New species of Neogene radiolarians from the Southern Ocean

Abstract. Antarctic Neogene radiolarians are abundant and have great potential for biostratigraphy and evolutionary research. Many of the species found in sediments have not yet been described and are thus unavailable for research purposes. In the first of a planned series, 24 new species of Antarctic Neogene radiolarians are described herein: two entactinarians (Orodapis hericina and Orodapis? ferrealuma), two spumellarians (Actinomma nigriniae and Carposphaera? annikae) and twenty nassellarians (Acrosphaera cuniculiauris, Amphimelissa? hibernifortuna, Antarctissa ballista, Artostrobus semazen, Botryopera gibbera, Carpocanium? uburex, Ceratocyrtis dolvenae, Cystophormis gargantua, Dendrospyris jobstae, Dictyophimus? kiwi, Dictyophimus larus, Gondwanaria clarae, Lithomelissa vespa, Lophophaena leberu, Siphonosphaera abelmannae, Siphostichartus jahnae, Spirocyrtis? hollisi, Stichophormis? cheni, Syscioscenium? wabisabi, Trisulcus pinguiculus).

in nassellarians follows De Wever et al. (1979), Dumitrica (1991) and Funakawa (1995) in which they are named after a combination of the initials of the spines they originate from (i.e. arch Av would be an arch connecting spine A and spine v, Fig. 3).
All holotypes are deposited in the micropaleontology collection of the Museum für Naturkunde, Berlin. Specimens are identified by circles on the slides.  (Lees, 2010).

Fig. 2.
Range chart of the 24 new species described herein. Antarctic radiolarian zonation follows Abelmann (1992b) and Lazarus (1992). Numerical age of zonal boundary after Lazarus (1992). Width of bars corresponds to a rough estimate of the species abundance: dashed line is 'sporadic', plain line 'rare' (<0.5% of the assemblages) and bold line 'common' (>0.5%). A. challengerae, Amphymenium challengerae; u, upper; m, middle; l, lower. cortical shell cavity and is a somewhat octahedral spicule from which arise six thin radial beams that connect to the cortical shell at six of its vertices and continue outside as long, tribladed or conical, serrated spines. Between the medullary and the cortical shell lies a thin and sparse meshwork of anastomosed bars that diverge from those radial beams. There are six other radial spines, similar in shape and length to the six main radial spines, that arise from the six other vertices and that seem to root in the median meshwork. The bases of the twelve spines are thickened by the cortical meshwork that is overgrowing along them.
occurrence. Rare from the A golownini to the Psi zone (Middle Miocene to Pleistocene); appears mostly as fragments.
remarks. Orodapis? ferrealuma differs from O. hericina n. sp. and O. spongiosa in having this polyhedral outline instead of being nearly spherical as they are.
description. Three concentric shells linked together by twelve tribladed radial beams that continue outside the cortical shell as twelve strongly tribladed radial spines. The innermost shell is an irregular sphere that tends to have a regular icosahedral (polygon having 20 faces) outline where each summit is linked to a radial beam. The median shell is approximately twice as big and has the same outline as the latter, except that the edges are smoother and therefore the shell is closer to a sphere. Pores are numerous, polygonal (penta-or hexagonal) and separated by thin bars. The outermost shell is approximately three times bigger than the median one and has an almost perfectly spherical outline. Pores on this shell are rounded, approximately equal in size and in shape, distributed according to a hexagonal pattern and separated by thin, rough, crested bars with raised nodes.
occurrence. Sporadic from the S. radiosa to the A.golownini zone (Early to Middle Miocene), rare from the middle A. golownini to the S. vesuvius zone (Middle to Late Miocene) and fairly common from the C. spongothorax to the A. australis zone (Late Miocene).
remarks. Carposphaera? annikae differs primarily from Liosphaera antarctica Nakaseko, 1959 and the species of genus Carposphaera in its shell ratio and in the shape and size of its cortical shell pores. It also differs from other Actinommidae in its numerous thin radial beams. It finally differs from Elatomma penicillus in having larger elliptical pores, a thicker wall, a considerably smaller medullary shell (shell ratio of 1:4 to 1:6 instead of 1: 2 for E. penicillus) and in lacking branching radial spines.
