A Stereo-Atlas of Ostracod Shells

edited by I. Boomer, D. J. Home, A. R. Lord and D. J. Siveter

Volume 24, Parts 1 and 2; 1998 (for 1977)

Published under the aegis of the British Micropalaeontological Society. London

ISSN 0952-7451

Editors

Dr Ian Boomer, Department of Geography, University of Newcastle, Newcastle-upon-Tyne, NE1 7RU.

Tel: +191 222 5111; Fax: +191 222 5241; Email: ian.boomer@ncl.ac.uk.

Dr David J. Horne, School of Earth Sciences, University of Greenwich, Chatham Maritime, Kent, ME4 4TB.

Tel: +181 331 9841; Fax: +181 331 9805; Email: d.j.home@greenwich.ac.uk.

Professor Alan R. Lord, Department of Geological Sciences, University College, Gower Street, London WC1E 6BT.

Tel: +171 380 7131; Fax: +171 388 7614; Email: dean.maps@ucl.ac.uk.

Dr David J. Siveter, Department of Geology, The University, Leicester LEI 7RH.

Tel: +116 523925; Fax: +116 523918; Email: djs@leicester.ac.uk.

Editorial Board

Dr J.-P. Colin, Esso Production Research - European, 213 Cours Victor Hugo, F-33321 Begles, France.

Dr M.A. Ayress, Ichron Ltd., 16 Dalby Court, Gadbrook Business Centre, Rudheath, Northwich, Cheshire, CW9 7TN.
Dr R.E.L. Schallreuter, Geologisches-Palaontologisches Institut, Universitat Hamburg, Bundesstrasse 55, D-20146
Hamburg, Germany.

Professor N. Ikeya, Institute of Geosciences, Shizuoka University, Shizuoka 422, Japan.

Subscriptions

Subscriptions should be sent to Prof. Alan Lord at the above address.
Subscriptions can be made by credit card (for which there is a £1 surcharge).

Officers of the British Micropalaeontological Society

Chairman: Prof. R.J. Aldridge, Department of Geology, The University, Leicester LEI 7RH.

Secretary: Dr A.J. Powell, Dinosystems.

Treasurer: Dr J.B. Riding, British Geological Survey, Keyworth, Nottingham, NG12 5GG.

Membership Treasurer: Dr L.T. Gallagher, Network Stratigraphic Consulting Ltd., Unit 57, The Enterprise Centre,
Cranbourne Road, Potters Bar, Hertfordshire EN6 3DQ.

Editor, Journal of Micropalaeontology : Prof. Malcolm Hart, University of Plymouth.

Editor, Newsletter of Micropalaeontology : Phil Donoghue, University of Birmingham.

Calcareous Nannofossil Group: Chairman - Jeremy Young; Secretary - Matthew Hampton.

Conodont Group: Chairman - Giles Miller; Secretary - Gail Radcliff.

Foraminifera Group: Chairman - Norman McLeod; Secretary - Mike Kaminski.

Ostracod Group: Chairman - Matthew Wakefield; Secretary - Ian Slipper.

Palynology Group: Chairman - Dave Jolley; Secretary - Duncan McLean.

Instructions to Authors

Contributions illustrated by scanning electron micrographs of Ostracoda in stereo-pairs are invited. All contributions
submitted for possible publication in A Stereo-Atlas of Ostracod Shells are peer-reviewed by an appropriate inter-
national specialist. “Instructions to Authors” and plate blanks for mounting micrographs may be obtained from Dr Ian
Boomer at the address above.

Manuscripts should be submitted with a copy of the text on disc in MS Word 6 for Windows (PC) or Rich Text
Format (RTF).

The editors wish to thank Dr Eugene Kempf (University of Koln) for his assistance in preparing this issue.

The front cover shows a paratype (LV, NHM no. OS 14855, upper, dorsal view and lower, external lateral view) of
Eucytherura allisonensis Boomer, 1996 from the Oligocene of ODP Site 865B, Central Pacific Ocean. This species
was described in A Stereo-Atlas of Ostracod Shells, 22, 1 12-1 15.

