Initial Reports of DSDP, 21, 819-835.

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phycean Cysts. Kluwer Academic Publishers, Dor-

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ständigen Lebens auf der Erde, Leipzig, Leopold Voss,

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Cosawhatchie Clay, Jasper County, South Carolina.

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Lipps, J. H. (ed.), Fossil prokaryotes and protists.

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Frenguelli, J., 1941, Sílicoflagelados y Radiolarios del

Middle Eocene ebridians from the central Arctic Basin

Jonaotaro Onodera1

and Kozo Takahashi2

1Center for Advanced Marine Core Research, Kochi University, B200 Monobe, Nankoku, 783-8502, Japan

2Department of Earth and Planetary Sciences, Kyushu University, Hakozaki6-10-1, Fukuoka, 812-8581, Japan

email: [email protected]; [email protected]

ABSTRACT:Abundant and diversified ebridians recovered during IODP Expedition 302 (ACEX) have been identified and counted inorder to establish their taxonomy and to decipher the biostratigraphic potential of ebridians in the central Arctic Ocean. In the ACEXsamples these fossils are preserved in Lithologic Units 1/6 and 2, which consist mainly of dark silty clay and biosiliceous ooze, respec-tively. Thirty taxa have been distinguished, three of which are described as new species (Ammmodochium lomonosovense, Pseud-ammodochium karyon, and Pseudammodochium psichion). The most dominant ebridian species is Pseudammodochium dictyoidesthroughout the biosiliceous section. The second dominant species varies alternately throughout the section. Based on the characteristicoccurrences ofmajor ebridian taxa, the ebridian assemblageswere divided intoGroupsA toD in stratigraphic order. The ebridian assem-blages in piston core USGS Fl-422 from the Alpha Ridge probably correlate to our assemblage Group A of early middle Eocene age, al-though rare younger taxa are irregularly included.

INTRODUCTION

Ebridians represent a group of marine zooflagellates that havetwo dissimilar flagella and a siliceous internal skeleton. Theebridians are cosmopolitan but usually rare in most marineplankton assemblages, with several exceptions in specific con-ditions such as in estuaries, bays, and semi-closed seas such asthe Baltic, and the Black Sea (Tappan 1980, Earnissee andMcCartney 1993, Korhola and Smol 2001, Hargraves 2002,Osawa et al. 2005).

Previous studies of Eocene sediments in the Arctic Ocean wereconducted only based on piston core samples. Thus thepaleoceanographic and paleontological understanding of theEocene Arctic Ocean remained fragmentary (Clark 1974,Kitchell and Clark 1982, Bukry 1984, Ling 1972, 1985a, Clarket al. 1986, Sims and Ross 1988, Dell’agnese and Clark 1994,Magavern et al. 1996). The IODP Expedition 302 (Arctic Cor-ing Expedition: ACEX) successfully cored middle Eocene sedi-ments in the central Arctic Ocean in the summer of 2004(Backman et al. 2006, 2008, Moran et al. 2006). This successfulcontinuous coring made high resolution studies of the EoceneArctic Ocean sediments possible.

The previous studies and the recent ACEX investigations dem-onstrated that the Eocene sediments from the Arctic Ocean con-tain siliceous microfossils assemblages mainly consisting ofdiatoms, silicoflagellates, chrysophyte cysts and ebridians(Bukry 1984, Ling 1985a, Dell’agnese and Clark 1994,Stickley et al. 2008). Radiolarians are nearly absent in theACEX samples (Backman et al. 2006). Ebridians represent oneof the significant groups of siliceous microfossil assemblages inthe Eocene Arctic Ocean (Dell’agnese and Clark 1994,Backman et al. 2006, Stickley et al. 2008). The age determina-tion potential of ebridians was generally limited to the level ofepoch for the Paleogene (Loeblich et al. 1968), because the“standard” ebridian biostratigraphy has only been establishedfor the Neogene (Locker and Martini 1986; Ernissee andMcCartney 1993) except for a single study of the Eocene andOligocene in the Southern Ocean (Bohaty and Harwood 2000).Consequently, the highly abundant and diversified occurrences

of ebridians in the ACEX samples are very important. It was ex-pected that the continuous Eocene sediment core samples fromthe Arctic Ocean obtained by the IODP Expedition 302 wouldbe able to improve the ebridian taxonomy and biostratigraphy.For this reason, this paper focuses on the ebridian taxonomy inthe ACEX cores.

