New middle Eocene radiolarian species (Rhizaria, Polycystinea) from Blake Nose, subtropical western North Atlantic Ocean

Abstract

Diverse and well-preserved radiolarian assemblages were recovered from the middle Eocene sedimentary sequences drilled at Ocean Drilling Program Site 1051 (Leg 171B; western subtropical Atlantic). In addition to biostratigraphically important species, several unknown morphotypes were observed in this material, leading to the description of three new spumellarian species and 18 new nassellarian species. Described herein are: Periphaena petrushevskayae n. sp. (Phacodiscidae), Stylodictya oligodonta n. sp. (Trematodiscidae), Excentrosphaerella delicata n. sp. (Heliodiscidae), Eucyrtidium granatum n. sp. (Eucyrtidiidae), Dictyoprora echidna n. sp., Spirocyrtis matsuokai n. sp. (Artostrobiidae), Elaphospyris cordiformis n. sp., Elaphospyris quadricornis n. sp. (Cephalospyrididae), Ceratocyrtis oconnori n. sp. (Lophophaenidae), Botryocella? alectrida n. sp., Pylobotrys? bineti n. sp. (Pylobotrydidae), Lychnocanium cheni n. sp., Lychnocanium cingulatum n. sp., Lychnocanium croizoni n. sp., Lychnocanium forficula n. sp. (Lithochytrididae), Apoplanius hyalinus n. sp., Apoplanius cryptodirus n. sp. (Lophocyrtiidae), Albatrossidium messiaeni n. sp., Phormocyrtis microtesta n. sp., Cryptocarpium? judoka n. sp. (Pterocorythidae), and Thyrsocyrtis kamikuri n. sp. (Theocotylidae). Biostratigraphic information is provided for each new species. In addition, we re-describe and illustrate the morphological variability of a remarkable Pterocyrtidium species formerly published by Bütschli (1882a).

UUID: http://zoobank.org/a01f7f03-73b0-458a-af7b-b85dc4666cc2

Non-technical Summary

Diverse and well-preserved radiolarians (siliceous planktonic microfossils) have been recovered from middle Eocene sediment cores drilled at Blake Nose, a submarine promontory in the western North Atlantic Ocean. In addition to known species, many unknown forms were observed in this material, including 21 new radiolarian taxa. The new species belong to 18 genera and 12 families. Information is provided on the position of each new species in the stratigraphic column. In addition, we have re-described and illustrated the morphological variability of the poorly known species Pterocyrtidium zitteli Bütschli, 1882.

Introduction

Polycystine radiolarians are a large group of marine planktonic protozoans that secrete a morphologically complex skeleton made of opaline silica. Known since the early Cambrian (Obut and Iwata, 2000; Pouille et al., 2011), their extensive fossil record makes them valuable biostratigraphic markers and an ideal taxonomic group for paleoceanography and macroevolutionary studies (De Wever et al., 2001; Lazarus et al., 2021). However, despite their importance in fossil plankton assemblages, a substantial portion of the radiolarian diversity preserved in the fossil record remains undocumented, hindering the expression of their full biostratigraphic and paleoceanographic potential.

Eocene radiolarians were the first to receive sustained attention from micropaleontologists, with the description of several hundred species from siliceous-rich chalk beds cropping out on Barbados Island (Ehrenberg, 1839, 1846, 1847, 1874, 1876; Bütschli, 1882a, b; Haeckel, 1887). This body of early taxonomic work has constituted the core of the Paleogene radiolarian taxonomy for nearly a century, although some contributions were also made in the first half of the twentieth century (e.g., Clark and Campbell, 1942, 1945). The launch of scientific ocean drilling programs in the early 1970s marked a pivotal change in the history of Cenozoic radiolarian research, allowing extensive recoveries of radiolarian assemblages around the world and rekindling interest in describing their diversity (e.g., Riedel and Sanfilippo, 1970, 1971, 1978; Petrushevskaya and Kozlova, 1972; Foreman, 1973; Sanfilippo and Riedel, 1973, 1982, 1992; Nigrini, 1977; Sanfilippo and Caulet, 1998). However, most of these studies have focused on biostratigraphically important species, which represent only a minute fraction of the total radiolarian diversity. As a result, numerous rare morphotypes that are of no interest for biostratigraphic correlations, or those belonging to poorly defined genera and families, were not documented and remained undescribed until recently (i.e., Meunier and Danelian, 2023).

To contribute to our understanding of Paleogene radiolarian diversity, 21 new species distributed among 16 genera and 13 families are formally described from the middle Eocene sequences cored at Ocean Drilling Program Site 1051 (Leg 171B; western subtropical Atlantic). Most of these new taxa were previously illustrated by Kamikuri (2015) in an extensive monograph conducted at neighboring ODP Site 1052, but they were left in open nomenclature. Biostratigraphic information is provided here for each new species, and stratophenetic relationships to previously described species are suggested.

Materials and methods

Materials

ODP Site 1051 (30°03′N, 76°21′W, modern water depth of ~1983 m below sea level, mbsl) was drilled on the Blake Nose, a promontory situated on the edge of the Blake Plateau, in the western North Atlantic Ocean (Fig. 1). This site provided an expanded and nearly continuous upper Paleocene through lower upper Eocene sedimentary sequence, dominated by silica-bearing nannofossil oozes rich in radiolarians, diatoms, and sponge spicules (Norris et al., 1998). Paleo-water depth estimates based on benthic foraminifera indicate lower bathyal depths (1000−2000 mbsl) at this site during the Eocene (Norris et al., 1998), with a slightly more southerly paleolatitude of ~25°N (Ogg and Bardot, 2001). The estimated sedimentation rate is ~4 cm/ka (Norris et al., 1998; Edgar et al., 2010). The species described in the present paper come from 16 samples collected from the richest and most diverse radiolarian interval, which spans cores 2H to 18X (12.73–174.28 meters composite depth [mcd]) in Hole 1051A (Sanfilippo and Blome, 2001).

Figure 1. Location of Blake Nose in the western North Atlantic Ocean (modified from Land et al., 1999). The box shows the detailed location of ODP Site 1051 (Leg 171B) on a bathymetric map (modified from Norris et al., 1998). Bathymetry is in meters.

Methods

Samples were treated according to the procedures described in Sanfilippo et al. (1985) and Tetard et al. (2020). About 2 cm² of untreated sediment were first soaked in a polypropylene beaker containing 30 mL of 30% hydrochloric acid (HCl) to dissolve calcium carbonate. At the end of this stage, a few mL of HCl were added to ensure the end of the reaction. The resulting residues were then washed with distilled water and soaked in 30 mL of 10% hydrogen peroxide (H₂O₂) to remove organic material. Finally, the siliceous residues were sieved through a 45-μm mesh to remove small radiolarian fragments and clay. Three slides were prepared per sample using ~3 mg of dry residues randomly spread on a coverslip (Witkowski et al., 2012). Coverslips were mounted on standard glass slides using Eukitt^® mounting medium (refractive index = 1.49).

Observation and identification of radiolarians were performed using a Zeiss Axio Imager. A2 transmitted light microscope at 20× magnification. Images were captured using a Zeiss AxioCam ERc5s digital camera. To create a fully focused composite image of a single specimen, a set of ~5 images was taken at different f-stops and stacked using Helicon Focus v.7.6.6 (HeliconSoft).

All measurements provided in the systematic paleontology section were performed on specimen images using the image analysis software ImageJ (Schneider et al., 2012). The stratigraphic occurrences of the new species are shown in Fig. 2, and the associated bioevents are summarized in Table 1.

Figure 2. Range chart of the 21 new radiolarian species from the late middle Eocene of ODP Site 1051 (Blake Nose, western subtropical Atlantic). Lithology column based on data from Norris et al. (1998). Geomagnetic timescale after calibration of Ogg and Bardot (2001). Radiolarian biostratigraphy after Sanfilippo and Blome (2001), planktonic foraminiferal biostratigraphy after Norris et al. (1998) and Edgar et al. (2010), and calcareous nannofossil biostratigraphy after Mita (2001). Black = normal-polarity intervals; white = reversed-polarity intervals; 1b = nannofossil ooze with siliceous microfossils to siliceous nannofossil ooze; 1c = nannofossil ooze with siliceous microfossils to siliceous nannofossil ooze; 1d = siliceous nannofossil chalk to nannofossil chalk with siliceous microfossils; mcd = meters composite depth.

Table 1. Summary of first occurrences (FO) and last occurrences (LO) at ODP Site 1051, drilled on the Blake Plateau (western North Atlantic). Abbreviations: mbsf, meters below seafloor; mcd, meters composite depth.

Repository and institutional abbreviation

All holotypes and figured specimens (Figs. 3–8) are deposited in the public paleontological collection of the University of Lille (USTL), France. Specimens are located according to hole number, core number, section number, interval depth, and England Finder coordinates.

Figure 3. Composite light micrographs of new radiolarian species from ODP Site 1051 (Blake Nose, western subtropical Atlantic). (1–4) Periphaena petrushevskayae n. sp.: (1) holotype, ODP 171B-1051A-9R-2W, 53–55 cm, USTL 4525-1, K55/2; (2) ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4524-2, S55/3; (3) ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4524-3, U55/1; (4) ODP 171B-1051A-9H-5W, 53–55 cm, USTL 4529-2, K44/2. (5–8) Stylodictya oligodonta n. sp.: (5) holotype, ODP 171B-1051A-11H-2W, 62–64 cm, USTL 4536-2, R52/1; (6) ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4526-3, R46/3; (7) ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4525-3, T41/3; (8) poorly developed form, ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4525-2, V64/1. (9–12) Excentrosphaerella delicata n. sp.: (9) holotype, cortical shell, ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4524-6, F73/1; (10) holotype, inner structure; (11) ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4526-2, V49/1; (12) inner structure, ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4524-4, O65/3. All scale bars equal 50 μm.