A Stereo-Atlas of Ostracod Shells

edited by I. Boomer, D. J. Horne, A. R. Lord and D. J. Siveter

Volume 24, Parts 1 and 2; 1998 (for 1977)

Published under the aegis of the British Micropalaeontological Society, London

Stereo-Atlas of Ostracod Shells 24, ii

Contents

Contents

1 On Cytheropteron crassiscutum Ayress sp. nov.; by M. Ayress. 1

2 On Cythere hanaii Tsukagoshi & Ikeya; by A. Tsukagoshi. 5

3 On Eodominina ema Schallreuter sp. nov.; by R.E.L Schallreuter. 13

4 On Severobolbina elliptica (Steusloff); by R.E.L. Schallreuter. 17

5 On Scrobisylthis reticulatus (Sarv); by R.E.L. Schallreuter. 25

6 On Kirkbyrhiza retifera (Roth); by G. Becker, L.E. Petersen & R.F. Lundin. 33

7 Index for volume 24 (1998 for 1997). 41

Stereo-Atlas of Ostracod Shells 24 (1) 1-4 (1998) Cytheropteron crassiscutum (1 of 4)

595.337.14(1 18.21 + 1 18.22) (265.7 : 163.165.37): 551.352

ON CYTHEROPTERON CRASSISCUTUM AYRESS sp. nov.

by Michael A. Ayress

(Department of Geology, The Australian National University, Canberra, Australia)
Cytheropteron crassiscutum sp. nov.

Holotvpe:
Type locality:

Derivation of name:

Figured specimens:

Diagnosis:

The Department of Geology, Australian National University number ANU 56378; Adult left valve.

Deep Sea Drilling Project Site 592, southern end of Lord Howe Rise, lat. 36° 28.4' S, long. 165° 26.53' E,
1088 m water depth. Core 31 core-catcher. Zone NN3, Early Miocene.

Latin, crassus meaning thick, combined with scutum meaning shield. Referring to the thick shell of this
species.

The Department of Geology, Australian National University number ANU 56378 (holotype, adult LV: PI. 24,
2, figs. 1, 2, 5; PI. 24, 4, figs. 1, 2). ANU 56379 (juv. RV: PI. 24, 2, fig. 3; PI. 24, 4, figs. 3, 4); ANU 56380
(juv. LV: PI. 24, 2, fig. 4), latter two specimens from core-catcher, core 6, DSDP Site 592 (Zone NN15, Early
Pliocene).

A very large, thick-shelled species of Cytheropteron with an arched dorsal margin and broadly convex ventral
margin formed by a weak flange-like alar process along valve length. Posterior margin obliquely truncate with
weakly acuminate caudal process which bears a strong, ventral, terminal spine in the right valve. Weak ribs
extend close and parallel to the anteroventral margin, short secondary vertical ribs extend medianly. Ventral
surface bears diffuse, concentrically aligned ribs. Hingement antimerodont. Frontal muscle scar ovate. Selvage
strongly developed with prominent anterior denticulation consisting of about 8 teeth in the right valve.

Explanation of Plate 24, 2

Figs. 1, 2, 5, adult LV (holotype, ANU 56378, 1 127 pm long): fig. 1, ext. lat.; fig. 2, dors.; fig. 5, ant. Fig. 3, juv. RV, ext. lat. (ANU 56379. 764 pm
long). Fig. 4, juv. LV, ext. lat. (ANU 56380, 800 pm long).

Scale A (100 pm; X55), figs. 1-5.