Order nassellaria Ehrenberg, 1876 Family artostrobiidae Riedel, 1967, emend. Foreman, 1973 Genus Siphostichartus Nigrini, 1977  description. Spindle-shaped four-to five-segmented shell. The cephalis bears a duck-billed, upward-directed vertical tube and a long, slender apical horn (at least as long as cephalis but mostly as long as cephalothorax). This horn is very variable in shape: it can be straight, rod-like, blade-shaped, strongly curved or even bifurcated. The axobate is a cluster of several thin rods extending straight down toward the lumbar stricture. The pores on the thick cephalic wall are few, small and rounded.
Collar stricture is slightly indented dorsally. The pores on the thorax are bigger, rounded and arranged randomly. Lumbar stricture is marked by a strong indentation and a wide poreless area below. Abdomen is barrel-shaped or truncated-conical and bears four to six transverse rows of rounded to elliptical pores increasing in size distally (pores on the first row are smaller than the thoracic pores while pores in the final row are only slightly smaller than the pores on the fourth segment). The fourth segment is either barrel-shaped or inverted truncated-conical and bears four to five more or less regular transverse rows of large, transversallyelongated (elliptical to quadrangular) pores. When present, fifth segment is thinner, flares distally and bears irregular rows of irregularly-shaped (but mostly quadrangular) pores. The largest segment is invariably the fourth and the longest is either the abdomen or the fourth segment. remarks. Siphostichartus jahnae differs from S. corona and S. praecorona Nigrini, 1977 in its peculiar apical horn and in having a considerably shorter fourth segment. It also differs from Botryostrobus auritus-australis (Ehrenberg) group Nigrini, 1977 in the apical horn and in the post-thoracic segments that are, in B. auritus-australis, more or less uniform whereas, in S. jahnae, the segments that follow the thorax differ in width, length, shape, thickness (fifth segment) as well as in the shape of their pores. description. Large conical shell with 7 or 8 segments.
Cephalis and thorax are separated only externally by shallow furrows. Apical horn is conical, long (2 to 3 times the length of the cephalothorax) and robust (c. as wide as cephalis). The cephalis also bears a triangular ventral horn (no vertical tube or vertical pore have been recognized though) and a dorsal horn (downwarddirected and smaller than the ventral one). Several small, additional horns are also present on both the cephalis and the thorax, and some specimens show small thorns on other segments as well. Pores on cephalis and thorax are small, numerous, closely packed, rounded to subhexagonal and loosely arranged in transverse rows.
The following segments (from the abdomen to the seventh segment) are barrel-shaped and expand distally both in width and in length (but considerably more in width than in length). The final segment (generally the eighth) tapers inwards (no specimen has a complete enough final segment to show the presence or absence of a mouth or any other feature). Pores on those segments are elliptical to hexagonal, arranged in transverse rows (3-6 per segment) and increase in size distally.
Two (?) strong ribs arise from the thoracic wall and continue as feet after the penultimate segment (generally the seventh). Some specimens show several weaker additional ribs.
occurrence. Sporadic from the S. radiosa to the lower Chi zone (Early Miocene to Early Pleistocene). This species has been reported by Hollis (2002) in zone RP6 (Late Paleocene).
The cephalis is trilobate with two chambers equal in size and a eucephalic lobe somewhat smaller. The three lobes are spherical and are arranged triradiately around spine A (see Pl. 6, fig. 9A). Cephalic pores are small and sparser than the thoracic ones. The internal spines do not seem to protrude outside the cephalic wall with the notable exception of spine A, which can continue as a small, thornlike spine. In apical view (see Pl. 6, fig. 8A; cf. Petrushevskaya, 1971, pl. 10, fig. 8), eucephalic chamber inner structure can be seen: spine v crosses the eucephalic chamber longitudinally while two wide, flat arches pj -according to Petrushevskaya's (1971) terminology -join spines v and L. The two other cephalic chambers are separated by spine D: therefore, it is not an antecephalic and postcephalic chamber but an antecephalic chamber split into two lobes.

occurrence.
Rare from the C. humerus to the Tau zone (Middle Miocene to Early Pliocene).
remarks. The cephalic lobe arrangement seems to be unique to this species amongst other Cannobotryidae. Because of this peculiar layout, where the three lobes are not ante-, eu-and postcephalic but rather an eucephalic and two antecephalic lobes, the affinity with the genus Amphimelissa remains putative.
description. Large two-segmented shell with a trilobate domeshaped cephalis and a barrel-shaped to spherical thorax ending with a wide hyaline peristome of variable length. The three lobes of the cephalis are not marked externally. The eucephalic lobe is slightly wider and taller than the two others. In some specimens, a small tribladed apical spine arises at the junction between the eucephalic and the antecephalic lobe. Externally, the collar stricture is marked by an indentation and, in some specimens, by a slight change in contour. Internally, the cephalis and the thorax are marked by a plate pierced by four adjacent collar pores (two large and two small). The cephalic wall is thick, crested and bears only a few, small, rounded pores.