Figure 4. Composite light micrographs of new radiolarian species from ODP Site 1051 (Blake Nose, western subtropical Atlantic). (1–4) Eucyrtidium granatum n. sp.: (1) holotype, ODP 171B-1051A-2H-5W, 55–57 cm, USTL 4513-1, M69/3; (2) ODP 171B-1051A-4H-5W, 56–58 cm, USTL 4517-1, V48/3; (3) ODP 171B-1051A-4H-5W, 56–58 cm, USTL 4515-4, T70/2; (4) ODP 171B-1051A-4H-5W, 56–58 cm, USTL 4515-3, T49/4. (5–8) Dictyoprora echidna n. sp.: (5) holotype, ODP 171B-1051A-6H-5W, 53–55 cm, USTL 4518-1, M41/3; (6) ODP 171B-1051A-6H-5W, 53–55 cm, USTL 4519-1, M47/1; (7) ventral view, ODP 171B-1051A-2H-5W, 55–57 cm, USTL 4512-1, N63/3; (8) ventral view, ODP 171B-1051A-6H-5W, 53–55 cm, USTL 4518-2, H64/2. (9–12) Spirocyrtis matsuokai n. sp.: (9) holotype, ODP 171B-1051A-14H-5W, 52–54 cm, USTL 4554-1, S69/2; (10) ODP 171B-1051A-14H-5W, 52–54 cm, USTL 4554-2, H48/3; (11) ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4524-1, N41/2; (12) ODP 171B-1051A-14H-5W, 52–54 cm, USTL 4554-3, M38/2. (13–16) Pterocyrtidium zitteli Bütschli, 1882a: (13) ODP 171B-1051A-4H-5W, 56–58 cm, USTL 4515-2, K40/4; (14) ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4526-1, Q53/1; (15) hyaline form, ODP 171B-1051A-18X-5W, 54–56 cm, USTL 4562-2, X63/1; (16) poorly developed form, ODP 171B-1051A-18X-5W, 54–56 cm, USTL 4562-1, P51/2. All scale bars equal 50 μm.

Figure 5. Composite light micrographs of new radiolarian species from ODP Site 1051 (Blake Nose, western subtropical Atlantic). (1–4) Elaphospyris cordiformis n. sp.: (1) holotype, ODP 171B-1051A-18X-5W, 54–56 cm, USTL 4562-4, N51/2; (2) ODP 171B-1051A-18X-5W, 54–56 cm, USTL 4561-3, R70/1; (3) ODP 171B-1051A-18X-5W, 54–56 cm, USTL 4562-3, U42/3; (4) ODP 171B-1051A-18X-5W, 54–56 cm, USTL 4560-3, W52/3. (5–8) Elaphospyris quadricornis n. sp.: (5) holotype, ODP 171B-1051A-4H-5W, 56–58 cm, USTL 4517-2, T47/2; (6) ODP 171B-1051A-2H-5W, 55–57 cm, USTL 4513-3, Q66/4; (7) ODP 171B-1051A-4H-5W, 56–58 cm, USTL 4516-2, G58/1; (8) ODP 171B-1051A-2H-5W, 55–57 cm, USTL 4513-4, D47/3. (9–12) Botryocella? alectrida n. sp.: (9) holotype, ODP 171B-1051A-4H-5W, 56–58 cm, USTL 4516-1, Z61/1; (10) ODP 171B-1051A-14H-5W, 52–54 cm, USTL 4554-4, E43/1; (11) ODP 171B-1051A-14H-5W, 52–54 cm, USTL 4554-5, G44/4; (12) ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4524-4, H60/4. (13–16) Pylobotrys? bineti n. sp.: (13) holotype, ODP 171B-1051A-10H-2W, 53–55 cm, USTL 4530-1, J41/2; (14) ODP 171B-1051A-11H-5W, 59–61 cm, USTL 4539-1, L48/3; (15) ODP 171B-1051A-10H-5W, 55–57 cm, USTL 4533-2, K46/2; (16) ODP 171B-1051A-11H-2W, 62–64 cm, USTL 4536-1, L71/2. All scale bars equal 50 μm.

Figure 6. Composite light micrographs of new radiolarian species from ODP Site 1051 (Blake Nose, western subtropical Atlantic). (1–4) Ceratocyrtis oconnori n. sp.: (1) holotype, ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4526-4, R49/4; (2) ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4526-5, Q55/2; (3) ODP 171B-1051A-9H-5W, 53–55 cm, USTL 4566-1, G57/4; (4) ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4525-5, S38/4. (5–8) Lychnocanium cheni n. sp.: (5) holotype, ODP 171B-1051A-18X-5W, 54–56 cm, USTL 4562-5, O41/3; (6) ODP 171B-1051A-18X-5W, 54–56 cm, USTL 4561-4, P70/3; (7) ODP 171B-1051A-18X-5W, 54–56 cm, USTL 4562-6, D52/3; (8) ODP 171B-1051A-18X-5W, 54–56 cm, USTL 4562-7, F60/3. (9–12) Lychnocanium cingulatum n. sp.: (9) holotype, ODP 171B-1051A-18X-5W, 54–56 cm, USTL 4561-1, X70/2; (10) ODP 171B-1051A-18X-5W, 55–56 cm, USTL 4560-1, C56/1; (11) ODP 171B-1051A-18X-5W, 54–56 cm, USTL 4561-5, O69/4; (12) ODP 171B-1051A-18X-5W, 54–56 cm, USTL 4560-2, T55/2. (13–16) Lychnocanium forficula n. sp.: (13) holotype, ODP 171B-1051A-18X-5W, 54–56 cm, USTL 4561-2, J55/3; (14) ODP 171B-1051A-11H-2W, 62–64 cm, USTL 4536-1, Q70/4; (15) holotype, ODP 171B-1051A-2H-5W, 55–57 cm, USTL 4513-2, H48/1; (16) ODP 171B-1051A-4H-5W, 56–58 cm, USTL 4515-5, W48/1. All scale bars equal 50 μm.

Figure 7. Composite light micrographs of new radiolarian species from ODP Site 1051 (Blake Nose, western subtropical Atlantic). (1–4) Lychnocanium croizoni n. sp.: (1) holotype, ODP 171B-1051A-9H-5W, 53–55 cm, USTL 4528-1, S67/2; (2) ODP 171B-1051A-10H-5W, 52–54 cm, USTL 4533-1, F53/3; (3) specimen showing short feet (arrow), ODP 171B-1051A-9H-5W, 53–55 cm, USTL 4528-4, V65/2; (4) specimen showing ventral horn (arrow), ODP 171B-1051A-10H-2W, 53–55 cm, USTL 4530-4, E60/4. (5–8) Albatrossidium messiaeni n. sp.: (5) holotype, ODP 171B-1051A-9H-5W, 53–55 cm, USTL 4529-1, X42/4; (6) ODP 171B-1051A-4H-5W, 56–58 cm, USTL 4515-1, X61/3; (7) ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4524-5, F47/3; (8) ODP 171B-1051A-9H-5W, 53–55 cm, USTL 4529-3, W09/3. (9–12) Cryptocarpium? judoka n. sp.: (9) holotype, ODP 171B-1051A-13H-5W, 58–60 cm, USTL 4551-1, R40/2; (10) ODP 171B-1051A-10H-2W, 53–55 cm, USTL 4530-2, F43/2; (11) ODP 171B-1051A-9H-5W, 53–55 cm, USTL 4565-1, S48/4; (12) ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4525-6, K69/1. (13–16) Phormocyrtis microtesta n. sp.: (13) holotype, ODP 171B-1051A-9H-5W, 53–55 cm, USTL 4529-4, W46/3; (14) ODP 171B-1051A-9H-5W, 53–55 cm, USTL 4528-3, P53/4; (15) ODP 171B-1051A-13H-2W, 52–54 cm, USTL 4549-1, W56/2; (16) ODP 171B-1051A-13H-2W, 52–54 cm, USTL 4550-1, H60/2. All scale bars equal 50 μm.

Figure 8. Composite light micrographs of new radiolarian species from ODP Site 1051 (Blake Nose, western subtropical Atlantic). (1–4) Apoplanius cryptodirus n. sp.: (1) holotype, showing dorsal horn (arrow), ODP 171B-1051A-10H-5W, 52–54 cm, USTL 4533-3, W52/3; (2) specimen showing dorsal horn (arrow), ODP 171B-1051A-14H-5W, 52–54 cm, USTL 4554-6, H58/4; (3) ODP 171B-1051A-9H-5W, 53–55 cm, USTL 4528-2, D64/1; (4) specimen showing mitral arches, ODP 171B-1051A-18X-5W, 54–56 cm, USTL 4562-8, O40/4; (5–7) Apoplanius hyalinus n. sp.: (5) holotype, ODP 171B-1051A-9H-5W, 53–55 cm, USTL 4566-2, S37/2; (6) specimen showing dorsal horn (arrow), ODP 171B-1051A-8H-5W, 53–55 cm, USTL 4521-1, S55/3; (7) ODP 171B-1051A-8H-5W, 53–55 cm, USTL 4522-1, N61/4; (8) Apoplanius kerasperus (Sanfilippo and Caulet, 1998): ODP 171B-1051A-10H-2W, 53–55 cm, USTL 4530-3, K60/2; (9–12) Thyrsocyrtis kamikuri n. sp.: (9) holotype, ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4563-1, B34/3; (10) ODP 171B-1051A-9H-5W, 53–55 cm, USTL 4529-5, J44/1; (11) ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4563-2, P37/1; (12) ODP 171B-1051A-9H-2W, 53–55 cm, USTL 4563-3, D46/3. All scale bars equal 50 μm.

Systematic paleontology

The higher-level classification adopted here is based on the most recent and integrative radiolarian classification of Suzuki et al. (2021). Genus assignments of the new species are consistent with the diagnosis provided by O'Dogherty et al. (2021).

The morphological terminology used in the text to designate different parts of the fundamental nassellarian spicule follows that of Petrushevskaya (1984). The reader is also invited to see Goll (1968, p. 1413, text-figure 6) for features specific to the family Cephalospyrididae, and Sanfilippo and Caulet (1998, p. 6, text-figure 2) for the family Lophocyrtiidae.