Stereo-Atlas of Ostracod Shells 24, 3 Cytheropteron crassiscutum (3 of 4)

Remarks:

Distribution:

Acknowledgements:

The species is distinguished from other deep-sea Cytheropteron species by its large size and extremely thick
shell. The strongly dentate selvage in the right valve and pattern of ribbed ornament is also characteristic,
although the latter feature is somewhat comparable to that of Cytheropteron testudo Sars, 1869. The species
is remarkably similar to Cytheropteron carinoalatum Bate, 1972 described from the Upper Cretaceous
Gingin Chalk of Western Australia (Spec. Pap. Palaeont., 10, 45, pi. 17 figs. 10, 11). The most conspicuous
differences are the more strongly arched dorsal margin and the ovate frontal muscle scar of C. crassiscutum.
In C. carinoalatum the frontal scar is “v” shaped and the dorsal margin more sinuous. Nevertheless, the close
morphological similarity of C. crassiscutum and C. carinoalatum and their geographical and stratigraphical
relationship (range of C. crassiscutum is indicated below) strongly suggest that the former is a descendant of
the latter. A second, related species described from the Gingin Chalk, Cytheropteron collisarboris Neale,
1 975 (Spec. Pap. Palaeont ., 16, 25, pi. 8 fig. 9) differs in possessing a spinose anterior margin, straight dorsal
margin and a maximum width behind mid-length.

The species was found intermittently, in core-catcher samples of cores 5 (U. Pliocene), 6, 11 (E. Pliocene),
26 (M. Miocene) and 31 (E. Miocene), at DSDP Site 592, Lord Howe Rise, and in core-catcher of core 42
(M. Miocene) of DSDP site 593 on the Challenger Plateau, Tasman Sea. In addition a single specimen was
recorded in the Timor Sea at DSDP Site 262, core 36, section 6, Early Pleistocene. The species has also been
documented in the Upper Oligocene of Tasman Sea DSDP Site 208 and Middle to Upper Eocene of Coral
Sea, DSDP Site 209 by Millson (1987, The Palaeobiologv of Palaeogene Ostracoda from Deep Sea Drilling
Project cores in the SfV Pacific, unpubl. Ph.D. thesis, Univ. Wales, pi. 35, figs. 15-20).

I am very grateful to Kerry Swanson for allowing me to study and document the ostracod specimens which
he collected from DSDP core-catcher samples of Leg 90, SW Pacific.

Explanation of Plate 24, 4

Figs. 1, 2, adult LV (holotype, ANU 56378, 1 127 pm long): fig. 1, int. lat.; fig. 2, subcentral muscle scars. Figs. 3, 4, juv. RV, int. lat. (ANU 56379,
764 pm long).

Scale A (100 pm; X55), figs. 1, 4; scale B (100 pm, X220), fig. 2; scale C (100 pm; X200), fig. 3.

Stereo-Atlas of Ostracod Shells 24 (2) 5-12 (1998) Cythere hanaii (1 of 8)

595.337.14 ( 1 19.9) (520: 161.13837): 551.351

ON CYTHERE HANAII TSUKAGOSHI & IKEYA

by Akira Tsukagoshi

(The University Museum, The University of Tokyo, Hongo 7-3-1, Tokyo 113, Japan)

Cythere hanaii Tsukagoshi & Ikeya, 1987

1987 Cythere hanaii sp. nov., A. Tsukagoshi, & N. Ikeya, Trans. Proc. Palaeontol. Soc. Japan New Sen, 148, figs. 5d, 7-la-d.

1990 Cythere hanaii ; Tsukagoshi & Ikeya; A. Tsukagoshi, Lethaia, 23, fig. 19.

1990 Cythere omotenipponica Hanai; E.-H. Lee, Pleistocene Ostracoda from the marine sedimentary strata of the Cheiu Island, Korea, pi. 10,
figs. 7-9, text-fig. 47.

1996 Cythere hanaii Tsukagoshi & Ikeya; H. Ozawa, Sci. Rep. Kanazawa Univ., 41, pi. 3, fig. 6.

Holotype: Institute of Geosciences, Shizuoka University [iGSU] no. O 527; o* RV (Length = 0.72 mm. Height =
0.44 mm). [Paratypes: nos. O 528-0 530].