The thoracic wall is also thick and crested. It bears larger, round pores that are aligned longitudinally (on half the equator, 8-11 rows of 7-10 pores). Transversally, they are arranged according to a hexagonal pattern. Because of the crests on the wall, each pore seems to be framed. The longitudinal alignment is not strict: it particularly tends to be irregular near the peristome.
The peristome is thick, smooth and hyaline, internally cylindrical and externally cylindrical to inverted truncated-conical. The pore frames of the pores closest to the peristome sometimes extend to its base.
occurrence. Common from the S. radiosa to the E. punctatum zone (Early to Middle Miocene).
remarks. Cystophormis gargantua differs from other carpocaniids primarily in its size. It also differs from Sethocorys odysseus Haeckel, 1887 in its cephalis being flat and distinctly trilobed, and in the collar stricture being less marked; from Carpocanopsis favosa (Haeckel) 1887 in the peristome being cylindrical or inverted conical rather than widening distally and in having a smooth termination. description. Spindle-shaped two-segmented shell. Cephalis is wide and separated externally into three lobes by a more or less pronounced furrow near spine A and another near spine v(?). Spine A is free in the cephalis and often continues outside as a small, tribladed apical horn. Post-cephalic lobe seems on some specimens to open on a vertical tube. The axobate was not observed.
The collar stricture is marked outside by a furrow and a more or less pronounced shoulder. Some specimens bear a small triangular wing as a continuation of spine D. Cephalic wall is crested and bears a few small, rounded, unevenly distributed pores. Pores on the thoracic wall, however, are bigger (but of variable size), often elongated in the longitudinal direction and somewhat aligned longitudinally. This alignment is not strict and tends to be very irregular near the peristome. Ridges can be seen in most specimens between the longitudinal row; they follow the irregularity of the pore alignment. The peristome is hyaline and is composed of a variable number of inward-orientated teeth. The teeth can be either shovel-shaped or triangular or simply a wavy aperture. There is rarely a change in contour between the thorax and the peristome.
occurrence. Rare from the Phi to the Psi zone (Pleistocene).
remarks. Carpocanium? uburex differs from Plannapus microcephalus (Haeckel) 1887, P. papillosus (Ehrenberg) 1872, P. mauricei O'Connor, 1999and P. hornibrooki O'Connor, 1999 in the presence of large teeth around the peristome, its cephalis/thorax ratio and the presence of ridges. It also differs from Carpocanium kinugasense Nishimura, 1990 in the cephalis being clearly separated externally from the thorax and in the inner structure of the cephalis; and from Carpocanium rubyae O'Connor, 1997 for the same reasons as the latter and in the pore alignment being far more irregular in C.? uburex. As the ventral tube present in the species of genus Plannapus was not clearly observed here, C.? uburex was assigned to genus Carpocanium even though it shares many other characteristics with the four Plannapus species cited above.
description. Large latticed sphere made of thin lamellar bars separating large subcircular pores. Each pore bears, at its margin, up to three appendices. Those projections are lamellar, of the same width as the bars of the latticed shell, and bi-or trifurcate distally.
There are a few smaller pores between the large ones, but those do not bear appendices.
occurrence. Rare to common from the A. australis to the A. challengerae zone (Late Miocene), appears mostly as fragments.
description. Small, smooth, hyaline sphere with two to seven large external tubes of variable diameter. Each tube is generally subcylindrical and as long as the diameter of the aperture. These tubes end with thin, irregularly shaped, filamentous appendices which can be twice as long as the tube itself.
occurrence. Rare from the S. radiosa to the C. golli regipileus zone (Early Miocene).
remarks. Siphonosphaera abelmannae differs from A. murrayana in having fewer apertures and in being considerably smaller (its diameter is approximately three times smaller). It also differs from species of the genus Trisolenia in having a poreless, hyaline wall; from S. hyalina Caulet, 1986 in having more numerous, larger tubes; from S. chonopora Haeckel, 1887 in the tubes widely expanding distally in the latter; and from the subspecies S. socialis Haeckel, 1887tubuliloba Strelkov & Reshetnjak, 1971 in the shell being totally poreless and lacking crests and in the tubes being larger.
description. Two-segmented shell with a small hemispherical cephalis and a thorax divided into an upper and a lower thorax by a change in contour at mid-height and a slight constriction.