Infrakingdom Rhizaria Cavalier-Smith, 2002, emend. Cavalier-Smith, 2003
Phylum Retaria Cavalier-Smith, 1999
Class Polycystinea Ehrenberg, 1839
Order Spumellaria Ehrenberg, 1876
Superfamily Lithocyclioidea Ehrenberg, 1846
Family Phacodiscidae Haeckel, 1882
Genus Periphaena Ehrenberg, 1874

Type species

Periphaena decora Ehrenberg, 1874, p. 246 (unfigured); Ehrenberg, 1876, p. 80, pl. 28, fig. 6; by monotypy.

Periphaena petrushevskayae new species
Figure 3.1–3.4

1972

Periphaena sp.; Petrushevskaya and Kozlova, p. 523, pl. 14, figs. 4, 5.

Holotype

Figure 3.1; collection number USTL 4525-1; coordinates K55/2; sample ODP 171B-1051A-9R-2W, 53–55 cm; upper part of the Podocyrtis (L.) chalara Zone (RP15; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Phacodiscid species with a thick equatorial hyaline girdle bearing 6–10 triangular spines of variable lengths.

Occurrence

Periphaena petrushevskayae n. sp. occurs throughout the studied interval, from the upper part of the Podocyrtis (L.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) goetheana Zone (RP15).

Description

Shell lenticular, externally smooth, with a phacodiscid center and a well-developed equatorial hyaline girdle. Six to 10 triangular equatorial spines of variable length arise from the girdle as extensions. Cortical shell about three times the diameter of the medullary shell, perforated by numerous small cylindrical pores that are uniform in size and shape (~10 pores in a radius). Medullary shell double, globular, attached to the cortical shell by a few thick rods.

Etymology

The specific epithet honors Dr. Maria G. Petrushevskaya, who was the first to illustrate this radiolarian taxon in the fauna of DSDP Site 144.

Dimensions

Based on 19 specimens (mean): shell diameter: 133–183 μm (160 μm), length of equatorial spines: 34–156 μm (76 μm).

Remarks

The new species differs from Periphaena contiguum (Ehrenberg, 1874), P. delta Sanfilippo and Riedel, 1973, P. heliasteriscus (Clark and Campbell, 1942), P. humboldti (Ehrenberg, 1847), and P. umbonatum (Ehrenberg, 1874) in having an equatorial hyaline girdle, and from P. decora Ehrenberg, 1874, in having well-developed equatorial spines. Finally, P. petrushevskayae n. sp. is distinguished from P. cingillum (Haeckel, 1887) in having fewer than 10 equatorial spines.

In many aspects, P. petrushevskayae n. sp. resembles P. decora, from which it probably evolved by modification of the equatorial girdle.

Superfamily Trematodiscoidea Haeckel, 1862, emend. Suzuki in Suzuki et al., 2021
Family Trematodiscidae Haeckel, 1862, emend. Suzuki in Suzuki et al., 2021
Genus Stylodictya Ehrenberg, 1846

Type species

Stylodictya gracilis Ehrenberg, 1854, pl. 36, fig. 28; by monotypy.

Stylodictya oligodonta new species
Figure 3.5–3.8

Holotype

Figure 3.5; collection number USTL 4536-2; coordinates R52/1; sample ODP 171B-1051A-11H-2W, 62–64 cm; Podocyrtis (L.) chalara Zone (RP15; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Small trematodiscid species with fewer than four annular rings, and a few short equatorial spines.

Occurrence

This species is found throughout the studied interval, from the upper part of the Podocyrtis (L.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell as a subcircular flat disc, tending to be angular in outline in some specimens. Disc concentrically chambered, with a decussate microsphere surrounded by one (Fig. 3.8) to three (Fig. 3.7) annular rings. Margin of the disc bearing many small, triangular to rounded spines of various lengths. Four longer spines are usually present, representing extensions of the cylindrical primary radial rays from the inner disc. Pores subcircular, scattered over the surface, and usually more widely spaced spaced and less numerous on the marginal ring.

Etymology

The specific epithet means ‘few teeth’ in Greek, in allusion to the sparse marginal spines of the new species.

Dimensions

Based on 11 specimens (mean): shell diameter: 72–119 μm (89 μm), spine lengths: 4–20 μm (10 μm).

Remarks

The new species is is placed in the genus Stylodictya because it had a decussate microsphere surrounded by several narrow concentric rings and from which four primary and many secondary equatorial spines extend. The small size of Stylodictya oligodonta n. sp. (shell diameter < 120 μm), as well as its short triangular to rounded spines, allow it to be distinguished from all other middle Eocene flattened spumellarian species with a decussate microsphere.

Superfamily Haliommoidea Ehrenberg, 1846
Family Heliodiscidae Haeckel, 1882, emend. Dumitrică, 1984
Genus Excentrosphaerella Dumitrică, 1978

Type species

Excentrosphaerella sphaeroconcha Dumitrică, 1978, p. 238, pl. 5, fig. 22; subsequent designation by O'Dogherty et al., 2021.

Excentrosphaerella delicata new species
Figure 3.9–3.12

Holotype

Figure 3.9, 3.10; collection number USTL 4524-6; coordinates F73/1; sample ODP 171B-1051A-9H-2W, 53–55 cm; Podocyrtis (L.) chalara Zone (RP15; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Relatively small Excentrosphaerella species with a shell ratio of 1:2:3.

Occurrence

Excentrosphaerella delicata n. sp. occurs sporadically throughout the studied interval, from the upper part of the Podocyrtis (L.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Delicate four-shelled test with a small eccentric microsphere embedded in a subspherical inner medullary shell. Outer medullary shell surrounded by two concentric spherical shells connected by numerous filamentous radial beams that protrude out of the cortical shell as long conical spines. Third shell and cortical shell perforated by numerous small, randomly arranged, subcircular pores.

Etymology

The name is derived from the Latin delicatus, meaning ‘soft, delicate’, for the thin-walled cortical shell of the new species.

Dimensions

Based on five specimens (mean): diameter of microsphere: 12–15 μm (13 μm), diameter of outer medullary shell: 38–44 μm (41 μm), diameter of third shell: 61–73 μm (67 μm), diameter of cortical shell: 102–118 μm (108 μm), length of cortical spines: 15–46 μm (23 μm).

Remarks

Excentrosphaerella delicata n. sp. differs from E. sphaeroconcha Dumitrică, 1978, and Actinomma capillaceum Haeckel, 1887, in being two times smaller and in having an inner medullary shell to cortical shell ratio of 1:3 instead of a ratio of 1:4 (Dumitrică, 1978, pl. 5, fig. 22), 1:5 (Dumitrică, 2019, fig. 11a, b), or 1:7 (Haeckel, 1887, pl. 29, fig. 2). The new species is also distinguished from the middle Miocene specimens illustrated as E. sphaeroconcha by Sugiyama and Furutani (1992, pl. 12, figs. 1, 2, pl. 16, fig. 3) in having a spherical outer medullary shell.

Order Nassellaria Ehrenberg, 1876
Superfamily Eucyrtidioidea Ehrenberg, 1846, emend. Suzuki et al., 2021
Family Eucyrtidiidae Ehrenberg, 1846, emend. Suzuki et al., 2021
Genus Eucyrtidium Ehrenberg, 1846

Type species

Lithocampe acuminata Ehrenberg, 1844, p. 84 (unfigured); Ehrenberg, 1854, pl. 22, fig. 27; subsequent designation by Frizzell and Middour, 1951, p. 33.

Eucyrtidium granatum new species
 Figure 4.1–4.4

2015

Eucyrtidium sp. A; Kamikuri, pl. 9, fig. 6a, b.

Holotype

Figure 4.1; collection number USTL 4513-1; coordinates M69/3; sample ODP 171B-1051A-2H-5W, 55–57 cm; lower part of the Podocyrtis (L.) goetheana Zone (RP16; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Eucyrtidium species with an abdominal segment that is more than twice as high as the thorax and is perforated by numerous small, closely spaced pores.

Occurrence

This rare species occurs sporadically from the upper part of the Podocyrtis (P.) chalara Zone (RP15) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell multi-segmented, subcylindrical, and very thick-walled. Cephalis relatively small, hemispherical to subspherical, perforated by a few small subcircular pores, bearing a short apical horn. Collar stricture marked by a slight constriction. Thorax campanulate to truncate conical, thick-walled, with subcircular pores scattered over the surface. Lumbar stricture marked by a moderate constriction and by a thin internal ridge that appears externally as a dark line. Abdomen subcylindrical, elongated and thick-walled, perforated by numerous, small subcircular pores, which are closely spaced and weakly arranged in longitudinal rows (18–23 in a row). Post-lumbar stricture almost invisible from the outside, marked only by a thin dark line. Fourth segment cylindrical, as broad as the abdomen but always shorter. Abdominal termination open, and invariably ragged along a row of pores.

Etymology

The name is derived from the Latin granatus, meaning ‘having many seeds or grains’, for the shell ornamentation of the new species.

Dimensions

Based on 5 specimens (mean): total length without the apical horn: 143–179 μm (162 μm), length of apical horn: 12–17 μm (15 μm), length of cephalothorax without the apical horn: 41–48 μm (44 μm), length of abdomen: 86–116 μm (96 μm), length of first post-abdominal segment: 31–45 μm (38 μm).

Remarks

Eucyrtidium granatum n. sp. differs from all other species of the genus Eucyrtidium in having a thick-walled shell with a characteristic ornamentation consisting of many small, closely spaced pores.

Superfamily Artostrobioidea Riedel, 1967
Family Artostrobiidae Riedel, 1967, sensu Sugiyama, 1998
Genus Dictyoprora Haeckel, 1887

Type species

Dictyocephalus amphora Haeckel, 1887, p. 1305, pl. 62, fig. 4; subsequent designation by Campbell, 1953, p. 296.

Dictyoprora echidna new species
Figure 4.5–4.8

1973

Theocampe amphora (Haeckel) group; Foreman, p. 431, pl. 9, fig. 8 (part).

2015

Dictyoprora sp. E; Kamikuri, pl. 12, figs. 11a, b.

Holotype

Figure 4.5; collection number USTL 4518-1; coordinates M41/3; sample ODP 171B-1051A-6H-5W, 53–55 cm; upper part of the Podocyrtis (L.) chalara Zone (RP15; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Dictyoprora species with a general ovoid outline and an abdominal segment perforated by 8 to ten closely spaced rows of pores.