Type locality: An exposure along Hanyu River, about 250m west of Hanyu Village, Sawane-machi. Sado Island Japan
(37° 59.4' N, 138° 15.9' E). The Middle Pleistocene Kaidate Formation.

Explanation of Plate 24, 6

Figs. 1, 2, 4-6, cr car. (RA 27586, 660 pm long): fig. 1, rt. lat.; fig. 2, It. lat.; fig. 4, funnel-type pore system (Type 3 pore system of Tsukagoshi.
1990); fig. 5, proximal part of sensillum and funnel structure; fig. 6, sieve-type pore (Type 5 pore system of Tsukagoshi, 1990). Fig. 3, cr car.
dors. (RA 27591, 660 pm long).

Scale A (200 pm; X70), figs. 1-3; scale B ( 10 pm; X 1750), figs. 4, 6; (2 pm; X8750), fig. 5.

Stereo-Atlas of Ostracod Shells 24, 7 Cythere hanaii (3 of 8)

Figured specimens:

Diagnosis:

Remarks:

Acknowledgements:

The University Museum, The University of Tokyo [UMUT] nos. RA 27585 (o' car.: PI. 24, 10, figs. 1, 2, 4,
5), RA 27586 (cr car. with soft parts: PI. 24, 6, figs. 1, 2, 4-6, PI. 24, 8, figs. 4, 5, text-fig. 2), RA 27587
( 9 car.: PI. 24, 8, figs. 1, 2), RA 27588 ( 9 car.: PI. 24, 12, figs. 1, 2, 4-7), RA 27589 ( 9 car.: PI. 24, 8,
fig. 3), RA 27590 ( 9 car.; PI. 24, 12, fig. 3), RA 27591 (O’ car.: PL 24, 6, fig. 3), RA 27592 (O' car.: PI. 24,
10, fig. 3), RA 27593 ( cr car.: PI. 24, 1 1, fig.l). All figured specimens collected from rocky inter-tidal zone,
Tsuyazaki, 20 km NE of Fukuoka City, Fukuoka Pref. Kyushu, Japan (33° 46.9' N, 130° 27.1' E) on
4 June, 1988.

A species of Cythere with distinct radial ridges on well calcified and thick carapace. The number of sieve-
type pores ranges from 70 to 74. Typical distribution pattern of lateral pore systems in PI. 24, 11, fig. 2. In
male copulatory organ, posterior-distal end of outer (supporting) lobe stout. Distal end of clasping apparatus
forks and one end is thin with very fine serrature.

This species was described from fossil material by Tsukagoshi & Ikeya (1987, op. cit.). It was widely distrib-
uted along the coast of the Sea of Japan in the Late Pliocene and Pleistocene. Subsequently, living specimens
were collected from inter-tidal, rocky shores in northern Kyushu from which soft parts are described, herein.
According to Tsukagoshi (1990, op. cit.) the ontogenetic change in the distribution of pores, suggests that
Cythere hanaii and C. omotenipponica are closely related and form a species group together with C. lutea, C.
urupensis and C. valentinei within the genus Cythere.

I express my deep appreciation to Dr. Ian Boomer for his critical reading of the manuscript and kind
encouragement. I also thank Ms. Shiori Tsukagoshi for providing valuable algal samples which yielded living
specimens of Cythere hanaii. This study was partly supported by the Grant-in-Aid for Scientific Research
(No. 09740636) of the Ministry of Education, Science and Culture, Government of Japan.

Explanation of Plate 24, 8

Figs. 1, 2, a car. (RA 27587, 670 pm long): fig. 1, rt. lat.; fig. 2, It. lat. Fig. 3, 9 car. dors. (RA 27589, 650 pm long). Figs. 4, 5, cr car.
(RA 27586): fig. 4, sieve-type pore system (Type 4 pore system of Tsukagoshi, 1990); fig. 5, proximal part of sensillum and sieve plate with
com-like processes

Scale A (200 pm; X70), figs. 1-3; scale B ( 10 pm; X 1750), fig. 4; (2 pm; X8750), fig. 5.