Cephalis has a poreless wall. Spine A runs in the cephalic wall as a rib from the collar stricture to the apex where it continues outside as a long (generally as long as the whole shell but can be longer), slender conical horn. Spines D, Ll and Lr protrude outside the cephalic wall at the collar stricture at first as ribs on the uppermost part of the thorax and then as curved, downward-directed, thin, slender wings. Spine v also continues as a short, thin and slender horn that forms a c. 50° angle with the apical horn. Arches AL form small ribs on the cephalic wall (see Pl. 4, fig. 10). A small axobate can be seen at the junction between spines v, Ll and Lr.
The upper thorax is somewhat barrel-shaped, whereas the lower thorax forms a short flaring skirt. Both have thin, smooth walls with transverse rows of circular to hexagonal or quadrangular pores. Some of these pores are infilled on the uppermost part of the thorax. Some specimens shows a differentiation in the size of the upper and lower thorax pores; but, most generally, pores are approximately even in size.
occurrence. Sporadic to rare from the lower C. spongothorax to the A. australis zone (Middle to Late Miocene). A. annulatus, A. joergenseni Petrushveskaya, 1967, A. quadriporus Bjørklund, 1976aand A.? pretabulatus Petrushevskaya, 1975 in its thorax being differentiated into an upper thorax and a flaring lower thorax. It also differs from Cycladophora davisiana Ehrenberg, 1872, C. conica Lombari & Lazarus, 1988, C. cosma Lombari & Lazarus, 1988 and C. robusta Lombari & Lazarus, 1988 in its pore size and disposition, in the constriction and change in contour between the upper and lower thorax, in the apical and ventral horns being slender and conical and in the presence of dorsal and lateral wings. description. Two-segmented shell with a small, spherical cephalis and a very large pyriform thorax.

remarks. Artostrobus semazen differs from
The cephalis is thick, rough, bumpy and poreless. It bears a conical, fairly long horn in relation with spine A, which is free in the cephalic cavity. The cephalis also bears many thorns that could be almost as long as the apical horn. Spines D, Ll and Lr continue in the thoracic wall as thick, cylindrical ribs that protrude at midlength outside the wall as long, widely (up to 80°) flaring wings.
Pores on thorax are large, unequal in size, circular to polygonal. The bars between the pores are relatively thin (compared to the pores), slightly crested and they bear spine-like thorns on the upper thorax at each node. At mid-length the thorax begins to taper inwards, to the closure which is a large peristome with the same lattice wall as the rest of the thorax. Bars often connect the wings with the upper part of this peristome.
occurrence. very rare from the S. radiosa to the E. punctatum zone (Early to Middle Miocene). According to Takemura (1992), this species originates in the Eocene or earlier.
remarks. Dictyophimus larus differs primarily from the other Pterocanids in its size. It also differs from D. crisiae, D. hirundo (Haeckel) 1887 and D. infabricatus Nigrini, 1968 in its thick, rough, thorn-bearing cephalis. The thorax termination seems to be also typical of this species. description. Two-segmented shell with a small spherical cephalis and a large, long, flaring thorax.
The cephalis bears several, scattered, very small circular pores, together with a long (almost twice the length of the cephalis), conical apical horn, a small and thin ventral horn and several additional thin and short horns, unconnected to any internal spines. Spine A and v are free in the cephalic cavity. Spines D, Ll and Lr extend as thin, cylindrical ribs on the upper part of the thorax and end up protruding outside the thoracic wall as very short and thin conical wings.
The thoracic pores are polygonal and get bigger along a gradient from the cephalis to the flaring termination of the thorax. The angle formed by the lower thorax (i.e. the part below the wings) is somewhat smaller than the angle formed by the upper thorax. The thin bars between the upper thoracic pores are crested and often bear thorns.
occurrence. very rare from the C. antiqua to the A. golownini zone (Early to Middle Miocene).
remarks. Dictyophimus? kiwi differs from the other species of the genus Dictyophimus in its short wings and its long thorax extending well below the wings.

diagnosis.
Apically elongated cephalis with a strong lanceolate apical horn; three strong tribladed wings; median constriction of the thorax.
description. Two-segmented shell with a narrow, apically elongated, ellipsoidal (almost twice as long as wide in some specimens) cephalis and a large (at least three times the width of the cephalis) thorax with a conical, quickly flaring, upper thorax with three long, tribladed wings and a broadly cylindrical lower thorax. The cephalis and the thorax are separated by a marked collar stricture. The cephalis is rough, crested and poreless. It bears a strong, lanceolated, tribladed, apical horn (up to twice the length of the cephalis) at the apex and a short, tribladed, ventral horn at the collar stricture, directed slightly upward.