Occurrence

Dictyoprora echidna n. sp. is abundant from the uppermost part of the Podocyrtis (L.) mitra Zone (RP14) to the lowermost part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell three-segmented, ovoid, and smooth externally. Cephalis subspherical to hemispherical, unarmed, deeply embedded in the thorax. Cephalic pores circular and closely spaced. Ventral pore relatively large, circular to ovoid (Fig. 4.7, 4.8). Ventral tube not developed. Collar stricture indistinct. Thorax short, trapezoidal to slightly inflated, with downwardly directed subcircular pores arranged in two or three transverse rows. Lumbar stricture marked by a thin obscure band. Abdomen barrel-shaped, thick-walled, and perforated by 8–10 closely spaced rows of downward directed subcircular pores. Shell tapers distally, ending in a hyaline, inverted-truncated conical peristome with a smooth margin.

Etymology

The specific epithet refers to the Latin name of the spiny anteaters (echidna), for the shell ornamentation of the new species, which evokes the texture of the back of these animals covered by spines.

Dimensions

Based on 26 specimens (mean): total length: 113–159 μm (135 μm), length of cephalothorax: 40–54 μm (47 μm), length of abdomen: 72–107 μm (89 μm), length of hyaline peristome: 13–23 μm (19 μm).

Remarks

Dictyoprora echidna n. sp. differs from other Dictyoprora species in having a large cephalis, which is deeply embedded in the thoracic segment, and no lumbar constriction, giving the shell an overall ovoid shape. It also differs from Phormostichoartus ashbyi Renaudie and Lazarus, 2015, in having a trisegmented shell.

A few specimens exhibiting an intermediate morphology between D. mongolfieri (Ehrenberg, 1854) and D. echidna n. sp. were observed at ODP Site 1051 (~136 mcd), suggesting that the latter is an offshoot of D. mongolfieri. This intermediate morphotype is characterized by a high number of abdominal pores, which are longitudinally aligned.

Genus Spirocyrtis Haeckel, 1882, emend. Nigrini, 1977

Type species

Spirocyrtis scalaris Haeckel, 1887, p. 1509, pl. 76, fig. 14; subsequent designation by Campbell, 1954, p. D142.

Spirocyrtis matsuokai new species
Figure 4.9–4.12

Holotype

Figure 4.9; collection number USTL 4554-1; coordinates S69/2; sample ODP 171B-1051A-14H-5W, 52–54 cm; upper part of the Podocyrtis (L.) mitra Zone (RP14; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Spirocyrtis species with a reduced ventral tube, whose shell is subcylindrical in shape, with slight post-thoracic constrictions.

Occurrence

This species is found in almost all the studied samples, from the lowermost part of the Podocyrtis (L.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell multisegmented, smooth, relatively thin-walled, subcylindrical in overall shape. Cephalis hemispherical, poreless, bearing a long straight apical tube and lacking a well-developed ventral tube. Collar stricture almost indistinct. Thorax truncate conical to cylindrical, only slightly longer than the cephalis, and penetrated by downwardly directed subcircular pores. Lumbar stricture marked by a thin dark band. Abdomen and post-abdominal segments barrel-shaped and rounded, the second post-abdominal segment being generally the widest. Each segment is perforated by subcircular pores arranged in three to four transverse rows, except for the third post-abdominal segment, which generally has only two rows of pores. Lumbar and post-lumbar strictures marked by a hyaline band. Last segment ragged along row of pores in all the observed specimens.

Etymology

This species is named in honor of Dr. Atsushi Matsuoka (Niigata University, Japan) for his contribution to the study of recent and fossil radiolarians.

Dimensions

Based on 13 specimens (mean): total length without the apical tube: 143–202 μm (164 μm), length of cephalothorax: 38–43 μm (40 μm), length of apical tube: 8–23 μm (14 μm), length of abdomen: 20–35 μm (27 μm); length of all post-abdominal segments: 77–133 μm (98 μm); maximum breadth of shell: 56–69 μm (63 μm).

Remarks

Spirocyrtis matsuokai n. sp. differs from Spirocyrtis cornutella Haeckel, 1887, in having lumbar and post-lumbar strictures marked by a poreless band; from S. gyroscalaris Nigrini, 1977, S. scalaris Petrushevskaya and Kozlova, 1972, and S. subscalaris Nigrini, 1977, in having a maximum of four transverse rows of pores on the post-abdominal segments, and a less prominent ventral tube; from S. proboscis O'Connor, 1994, in having a smaller apical tube and a more cylindrical shell; from S. scalaris Haeckel, 1887, in having fewer than five post-abdominal segments, the constrictions of which are rounded rather than sharply angular; from S. subtilis Petrushevskaya and Kozlova, 1972, in having less-developed constrictions between segments, conferring the shell a smoother outline; from S.? hollisi Renaudie and Lazarus, 2012, and S.? renaudiei Meunier and Danelian, 2023, in having a subcylindrical shell rather than a conical or a pupoid shell.

Family Rhopalosyringiidae Empson-Morin, 1981
Genus Pterocyrtidium Bütschli, 1882

Type species

Pterocanium barbadense Ehrenberg, 1874, p. 254 (unfigured); Ehrenberg, 1876, p. 82, pl. 17, fig. 6; subsequent designation by Petrushevskaya and Kozlova, 1972, p. 552.

Pterocyrtidium zitteli Bütschli, 1882
Figure 4.13–4.16

1882a

Pterocyrtidium Zitteli [sic] Bütschli, p. 531, pl. 33, fig. 28a, b.

2015

Pterocyrtidium zitteli Bütschli; Kamikuri, pl. 9, fig. 8.

Diagnosis

Pterocyrtidium species with a dichotomous apical horn, and a sparsely pored thorax and abdomen.

Occurrence

This species occurs sporadically throughout the studied interval, from the upper part of the Podocyrtis (L.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell composed of three segments, cylindrical, and thick-walled. Cephalis subspherical to globular, poreless, or perforated by a few small circular pores. Apical spine protruding as a stout, dichotomous, bladed apical horn. The main branch of the apical horn lies on the axis of the shell, the second branch extends from the cephalic wall or the proximal part of the main branch at an angle of 45–90°. Ventral spine is protruding as a pointed vertical spine, which is always shorter than the apical horn. Collar stricture slightly expressed. Thorax thick-walled, subcylindrical to ovoid-elongated. Thoracic pores vary in number and size. They may be scattered over the surface or quincuncially arranged. In the larger specimens, the primary lateral spines and the dorsal spine usually extend into the upper thorax as long, bladed, pointed wings. Thorax and abdomen separated by an internal ridge that appears externally as a thin dark band. Abdomen subcylindrical, longer than the thorax, pierced by subcircular pores that may be either longitudinally aligned or randomly arranged. Abdomen terminates in an undifferentiated margin, usually ragged along a row of pores.

Dimensions

Based on 19 specimens (mean): length of main branch of the apical horn: 32–81 μm (64 μm), length of secondary branch of the apical horn (when present): 14–51 μm (32 μm), length of ventral horn (when present): 18–55 μm (33 μm), length of wings (when present): 13–67 μm (36 μm), total length without the apical horn: 87–192 μm (127 μm), length of cephalothorax without the apical horn: 57–88 μm (76 μm), length of abdomen: 31–114 μm (60 μm).

Remarks

Pterocyrtidium zitteli differs from all other species of the genus Pterocyrtidium by its distinctive dichotomous apical horn. This species shows a great morphological variability in terms of size, number of thoracic wings, and number of thoracic and abdominal pores. Several small, stunted, aberrant morphotypes were found in the material examinated, possibly represeting juvenile specimens or aberrant forms.

Superfamily Acanthodesmioidea Haeckel, 1862
Family Cephalospyrididae Haeckel, 1882
Genus Elaphospyris Haeckel, 1882

Type species

Ceratospyris heptaceros Ehrenberg, 1874, p. 219 (unfigured); Ehrenberg, 1876, p. 66, pl. 20, fig. 2; subsequent designation by Chediya, 1959, p. 180.

Elaphospyris cordiformis new species
 Figure 5.1–5.4

Holotype

Figure 5.1; collection number USTL 4562-4; coordinates N51/2; sample ODP 171B-1051A-18X-5W, 54–56 cm; upper part of the Podocyrtis (L.) mitra Zone (RP14; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Cephalospyridid species with a smooth-surfaced shell perforated by small subcircular pores, and a pair of very short lateral cephalic spines.

Occurrence

Only the end of the stratigraphic range of the species is documented here. This corresponds to the upper part of the Podocyrtis (L.) mitra Zone (RP14).

Description

Lattice shell quadrate to cordiform, smooth-surfaced, with a slight sagittal constriction. The sagittal ring appears by transparency as a thick opaque band. Cephalis bearing a short apical horn and two reduced lateral horns. Ventral side of the cephalis perforated by four elongated unpaired sagittal-lattice pores. Other cephalic pores small, subcircular, and quincuncially arranged. Five conical feet, straight and slightly divergent, arise from the basal ring.

Etymology

Derived from the Latin cordi meaning ‘heart’ and forma meaning ‘shape’.

Dimensions

Based on 21 specimens (mean): length of cephalis: 43–57 μm (50 μm), maximum breadth of cephalis: 65–86 μm (76 μm), length of apical horn (when present): 4–12 μm (8 μm), length of lateral cephalic horns (when present): 3–6 μm (4 μm), length of feet: 27–60 μm (38 μm).

Remarks

This species is assigned to the genus Elaphospyris because of its very short apical horn, its pair of lateral cephalic horns, and its five divergent basal feet. E. cordiformis n. sp. is distinguished from other species of Elaphospyris by its smooth cephalis, which is perforated by relatively small pores and bears three very short spines. The presence of conical feet allows this species to be easily distinguished from cordiform, smooth-surfaced species of the genus Desmospyris such as Desmospyris acuta (Goll, 1968) or D. lata (Goll, 1969).