Stereo-Atlas of Ostracod Shells 24, 6

Cy there hanaii (2 of 8)

Stereo- Atlas of Ostracod Shells 24, 8 Cythere hanaii (4 of 8)

Stereo-Atlas of Ostracod Shells 24, 9

Cy there hanaii (5 of 8)

Text-fig. 1. Appendages of C. hanaii , o- (RA 27585). A, antennule; B, antenna; C, mandible; D, maxilla; E, walking leg; F, male copulatory organ. Scale = 100 pm
(approx.) for A-F.

Explanation of Plate 24, 10

; j Figs. 1, 2, 4, 5, o* car. (RA 27585, RV 660 pm long, LV 680 pm long): fig. 1, disarticulated car., rt. valve, int. lat. ; fig. 2, disarticulated car., It.

| | valve, int. lat.; fig. 4, adductor muscle scars, RV; fig. 5, adductor muscle scars, LV; Fig. 3, cr car. vent. (RA 27592, 680 pm long).

; j Scale A (200 pm; X70), figs. 1-3; scale B (40 pm; X450), figs. 4, 5.

•••!••! V

Stereo-Atlas of Ostracod Shells 24, 1 1

Cythere hanaii (7 of 8)

Text-fig. 2. (RA 27593). A, distribution of marginal pore canals; B, typical distribution pattern of lateral pores in Cythere hanaii , black dots and asterisks indicate
sieve-type and funnel-type pores respectively; C, geographical and geological distribution of Cythere /ia«a;7Tsukagoshi & Ikeya. 1987 (op. cit.). Solid black circles
indicate Recent records, triangles mark Late Pliocene to Late Pleistocene localities. Scale = 200 pm (approx.) for A, B.

Explanation of Plate 24, 12

Figs. 1, 2, 4-7, 9 car. (RA 27588, 650 pm long): fig. 1, disarticulated car., rt. valve, int. lat.; fig. 2, disarticulated car.. It. valve, int. lat.; fig. 4,
anterior hinge element, RV; fig. 5, posterior hinge element, RV; fig. 6, posterior hinge element, LV; fig. 7, anterior hinge element, LV Fig. 3,
car. dor. (RA 27590, 680 pm long).

Scale A (200 pm; X70), figs. 1-3; scale B (50 pm; X360), figs. 4-7.

Stereo-Atlas of Ostracod Shells 24, 10

Cythere hanaii (6 of 8)

Stereo-Atlas of Ostracod Shells 24, 12

Cythere hanaii (8 of 8)

Stereo-Atlas of Ostracod Shells 24 (3) 13—16 (1998) Eodominina ema (1 of 4)

595.336.12 (113.311) (941:163.126.18): 515.351

ON EODOMININA EMA SCHALLREUTER sp. nov.

by Roger E. L. Schallreuter
(University of Hamburg, Germany)

Eodominina ema sp. nov.

Holotype:

Type locality:

Derivation of name:
Diagnosis:

Commonwealth Palaeontological Collections, Australian Geological Survey, Canberra, A.C.T., Australia
(CPC), no. 23054; right valve.

[Paratypes: CPC nos. 23055-23057; Museum fur Naturkunde, Berlin, Germany (MB), nos.
0.218-0.219]

Type section of the Emanuel Formation at Prices Creek, northern Western Australia; approximately lat.
18° 35' 48" S, long. 125° 53' 00" E. Sample no. WCB 705/1 17, from the Lower Emanuel Formation (exact
horizon not determined), Arenig Series, Ordovician.

With reference to the stratigraphical occurrence of the species, in the Lower Emanuel Formation.
Eodominina with lobes relatively broad, dorsally somewhat bulb-like, at best only weakly protruding over the
hinge line; tips of the lobes are weakly inclined to each other. Adult valves are up to at least 1.07 mm long.