MATERIALS AND METHODS

Siliceous sediments were retrieved from Sites M0002 andM0004 on the Lomonosov Ridge in the central Arctic Ocean bythe ACEX IODP Expedition 302 in summer 2004 (text-fig. 1;Table 1). In the Lithologic Units of the ACEX cores, the studiedsamples from Hole M2A represent Lithologic Unit 1/6 and theupper part of Unit 2, whereas the samples from Hole M4Arepre-sent mainly the lower part of the Lithologic Unit 2 (text-fig. 2).By combining the available samples from both sites it is possi-ble to study the Eocene siliceous fossiliferous section as onecontinuous sequence. The samples and methods for this studyare the same as those for the silicoflagellate study by Onoderaand Takahashi (in this volume) and are described below.

Sample preparation and counts

A total of 122 core-sediment and 29 core catcher samples fromHoles M2A and M4A were quantitatively processed in order todetermine the abundances of ebridian species. For biostrati-graphy and paleoceanographic reconstruction, samples wereusually taken at 20cm intervals in each section. The sampleswere freeze dried, measured for dry weight, and then treatedwith hydrogen peroxide, hydrochloric acid, and Calgon®

(mainly composed of sodium hexametaphosphate). In thechemical treatment process, ultra sonic was applied for 10 sec-onds in order to disaggregate consolidated clay particles. Afteradequately diluting the acid and other chemicals by decantationseveral times, the remaining sample material was sievedthrough a 45µm mesh, and then both fractions were filteredthrough 0.45µm nominal pore size membrane filters. The fil-tered volume of the fine fraction is 1/20 of total volume of thematerial. Dried membrane filters were mounted with Canadabalsam onto glass slides.

micropaleontology, vol. 55, nos. 2-3, pp. 187-208, text-figures 1-2, plates 1-7, tables 1-2, appendix 1, 2009 187

TAXONOMY

The ebridian species in the ACEX samples belong to 26 taxa.These taxa are described or discussed in alphabetical order.Their morphological terminologies are mainly based onDeflandre (1934).

Class Ebriophyceae Loeblich III, 1970Order EBRIALES, Honigberg et al. 1964Genus Ammodochium Hovasse 1932c

Ammodochium complexum Dumitrica and Perch-Nielsen 1976Plate 1, figure 1

Ammodochium complexum Dumitrica & Perch-Nielsen, in PERCH-NIELSEN, 1976, p. 152, pl. 8, figs. 15, 16; pl. 10, fig. 11.

Ammodochium fletcheri Ling 1985Plate 1, figures 2-9

Ammodochium fletcheri LING, 1985a, p. 85, pl. 11, figs. 17-20 (not pl.13, fig. 5).

Remarks: In this species, the proclades and opisthoclades arisefrom the bifurcated end of the actins. Ammodochium complex-um and A. speciosum Deflandre are similar to this taxon, but A.fletcheri has no mesoclades (Ling 1985a). In the double skele-tons, two individuals have in common a proclade andopisthoclade skeleton set beside the other flipped skeleton.

Ammodochium sp. cf. A. fletcheri Ling 1985Plate 1, figure 10

cf. Ammodochium fletcheri LING 1985a, p. 85, pl. 11, figs. 17-20 (notpl. 13, fig. 5).

Remarks: The pore member and alignment on the pro- andopisthoclades differ from those of the typical species. It is pos-sible that this specimen belongs to a new species.

Ammodochium lomonosovense, Onodera and Takahashi sp. nov.

