APPENDIX A
The systematic paleontology section includes taxonomic discussion of key taxa, the description of one new genus (Mattiolia furva) and 13 new species (Zeugrhabdotus clarus, Zeugrhabdotus petrizzoae, Helicolithus leckiei, Rhagodiscus amplus, Rhagodiscus robustus, Rhagodiscus sageri, Rhagodiscus adinfinitus, Tubodiscus bellii, Tubodiscus frankiae, Gartnerago ponticula, Haqius peltatus, Mattiolia furva, and Kokia stellata). The taxonomy follows the classification and organization of Bown and Young (1997) and Bown et al. (1998). Only bibliographic references not included in Perch-Nielsen (1985) and Bown (1998) are included in the reference list. A full taxonomic list of species cited in this paper follows in
"Appendix B." Descriptive terminology follows the guidelines of Young et al. (1997), and the following abbreviations are used in taxonomic descriptions: LM = light microscope, XPL = cross-polarized light, PC = phase-contrast illumination. Holotype dimension are given in parentheses. The taxa are illustrated in Plates P1–P13.
Family Chiastozygaceae Rood et al., 1973, emend. Varol and Girgis, 1994
Zeugrhabdotus clarus sp. nov.
Derivation of name: From clarus, meaning bright, referring to the birefringent inner cycle that distinguishes this coccolith.
Diagnosis: Bicyclic murolith with a prominent bright, inner-rim cycle (LM XPL) and a central area spanned by a single bar that tapers at both ends. The two rim cycles are comparable in width, but the inner cycle may be broader and is usually complete around the inner edge of the rim. Strongly curved extinction lines cross the bright inner cycle.
Differentiation: Closest in morphology to Zeugrhabdotus trivectis Bergen, 1994, but Z. clarus has a plainer, more simply constructed bar. It is also comparable to the rim morphologies seen in the genera Placozygus and Eiffellithus.
Dimensions: length = 4.0–5.5 (5.1) µm; width = 2.5–3.6 (3.6) µm.
Holotype: Pl. P1, fig. 34 (figs. 34–36 are the same specimen).
Paratypes: Pl. P1, figs. 38, 41.
Type locality: ODP Leg 198 Hole 1207B, Shatsky Rise, northwest Pacific.
Type level: upper Albian, Sample 198-1207B-29R-CC (Subzone NC9b).
Range: lower Albian–lower Cenomanian (Subzone NC8a–Zone UC1). Found in all mid-Cretaceous Shatsky Rise sections and also in the Albian of southern France (pers. observ.).
Zeugrhabdotus embergeri (Noël, 1958) Perch-Nielsen, 1984
Remarks: A great variety of morphologies are classified within this species concept, most obviously in size range (5–15 µm) but also bar and spine morphology. The species name is used herein for bicyclic loxoliths possessing a broad, disjunct, birefringent, simply constructed transverse bar that bears a spine. The spine clearly divides the bar into two lateral parts.
The consistently expressed bicyclicity in this species group perhaps warrants separate generic status, as they can be clearly distinguished from the broad range of zeugrhabdotid coccoliths that range through the Cretaceous. However, this group remains poorly understood in terms of phylogeny, and therefore higher taxonomy, and we prefer to continue with the use of Zeugrhabdotus as a broad generic grouping until further progress is made. The genus Gorkaea Varol and Girgis, 1994, includes bicyclic morphologies but has a "very narrow" outer cycle rather than the near-equal width cycles seen in the embergeri group. In this study, smaller embergeri coccoliths (<6 µm) were logged as cf. Z. embergeri (Pl. P2, figs. 2–6) and forms with very broad spines as cf. Z. kerguelenensis (Pl. P2, figs. 10–12).
Range: Upper Jurassic–Cretaceous/Tertiary boundary.
Zeugrhabdotus erectus (Deflandre in Deflandre and Fert, 1954)
Reinhardt, 1965
Remarks: Used here for unicyclic loxoliths with a disjunct, birefringent, simply constructed transverse bar that bears a spine. The spine is marked by a black dot in XPL.
A wide range of zeugrhabdotid morphologies occur through the Jurassic/Cretaceous boundary interval, and the differentiation between Z. erectus and Z. embergeri has been much discussed (see review in Bralower et al., 1989). The definition adopted here, when strictly applied, results in a Berriasian last occurrence for Z. erectus, and they are only frequently present in the lowermost two nannofossiliferous cores of Hole 1213B (Cores 198-1213B-26R and 27R; lower Berriasian).
Range: Pliensbachian–?Berriasian; lower Berriasian (Zones NK1–NK2a) in Hole 1213B.
Zeugrhabdotus petrizzoae sp. nov.
Derivation of name: Named for Maria Rose Petrizzo, micropaleontologist and ODP 198 shipboard scientist.
Diagnosis: Medium-sized unicyclic murolith with a central area spanned by a broad, disjunct, transverse bar. The bar is usually brighter than the rim in LM XPL and formed from two plain blocks divided by a median suture; the two blocks are offset at each end of the bar.
Differentiation: The blocks making up the bar are brighter and blockier than those of Zeugrhabdotus diplogrammus and offset at their ends.
Dimensions: length = 5.3 µm; width = 3.8 µm.
Holotype: Pl. P2, fig. 34 (figs. 34–36 are the same specimen).