Elaphospyris quadricornis new species
Figure 5.5–5.8

2015

Dendrospyris sp. F; Kamikuri, pl. 13, figs. 3, 4.

Holotype

Figure 5.5; collection number USTL 4517-2; coordinates T47/2; sample ODP 171B-1051A-4H-5W, 56–58 cm; lowermost part of the Podocyrtis (L.) goetheana Zone (RP16; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Cephalospyridid species with a latticed shell and two pairs of lateral cephalic spines.

Occurrence

Elaphospyris quadricornis n. sp. occurs sporadically throughout the studied interval, from the upper part of the Podocyrtis (L.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell unisegmented, thick-walled, and weakly tuberculate. Sagittal ring D-shaped, dividing the cephalis into two lobes. Cephalis bearing a needle-shaped apical horn, and two pairs of straight, pointed, lateral horns. First pair of lateral horns of about the same length as the apical horn, forming an angle of ~30° with the sagittal ring; second pair of lateral horns usually longer and stronger, forming an angle of ~90° with the sagittal ring. Ventral side of the cephalis pierced by four large, unpaired sagittal-lattice pores, while the dorsal side has no sagittal-lattice pores. Other cephalic pores subcircular, hexagonally framed, and arranged in symmetry with respect to the sagittal constriction. Five straight, pointed, and slightly divergent feet arise from the basal ring.

Etymology

The specific epithet means four-horned in Latin.

Dimensions

Based on 12 specimens (mean): length of cephalis: 45–103 μm (74 μm), maximum breadth of cephalis: 58–99 μm (80 μm), length of apical horn: 6–49 μm (25 μm), length of first pair of lateral cephalic horns: 8–50 μm (33 μm), length of second pair of lateral cephalic horns: 19–58 μm (39 μm), length of feet: 27–116 μm (69 μm).

Remarks

Elaphospyris quadricornis n. sp. is assigned to the genus Elaphospyris because of the general morphology of its shell, which is similar to that of E. didiceros (Ehrenberg, 1874). Elaphospyris quadricornis n. sp. differs from all other species of the genus Elaphospyris in having two pairs of well-developed lateral cephalic horns and five long basal feet.

Superfamily Plagiacanthoidea Hertwig, 1879, emend. Sandin et al., 2019
Family Lophophaenidae Haeckel, 1882, sensu Petrushevskaya, 1971
Genus Ceratocyrtis Bütschli, 1882, emend Sugiyama, 1993

Type species

Cornutella? cucullaris Ehrenberg, 1874, p. 221 (unfigured); 1876, p. 68, pl. 2, fig. 7; subsequent designation by Petrushevskaya, 1971, p. 98.

Ceratocyrtis oconnori new species
 Figure 6.1–6.4

Holotype

Figure 6.1; collection number USTL 4526-4; coordinates R49/4; sample ODP 171B-1051A-9H-2W, 53–55 cm; Podocyrtis (L.) chalara Zone (RP15; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Ceratocyrtis species with a large, thorny cephalis that is deeply embedded in the thoracic segment.

Occurrence

This relatively rare species occurs sporadically throughout the studied interval, from the upper part of the Podocyrtis (L.) mitra Zone (RP14) to the Podocyrtis (L.) chalara Zone (RP15).

Description

Shell composed of two segments, relatively thick-walled and conical to inflated in general shape. Cephalis deeply embedded in the thoracic segment, perforated by subcircular pores, and bearing multiple horns. Delineating the cephalis from the thorax is difficult because there is no clear expression of the collar stricture. Thorax conically truncated to inflated ovate, and may have an irregular surface that is roughened by slender spines arising from the intervening pore bars (e.g., Fig. 6.2). Thoracic pores circular to elongated and randomly arranged. They are noticeably larger towards the oral end, although their size is not consistent. Distal part of the thorax ragged (Fig. 6.2–6.4) or flanked by a few long conical spines (Fig. 6.1). Aperture open wide.

Etymology

The species is dedicated to Dr. Barry O'Connor (University of Auckland, New Zealand) in honor of his detailed taxonomic study of Cenozoic polycystine radiolarians.

Dimensions

Based on seven specimens (mean): cephalothorax length without the apical horn: 121–227 μm (159 μm), length of apical horn: 8–41 μm (22 μm), maximum breadth of cephalothorax: 57–163 μm (93 μm).

Remarks

The newly discovered species bears a close morphological resemblance to the middle Oligocene species C. mashae Bjorklund, 1976 and C. robustus Bjorklund, 1976, with which it shares a spiny shell and a relatively small cephalis that is partially embedded in the thorax. However, the two latter species are different from C. oconnori n. sp. because their cephalis is clearly distinguishable from the thorax, and their thorax is less tapered in its distal half. Ceratocyrtis oconnori n. sp. is also distinguished from similar-looking spumellarian species Zealithapium mitra (Ehrenberg, 1874) and Z. oamaru O'Connor, 1999 by its rounder overall shape and its more irregularly arranged thoracic pores.

Superfamily Pylobotrydoidea Haeckel, 1882
Family Pylobotrydidae Haeckel, 1882, sensu Sugiyama, 1998
Genus Botryocella Haeckel, 1887

Type species

Lithobotrys nucula Ehrenberg, 1874, p. 238 (unfigured); Ehrenberg, 1876, p. 76, pl. 3, fig. 16; subsequent designation by Campbell, 1954, p. D144.

Botryocella? alectrida new species
Figure 5.9–5.12

Holotype

Figure 5.9; collection number USTL 4516-1; coordinates Z61/1; sample ODP 171B-1051A-4H-5W, 56–58 cm; lower part of the Podocyrtis (L.) goetheana Zone (RP16; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Pylobotrydid species with a shell that is densely perforated and has a crest of long, bladed cephalic horns.

Occurrence

This rare species occurs sporadically from the lower part of the Podocyrtis (L.) chalara Zone (RP15) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell two-segmented, laterally flattened, and relatively thick-walled. Cephalis trilobed, and perforated by numerous small, closely spaced pores, giving it a rough appearance. The anterior part of the eucephalic lobe is covered by a reniform to ovoid ante-cephalis lobe, which has three long-bladed horns (the third/posterior one corresponding to the apical spine). Absence of upper tube. Eucephalic lobe inflated, thick-walled, bearing a long, straight or curved horn. Post-cephalic lobe very reduced, and may have a short protruding horn (Fig. 5.9), which likely corresponds to the ventral spine. Collar stricture indistinct. Thorax subcylindrical, densely perforated by small, circular pores that are irregularly distributed on its surface. A small thoracic wing may develop from the dorsal spine (Fig. 5.9). Distal part of the thorax invariably ragged.

Etymology

The specific epithet means ‘rooster-like’ in Greek, in allusion to the remarkable cephalic horns of the new species.

Dimensions

Based on seven specimens (mean): length of cephalothorax without the cephalic spines: 97–78 μm (88 μm), length of eucephalic lobe: 28–33 μm (31 μm), length of ante-cephalic lobe: 36–40 μm (38 μm), length of cephalic spines: 13–39 μm (25 μm), length of thorax: 42–61 μm (51 μm).

Remarks

The newly discovered species has been tentatively assigned to the genus Botryocella due to the fact that its eucephalic lobe is partially embedded into the shell and its collar stricture is not externally well-defined (Petrushevskaya, 1971). However, this classification is only provisional because the new species lacks a galea above the eucephalic lobe. Finally, B. ? alectrida n. sp. is distinguished from other middle Eocene pylobotrydid species by its remarkable crest of cephalic horns.

Genus Pylobotrys Haeckel, 1882

Type species

Pylobotrys putealis Haeckel, 1887, p. 1121, pl. 96, fig. 21; subsequent designation by Campbell, 1954, p. D144.

Pylobotrys? bineti new species
Figure 5.13–5.16

Holotype

Figure 5.13; collection number USTL 4530-1; coordinates J41/2; sample ODP 171B-1051A-10H-2W, 53–55 cm; Podocyrtis (L.) chalara Zone (RP15; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Pylobotrydid species with an almost poreless thorax and two cephalic tubes protruding vertically and horizontally.

Occurrence

This rare species is found throughout the investigated stratigraphic interval, from the upper part of the Podocyrtis (L.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell composed of two segments and almost hyaline. Cephalis poreless and distinctly trilobed, with a small tubular post-cephalic lobe and a large globular eucephalic lobe partially embedded in a reniform ante-cephalic lobe. Ante- and post-cephalic lobes are extended into short, wide tubes that contain the apical and ventral spines. In some specimens, these tubes are open at the distal end. Thorax cylindrical, perforated by a few subcircular pores that are irregular in size and distribution. Aperture closed or undifferentiated.

Etymology

This species is named after the French architect and artist René Binet, who modeled the main entrance of the Paris Exposition Universelle of 1900 after Haeckel's drawing of Cenozoic radiolarians.

Dimensions

Based on eight specimens (mean): height of eucephalic lobe: 23–30 μm (27 μm), height of antecephalic lobe without the apical tube: 20–26 μm (23 μm), length of apical tube: 8–33 μm (22 μm), length of ventral tube: 14–42 μm (29 μm), length of thorax: 33–60 μm (48 μm).

Remarks

Pylobotrys? bineti is tentatively assigned to the genus Pylobotrys because of its distally closed, smooth-surfaced shell, and its two cephalic tubes, which include the apical and vertical spines. The new species is distinguished from Acrobotrys disolenia Haeckel, 1887 by its nearly hyaline shell and its smaller post-cephalic lobe, and from A. tritubus Riedel, 1957 in having only two cephalic tubes.

Superfamily Lithochytridoidea Ehrenberg, 1846
Family Lithochytrididae Ehrenberg, 1846, sensu Suzuki in Matsuzaki et al., 2015
Genus Lychnocanium Ehrenberg, 1846

Type species

Lychnocanium lucerna Ehrenberg, 1847, p. 55, fig. 5; subsequent monotypy (Suzuki et al., 2021).

Lychnocanium cheni new species
Figure 6.5–6.8

1975

Lychnocanium sp.; Chen, p. 462, pl. 1, figs. 8, 9.

2020

Lychnocanium tripodium Ehrenberg; Hollis et al., pl. 14, figs. 8–10b.