Plate 1, figures 11, 12; Plate 2, figures 1-5, 6?; Plate 4, figure 10

Ammodochium fletcheri LING 1985a, pl. 13, fig. 5 (only).

Derivation of Name: The specific name lomonosovense is de-rived from the Lomonosov Ridge of the central Arctic Ocean,where IODP Expedition 302 drilled and cored the sampleswhich contain the present taxon.

Holotype: Plate 1, figure 11a, b, Sample IODP302-M2A-61X-2, 76-78cm, slide MPC-02687 (Micropaleontology Col-lection, National Science Museum, Tokyo), England finderK21/3.

Type locality: IODP302 Site M0002 Hole A, 264.76-264.78mbsf, Lomonosov Ridge, central Arctic Ocean.

Description: Skeleton ovoid in dorsal-ventral view with tworings of different diameters. Each bifurcated proclade andopisthoclade with three large pores of which one, in both theproclade or opisthoclade, is located near the distal end of theactine, and two are collaterally located on the ring, at the distalend of the clades. Anterior and posterior synclade very broadwith three pairs of pores, each pair located at the connection be-tween the proclades and opisthoclades and the anterior and pos-terior synclades, respectively. In highly silicified species theposterior synclades are so broad that their inner borders reachthe core of the triactine. In this case in lateral view, the SEM andLM images (Pl. 2, Figs. 2 and 3) show a wide central pore (be-tween the triactine spicule and the anterior synclade) borderedby eight pores. Of these pores two pairs are on the synclades andtwo pairs on the proclades and opithiclades respectively.

Dimensions: Length 20-33µm; width 18-33µm [N = 25].

Occurrence: From Samples M4A-15X-CC, 24-26cm to M2A-53X-1, 36-38cm. This taxon usually co-occurs with A. fletcheriand the silicoflagellate Dictyocha arctios.

Remarks: This species is similar to the holotype of Ammo-dochium complexum, from which it differs in having no porebetween the mesoclades and the ends of actins and in having aheavily silicified skeleton. It differs from A. novum Perch-Niel-sen by the absence of the extra pore between the proclade andopisthoclade.

191

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

TABLE 2Mean abundance of ebridian taxa in each ebridian assemblage group in this study. The symbol “+” represents the mean abundance of <1% in totalebridians.

Ammodochium rectangulare (Schulz) Deflandre 1933Plate 2, figures 7-12

Ebria antiqua rectangularis SCHULZ 1928, p. 274, figs. 72a-72d.Ammodochium prismaticum HOVASSE 1932a, p. 121, figs. 2a-2d.Ammodochium rectangulare (Schulz) DEFLANDRE 1933, p. 517-518,figs. 5-7.

Ammodochium speciosum Deflandre 1934Plate 2, figure 14

Ammodochium speciosum DEFLANDRE 1934, p. 92-94, figs. 37, 38.

Remarks: The skeleton of this species has one large pore in eachproclade and opisthoclade, and six small pores, framed byproclade, opisthoclade, and mesoclade in the middle of the skel-eton.

Ammodochium sp. 1

Plate 2, figure 13

Remarks: The proclades of this species bifurcate twice givingrise to three pores: one is on the proclade and two at the contactbetween proclade and two synclades. The posterior half of thisspecies resembles A. rectangulare and the anterior half struc-ture resembles a half of A. complexumDumitrica & Perch-Niel-sen. This taxon is rare in the lower part of Lithologic Unit 2.

Ammodochium sp. 2

Plate 2, figure 15

Remarks: This taxon resembles Ammodochium complexum inthe general structure, but differs from it in the absence of the

two lateral pores. The rare occurrence of this taxon was re-corded in Lithologic Unit 2 in the Core 302-M4A.

Ammodochium sp. 3

Plate 2, figures 16, 17

Remarks: The pro- and opisthoclade look like a wall rather thanbar structure. The forms of the pores are different from one an-other. This rare taxon was observed in Lithologic Unit 2.