Paratype: Pl. P2, fig. 37 (fig. 38 is the same specimen).
Type locality: ODP Leg 198 Hole 1213B, Shatsky Rise, northwest Pacific.
Type level: lower Albian, Sample 198-1213B-4R-1, 48 cm (Subzones NC8a/NC8b).
Range: Albian (Subzones NC8a/NC8b) at Site 1213.
Family Eiffellithaceae Reinhardt, 1965
Helicolithus leckiei sp. nov.
Pl. P3, figs. 40–42; Pl.
P4, figs. 1, 2
Derivation of name: Named for Mark Leckie, micropaleontologist and ODP 198 shipboard scientist.
Diagnosis: Small, bicyclic murolith with a prominent bright, inner cycle (LM XPL) and central area spanned by a birefringent, diagonal cross. The two rim cycles are comparable in width but the inner cycle may be broader. The junction between the two cycles is usually distinctly scalloped.
Remarks: Three Cretaceous genera incorporate bicyclic, murolith coccoliths with diagonal crosses, Eiffellithus, Tegumentum, and Helicolithus, and the relationships within and between them is presently poorly understood. This new species is included within Helicolithus, based on the nature of the cross bars, which are straight and simply constructed.
Differentiation: Close in morphology to Corollithion? madagascarensis Perch-Nielsen, 1973, but the latter has a delicate cross, does not show the distinctive scalloped cycle junction, and has a rim that shows Corollithion-like characteristics (i.e., a protolith-like rim) (see Bown, 1987; Young et al., 1997). In addition, it has only been recorded from much younger strata (i.e., Maastrichtian). It also resembles Ellipsochiastus quadriserratus Worsley, 1971, but the latter is larger with narrower bars and more open central area.
Dimensions: length = 3.4 (3.7) µm; width = 2.4 (2.5) µm.
Holotype: Pl. P3, fig. 41 (fig. 40 is the same specimen).
Paratype: Pl. P3, fig. 42.
Type locality: ODP Leg 198 Hole 1207B, Shatsky Rise, northwest Pacific.
Type level: upper Albian, Sample 198-1207B-28R-CC (Subzone NC10a).
Range: Aptian (Zone NC7)–Cenomanian (Zones UC3/UC4). Found in all mid-Cretaceous Shatsky Rise sections and also in the Albian of southern France (pers. observ.).
Family Rhagodiscaceae Hay, 1977
Rhagodiscus asper (Stradner, 1963) Reinhardt, 1967, Group
Pl. P4, figs. 7–42; Pl. P5, figs. 1–6
Remarks: Murolith (loxolith) coccoliths with a relatively broad central area spanned by a granular plate that may or may not bear a spine; the rim appears unicyclic in LM.
Considerable morphological variation is observed within this species concept, and this is somewhat reflected in the number of species names that have been applied to similar but poorly defined morphotypes that in many cases may be synonyms (e.g., Rhagodiscus reightonensis [Taylor, 1978] Watkins in Watkins and Bowdler 1984 [wider rim]; Rhagodiscus eboracencis Black, 1971 [no spine]; "Rhabdolithina" swinnertoni Black, 1971 [large spine]; and "Zygolithus" fenestratus Stover, 1966 [perforate plate]). A number of distinctive morphologies were observed in the mid-Cretaceous sediments of Shatsky Rise, and these are described below as three new species.
Rhagodiscus amplus sp. nov.
Derivation of name: From amplus, meaning large, and referring to the size of the coccoliths.
Diagnosis: Large (>8.0 µm) loxolith coccoliths with a wide central area (usually greater than twice as wide as the rim) that is spanned by a granular plate. A relatively large spine or spine base may or may not be present. The rim and plate usually show yellow interference colors under XPL.
Differentiation: Similar in general morphology to Rhagodiscus asper but distinguished by its larger size.
Dimensions: length = 9.8 µm; width = 7.2 µm.
Holotype: Pl. P4, fig. 13 (figs. 13–15 are the same specimen).
Paratype: Pl. P4, fig. 17.
Type locality: ODP Leg 198 Hole 1207B, Shatsky Rise, northwest Pacific.
Type level: Aptian, Sample 198-1207B-42R-CC (Zone NC7).
Range: Aptian (Zone NC6)–middle Albian (Subzone NC8b) at Sites 1207, 1213, and 1214.
Rhagodiscus robustus sp. nov.
Derivation of name: From robustus, meaning robust, and referring to the broad, blocky rim of this species.
Diagnosis: Large (>8.0 µm) loxolith coccoliths with a broad rim (usually as broad or broader than the central area) and a central area spanned by a granular plate; a relatively large spine or spine base is usually present. The broad and blocky rim shows yellow interference colors under XPL.
Differentiation: Distinguished from other rhagodiscids by its large size and relatively closed central area, with some specimens resembling the Jurassic coccolith species Crepidolithus crassus. The Albian "Crepidolithus" burwellensis Black, 1972 (holotype scanning electron micrograph [SEM] only), displays a Crepidolithus-like rim but is small (~4.0 µm) and has an open central area crossed by a transverse bar.
Dimensions: length = 8.7 µm; width = 6.7 µm.
Holotype: Pl. P4, fig. 22 (figs. 22–24 are the same specimen).
Paratypes: Pl. P4, figs. 20, 29, 33.