Explanation of Plate 24, 14

Fig. 1, RV ext. lat. (holotype, CPC 23054, 1.07 mm long). Fig. 2, RV ext. lat. (paratype, CPC 23055, 0.81 mm long). Fig. 3, juv. LV, ext. lat.
(paratype, CPC 23056, 0.62 mm long).-

Scale A ( 100 pm; X72), fig. 1 ; scale B ( 100 pm; X94), fig. 2; scale C ( 100 pm; X88), fig. 3.

Stereo-Atlas of Ostracod Shells 24, 15 Eodominina ema (3 of 4)

Figured specimens: CPC nos. 23054 (holotype, RV: PI. 24, 14, fig. 1), 23055 (paratype, RV: PI. 24, 14, fig. 2), 23056 (paratype,
LV: PI. 24, 14, fig. 3) and 23057 (paratype, car.: PI. 24, 16, fig. 3). MB nos. 0.218 (paratype, car.: PI. 24, 16,
fig. 1 ) and 0.219 (car.: PI. 24, 16, fig. 2).

All of the figured specimens were obtained from the same sample (WCB 705/117) as the holotype.

Remarks: In the younger Eodominina nuela Schallreuter ( Stereo-Atlas Ostracod Shells 20, 121-124, 1993) the main
lobes (Lj , L3) are more spine-like and the dorsal ends are more parallel to each other. In E. ema the tips of
the lobes are inclined to each other and normally are not spine-like. These differences are evident in the
populations of specimens of the two forms.

Distribution: Known only from the Lower Emanuel Formation at the type section; Arenig Series, Ordovician. Recovered
from samples WCB 705/46, 68, 78, 105,1 17, 124, 130, 141, 143-5, 149, 150, 167 and 174.

Explanation of Plate 24, 16

Fig. 1, car. ext. It. lat. (paratype, MB 0.218, 1.07 mm long). Fig. 2, car. ext. It. lat. (paratype, MB 0.219, 1.09 mm long). Fig. 3, car. ext. vent.

(paratype, CPC 23057, 1.02 mm long).

Scale A (100 pm; X70), figs. 1, 2; scale B (100 pm; X54), fig. 3.

Eodominina ema (2 of 4)

Stereo-Atlas of Ostracod Shells 24, 14

Stereo-Atlas of Ostracod Shells 24, 16 Eodominina ema (4 of 4)

Stereo-Atlas of Ostracod Shells 24 (4) 17-24 (1998) Severobolbina elliptica (1 of 8)

595.336.13 (1 13.31) (485:161.014.55 + 161.018.57): 551.351 + 552.55

ON SEVEROBOLBINA ELLIPTICA (STEUSLOFF)

by Roger E. L. Schallreuter
(University of Hamburg, Germany)

Genus SEVEROBOLBINA Schallreuter, 1974
Type-species (by original designation): Strepula elliptica Steusloff, 1895

Diagnosis: Large, unisulcate Severobolbina ; sulcus (S2) short. Preadductorial node (L2) flat and indistinct. No distinct posteroventral lobe (L3

ventral). Tecnomorphic velum reduced, manifest only as an indistinct, flat, bulge-like ridge. No histium in tecnomorphs. Female velum
and histium occur as flanges which unite in the anteroventral part of the valve. Marginal sculpture is a row of spines. Surface smooth or
tuberculate. Adults up to more than 2 mm long.

Remarks: Severobolbina (= Severella Schallreuter, 1964 non Sapelnikov, 1963) is a member of the Sigmoopsinae (Tetradellidae). It is characterized

by having only one short sulcus and also by tecnomorphs which lack a histium and have a much reduced velum.

In the morphology of its adventral sculptures Severobolbina resembles the perspicilline Pentagona Schallreuter, 1964. The latter differs
by its long sigmoidal sulcus, its distinct tecnomorphic velar ridge and its flange-like marginal sculpture.