Holotype

Figure 6.5; collection number USTL 4562-5; coordinates O41/3; sample ODP 171B-1051A-18X-5W, 54–56 cm; upper part of the Podocyrtis (L.) mitra Zone (RP14; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Lithochytridid species with a thick-walled, hemispherical thorax and three straight, robust, and subparallel feet that are ovoid to rectangular in cross-section and longer than twice the length of the thorax.

Occurrence

Lychnocanium cheni n. sp. occurs sporadically from the upper part of the Podocyrtis (P.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell composed of two segments. Cephalis thick-walled, globular, with a short and robust conical apical horn of approximately the same length. Cephalic pores subcircular, few in number and scattered. Collar stricture expressed externally as a slight change in the shell contour. Thorax hemispherical to truncate-conical, with a thick, rough wall. Thoracic pores subcircular and quincuncially arranged. Distal margin of the thorax constricted and marked by a relatively thick hyaline band. Feet straight, subparallel and ovoid to subrectangular in cross-section. They are more than twice as long as the thorax and extend from the peristome.

Etymology

Named after Dr. Pei-Hsin Chen (Columbia University, New York), who was the first to illustrate it.

Dimensions

Based on 12 specimens (mean): length of apical horn: 21–46 μm (32 μm), length of cephalis without the apical horn: 21–33 μm (27 μm), length of thorax: 45–72 μm (56 μm), length of feet: 131–256 μm (164 μm).

Remarks

Lychnocanium cheni n. sp. differs from similar appearing lithochytridid species as follows: from Lychnocanium babylonis Clark and Campbell, 1942, group and L. tribulus Ehrenberg, 1874, in having longer, subparallel feet, and a hemispherical thorax, rather than a pyramidal to truncate conical thorax; from L. nimrodi Meunier and Danelian, 2023, by the absence of distally dilated apical horn and feet; from L. falciferum Ehrenberg, 1874, and L. forficula n. sp. by its straight feet; from L. cypselus Ehrenberg, 1874, in having longer, straighter feet and a hemispherical thorax, rather than an elongated, barrel-shaped thorax; from L. tripodium Ehrenberg, 1874, in having bigger thoracic pores and conical feet; from L. trichopus Ehrenberg, 1874, in having shorter and sturdier feet; from L. alma O'Connor, 1999, and L. waiareka O'Connor, 1999, in having conical feet and no vestigial abdomen. Finally, L. cheni n. sp. differs from L. cingulatum n. sp. in having three straight and robust feet, while those of L. cingulatum are slenderer and tend to become sinuous in their distal half. Additionally, L. cheni n. sp. has a shorter thorax, which is less than twice the height of the cephalis without the apical horn.

Lychnocanium cingulatum new species
Figure 6.9–6.12

1995

Lychnocanium conicum Clark and Campbell; Shilov, p. 126, pl. 2, fig. 1.

Holotype

Figure 6.9; collection number USTL 4561-1; coordinates X70/2; sample ODP 171B-1051A-18X-5W, 54–56 cm; upper part of the Podocyrtis (L.) mitra Zone (RP14; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Lithochytridid species with a subspherical thorax terminating in a hyaline constricted peristome and three slender feet, the distal half of which is sinuous.

Occurrence

Lychnocanium cingulatum n. sp. is quite abundant throughout the studied interval, from the upper part of the Podocyrtis (L.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell composed of two segments, broadly conical in general shape. Cephalis subspherical, with small subcircular pores, bearing a slender conical apical horn, usually longer than the cephalis height. Collar stricture distinct. Thorax subspherical, penetrated by small subcircular pores quincuncially arranged. Peristome thick, poreless and constricted, with a smooth margin. Feet slender, downwardly directed, and slightly sinuous in their distal half, originating above the peristome. In some specimens, the feet are reduced to three short claws.

Etymology

The specific epithet cingulatum means ‘with a girdle’ in Latin and refers to the hyaline peristome of the new species.

Dimensions

Based on 30 specimens (mean): length of apical horn: 16–73 μm (36 μm), length of cephalis without the apical horn: 19–30 μm (24 μm), length of thorax: 46–80 μm (61 μm), thickness of peristome: 5–12 μm (8 μm), length of feet: 44–121 μm (84 μm).

Remarks

Lychnocanium cingulatum n. sp. differs from other middle Eocene lithochytridid species in that its feet originate above the peristome, which is marked by a thick hyaline band.

Lychnocanium croizoni new species
Figure 7.1–7.4

1973

Theoperid gen. et sp. indet., Sanfilippo and Riedel, pl. 35, fig. 6.

Holotype

Figure 7.1; collection number USTL 4528-1; coordinates S67/2; sample ODP 171B-1051A-9H-5W, 53–55 cm; Podocyrtis (L.) chalara Zone (RP15; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Lithochytridid species whose feet are absent or reduced to three short claws.

Occurrence

Lychnocanium croizoni n. sp. occurs throughout the studied interval, from the upper part of the Podocyrtis (L.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell composed of two segments, thick-walled, and small. Cephalis globular, poreless, partially embedded in the thorax, and bearing a short conical apical horn. Thorax spindle-shaped to pyriform. Thoracic pores subcircular, and quincuncially arranged, but their arrangement tends to be less regular in the upper part of the thorax. Aperture open and bordered by a thick hyaline peristome with a smooth margin. Three inconspicuous conical feet originating just above the peristome are present in some specimens (Fig. 7.3).

Etymology

This species is named after the French athlete Philippe Croizon, the first limbless person to swim across the English Channel.

Dimensions

Based on 14 specimens (mean): length of cephalothorax without the apical horn: 101–123 μm (112 μm), length of cephalis without the apical horn: 19–26 μm (23 μm), length of apical horn: 7–23 μm (16 μm), length of thorax: 79–98 μm (89 μm), maximum breadth of thorax: 67–78 μm (73 μm), length of feet (when present): 10–12 μm (11 μm).

Remarks

This remarkable species differs from all other lithochytridid species in being footless, or in having its feet reduced to three short claws. Lychnocanium croizoni n. sp. is distinguished from Dictyophimus ceratium Clark and Campbell, 1942, in having shorter feet and a more slender shell with no collar constriction. It also differs from Plannapus hornibrooki O'Connor, 1999, and P. mauricei O'Connor, 1999, in having a thicker cephalic wall, a stronger apical horn, and in lacking a vertical tube.

Lychnocanium forficula new species
Figure 6.13–6.16

Holotype

Figure 6.13; collection number USTL 4561-2; coordinates J55/3; sample ODP 171B-1051A-18X-5W, 54–56 cm; upper part of the Podocyrtis (L.) mitra Zone (RP14; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Lithochytridid species with a thorax pierced by numerous closely spaced, quincuncially arranged pores and three bladed, inwardly curved feet.

Occurrence

Lychnocanium forficula n. sp. is abundant throughout the investigated interval, from the upper part of the Podocyrtis (L.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell conical, composed of two segments. Cephalis subspherical, perforated by numerous small subcircular pores, bearing a stout conical apical horn. Collar stricture marked by a sharp change in the contour of the shell. Thorax truncate conical to campanulate, with numerous closely spaced subcircular pores that are hexagonally framed and quincuncially arranged. Peristome slightly constricted and marked by a thin internal ridge. Feet three-bladed, longer than the thorax, and inwardly curved, extending from the thoracic margin. In some specimens, an inconspicuous row of reticulations has been observed on the distal margin of the thorax.

Etymology

The specific epithet refers to the Latin genus name of the European earwig (Forficula), whose male forceps are curved like the feet of the new species.

Dimensions

Based on 23 specimens (mean): length of cephalis without the apical horn: 22–34 μm (29 μm), length of apical horn: 21–53 μm (40 μm), length of thorax: 66–86 μm (76 μm), length of feet: 117–188 μm (145 μm).

Remarks

Lychnocanium forficula n. sp. differs from the similar-looking species L. cypselus Ehrenberg, 1874, in having a truncate conical thorax rather than a barrel-shaped elongated thorax. It is also distinguished from L. falciferum Ehrenberg, 1854, L. bellum Clark and Campbell, 1942, and L. trichopus Ehrenberg, 1874 by its shorter, regularly arcuate feet, which are approximately as long as the cephalothorax (excluding the apical horn). Lychnocanium forficula n. sp. can be distinguished from L. turgidum Ehrenberg, 1874, by its longer feet and its longer apical horn; from L. crassipes Ehrenberg, 1874, and L. conicum Clark and Campbell, 1942, by the presence of bladed feet; from L. tetrapodium Ehrenberg, 1874, in having three convergent feet rather than four divergent feet; and from L. cheni n. sp., L. cingulatum n. sp., and L. tripodium Ehrenberg, 1874, in having curved feet rather than straight, subparallel feet. The new species also differs from L. carinatum Ehrenberg, 1874, L. continuum Ehrenberg, 1874, L. tridentatum Ehrenberg, 1874, and L. trifolium Riedel and Sanfilippo, 1971, in having a porous thorax rather than a hyaline or partially hyaline thorax. Finally, the lack of sigmoid feet distinguishes the new species from Lychnocanoma bajunensis Renz, 1984.

Superfamily Pterocorythoidea Haeckel, 1882, emend. Suzuki et al., 2021
Family Pterocorythidae Haeckel, 1882
Genus Albatrossidium Sanfilippo and Riedel, 1992

Type species

Albatrossidium minzok Sanfilippo and Riedel, 1992, p. 16, pl. 2, fig. 7; original designation.

Albatrossidium messiaeni new species
Figure 7.5–7.8

2015

Eucyrtidium? sp. D; Kamikuri, pl. 9, fig. 9a, b.

Holotype

Figure 7.5; collection number USTL 4529-1; coordinates X42/4; sample ODP 171B-1051A-9H-5W, 53–55 cm; Podocyrtis (L.) chalara Zone (RP15; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Albatrossidium species with a thick-walled cephalis perforated by ovoid to elongated pores.