Spine A is free in the cephalic cavity. Arches AL are clearly seen at approximately the first quarter of the length of the cephalis and appear parallel to MB; they are not, however, expressed externally by any furrows or strictures. Spines D, Ll and Lr protrude outside the upper thorax wall as three long (as long as the apical horn), tribladed spines.
The upper and the lower thorax are separated by a superficial constriction below the wings. The pores on the upper thorax are rather small and increase in size from the collar stricture to the mid-thorax constriction; on the lower thorax, the pores are large, rounded and somewhat aligned longitudinally. occurrence. Sporadic from the C. antiqua through the E. punctatum zone (Early to Middle Miocene); rare from the C. humerus to the C. spongothorax zone (Middle to Late Miocene). Funakawa, 2000 in the shape of the cephalis (ellipsoidal in G. clarae and hemispherical in G. cylindrica) and the presence in G. clarae of both a clear, strong collar stricture and a constriction of the thorax below the wings. It differs from G. nigriniae Petrushevskaya in Petrushevskaya & Kozlova, 1979 in having three long, subhorizontal, tribladed wings and in the lower part of the thorax being approximately the same width as the upper part. It differs from the specimens illustrated in Caulet (1991, pl. 2, fig. 11) as Pteropilium contiguum (Ehrenberg) and in Petrushevskaya & Kozlova (1972, pl. 29, figs 8-10) as Pteropilium? sp. aff. Pterocanium contiguum (Ehrenberg) group in the absence of longitudinal alignment of the thoracic pores (which are also larger in G. clarae) and the postcephalic part of the shell being, in Caulet's specimen, seemingly separated into a thorax and an abdomen by a lumbar septum, whereas in G. clarae there is no separation between the upper and the lower thorax. It also differs from Stichopilium campanulatum Haeckel, 1887 for the same reasons as from the latter, in the wings being longer and tribladed and in the cephalis being longer. The specimen illustrated as S. campanulatum in Nishimura & Yamauchi (1984, pl. 35, fig. 7) also seems to have a somewhat pyramidal thorax whereas G.clarae has a campanulate upper thorax.  Ehrenberg, 1874in Ogane et al., 2009 fig. 2a-c). 1975 Stichophormis sp. Chen: 462-463, pl. 13, fig. 8. 1990 Stichophormis sp. Chen;Abelmann: 698, pl. 8, fig. 9. 1992 Cyrtolagena aglaogena (Takahashi)  description. Spindle-shaped shell consisting of usually 11 thickwalled segments (10-12). Up to the nine first segments, the shell is conical and the segments barrel-shaped. The two last segments are inverted truncate-conical. The change in contour occurs either on the lower part of the ninth segment or on the upper part of the tenth. The hyaline cephalis consists of two parts: an upper part which is spherical and a cylindrical lower part. The two parts are separated by a constriction (see Pl. 4, fig. 2B). None of the internal spines was observed in our material. The upper part of the cephalis is rough and poreless while the lower part bears a few randomly distributed, small pores.

remarks. Gondwanaria clarae differs from G. cylindrica
Pores on the following segments are relatively small, rounded and aligned transversally. The second through the eighth segments are approximately equal in length and have three to five rows of pores. The ninth and the tenth segments are usually longer and, therefore, have more pore rows. The last segment has somewhat larger pores that are loosely aligned transversally too. This segment ends in a distal opening or mouth with a poreless rim that may have some small poreless teeth.
Most specimens have three wings that are flat and end with a conical spine. Large rounded pores can sometimes be observed on the panel that connects the wings with the main body. They arise from the third or fourth segment.
occurrence. very rare from the C. golli regipileus to the lower A. golownini zone (Early to Middle Miocene). Haeckel, 1887 in having a thick wall, in ending on a differentiated mouth and in the shape of the cephalis; and from Cyrtopera aglaolampa Takahashi, 1991 in the last segment, in the latter, being globular and accounting for more than a third of the total height, and in the absence of an apical horn. The cephalis of S.? cheni seems rather similar to that of the Cretaceous Amphipyndax but, since the internal spines were not actually seen on any of the specimens, the two cannot be compared efficiently. The lack of apical horn or any discernable apical spine makes the affinity with S. cornutella and, therefore, the generic assignment to Stichophormis doubtful. Petrushevskaya's tentative assignment of her form to L. clava Ehrenberg, 1874 is clearly incorrect, as the newly figured type-series material in Ogane et al. (2009) shows. L. clava has much longer segments, fewer in number, lacks wings and is more similar to the modern concept of Stichocorys. We are not sure if Petrushevskaya's specimens are conspecific with ours, as the photographs are of poor quality. The number of segments and development of external wings, however, appear to differ from our material. Petrushevskaya's material is of Paleocene age.