Genus Ebriopsis Hovasse, 1932a

Ebriopsis crenulata Hovasse, 1932

Plate 3, figure 1

Ebria antiqua SCHULTZ 1928, p. 272, (in part).Ebriopsis crenulata HOVASSE 1932b, p. 281, fig. 4.

Remarks: This taxon was previously reported from upperEocene and the Oligocene sediments (Schultz 1928; Hovasse,1932b; Perch-Nielsen, 1976). However, this taxon is usuallyobserved in this study in Cores 302-M4A-8X, 9X, and 10X ofearly middle Eocene age.

Genus Falsebria Deflandre, 1951

Falsebria spp.

Plate 3, figures 2-4

Falsebria ambiguaDEFLANDRE 1951, p. 33, 73, figs. 88, 89, 100, 101.“Falsebria” sp. in PERCH-NIELSEN 1976, p. 153, pl. 10, figs. 1-10.

Remarks: The forms of the simple Falsebria skeleton definedby Deflandre (1951) are constituted by the triaene, actins,

192

Jonaotaro Onodera and Kozo Takahashi: Middle Eocene ebridians from the central Arctic Basin

PLATE 1Middle Eocene ebridians. All scale bars = 10µm.

1 Ammodochium complexum Dumitrica and Perch-Nielsen, Sample IODP302-M4A-4X-CC, 0-3cm,

2-9 Ammodochium fletcheri Ling 2-7, 8 (Double skele-ton), (2-5: IODP302-M2A-61X-CC, 0-1cm; 6:IODP302-M2A-61X-2, 36-38cm; 7: IODP302-M4A-6X-1, 36-38cm; 8: IODP302-M2A-58X-2,96-98cm; 9: IODP302-M2A-61X-1, 56-58cm),

10 Ammodochium sp. cf. fletcheri Ling, IODP302-M2A-58X-4, 56-58cm,

11,12 Ammodochium lomonosovense, sp. nov., (11(Holotype): IODP302-M2A-61X-2, 76-78cm, 12:IODP302-M2A-59X-2, 136-138cm).

micropaleontology, vol. 55, nos. 2-3, 2009 193

Jonaotaro Onodera and Kozo Takahashi Plate 1

rhabde, and rarely an incomplete proclade or synclade. Theseforms are considered as early ontogenic stages of the ebridians(Perch-Nielsen, 1976; Tappan 1980).

Genus Haplohermesinum Hovasse, 1943

Haplohermesinum cornuta (Dumitrica and Perch-Nielsen) Locker1996Plate 3, figures 5-11

Ebriopsis cornuta Dumitrica and Perch-Nielsen, in PERCH-NIELSEN1975, p. 152, pl. 8, figs. 15, 16; pl. 10, fig. 11; LING1985, p. 85, pl. 11,fig. 24, pl. 13, fig. 4.

Haplohermesinum cornuta (Dumitrica and Perch-Nielsen) LOCKER1996, p. 114, pl. 5, fig. 19.

Remarks: The hypersilicified skeleton has the external silicarods or silica wall formed around the original skeletal structurein the lorica development process. The abundance of the skele-tons with lorica was 5% of all skeletons of Ebriopsis conuta .

Genus Hermesinella Deflandre 1934

Hermesinella transversa Deflandre 1934Plate 3, figures 12-16

Hermesinella transversa DEFLANDRE 1934, p. 82, 83, figs.14-17.

Hermesinella schulzii (Hovasse) Locker and Martini 1989Plate 4, figures 1-3

Hermesinum schulzii HOVASSE 1932b, p.125.Hermesinella schulzii (Hovasse) LOCKER andMARTINI 1989, p. 572,pl. 7, fig. 8.

Remarks: The species is previously known to occur in the Mio-cene (Loeblich et al. 1968). However, this species in this studyis sometimes observed throughout Lithologic Units 2 and 1/6(Appendix 1). It may suggest the extension of occurrence age orthe rework.