Both S. elliptica and the other known congeneric species, Ctenobolbina kuckersiana Bonnema, have previously been assigned to Cari-
nobolbina Henningsmoen, 1953. The latter differs from Severobolbina by the development of two long sulci (S2 and S3) and by lacking
a confluence of its histium and velum anteriorly. Carinobolbina is now considered a subgenus of Kiesowia (Schallreuter, R.E.L., Stereo-
Atlas Ostracod Shells , 6 (2), 79, 1979).

Severobolbina elliptica (Steusloff, 1895)

1895 Strepula elliptica sp. n. A. Steusloff, Z. Dt. geol. Ges ., 46 (4), 778, pi. 58, fig. 21.

1924 Steusloffia (Strepula) elliptica (“wahrscheinlich eine Ctenobolbina- Art”); E. Kummerow, Jb. Preuss. geol. Landesanst., 44, 407, 408.

1955 Carinobolbina severa sp.n. (nom. nud). L. I. Sarv, Fauna ostrakod ordovika Estonskoj SSR, Avtoref. diss., 10, table 2(15).

1959 Carinobolbina severa sp. n. L. I. Sarv, Eesti NSV Teaduste Akad. Geol. Inst. Uurimused , 4, 138-9, 193, table 2 (189), pi. 24, figs. 8-15.

1964 Severella elliptica (Steuslov, 1894) (= Carinobolbina severa Sarv, 1959); R.E.L. Schallreuter, Ber. geol. Ges. DDR , 9 (3), 395.

1966 Severella severa (Sarv); R. M. Mannil, Istorija razvitiya Baltijskogo bassejna v ordovike , 68, 69 (cf.).

1966 Severella elliptica (Steusloff, 1894) & Severella severa (Sarv, 1959); V. Jaanusson, Publ. Palceo. Inst. Univ. Uppsala , 66 = Bull. Geol. Inst. Univ. Uppsala , 43 (6/8), 7, 1963, 14-15, pi. 1, figs. 1-5. text-fig. 3.

1967 Severella elliptica (Steusloff, 1895) = Carinobolbina severa Sarv, 1959; R.E.L. Schallreuter, N. Jb. Geol. Paldont. Mh ., 1967, 436-7.

1969 Severella elliptica ; V.S. Krandievsky, Dopovidi Akad. nauk Ukrainsk. RSR, ser. B , 1969 (10), 872, table 1.

1973 Severella severa Sarv; N. Sidaravichene, Doklady Akad. nauk SSSR, 209, 83.

Explanation of Plate 24, 18

Fig. 1, 9 LV, ext. lat. (AGH G161-1, 1.96 mm long). Fig. 2, 9 RV, ext. lat. (AGH G161-2, 1.98 mm long).
Scale A (250 pm; X50), figs. 1, 2.

Stereo- Atlas of Ostracod Shells 24, 19

Severobolbina elliptica (3 of 8)

1974 Carinobolbina severa ; V. Nestor, Cat. Paleont. Coll., 75.

1978 Carinobolbina severa Sarv; L.K. Gailite, Ocherki geol. Latvii, 31.

1982 Severobolbina elliptica (Steusloff, 1895); R. Schallreuter, Palaeontographica A, 178 (1/3), 24, 25-26, pi. 3, figs. 7-1 1, pi. 4, fig. 4, table 8 (q.v. for full synonymy).

1982 Severella severa (Sarv); L.K. Gailite in R. Zh. Ulst (ed), Ordovik Latvii, table 9 (125).

1983 Severobolbina elliptica (Steusloff, 1895); R.E.L. Schallreuter, Palaeontographica A, 180, 166, 180, pi. 10, fig. 4 (q.v. for further synonymy).

1984 Severobolbina elliptica (Steusloff, 1895); R.E.L. Schallreuter, N. Jb. Geol. Palao. Abh., 169 (1), 5.

1985 Severobolbina severa (Sarv); L. Sarv et al ., Eesti NSV Teaduste Akad. Toimetised, Geol., 34 (2), 44, faunal log on p. 42.