remarks. Stichophormis? cheni differs from Cyrtolagena laguncula
Family Plagiacanthidae Hertwig, 1879, emend. Petrushevskaya, 1971 Genus Antarctissa Petrushevskaya, 1967 type species. Lithobotrys denticulata Ehrenberg, 1844b Antarctissa ballista n. sp. description. Two-segmented shell with a cephalis and a thorax that are not distinguishable externally by any constriction, furrow or shoulder. The thorax is short and closed in most specimens. The cephalis apex is slightly rounded (just a little less squared than the thorax termination). Spine A is robust (as are the other spines) and free in the cephalic cavity; it reaches the wall approximately at mid-width (slightly closer to the dorsal side than to the opposite side) and thus creates a furrow, in most specimens, that can make the cephalis look bilobate. The axobate is just below spine A and is almost long enough to reach termination of the thorax. Spine D is directed downward -very similar to that of A. denticulata and A. cylindrica Petrushevskaya, 1975 -and reaches the wall near the thorax closure. Specimens seen from below or above (see Pl. 6, fig. 4A) show the presence of an internal ring, similar to that of Helotholus vema Hays, 1965. The ring structure is supported by six beams: five horizontal or subhorizontal (Ll, Lr, v' and two l' according to Sugiyama's (1993) terminology, see Fig. 4), plus the downward-directed D spine. This structure is almost at the equator of the shell; the cephalic chamber and the thorax are thus of almost the same length as well as the same width.
The wall is rough, crested and bears only a few pores, unequal in size and arranged randomly. No other ornamentation (such as horns) has been seen on any specimens. remarks. Antarctissa ballista differs from all other members of the genus Antarctissa mostly in its median, free, robust spine A. Its overall shape is rather similar to that of Botryopera pseudoantarctissa Petrushevskaya in Petrushevskaya & Kozlova (1979) and A. whitei Bjørklund, 1976a, yet the length and width ratio of the two segments, the closed thorax and the lack of any external spine or spongy meshwork make it unique.

diagnosis.
Characterized by a large hump between spine A and spine D.
description. Two-segmented shell with a thorax slightly longer (c. 1.2 times) than the cephalis which is separated into two chambers: an antecephalic 'hump' between spines A and D and a eucephalic chamber between spines A and v. Externally, the two chambers are separated by a furrow along AL while the eucephalic chamber wall and the thoracic wall are separated by a furrow along vL. Spines A and v both continue outside as small triangular horns. The wall of both cephalic chambers also bears numerous thorns. The antecephalic chamber is variable in size: it can be only a quarter of the volume of the eucephalic chamber (see Pl. 7, figs 4A-B and 6A-B) as well as up to three-quarters (see Pl. 7, figs 3A-B). The thorax is short and somewhat barrel-shaped. Its termination is ragged; it bears no specific ornamentation nor does it flare. Pores on both segments are circular to elliptical and irregular both in size and in disposition. description. Two-segmented, conical shell with a cephalis and a thorax that are not separated externally by any furrow, constriction, shoulder or even change in contour. The cephalis is considerably smaller than the thorax. The angle formed by the shell is obtuse. Fig. 4. Schematic illustration of Antarctissa ballista n. sp. inner structure. Terminology after Sugiyama, 1993. PR, proximal ring;v', secondary vertical spine.
The cephalis is dome-shaped. Spines v, Ll, Lr, A and D are usually all protruding outside as thin, conical spines. Spines Ll, Lr and D are roughly in the same plane as the median bar (Pl. 5, fig.  2B), whereas spine A is orthogonal to it. The axobate is also present as relatively short, simple, downward-orientated, cylindrical spines approximately at the junction between Ll, Lr, v and the median bar.
The cephalic wall is thorny and bears small, circular to subelliptical, irregularly distributed pores. Pores on the thoracic wall are rectangular with rounded angles, becoming larger and aligned along thin longitudinal bars as they are further from the cephalis.
occurrence. Sporadic from the C. golli regipileus to the lower Upsilon zone (Early Miocene to Early Pliocene).
remarks. Ceratocyrtis dolvenae differs from C. galeus (Cleve) 1899 in the pattern, the size and the shape of its thoracic pores. It also differs from C. morawanensis Funakawa, 1995 in the latter having a cephalis distinct from the thorax by a collar stricture, and having a tribladed apical horn. It finally differs from other known members of Ceratocyrtis in having prominent lateral spines extending from the cephalic suture.