Genus Hermesinopsis Deflandre, 1934

Hermesinopsis valida (Deflandre) Locker 1996Plate 4, figures 4-6

Parebria valida DEFLANDRE 1934, p. 91, figs. 33-36.Haplohermesinum validum (Deflandre) HOVASSE 1944, p. 68.Ebriopsis valida (Deflandre) DEFLANDRE 1950, p. 1683.Hermesinopsis valida (Deflandre)LOCKER1996, p. 114, pl. 5, fig. 25.

Genus Hermesinum Zacharias 1906

Hermesinum sp.

Plate 4, figure 7

Remarks: This taxon with lorica occurs in the coarse fraction ofSamples 302-M4A-10X-1 and 10X-2.

Genus Parebriopsis Hovasse, 1932c

Parebriopsis symmetrica Dumitrica and Perch-Nielsen 1976Plate 4, figure 8

Parebriopsis symmetrica Dumitrica and Perch-Nielsen in PERCH-NIELSEN 1976, p. 153, pl. 10, figs. 10, 14.

194



1-5,6? (6: Double skeleton?). Ammodochium lomonoso-vense, sp. nov., (1: IODP302-M4A-4X-1, 0-3cm; 2, 6:IODP302-M2A-61X-CC; 3, 5: IODP302-M2A-59X-2, 136-138cm; 4: IODP302-M4A-6X-1,36-38cm),

7-12 (11, 12: double skeleton). Ammodochium rect-angulare (Schulz) Deflandre, (7: IODP302-M2A-48X-CC, 4-6cm; 8: IODP302-M2A-53X-1,36-38cm; 9, 10: IODP302-M2A-48X-4, 14-16cm;11: IODP302-M2A-48X-CC, 4-6cm; 12:IODP302-M2A-53X-2, 14-16cm),

13 Ammodochium sp. 1, IODP302-M2A-61X-2,76-78cm,

14 Ammodochium speciosum Deflandre, IODP302-M2A-49X-4, 14-16cm,

15 Ammodochium sp. 2, IODP302-M4A-11X-3,128-130cm,

16,17 Ammodochium sp. 3, IODP302-M2A-48X-2,14-16cm.

Remarks: The occurrence of this taxon is very rare. This taxonwas common in the Eocene Norwegian Sea sediments(Perch-Nielsen 1976).

Genus Polyebriopsis Hovasse, 1932c

Polyebriopsis sp.

Plate 4, figure 9

Genus Pseudammodochium Hovasse, 1932c

Pseudammodochium dictyoides Hovasse 1932Plate 5, figures 1-10

PseudammodochiumdictyoidesHOVASSE 1932c, p. 463, figs. 12-15.Pseudammodochium sp. in PERCH-NIELSEN 1976, p. 154, pl. 6, figs.17-20.

Remarks: In the ACEX samples, the pores framed by the net-work of the skeleton are usually fine compared to those of theholotype. The skeletons with coarser pores were rare comparedto those having fine pores. The specimens with small pores re-semble those of Pseudammodochium sp. in Perch-Nielsen(1976).

Pseudammodochium eximium Deflandre 1951Plate 5, figures 11, 12

Pseudammodochium eximiumDEFLANDRE 1951, p. 56, 80, fig. 213.

Remarks: This species with ovoidal outline differs fromPseudammodochium dictyoides in having almost the same api-cal and antapical ring diameters.

Pseudammodochium karyon, Onodera and Takahashi sp. nov.


Derivation of Name: The specific name karyon was derivedfrom the Greek word (neuter) meaning walnut.

Holotype: Plate 6, figure 3, sample IODP-302-M2A-49X-2,136-138cm, slide MPC-02688 (Micropaleontology Collection,National Science Museum, Tokyo), England finder J28/4.

Type locality: IODP-302 Site M0002 Hole A, 211.51-211.53mbsf, Lomonosov Ridge in the central Arctic Ocean

Description: The outline is ovoid in lateral view. The ring diam-eter of one end is larger than that of the other end. The outline inapical view is nearly triangular with rounded corners. Actinesbifurcated in horizontal plane, their ends reaching to therounded corners. Clades, arising from the distal ends of actines,represent the scaffolding on which the skeletal wall is built.Pores regularly arranged.