Occurrence

This species is common from the upper part of the Podocyrtis (L.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell three-segmented, cylindrical, and thick-walled. Cephalis hemispherical, very thick-walled, and bearing a prominent, broad-based apical horn. Cephalic pores subcircular, except at the base of the horn where they are longitudinally elongated and form grooves in the proximal part of the horn. Lateral lobes of the cephalis indistinct. Collar stricture marked by a moderate change in the contour of the shell. Thorax hemispherical, elongated to subcylindrical. Thoracic pores circular and quincuncially arranged. Thorax and abdomen separated by an internal ridge, that appears externally as a thick dark band. Abdomen subcylindrical, approximately as long as the thorax, or slightly shorter. Abdominal pores less regular in size and shape compared to the thoracic ones, tending toward longitudinal arrangement. Abdomen terminates in an undifferentiated, ragged margin in all observed specimens.

Etymology

Named after the French composer, organist, and ornithologist Olivier Messiaen.

Dimensions

Based on 30 specimens (mean): total length without the apical horn: 161–207 μm (183 μm), length of apical horn: 18–51 μm (37 μm), length of cephalis without the apical horn: 23–47 μm (32 μm), length of thorax: 73–101 μm (83 μm), length of abdomen: 42–97 μm (70 μm).

Remarks

Albatrossidium messiaeni n. sp. differs from A. annikasanfilippoae Meunier and Danelian, 2023 and A. regis Meunier and Danelian, 2023 in that it lacks a cephalic hole accessory cephalis spines. The new species is also distinguished from A. minzok Sanfilippo and Riedel, 1992, and A. tenellum (Foreman, 1973) by its very thick-walled cephalis, which is perforated by ovoid to elongated pores.

Genus Cryptocarpium Sanfilippo and Riedel, 1992

Type species

Cryptoprora ornata Ehrenberg, 1874 (unfigured); 1876, p. 222, pl. 5, fig. 8; original designation.

Cryptocarpium? judoka new species
Figure 7.9–7.12

non 1973

Cryptoprora ornata Ehrenberg; Sanfilippo and Riedel, pl. 35, figs. 7, 8.

?1995

Cryptocarpium? ornatum (Ehrenberg); Strong et al., p. 208, pl. 11, figs. S, T.

1997

Cryptocarpium ornatum (Ehrenberg); Hollis et al., p. 66, pl. 6, figs. 24, 25 (part).

2012

Cryptocarpium ornatum (Ehrenberg); Moore and Kamikuri, p. 6, pl. P2, fig. 4 (part).

Holotype

Figure 7.9; collection number USTL 4551-1; coordinates R40/2; sample ODP 171B-1051A-13H-5W, 58–60 cm; upper part of the Podocyrtis (L.) mitra Zone (RP14; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Pterocorythid species with a bullet-shaped shell and a short, broad-based apical horn.

Occurrence

This species is present in all of the analyzed samples, from the upper part of the Podocyrtis (L.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell three-segmented, thick-walled, and bullet-shaped. Cephalis hemispherical and composed of three lobes: a large unpaired eucephalic lobe and two smaller lateral lobes (Figures 7.10, 7.11). The thickness of the shell and the poorly developed external furrows can make the cephalic lobes difficult to distinguish. The cephalis is also a slightly embedded in the thorax, giving the species the appearance of a carpocaniid. A short, broad-based apical horn is present in most observed specimens. Thorax campanulate to subcylindrical, thick-walled and pierced by small circular pores quincuncially arranged. Lumbar stricture defined by a thick internal septum that appears externally as a dark band. Abdomen subcylindrical, perforated by subcircular pores that are less regular in size and arrangement than those of the thorax. The end of the abdomen is ragged along a row of pores.

Etymology

From the Japanese judoka, which designates the practitioner of the martial art of judo. The specific epithet refers to the large lumbar septum of the new species, which resembles the black belt of a judoka.

Dimensions

Based on 19 specimens (mean): total length without the apical horn: 109–168 μm (132 μm), length of apical horn: 6–10 μm (7 μm), length of cephalothorax without the apical horn: 20–31 μm (24 μm), length of abdomen: 28–78 μm (41 μm).

Remarks

Cryptocarpium? judoka n. sp. is tentatively assigned to the genus Cryptocarpium because of its general “carpocaniid-like” morphology, Cryptocarpium? judoka n. sp. is tentatively assigned to the genus Cryptocarpium because of its general “carpocaniid-like” morphology, its very reduced apical horn, and its trilobed cephalic shield, which is partially embedded in the thoracic segment.

Cryptocarpium? judoka n. sp. differs from the lectotype of Cr. ornatum (Ehrenberg, 1874) designated by O'Dogherty et al. (2021) in having a symmetrical cephalis bearing a short apical horn rather than a hornless asymmetrically placed cephalis, and in having more thoracic pores (~10 in a longitudinal row). Cryptocarpium? judoka n. sp. is also differs from Cr.? azyx (Sanfilippo and Riedel, 1973) by having a subcylindrical, three-segmented shell. In addition to the cephalis structure, the new species differs from the carpocaniid species Carpocanopsis cingulata Riedel and Sanfilippo, 1971, by having a subcylindrical thorax and abdomen, rather than an inflated thorax and a tapered abdomen, and from Carpocanopsis bramlettei Riedel and Sanfilippo, 1971, by having a porous abdomen. Cryptocarpium? judoka n. sp. also differs from the specimens illustrated as “pterocoryid gen. and sp. indet” by Sanfilippo and Riedel (1973, pl. 35, figs. 7, 8) in having a smaller apical horn and a cephalis that is more deeply embedded in the thoracic segment, and from the specimens illustrated as Cr. ornatum by Sanfilippo and Riedel (1992, pl. 2, figs. 18–20) in having a subcylindrical shell without a lumbar constriction.

Genus Phormocyrtis Haeckel, 1887

Type species

Phormocyrtis longicornis Haeckel, 1887, p. 1370, pl. 69, fig. 15; subsequent designation by Campbell (1954), p. D134.

Phormocyrtis microtesta new species
Figures 7.13–7.16

Holotype

Figure 7.13; collection number USTL 4529-4; coordinates W46/3; sample ODP 171B-1051A-9H-5W, 53–55 cm; Podocyrtis (L.) chalara Zone (RP15; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Phormocyrtis species with a small two-segmented shell.

Occurrence

Phormocyrtis microtesta n. sp. is very abundant in almost all the studied samples, from the upper part of the Podocyrtis (L.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell small, two-segmented, and thick-walled. Cephalis hemispherical, poreless or penetrated by a few subcircular pores, bearing a short, bladed apical horn. Collar stricture slightly expressed externally. Thorax barrel-shaped to subcylindrical, thick-walled, and twice as long as the cephalis. Thoracic pores subcircular, irregular in size, and weakly arranged in longitudinal rows. These rows contain three to six pores and are sometimes separated by inconspicuous longitudinal ridges. Distal margin of thorax undifferentiated (Fig. 7.15, 7.16) or surrounded by a few short, triangular, or rectangular spines (Fig. 7.13, 7.14).

Etymology

The specific epithet means ‘small shell’ in Greek and refers to the relatively small size of the new species compared to other members of the genus Phormocyrtis.

Dimensions

Based on 18 specimens (mean): length of apical horn: 7–16 μm (10 μm), length of cephalis without the apical horn: 16–29 μm (23 μm), length of thorax: 36–67 μm (51 μm), length of lamellar teeth: 11–30 μm (19 μm).

Remarks

Phormocyrtis microtesta n. sp. is distinguished from other Phormocyrtis species by its two-segmented shell, which as an undifferentiated peristome, or a vestigial abdomen reduced to a crown of short spines.

Family Lophocyrtiidae Sanfilippo and Caulet in De Wever et al., 2001
Genus Apoplanius Sanfilippo and Caulet, 1998

Type species

Lophocyrtis (Apoplanius) klydus Sanfilippo and Caulet, 1998, p. 12, pl. 5, fig. 5a; original designation.

Apoplanius cryptodirus new species
Figure 8.1–8.4

Holotype

Figure 8.1; collection number USTL 4533-3; coordinates W52/3; sample ODP 171B-1051A-10H-5W, 52–54 cm; Podocyrtis (L.) chalara Zone (RP15; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Apoplanius species with a short hemispherical to inflated thorax that envelopes the lower part of the cephalis.

Occurrence

Apoplanius cryptodirus n. sp. is common throughout the studied interval, from the upper part of the Podocyrtis (L.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell three-segmented, robust, and broadly cylindrical. Cephalis globular, poreless, very thick-walled, and partially embedded in a loose lattice of spines that originate from the upper margin of the thorax. Apical spine merges with the cephalic wall and is extended outward by a short conical apical horn. A secondary horn may develop on the dorsal side of the cephalis (Fig. 8.1, 8.2). Mitral arches depart from the apical spine in the middle of the cephalis and diverge quickly at a great angle (Fig. 8.4). The collar stricture is indicated by a change in the contour of the shell. Thorax hemispherical to inflated, penetrated by subcircular pores that are irregular in size and and arranged in a weak quincuncial pattern. Lumbar stricture marked by an external constriction that is underlined by a thin dark band. Abdomen subcylindrical to inflated campanulate, with subcircular pores smaller than the thoracic ones. Abdominal end ragged along a row of pores or surrounded by a crown of small spines.

Etymology

The specific epithet means ‘hidden neck’ in Greek.

Dimensions

Based on 17 specimens (mean): total length without the apical horn: 77–115 μm (103 μm), length of cephalis without the apical horn: 17–25 μm (14 μm), length of apical horn: 7–18 μm (14 μm), length of ventral horn (when present): 4–10 μm (7 μm), length of thorax: 27–40 μm (32 μm), maximum breadth of thorax: 47–60 μm (56 μm), length of abdomen: 33–60 μm (49 μm), maximum breadth of abdomen: 62–81 μm (68 μm).