Type locality: ODP Leg 198 Hole 1214A, Shatsky Rise, northwest Pacific.
Type level: lower Albian, Sample 198-1214A-19R-1, 37 cm (Subzones NC8A/NC8B).
Range: Barremian (Zone NC5)–upper Albian (Subzone NC10a) at Sites 1207, 1213, and 1214.
Rhagodiscus sageri sp. nov.
Pl. P4, figs. 37–42; Pl. P5, figs. 1–6
Derivation of name: Named for Will Sager, paleomagnetist and ODP Leg 198 shipboard scientist.
Diagnosis: Loxolith coccoliths with a relatively broad central area spanned by a granular plate that incorporates a transverse, raised, bridgelike structure.
Differentiation: Similar in general morphology to Rhagodiscus asper but distinguished by the raised ridge/bridge of the central area plate.
Dimensions: length = 9.8 µm; width = 7.2 µm.
Holotype: Pl. P4, fig. 37 (figs. 37–40 are the same specimen).
Paratype: Pl. P5, fig. 1 (figs. 1–3 are the same specimen).
Type locality: ODP Leg 198 Hole 1207B, Shatsky Rise, northwest Pacific.
Type level: Aptian, Sample 198-1207B-39R-CC (Zone NC7).
Range: Hauterivian (Zone NC4)–Cenomanian (Zones UC3/UC4) at Sites 1207, 1208, 1212, 1213, and 1214.
Rhagodiscus adinfinitus sp. nov.
Derivation of name: From ad, meaning near or like, and referring to the similarity to the existing species Rhagodiscus infinitus.
Diagnosis: Medium-sized unicyclic loxolith coccoliths with a wide central area spanned by a butterfly-shaped bar with raised, birefringent edges.
Remarks: Specimens from the deepest nannofossiliferous core at Site 1213 (Core 198-1213B-27R) are slightly smaller and have less flaring bars than those higher in the hole. The raised edges of the bar make an angle of ~20°–25° with the transverse axis increasing to 40°–50° for specimens in higher cores. This may represent a shift in morphology toward the R. infinitus structure.
Differentiation: Comparable in general morphology to Rhagodiscus infinitus, with a central granular plate pierced by two large holes. However, R. infinitus has a plate that extends completely around the central area with distinct circular pores surrounded by raised, birefringent edges, whereas R. adinfinitus has only a broad, flaring bar (butterfly shaped) with raised edges that terminate against the inner edge of the rim.
Dimensions: length = 7.2 µm; width = 5.3 µm.
Holotype: Pl. P5, fig. 15 (fig. 16 is the same specimen).
Paratypes: Pl. P5, figs. 7, 18.
Type locality: ODP Leg 198 Hole 1213B, Shatsky Rise, northwest Pacific.
Type level: Berriasian, Sample 198-1213B-25R-1, 26 cm (Subzone NK2a).
Range: Berriasian (Zone NK1–Subzone NK2b) at Site 1213.
Rhagodiscus dekaenelii Bergen, 1994
Remarks: Distinctive, small rhagodiscids that have a birefringent spine/spine base that almost fills the central area. Used herein as a secondary marker species approximating the base of Zone NK3 in the absence of Calcicalathina oblongata and Tubodiscus verenae.
Range: lower Valanginian (lower Subzone NK3a)–lower Hauterivian (Subzone NC4b), according to Bergen (1994) and supported herein at Site 1213.
Family Stephanolithiaceae Black, 1968
Rotelapillus laffittei (Noël, 1957) Noël, 1973
Pl. P5, figs. 39–42; Pl. P6, figs. 1–9
Remarks: Circular muroliths with high walls, lateral rim spines, and central area spanned by six radial bars. This basic coccolith plan ranges throughout the Cretaceous with little change; however, a number of varieties were observed in the mid-Cretaceous material from Shatsky Rise. It is uncertain whether these morphotypes represent preservational differences or simply intraspecific variation, and until this can be better ascertained they are described here in informal nomenclature.
Rotelapillus laffittei (Noël, 1957) Noël, 1973, var. 1 (small)
Description: Small variety of R. laffittei with rim diameter <5.0 µm.
Range: upper Tithonian–Cretaceous/Tertiary boundary (Bown et al., 1998).
Rotelapillus laffittei (Noël, 1957) Noël, 1973, var. 2 (petaloid)
Description: Small variety of R. laffittei with a distal rim cycle that is strongly flaring and, at high focus, distinctly petaloid in outline.
Range: lower Aptian (Zone NC6)–Cenomanian (Zone UC4) at Site 1207.
Rotelapillus laffittei (Noël, 1957) Noël, 1973, var. 3 (large)
Description: Medium-sized variety of R. laffittei with rim diameter >5.0 µm.
Remarks: upper Hauterivian (Subzone NC4b)–lower Aptian (Zone NC6) at Sites 1207 and 1214.
Family Axopodorhabdaceae Bown and Young, 1987
Axopodorhabdus cylindratus (Noël, 1965) Wind and Wise
in Wise and Wind, 1977
Remarks: This species has not previously been recorded from the Early Cretaceous. It may have an extended stratigraphic range in the Pacific, or has simply not been identified due to the transitional nature of the lineage that gave rise to the typically Cretaceous species Axopodorhabdus dietzmannii. The latter is distinguished by a rather elongated rim with flattened sides (oblong shaped) (Pl. P6, figs. 23, 24).