Material. 56 specimens were observed on Sites 744 and 751.
description. Two-segmented shell with a cephalis and a thorax that are not distinguishable externally by any constriction, furrow or shoulder. The cephalis is longer than the thorax.
Spine A is free in the cephalic cavity and protrudes as a long (1.5 times to twice as long as the shell itself), slender, cylindrical horn. Spines D, Ll and Lr protrude as short, triangular (with a thick base) wings from the thoracic wall, slightly lower than the level of the median bar. The axobate is short. Spine v joins the cephalic wall subhorizontally and does not seem to extend outside the wall. Two (three?) short, thin, conical, upward-directed spines appear to extend subapically from apophyses branching from spine A: apophyses a, according to Petrushevskaya's (1971) terminology.
Some specimens have a thick, crested wall (see Pl. 7, figs 7A-B and 9A-B), but commonly the wall is thin and smooth (see Pl. 7, fig. 10). Specimens with a thick wall have their thorax closed by a sieve plate. In both cases, pores on thorax are somewhat bigger than the cephalic ones; but, on both segments, they are randomly distributed, uneven in size and subelliptical. remarks. Lithomelissa vespa differs from most Lophophaenidae in its horn combination: A, D, Ll, Lr and two more branching from spine A. This combination, however, is shared by L. tricornis Chen, 1975. L. vespa differs from the latter in its unusually long apical horn, in its cephalis/thorax ratio and in the overall shape of the shell. Furthermore, the horns of L. tricornis are all of rather similar size and shape, whereas each set of horns in L. vespa is different from one another. description. Two-segmented shell with a long, truncated-conical thorax, approximately twice as long as the ellipsoidal cephalis. The shell tilts on the ventral side. The cephalis and the thorax are separated by a shoulder along AL and a furrow following vL. Spine A is fused to the cephalic wall and protrudes outside the wall apically as a robust, blade-shaped horn (c. 1-1.5 times the height of the cephalis). Spine v protrudes at the junction of the cephalis and the thorax as a short triangular horn. Spines D, Ll and Lr join the thoracic wall and, sometimes, spine D extends outside as a very short wing. There is a change in contour of the thorax where those spines join the wall (concave for spine D, convex for spines Ll and Lr). The cephalis bears an additional horn halfway between the apical and the ventral horn: it is rather similar in shape to the apical horn but smaller; it does not seem to be linked to any internal spine. Some rare specimens also bear numerous small additional horns scattered on the cephalis (see Pl. 5, figs 11A-B).
The thoracic wall is smooth, with numerous small pores, more or less arranged in a hexagonal pattern, but somewhat irregular in size. The cephalic wall is similar to the thoracic wall, yet some specimens have a crested cephalis. Thorax termination is ragged. description. Two-segmented shell with a short (up to c. 1.2 times the length of the cephalis) flaring thorax and a cephalis with an approximately median indentation where spine A joins the wall. Spine A is free in the cephalis and continues outside as a small, tribladed -at least at the base -apical horn. Spines D, Ll and Lr extend approximately horizontally and sometimes continue outside as slender downward-directed horns. The median bar bears a very small axobate (most often just an indentation, see Pl. 6, fig. 3B). Spine v is present and is almost horizontal too; it sometimes protrudes outside the wall as a very short, upward-directed tribladed horn. All the internal spines are rather thick. Collar stricture is marked by a small constriction externally.
The cephalic wall is thick, it can be smooth or rough depending on the specimen, and is almost poreless: some specimens have a few small, rounded pores. The thoracic wall is smooth and bears some larger, circular to elliptical pores of variable size and uneven distribution. The thorax ends with upward-directed small thorns. Both the cephalis and the thorax bear a fairly large amount of slender thorns (that can be as long as the apical horn). Those thorns branch distally to form ultimately on some specimens a secondary 3D meshwork made of thin anastomosed bars. remarks. Syscioscenium? wabisabi differs from S. velamen in the thorns branching to form a secondary meshwork and in having a spine v. The sethophormid structure described by Sugiyama (1992)  description. Two-segmented shell with a trilobate thorax, c. three times wider than the cephalic chamber. The lobes are separated by short, rather shallow furrows formed by the junction of spines D, Ll and Lr with the thoracic wall. Those spines protrude outside the wall as really small, slender spines on most specimens. Thorax termination is ragged and of nearly the same width as its upper part. In some specimens, the dorsal side of the upper thorax (i.e. the two lobes separated by the dorsal furrow) is slightly bigger than the lateral one.