Dimensions: length 27-35µm; width 24-33µm [N = 30].

Occurrence: Cores M2A-50X to 48X with the abundances of<30% of all ebridians.

Remarks: This taxon is distinguished from Pseudammodochiumdictyoides by its more triangular outline in axial view, slightlylarger size than the latter, and regularly arranged pores.

Pseudammodochium sp. cf. karyon, Onodera and Takahashi sp.

nov.

Plate 6, figures 4, 5

196



1 Ebriopsis crenulata Hovasse, IODP302-M4A-4X-1,0-3cm,

2-4 Falsebria spp., IODP302-M4A-4X-CC, 0-3cm,

5-11 Haplohermesinum cornuta (Dumitrica and Perch-Nielsen) Locker, (5: IODP302-M2A-58X-1,36-38cm; 6: IODP302-M2A-48X-CC, 4-6cm; 7:IODP302-M4A-4X-1, 0-3cm; 8: IODP302-M2A-

49X-4, 14-16cm; 9, 11: IODP302-M2A-48X-4,14-16cm; 10: IODP302-M2A-48X-4, 14-16cm),

12-16 Hermesinella transversa Deflandre, (12: IODP302-M4A-6X-1, 36-38cm; 13: IODP302-M4A-4X-1,0-3cm; 14: IODP302-M2A-58X-1, 36-38cm; 15:IODP302-M2A-59X-2, 136-138cm; 16: IODP302-M2A-61X-2, 76-78cm).

Remarks: It differs from Pseudammodochium karyon by the ab-sence of two pores on the crest between proclade andopisthoclade.

Pseudammodochium robustum Deflandre 1934Plate 5, figures 13-14

Pseudammodochium robustum DEFLANDRE 1934, p. 94, 95, figs.39-42.

Remarks: In the ACEX samples, this taxon usually occurred asdouble skeletons.

Pseudammodochium psichion Onodera and Takahashi sp. nov.


Derivation of Name: From psichion, is Greek word (neuter)meaning grain or small drop.

Holotype: Plate 6, figure 8, sample IODP-302-M4A-11X-1,8-10cm, slide MPC-02689 (Micropaleontology Collection, Na-tional Science Museum, Tokyo), England finder O22/1.

Type locality: IODP Exp. 302 Site M0004 Hole A,297.38-297.40 mbsf, Lomonosov Ridge in the central ArcticOcean

Description: Skeleton small, ovoid or nearly circular in lateralview, triangular with rounded corners in axial view. The sidesof the triangle are concave. Skeleton consisting of essentially asiliceous wall, probably due to heavy silicification. The wall isthick with small pores.

Dimensions: length 19-28µm; width 18-26µm [N = 20].

Occurrence: Constant occurrence in Lithologic Unit 2 withabundances below 10%.

Remarks: This species differs from other Pseudammodochiumspecies in that the proclades and opisthoclades are relativelybroad, and the pores are scarce and small. It is smaller than otherebridian species in the assemblage.

Pseudammodochium sp. 1

Plate 6, figure 9

Remarks: This species resembles Pseudammodochium karyon,but is distinguished from the latter by smaller and denser pores.This taxon is very rare in Unit 2 and the lower part of Unit 1/6.

Pseudammodochium sp. 2

Plate 4, figure 10

Remarks: In the lateral view, relatively large elliptic pores areobserved analogous to those in Ammodochium lomonosovense.However, the number of pores is larger than that of A.lomonosovense. The denser arrangement of pores are character-istic for the genus Pseudammodochium in contrast with that ofAmmodochium. The pore arrangement is different from that ofP. dictyoides and P. karyon. This taxon was rarely observed inLithologic Unit 2.