Range: upper Pliensbachian–upper Tithonian (Bown and Cooper, 1998); Berriasian–upper Valanginian (Zone NK1–Subzone NK3b) at Site 1213.
Hexapodorhabdus cuvillieri Noël, 1965
Remarks: Not previously recorded from the Early Cretaceous and found here in only one Berriasian sample from Site 1213 (Sample 198-1213B-24R-1, 37 cm).
Range: upper Bajocian–upper Kimmeridgian (Bown and Cooper, 1998); Berriasian (Subzone NK2a) at Site 1213.
Podorhabdus grassei Noël, 1965
Remarks: Not previously recorded from the Early Cretaceous but found here consistently in the Berriasian of Site 1213 (Zone NK1–Subzone NK2a).
Range: lower Bajocian–lower Tithonian (Bown and Cooper, 1998); present in the upper Tithonian according to de Kaenel and Bergen (1996); Berriasian (Zone NK1–Subzone NK2a) at Site 1213.
Family Biscutaceae Black, 1971
Biscutum constans (Górka, 1957) Black in Black and Barnes, 1959 (large)
Remarks: Large B. constans coccoliths (>5 µm) become conspicuous in the Albian and are shown on range charts as B. constans (large) (Pl. P6, fig. 38). These are probably equivalent to the Biscutum "magnum" of Erba (1988) that were also first recorded in the middle Albian (Subzone NC9a).
Range: Albian (Zone NC8)–Cenomanian (Zone UC2) at Sites 1207, 1213, and 1214.
Biscutum dorsetensis (Varol and Girgis, 1994) Bown
in Bown and Cooper, 1998
Description: Circular to subcircular bicyclic Biscutum with a narrow central area and tall spine.
Range: upper Bathonian–Tithonian (Bown and Cooper, 1998); Berriasian–lower Valanginian (Zone NK1–Subzone NK3a) at Site 1213. Recorded for the first time in the Lower Cretaceous herein.
Crucibiscutum bosunensis Jeremiah, 2001
Range: upper Aptian (Jeremiah, 2001). Observed rarely in the uppermost Aptian–lowermost Albian (top Zone NC7–base Zone NC8) at Sites 1207 and 1214.
Family Cretarhabdaceae Thierstein, 1973
Cretarhabdus cf. C. conicus Bramlette and Martini, 1964
Remarks: The name Cretarhabdus conicus is used here for cretarhabdid coccoliths with a distinct central area axial cross and net (Pl. P7, figs. 7–9). Similar coccoliths with slightly narrower central areas and less prominent axial cross-bars were called Cretarhabdus cf. C. conicus. Possibly equivalent to "Miravetesina" ficula of Bralower and Bergen (1998, pl. 2, fig. 11).
Range: Not consistently differentiated in this study but recorded from the Aptian (Zones NC6–NC7) at Sites 1207 and 1214.
Flabellites oblongus (Bukry, 1969) Crux in Crux et al., 1982
Remarks: A significant size increase in this species is observed through the Aptian of the Shatsky mid-Cretaceous sections, with small sizes (3.5–5.0 µm) recorded in the lowermost Aptian (base Zone NC6) increasing to 7.0 µm at the top of Zone NC6, and reaching 10.0 µm by the lower Albian (Zone NC8).
Grantarhabdus bukryi Black, 1972
Remarks: Used here for medium-sized cretarhabdid coccoliths with unicyclic shield image and central area diagonal cross bars. The Albian holotype specimens have bars that make an angle of ~45° with the transverse axis of the coccolith; many of the earlier representatives included here have bars arranged at lower angles. Probably equivalent to Grantarhabdus meddii of many authors (e.g., Bown et al., 1998).
Range: ?Tithonian–Albian (de Kaenel and Bergen, 1996; Bown et al., 1998).
Grantarhabdus meddii Black, 1971
Remarks: Used here for cretarhabdid coccoliths with unicyclic shield image and central area diagonal cross bars that form a solid bar where they meet for around half of their length. They resemble both Speetonia colligata and Grantarhabdus bukryi but have distinctive cross-bar morphology.
Range: Uncertain, but Berriasian–lower Valanginian at Site 1213 (Zone NK1–Subzone NK3a).
Helenea Worsley, 1971, emend.
Emended Diagnosis: Elliptical to subcircular cretarhabdid coccoliths that in LM show a change in birefringence toward the edge of the shield/rim, creating a diffuse bicyclic image; the outer cycle is narrowest. The central area structures are dominated by primary cross bars rather than lateral bars or grills, although the former may be present. Both axial and diagonal cross structures occur. The bars often flare toward their ends.
Remarks: A degree of confusion has arisen due to the description of two identical genera, Helenea and Microstaurus, in the same year by Worsley (1971) and Black (1971), which, after recombination, include one shared species name for different coccoliths. The genus Microstaurus is regarded here as a junior synonym of Helenea, and Microstaurus quadratus Black, 1971, a junior synonym of Helenea staurolithina. Helenea quadratus (Worsley, 1971) is included in the genus here and is distinguished by coccoliths with diagonal cross bars.
Helenea chiastia Worsley, 1971, emend. Bralower et al., 1989
Remarks: Broadly elliptical to subcircular coccoliths with a narrow central area spanned by an axial cross that bears a distinctly blocky (square) short spine. The long axis of the central area is less than one-half of the coccolith length (Bralower et al., 1989).