The cephalic chamber is approximately hemispherical; spine A is fused to the wall and protrudes outside subapically as a very short three-bladed horn. There is a furrow between the cephalis and the thorax, where spine v joins the wall. None of the specimens bears a ventral horn, but some rare specimens (see Pl. 7, figs 12A-B) bear some short (nearly equal to the apical horn in length and width), additional horns at the apex and on the thoracic lobes. The axobate has never been observed.
The cephalic pores are small and roundish, but somewhat larger and downwardly elongated near the furrow between the cephalis and the thorax. The thoracic pores are larger yet unequal in size, elliptical and randomly distributed. Pores on the lower part of the thorax are larger than the ones on the upper part. The cephalic wall is rougher than the thoracic wall (some specimens have a slightly crested cephalic wall).
occurrence. T. pinguiculus is common in samples from the S. radiosa to the C. golli regipileus zone (Early Miocene) and rare from the E. punctatum to the A. golownini zone (Early to Middle Miocene).
remarks. Trisulcus pinguiculus differs from T. triacanthus in having a rougher surface, larger pores and smaller apophyses. The thorax in T. pinguiculus is shorter and does not taper downward.
The furrows between the thoracic lobes are deeper than in T. triacanthus. It also differs from other small dicyrtids, such as species of the genera Antarctissa, Botryopera or Lithomelissa, in that the cephalis is partially sunken into the thorax cavity, in the cephalis/ thorax width ratio and in the three distinctive shoulders present in the genus Trisulcus.
description. The latticed shell is made of few large, circular to subelliptical pores that are loosely arranged according to a hexagonal pattern and are separated by relatively thin, crested bars. Some smaller pores are sometimes intercalated between the larger ones, and the pores at the apex are also usually smaller. The latticed shell continues below the basal ring as a cylindrical thorax. Some specimens show a slight constriction at the basal and the sagittal ring. The latticed shell is linked to the D-shaped sagittal ring by 8(?) pairs of bars and, on front view, by the frontal bar. The two sagittal-lattice pores just above this frontal bar are generally larger than the others (see Pl. 4, figs 8A, 11A and 12B).
The shell outline is somewhat narrow (laterally) but elongated (longitudinally).
occurrence. Rare to common from the Tau to the lower Upsilon zone (Early Pliocene).
remarks. Dendrospyris? jobstae differs from D. stabilis Goll, 1968 andD. haysi Chen, 1975 in its outline being narrower but longer, in its sagittal and basal constriction being slighter (and even absent in some most specimens) and in its pores being larger with smaller crested bars.

conclusIons
With the exception of a few highly sporadic taxa (Ceratocyrtis dolvenae, Actinomma nigriniae, Carposphaera? annikae and Spirocyrtis? hollisi), the species described in this paper were all, even for the rarest one, present relatively continuously in the studied sections: it is likely that they will be of stratigraphical or palaeoenvironmental interest in the future. Early and Late Miocene radiolarian zonations are particularly poor in marker species in the Southern Ocean (Lazarus, 1992), therefore fairly common species such as Cystophormis gargantua, Orodapis hericina or Trisulcus pinguiculus (for the Early Miocene) and short-ranging taxa such as Acrosphaera cuniculiauris, Antarctissa ballista, Dendrospyris? jobstae, Botryopera gibbera, Lithomelissa vespa, Siphostichartus jahnae or Amphimelissa? hibernifortuna (for the Late Miocene) might prove useful to increase the biostratigraphical resolution of this region. Trisulcus pinguiculus, Cystophormis gargantua, Orodapis hericina, O.? ferrealuma and Antarctissa ballista are quantitatively important components of these faunas as well: T. pinguiculus in particular peaks at c. 15% near the Oligocene/Miocene boundary and should be included in future palaeoecological studies. Furthermore, such species as Amphimelissa? hibernifortuna and Syscioscenium? wabisabi exhibit unique morphological features that may shed a new light on nassellarian recent evolution. Similarly, Antarctissa ballista, with its proximal ring, provides more information to help untangle the intricate taxonomy of the Antarctissids and the species close to Helotholus vema (Kellogg, 1975;Petrushevskaya, 1986;Lazarus, 1990;Sugiyama, 1993).