Genus Spongebria Deflandre, 1950

Spongebria marthae Deflandre 1950Plate 6, figures 9-11

Spongebria marthae DEFLANDRE 1950, p. 159, figs. 10, 11.

198



1-3 Hermesinella schulzii (Hovasse) Locker and Martini,(1: IODP302-M2A-61X-2, 76-78cm; 2: IODP302-M2A-61X-CC, 0-1cm; 3: IODP302-M4A-6X-1,14-16cm),

4-6 Hermesinopsis valida (Deflandre) Locker, (4:IODP302-M2A-53X-4, 36-38cm; 5: IODP302-M4A-4X-1, 0-3cm; 6: IODP302-M2A-61X-1,56-58cm),

7 Hermesinum sp. with lorica, IODP302-M4A-10X-2,56-58cm,

8 Parebriopsis symmetrica Dumitrica and Perch-Niel-sen, IODP302-M2A-48X-2, 14-16cm,

9 Polyebriopsis sp., IODP302-M2A-54X-CC, 5-7cm.

10 Double skeleton of Ammodochium lomonosovense,IODP302-M2A-59X-2, 136-138cm.

Remarks: In this species each face of the triode center has a tri-angular button with rough surface giving an impression of“sponge” structure by LM observation. Some specimens showthat the actines may be connected by synclades, a fact illus-trated also by Deflandre (1950).

ACKNOWLEDGMENTS

We thank the co-chief scientists Professor Jan Backman andProfessor Kate Moran, who brought the ACEX cruise to fru-ition, and the ACEX scientists together with the captains andcrew of the IODP Expedition 302 ACEX for their assistance invarious phases. We thank Prof. Dimitrios Zafiropoulos of theAmerican University of Athens who assisted us with the newtaxonomic names. Drs. Paulian Dumitrica and Katharina vonSalis Perch-Nielsen significantly improved this manuscript aspre-reviewers, and their input gratefully appreciated. The SEMphotography was performed using a Shimazu SS-550 at theCenter of Advanced Instrumental Analysis, Kyushu University.This research was partially supported by a JSPS Research Fel-lowship to JO as well as JSPS B Project No. 17310009, JSPSB2 No. 10480128, B1 No. 13440152, and B2 No. 15310001 toKT. A part of this research has been supported by Prof. TatsuroMatsumoto Scholarship Funds of the Kyushu University.

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1-10 (6-10: double skeleton). Pseudammodochiumdictyoides Hovasse, (1, 6, 9, 10: IODP302-M2A-49X-2, 14-16cm; 2: IODP302-61X-CC, 0-1cm;3: IODP302-M2A-53X-1, 36-38cm; 4: IODP302-M2A-48X-CC, 4-6cm; 5: IODP302-M4A-6X-1,36-38cm; 7: IODP302-M2A-53X-1, 36-38cm; 8:IODP302-M2A-49X-4, 14-16cm),

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202



1-3 Pseudammodochium karyon , sp . nov. , (1:IODP302-M2A-48X-2, 14-16cm; 2: IODP302-M2A-48X-4, 14-16cm; 3 (Holotype): IODP302-M2A-49X-2, 136-138cm),

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M2A-59X-2, 136-138cm; 8 (Holotype): IODP302-M4A-11X-1, 8-10cm),

9 Pseudammodochium sp. 1, IODP302-M2A-48X-CC,4-6cm,

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204



1-8 Ebridian gen. et. sp. indet. sp. 1 (1: IODP302-M4A-4X-1, 0-3cm; 2: IODP302-M2A-48X-4,14-16cm; 3-5, 7, 8: IODP302-M2A-48X-4, 14-16cm;6: Sample 302-M2A-48X-CC, 4-6cm),

9 Ebridian gen. et. sp. indet. sp. 2, Sample 302-M2A-48X-4, 14-16cm,

10-12 Ebridian gen. et. sp. indet. sp. 3, (10: IODP302-M2A-48X-CC, 4-6cm; 11: IODP30-4X-1, 4-6cm).

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