Range: Tithonian–lower Turonian (Bown et al., 1998).
Helenea conus (Worsley, 1971) Bown and Rutledge in Bown et al., 1998
Remarks: Subcircular to broadly elliptical coccoliths with a central area spanned by a vaulted axial cross that bears a spine. The bars usually display a dark median line under XPL and flare at their ends. The vaulted nature of the central structure makes focusing on the cross bars difficult.
The LM appearance of the rim of this species is not particularly typical of Helenea, as it is larger and shows no clear outer cycle; however, the cross bars conform to the generic characteristics, hence its inclusion here.
Range: ?upper Berriasian–?lower Barremian (Bown et al., 1998). Berriasian (Subzone NK2a)–upper Valanginian (Subzone NK3b) at Site 1213.
Helenea quadrata (Worsley, 1971) Bown and Rutledge in Bown et al., 1998
Remarks: Small broadly elliptical cretarhabdid coccoliths with a central area spanned by diagonal cross bars. The bars may display median black lines under XPL.
Range: lower Berriasian (grandis Tethyan Ammonite Zone)–upper Hauterivian (inversum/ligatus Ammonite Zones) (Bown et al., 1998). Restricted to the Berriasian at Site 1213 (Zone NK1–Subzone NK2a).
Helenea staurolithina Worsley, 1971
Remarks: Normally to broadly elliptical coccoliths with a narrow central area spanned by an axial cross. The long axis of the central area is equal to or greater than one-half of the coccolith length (Bralower et al., 1989).
In the Site 1213 material a number of specimens that resembled small Cruciellipsis cuvillieri coccoliths were included in this species.
Range: Tithonian–Hauterivian (Bown et al., 1998). Berriasian (Zone NK1)–lower Hauterivian (Subzone NC4b) at Site 1213.
Remarks: Broadly elliptical placolith with relatively broad, moderately birefringent shields and an open central area.
Range: Aptian (Zone NC7)–lower Albian (lower Zone NC8) at Sites 1207 and 1214.
Remarks: Small cretarhabdid rims (<5.0 µm) with empty central areas, but which in some cases have remnant axial crosses. They are relatively distinctive, being considerable smaller than most other cretarhabdid coccoliths, which are usually >6.0 µm.
Range: Not consistently logged in this study but lower Aptian (Zone NC6)–middle Albian (Subzone NC9a) at Site 1207.
Family Watznaueriaceae Rood et al., 1971
Cyclagelasphaera brezae Applegate and Bergen, 1988
Range: Berriasian (Zone NK1–Subzone NK2a) at Site 1213. Recorded from the Valanginian by Applegate and Bergen (1988).
Cyclagelasphaera jiangii Covington and Wise, 1987
Remarks: Medium-sized Cyclagelasphaera with an open central area, equivalent in width to that of the shield width. Covington and Wise (1987) described a small Cyclagelasphaera with an open central area spanned by radial bars, under SEM only. The rim to central area proportions are similar to those observed here (central area equivalent in width to that of the shield), although the central area bars have not been seen. Distinguished from other species of Cyclagelasphaera by the large central opening.
Dimensions: length = 4.3–6.5 µm
Range: Valanginian of the North Atlantic (Covington and Wise, 1987); Berriasian (Subzone NK2a)–upper Hauterivian (Subzone NC4b) at Sites 1213 and 1214.
Watznaueria cynthae Worsley, 1971
Remarks: Broadly elliptical Watznaueria coccoliths that have two variably developed central pores that pierce the inner cycle. These coccoliths resemble Watznaueria biporta Bukry, 1969, but are more subcircular in outline and do not routinely display clear pores.
Range: Berriasian (Subzone NK2a)–Albian (Zone NC8) at Sites 1207, 1213, and 1214.
Watznaueria sp. 1 (?Watznaueria bayackii Worsley, 1971)
Remarks: Birefringent placolith coccoliths with closed central area. Watznaueria-like in appearance but appear flat and have relatively large, visible rim elements. They resemble Watznaueria bayackii Worsley, 1971, but the three holotype images provided are not good enough to allow unequivocal identification. They may represent disaggregated, isolated shields of Watznaueria barnesiae.
Remarks: Placoliths with relatively narrow shields and broad central area (central area is greater than twice the width of the rim). The LM XPL image of the rim is similar to that of Watznaueria, although the rim to central area proportions are not typical.
Range: Albian (Zone NC8)–Cenomanian (Zone UC4) at Sites 1207, 1208, 1212, and 1214.
Family Tubodiscaceae Bown and Rutledge in Bown and Young, 1997
Remarks: The lowermost Cretaceous assemblages of Site 1213 yield a large number of tubodiscid-like coccoliths that do not easily conform to currently described species morphologies (Manivitella pemmatoidea, Tubodiscus burnettiae, Tubodiscus verenae, and Tubodiscus jurapelagicus). The morphotypes are difficult to systematically differentiate due to the lack of characters, essentially two variably broad, contrastingly birefringent cycles. Two new species are described here, but a number of images on Pl. P9 are retained in informal nomenclature.
Tubodiscus bellii sp. nov.
Derivation of name: Named for Ben Walsworth-Bell, Mesozoic nannopaleontologist.