Remarks

Apoplanius cryptodirus n. sp. is assigned to the genus Apoplanius based on its simple, short apical horn without three proximal openings, and its apical spine that is partially embedded in the cephalic wall (Sanfilippo and Caulet, 1998; O'Dogherty et al., 2021). Apoplanius cryptodirus n. sp. differs from A. asperus (Ehrenberg, 1874) and A. nomas (Sanfilippo and Caulet, 1998) in having a less inflated thorax, which is always narrower than the abdomen; from A. kerasperus (Sanfilippo and Caulet, 1998) in having a smaller apical horn and no auxiliary horns on the cephalis; from A. klydus (Sanfilippo and Caulet, 1998) in having a subcylindrical abdomen rather than a wavy abdomen, no thoracic wings, and no holes at the base of the apical horn. Finally, A. cryptodirus n. sp. is distinguished from Theocorys minuta Takemura and Ling, 1998, T. perforalvus O'Connor, 1997, and T. saginata Takemura and Ling, 1998, in having a horned cephalis that is partially embedded in the thorax.

Apoplanius hyalinus new species
Figure 8.5–8.7

Holotype

Figure 8.5; collection number USTL 4566-2; coordinates S37/2; sample ODP 171B-1051A-9H-5W, 53–55 cm; Podocyrtis (L.) chalara Zone (RP15; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Apoplanius species with a thick-walled hyaline thorax.

Occurrence

Apoplanius hyalinus n. sp. occurs sporadically throughout the studied interval, from the upper part of the Podocyrtis (L.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) chalara Zone (RP15), and it becomes very abundant from the upper part of the Podocyrtis (L.) chalara Zone to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell composed of three segments, cylindrical, and almost hyaline. Cephalis globular, thick-walled, and poreless, bearing a stout conical apical horn and sometimes a reduced dorsal horn (Fig. 8.6). Apical spine incorporated into the cephalic wall before dividing into two mitral arches near the top of the cephalis. Collar stricture well defined externally by a sharp change in the shell contour. Thorax short, globular flattened to inflated, thick-walled, and hyaline. The maximum thickness of the thoracic wall is reached in the middle part of the thorax, giving the thoracic wall a crescent appearance when viewed under a light microscope. Lumbar stricture marked by a slight constriction. Abdomen subcylindrical, sinuous and twice as long as the thorax. Abdominal pores subcircular, ariable in shape and size, scattered over the surface, or weakly aligned in longitudinal rows. Abdomen terminating in an undifferentiated margin.

Etymology

From the Greek hualinos, meaning ‘hyaline, transparent’.

Dimensions

Based on 24 specimens (mean): total length without the apical horn: 112–159 μm (133 μm), length of cephalis without the apical horn: 19–26 μm (22 μm), length of apical horn: 32–47 μm (37 μm), length of thorax: 32–47 μm (37 μm), maximum breadth of thorax: 47–72 μm (54 μm), length of abdomen: 55–90 μm (74 μm).

Remarks

The generic assignment of Apoplanius hyalinus n. sp. is based on its short, conical apical horn without three proximal arches, and its apical spine, which partially extends into the cephalic cavity as a columella (Sanfilippo and Caulet, 1998; O'Dogherty et al., 2021). Apoplanius hyalinus n. sp. differs from all other documented lophocyrtiid species in having a thick-walled hyaline thorax. Apoplanius hyalinus n. sp. shares many characteristics with A. kerasperus (Sanfilippo and Caulet, 1998) (Fig. 8.8), especially regarding the initial spicule, suggesting that the two species are closely related. The occurrence of relatively small and nearly poreless forms is recurrent in several Paleogene naselarian families. These hyaline species appear to be particularly abundant during the middle Eocene. They include the following taxa: Lychnocanium trifolium Riedel and Sanfilippo, 1971, and L. continuum Ehrenberg, 1874 (Lithochytrididae), Calocyclas aphradia Sanfilippo and Blome, 2001 (Theoperidae), Theocorys anapographa var. A Riedel and Sanfilippo, 1970 (Theocotylidae) and Dendrospyris fragoides Sanfilippo and Riedel, 1973 (Cephalospyrididae). Some of these species may be juveniles or aberrant forms belonging to species with a perforated skeleton; see, for example, T. anapographa var. A, which always occurs with typical T. anapographa (e.g., Sanfilippo and Blome, 2001; Meunier and Danelian, 2022).

Family Theocotylidae Petrushevskaya, 1981
Genus Thyrsocyrtis Ehrenberg, 1847

Type species

Thyrsocyrtis rhizodon Ehrenberg, 1874, p. 262 (unfigured); Ehrenberg, 1876, p. 84, pl. 12, fig. 1; subsequent designation by Campbell, 1954, p. D130.

Thyrsocyrtis kamikuri new species
Figure 8.9–8.12

2015

Thyrsocyrtis sp. D; Kamikuri, pl. 5, figs. 1a–2b.

2020

Thyrsocyrtis sp. D; Hollis et al., pl. 11, fig. 22a–c.

Holotype

Figure 8.9; collection number USTL 4563-1; coordinates B34/3; sample ODP 171B-1051A-9H-2W, 53–55 cm; Podocyrtis (L.) chalara Zone (RP15; Sanfilippo and Blome, 2001); middle Eocene.

Diagnosis

Thyrsocyrtis species with an inflated abdomen perforated by pores of the same diameter as those of the thorax, and three short, perforated feet.

Occurrence

Thyrsocyrtis kamikuri n. sp. occurs sporadically throughout the studied interval, from the upper part of the Podocyrtis (L.) mitra Zone (RP14) to the lower part of the Podocyrtis (L.) goetheana Zone (RP16).

Description

Shell composed of three segments, conical to campanulate. Cephalis small, hemispherical, sparsely perforated, and bearing a stout, bladed apical horn. Collar stricture moderately expressed. Thorax campanulate, perforated by subcircular pores of variable sizes, the largest being in the middle part of the segment. Thoracic surface sometimes slightly thorny. Lumbar stricture marked externally by a constriction and a thin internal ridge. Abdomen inflated to truncate conical, wider and longer than the thorax, with 8–10 pores on half-circumference. Abdominal pores subcircular to ovoid, of variable size but usually twice as wide as the thoracic ones. Thoracic and abdominal pores quincuncially arranged, and usually hexagonally framed. Peristome differentiated, widely open. Three short feet arising above the peristome, subparallel to divergent, and perforated by small subcircular pores.

Etymology

Thyrsocyrtis kamikuri n. sp. is named in honor of Dr. Shin-ichi Kamikuri (Ibaraki University, Japan) who first illustrated this species.

Dimensions

Based on 17 specimens (mean): total length without the apical horn: 161–228 μm (194 μm), length of apical horn: 13–55 μm (45 μm), length of cephalis without the apical horn: 20–29 μm (24 μm), length of thorax: 41–75 μm (63 μm), maximum breadth of thorax: 90–125 μm (102 μm), length of abdomen: 76–138 μm (106 μm), maximum breadth of abdomen: 114–193 μm (153 μm), length of feet: 34–70 μm (56 μm).

Remarks

Thyrsocyrtis kamikuri n. sp. differs from T. lochites (Sanfilippo and Riedel, 1982), T. orthotenes Nigrini, Sanfilippo, and Moore, 2005, T. tetracantha (Ehrenberg, 1874), and T. triacantha (Ehrenberg, 1874) in having abdominal pores less than twice the size of thoracic pores and three short, perforated feet. The new species differs from T. hirsuta (Krasheninnikov, 1960), T. rhizodon (Ehrenberg, 1874), and T. tarsipes Foreman, 1973, in having an abdomen considerably wider than the thorax, and three short, usually divergent feet without distal enlargement. Thyrsocyrtis kamikuri n. sp. also differs from T. norrisi Sanfilippo and Blome, 2001, in not having a flared peristome and an unserrated apical horn. Finally, Thyrsocyrtis kamikuri n. sp. is distinguished from Dictyopodium oxylophus Ehrenberg, 1874, in having a campanulate thorax, a relatively larger cephalis that is not partially embedded in the thorax, and no tubular latticed feet.

Conclusion

Examination of the middle Eocene radiolarian fauna recovered from ODP Site 1051 resulted in the description of 21 new species, including three spumellarians and 18 nassellarians. We also took advantage of the richness of this material to re-describe and illustrate the morphological variability of the poorly known rhopalosyringiid species Pterocyrtidium zitteli Bütschli, 1882a.

Most of the new species described here are abundant throughout the studied interval and can thus be found in almost all the samples. Fourteen bioevents were recorded: these include the first occurrences of Albatrossidium messiaeni n. sp., Botryocella ? alectrida n. sp., Ceratocyrtis oconnori n. sp., Cryptocarpium? judoka n. sp., Elaphospyris quadricornis n. sp., Eucyrtidium granatum n. sp. and Periphaena petrushevskayae n. sp., and the last occurrences of Apoplanius cryptodirus n. sp., A. hyalinus n. sp., Ceratocyrtis oconnori n. sp., Elaphospyris cordiformis n. sp., Lychnocanium croizoni n. sp., Spirocyrtis matsuokai n. sp. and Stylodictya oligodonta n. sp. These species might prove to be useful in the future to improve the stratigraphic resolution of the subtropical Atlantic Ocean, where many biostratigraphically relevant species that define the tropical radiolarian biozonation are missing or have different ranges compared to the tropics (Sanfilippo and Blome, 2001).

With the exception of Periphaena petrushevskayae n. sp., which was observed at Demerara Rise (DSDP Site 144; Petrushevskaya and Kozlova, 1972), Dictyoprora echidna n. sp. and Lychnocanium cingulatum n. sp., which were recovered from the Yucatan Shelf (DSDP Site 94; Foreman, 1973; Sanfilippo and Riedel, 1973), Thyrsocyrtis kamikuri n. sp., which was found in the Caledonian Basin (DSDP Site 206C; Hollis et al., 2020), and Lychnocanium cheni n. sp., which is known from the Naturaliste Plateau (DSDP Site 264), the new species described here have never been reported elsewhere. For some species, such as Botryocella? alectrida n. sp. or Pylobotrys? bineti n. sp., the lack of previous mention may be due to their relative scarcity in the fossil record. On the other hand, the absence in the literature of abundant and easily identifiable species, such as Albatrossidium messiaeni n. sp. or Apoplanius hyalinus n. sp., suggests that the geographic range of these species is relatively limited. These results highlight the potential interest of these species for future paleoceanographic and paleoenvironmental studies.