Diagnosis: Bicyclic placolith with narrow shields and wide, open, central area. In LM XPL the two cycles have contrasting birefringence, the inner cycle being distinctly bright. The inner cycle is usually slightly narrower than the outer.
Differentiation: The shields and individual cycles are narrower than those of other tubodiscids.
Dimensions: length = 5.5–6.5 µm.
Holotype: Pl. P9, fig. 14 (figs. 14–17 are the same specimen).
Paratype: Pl. P9, fig. 19 (figs. 19–23 are the same specimen).
Type locality: ODP Leg 198 Site 1213, Shatsky Rise, northwest Pacific Ocean.
Type level: Berriasian, Sample 198-1213B-20R-1, 31 cm (Subzone NK2a).
Range: Berriasian (Zones NK1–Subzone NK2a) at Site 1213.
Tubodiscus frankiae sp. nov.
Derivation of name: Named for Tracy Frank, paleoceanographer and ODP 198 shipboard scientist.
Diagnosis: Bicyclic placolith with relatively broad shields and open central area. In LM XPL the two cycles have contrasting width and birefringence, the inner cycle being distinctly bright and narrow, the outer being broad and dark. The central area is usually slightly broader than the shield width.
Differentiation: The width contrast between the two rim cycles is greater than that seen in other tubodiscids. The shield morphology and LM appearance are similar to Sollasites coccoliths, but no central area structures have been observed.
Dimensions: length = 5.5–6.5 µm.
Holotype: Pl. P9, fig. 25 (figs. 25–28 are the same specimen).
Paratype: Pl. P9, fig. 34 (figs. 34 and 35 are the same specimen).
Type locality: ODP Leg 198 Site 1213, Shatsky Rise, northwest Pacific Ocean.
Type level: Berriasian, Sample 198-1213B-23R-1, 20 cm (Subzone NK2a).
Range: Berriasian (Subzone NK2a)–upper Hauterivian (Subzone NC4b) at Sites 1213 and 1214.
Tubodiscus cf. T. verenae Thierstein, 1973
Remarks: Single specimens in side view in Samples 198-1213B-19R-1, 10 cm, and 19R-1, 119–122 cm, showed T. verenae-like morphology (i.e., high, proximal collar). Their presence close to the first occurrence of Percivalia fenestrata (Subzone NK2a) conforms to the upper Berriasian first occurrence for this species reported by Bergen (1994).
Family Kamptneriaceae Bown and Hampton in Bown and Young, 1997
Gartnerago ponticula Bown and Hampton sp. nov.
Derivation of name: From ponticulus, meaning small bridge, and referring to the central structure that characterizes the coccoliths.
Diagnosis: Small- to medium-sized (usually <7.0 µm) Gartnerago species with an open central area spanned by a transverse, conjunct bar.
Differentiation: Similar in morphology to Gartnerago theta but smaller in size, has a relatively small, often diamond-shaped central area and a relatively broader inner rim cycle. The name Gartnerago nanum Thierstein, 1974, has previously been applied to these coccoliths (e.g., Crux, 1982; Burnett, 1998), but the holotype of the latter has a complete central area plate rather than a discrete bar.
Dimensions: length = 5.5–7.0 µm.
Holotype: Pl. P10, fig. 22 (fig. 23 is the same specimen).
Paratype: Pl. P10, fig. 24.
Type locality: ODP Leg 198 Site 1207, Shatsky Rise, northwest Pacific Ocean.
Type level: Cenomanian, Sample 198-1207B-20R-CC (Zone UC3/UC4).
Range: uppermost Albian (Zone UC0)–upper Cenomanian (Zone UC3/UC4) (Burnett in Gale et al., 1996; Burnett, 1998). Rare occurrences in the Cenomanian at Sites 1207 and 1213.
Gartnerago stenostaurion (Hill, 1976) Perch-Nielsen, 1984
Description: Small to large coccoliths characterized under LM XPL by a conspicuous, narrow, bright rim cycle and wide central area spanned by a plate. The plate is usually crossed by four radial extinction lines (two in the major axes of the coccolith ellipse and two diagonally orientated) and narrow, bright, barlike structures, which are longitudinal and near transverse (rotated by ~10°), and birefringent when the coccolith is at 45° to the polarizing directions.
Remarks: These coccoliths have an LM image that is much closer to that of Gartnerago than Broinsonia. The narrow, bright rim cycle is a unique feature of Gartnerago, and the dark central area plate is almost identical to those seen in Gartnerago segmentatum and Gartnerago obliquum. Small specimens of G. stenostaurion most closely resemble Crucicribrum anglicum Black, 1973 (? = Arkhangelskiella erratica Stover, 1966), a close ally of Gartnerago with a distinctly perforate central area plate. The relationships between these early Gartnerago taxa are not fully understood.
Range: uppermost Aptian–uppermost Albian (Burnett, 1998; Bown in Kennedy et al., 2000; Bown, 2001); mid-Albian (upper Zone NC8) to lower Cenomanian (Zone UC1/UC2) at Sites 1207, 1213, and 1214.
Heterococcoliths of uncertain affinity
Remarks: This genus comprises unicyclic placolith coccoliths with a narrow or closed central area and a characteristically dark gray (low birefringence) LM XPL image. These coccoliths are common and consistent components of the Shatsky Lower Cretaceous assemblages and show considerable variation in size. A new species is described below.
It should be noted that Worsley (1971) described the genus Esgia based on a specimen similar to Haqius circumradiatus. I have retained the use of Haqius, as it alone has consistently been used for coccoliths of this group. The nature of Worsley's Esgia junior holotype is unclear, but it may represent a transitional morphology between H. ellipticus and Haqius circumradiatus.
Haqius ellipticus Grün in Grün and Allemann, 1995, emend.
Emended diagnosis: Large (>7.0 µm) unicyclic placolith with a narrow or closed central area. Under LM XPL the shields appear gray and the numerous individual elements are usually visible. The proximal shield is significantly smaller than the distal and is often clearly distinguishable (Pl. P11, fig. 17).
The emendation is proposed in order to allow for the differentiation of the small species, Haqius peltatus, described below. The size chosen for differentiation is arbitrary, and a more appropriate figure may be forthcoming with further biometric analysis of Haqius populations. H. ellipticus coccoliths range in size from 7.0 to 14.0 µm in the Shatsky Rise material and are restricted to the Berriasian; the largest forms are particularly conspicuous.
Range: Upper Jurassic–Hauterivian/lower Barremian (Bralower et al., 1989; Bergen, 1994) but this range may include the smaller species, H. peltatus. Berriasian (Zone NK1–Subzone NK2b) at Site 1213.
Derivation of name: From pelta, a small shield, referring to the size and morphology of this placolith coccolith.
Diagnosis: Small (<6.5 µm) unicyclic placolith with a narrow or closed central area. Under LM XPL the shields appear gray and individual elements are usually visible. Some specimens possess small barlike structures that cross the narrow central area.
Differentiation: Differentiated from Haqius ellipticus by size and from Haqius circumradiatus by outline.
Dimensions: length = 3.0–6.5 µm; width = 2.4–4.5 µm.
Holotype: Pl. P11, fig. 5 (fig. 6 is the same specimen).
Paratypes: Pl. P11, fig. 8 (figs. 9 and 10 are the same specimen).
Type locality: ODP Leg 198 Site 1213, Shatsky Rise, northwest Pacific Ocean.
Type level: Berriasian, Sample 198-1213B-27R-1, 1 cm (Zone NK1).
Range: Berriasian (Zone NK1)–Albian (Subzone NC8a). Small elliptical Haqius coccoliths have not previously been reported from the Albian, and this may be a species that developed restricted paleobiogeographic distribution in the mid-Cretaceous.
Description/Remarks: Large coccoliths (>10 µm) with low birefringence, blocky, flaring rim, and open central area. Most closely resemble coccoliths of the Jurassic genus Calyculus, but they have not been recorded in sediments younger than Tithonian (de Kaenel and Bergen, 1996; Bown and Cooper, 1999).
Range: Recorded in a single Berriasian sample from Site 1213 (Sample 198-1213B-24R-1, 37 cm).
Type species: Mattiolia furva sp. nov.
Derivation of name: Named for Emanuela Mattioli, Mesozoic nannopaleontologist.
Diagnosis: Placoliths with a distinctly dark image under XPL. The type species has broadly elliptical shields and a narrow central area, filled with a broad plate/axial cross; the plate is also dark under XPL but is crossed by at least four extinction lines.
Differentiation: The new genus is proposed because the coccoliths are quite unlike any other Cretaceous taxa. Other Cretaceous placolith coccoliths appear dark under XPL (e.g., Haqius and Repagulum); however, the rim outline, rim to central area proportions, and central area structures are quite different in Mattiolia furva. Until SEM images are forthcoming we cannot comment further on the taxonomic affinities of the genus.
Derivation of name: From furvus, meaning dark, and referring to the appearance of this species under XPL.
Diagnosis: Medium-sized (~5.5 µm), broadly elliptical placoliths with a distinctly dark image under XPL and a central area equivalent in width to the shield. The central area is filled by a broad axial cross that may form a complete plate. The central area plate, like the shields, has a dark appearance under XPL but is crossed by at least four extinction lines, axially and diagonally orientated.
Differentiation: See remarks for the genus.
Dimensions: length = 5.1–5.9 µm; width = 4.1–4.9 µm
Holotype: Pl. P10, fig. 37 (fig. 38 is the same specimen).
Paratype: Pl. P10, fig. 42 (figs. 40–42 are the same specimen).
Type locality: ODP Leg 198 Site 1208, Shatsky Rise, northwest Pacific Ocean.
Type level: Albian, Sample 198-1208A-42X-CC (Subzones NC8c–NC9a).
Range: Albian (Subzones NC8a/NC8b–Zone NC9) at Sites 1208, 1213, and 1214.
Assipetra terebrodentarius (Applegate et al. in Covington and Wise, 1987) Rutledge and Bergen in Bergen, 1994
Description: Blocky, globular nannoliths formed from six or more complexly intergrown calcite blocks that are joined along broadly radial sutures; roughly circular in plan and rectangular in side view.
Remarks: Tremolada and Erba (2002) recognized considerable size variation within the species and proposed a division into two subspecies with the limit at 7.5 µm. Unfortunately, they renamed the larger morphotype, which was already represented by the original holotype of Applegate et al. in Covington and Wise, 1987 (holotype = 7.7 µm). We have emended the diagnosis of the subspecies here, raising the size limit between them to 8.0 µm. This represents a clearer cutoff point between the two morphotypes and brings the original species holotype into the smaller subspecies, thus avoiding the need for renaming.
Assipetra terebrodentarius (Applegate et al. in Covington and Wise, 1987) Rutledge and Bergen in Bergen, 1994, ssp. terebrodentarius
Description: Small- to medium-sized (<8.0 µm diameter) subspecies of A. terebrodentarius.
Dimensions: diameter = 4.0–7.6 µm.
Range: The first occurrence is usually considered to be upper Hauterivian (Bergen, 1994; Channell et al., 1995; Gardin et al., 2000) but is slightly earlier in this material, where its range overlaps with Cruciellipsis cuvillieri, in sediments assigned to upper Subzone NC4b. This range overlap has also been reported by Erba et al. (1999) and Lozar and Tremolada (2003). The upper range is uncertain but specimens have been observed as high as the Campanian (pers. observ.;
Lees and Bown, this volume; Lozar and Tremolada, 2003).
Assipetra terebrodentarius (Applegate et al. in Covington and Wise, 1987) Rutledge and Bergen in Bergen, 1994,
youngii Tremolada and Erba, 2002, emend.
Diagnosis: A large (>8.0 µm diameter) subspecies of A. terebrodentarius.
Remarks: A number of the specimens named Assipetra infracretacea larsonii by Tremolada and Erba (2002) are considered to be side views of A. terebrodentarius.
Range: Aptian, according to Tremolada and Erba (2002), and particularly abundant in sediments associated with OAE 1a. Recorded well into the Upper Cretaceous (Campanian: herein, pers. observ., and
Lees and Bown, this volume), but the last common and consistent occurrence may be toward the top of the Aptian.
Braarudosphaera africana Stradner, 1961
Remarks: Braarudosphaera was practically absent in the Shatsky Rise sections; however, the single mid-Cretaceous sample at Site 1208 yielded relatively frequent B. africana, including specimens tall enough to be orientated on their sides. Such tall pentaliths are common in the Eocene but have rarely been documented in the Cretaceous; the best known were published by Lambert (1986), who documented spectacular specimens from the upper Albian of Cameroon.
Hayesites Manivit, 1971, emend. Applegate et al.
in Covington and Wise, 1987
Hayesites cf. H. albiensis Manivit, 1971
Remarks: Of the genus Hayesites, only H. irregularis was unequivocally identified from the Shatsky Rise mid-Cretaceous sections (Pl. P12, figs. 21–24). Forms with five or six radially arranged rays were logged as Hayesites cf. H. albiensis but did not have the long, symmetrically arranged free rays characteristic of the species. The problematic nature of H. albiensis prevents the identification of Subzone NC8b (see discussion in Kennedy et al., 2000).
Range: Hayesites cf. H. albiensis was logged in the Albian at Sites 1207, 1213, and 1214.
Kokia borealis Perch-Nielsen, 1998
Description: Stellate, multiradiate, rosette-shaped nannolith constructed from 8–10 single crystal-unit radial rays that show low birefringence under XPL (van Niel, 1994).
Range: Mostly reported from the Berriasian to lowermost Valanginian of the Boreal North Sea Basin (Bown et al., 1998), but Lozar and Tremolada (2003) recorded it (unillustrated) from the Hauterivian of the northwest Pacific Ocean. It was found herein in one Berriasian (Subzone NK2a) sample from Site 1213.
Derivation of name: From stellata, meaning starry, referring to the stellate morphology of this nannolith.
Diagnosis: Stellate, multiradiate, rosette-shaped nannolith constructed from 10–15 single crystal-unit rays joined for most of their length along curved sutures; low birefringence under XPL.
Differentiation: Kokia borealis has fewer rays joined along straight sutures, and Kokia curvata has fewer rays that are overlapping.
Dimensions: diameter = 4.5–8.0 µm
Holotype: Pl. P12, fig. 28 (figs. 28–30 are the same specimen).
Paratypes: Pl. P12, figs. 32, 35.
Type locality: ODP Leg 198 Site 1213, Shatsky Rise, northwest Pacific Ocean.
Type level: Berriasian, Sample 198-1213B-27R-1, 38 cm (Zone NK1).
Range: Berriasian (Zone NK1) at Site 1213.
Kokia cf. K. stellata sp. nov.
Description: Stellate, multiradiate, rosette-shaped nannolith (7.0–8.5 µm) constructed from ~12 single crystal-unit rays joined for most of their length along straight sutures; low birefringence under XPL.
Differentiation: Less uniform in birefringence than other species of Kokia, with near-radial c-axis orientation in the rays but resembles Kokia stellata in general morphology. Less regularly constructed, more rays, and less free-ray than cretarhabdid spine tops (calyxes) such as Retecapsa radiata (Worsley, 1971) Applegate and Bergen, 1988.
Range: upper Hauterivian (Subzone NC4b) at Site 1213.
Rucinolithus wisei Thierstein, 1971
Remarks: Stellate, six-rayed nannoliths that in this study ranged in size from 2.5 to 5.5 µm. Specimens in the lowermost part of the range (Cores 198-1213B-22R to 21R) were smaller than 3.0 µm, and size increased upsection.
Range: upper Berriasian (Subzone NK2a)–upper Valanginian (Subzone NK3a) (Bralower et al., 1989; Bergen, 1994) at Site 1213.