1985 Severobolbina elliptica (Steusloff), 1894; J. Sztejn, Biul. Inst. Geol., 350, 78, tables 1, 2, pi. 5, fig. 9.

1986-7 Severella elliptica (Steusloff, 1894A) of Schallreuter, 1964D; Severobolbina elliptica (Steusloff, 1894A) of Schallreuter, 1974B; Strepula elliptica Steusloff, 1894 A; Strepula ? elliptica (Steusloff, 1894A) of
Bassler & Kellett, 1934A; E. K. Kempf, Geol. Inst. Univ. Koln Sonderveroeff. , 50, 691,704; 51, 200; 52, 438, 609, 109, 184.

1986-7 Carinobolbina severa Sarv, 1959A; Severella severa (Sarv, 1959A) of Schallreuter, 1964D; E.K. Kempf, Ibid. , 50, 158, 691; 51, 539; 52, 352, 438.

1987 Severobolbina elliptica (Steusloff, 1895); R.E.L. Schallreuter, N. Jb. Geol. Palao. Abh., 174 (1): 25.

1987 Severobolbina elliptica (Steusloff, 1895); R.E.L. Schallreuter, Geol. Palao. Westfalen , 7, 16.

1987 Severella severa (Sarv); V.F Ropot & V.I. Pushkin, Ordovik Belorussii, fig. 8 (faunal log).

1988 Severobolbina ( Severobolbia resp.) elliptica (Steusloff); L. Polma et al., Lithology and fauna of the Caradoc Series type sections in North Estonia, 26, 28, 29, 41, 44, 60, figs. 9-1 1, 16-19, 26-27 (faunal logs).

1989 Severobolbina elliptica (Steusloff, 1895); R.E.L. Schallreuter, N. Jb. Geol. Palao. Mh., 1989 (4), 244, 245.

1989 Strepula elliptica Steusloff, 1894; E. Herrig & H. Nestler, Katalog der paldozoologischen Typen, 25 (no. 204).

1990 Severobolbina elliptica (Steusloff, 1894); V. A. Ivanova in A.F Abushik et al., Prakticheskoe rukovodstvo po mikrofaune SSSR, 4. 67, 235, pi. 10, fig. 9.

1990 Severella or Carinobolbina resp. severa Sarv; H. Aru et al.. Field Meeting Estonia 1990, fig. 60 A (190).

1990 Severobolbina elliptica (Steusloff, 1895); R.E.L. Schallreuter, Fossilien von Sylt, 3, pi. 3, fig. 1 1.

1992 Severobolbina elliptica (Steusloff, 1895); N. Sidaraviciene, Ostrakody ordovika Litvy, 57, 58, 233, table 2 (208), pi. 12, figs. 10-12.

1993 Severobolbina [ Strepula ] elliptica (St.) Sch.,1973; R.E.L. Schallreuter, Geol. Palao. Westfalen, 27, table 2.

1996 Severobolbina elliptica (Steusloff, 1895); N. Sidaraviciene, Lietuvos ordoviko ostrakodai, biostratigrafija, 16, 23, table 4—7, figs. 3, 5-9 (faunal logs).

1996 Severobolbina elliptica ; J. Nolvak & L. Hints in T. Meidla et al.. The 3rd Baltic Stratigraphical Conference, fig. A5.

Holotype:
Type locality:
Diagnosis:
Figured specimens:

Institut fur Geologie und Palaontologie (UGIGP), University of Greifswald, Germany, no. 114/60 (catalogue no. 204); external mould and
steinkern of a female right valve.

Neubrandenburg, Mecklenburg, Germany; approximately lat. 53° 34' N, long. 13° 16' E. Upper Viruan Geschiebe (glacial erratic boulder);
incorrectly designated by Steusloff as “Brandschiefer” (kuckersite). Caradoc Series, Ordovician.

Severobolbina with short sulcus and relatively distinct preadductorial node. Histium oblique to dorsal border. Surface smooth or weakly tuber-
culate. Females mostly between 1.70 and 2.30 mm long.

Archiv fur Geschiebekunde, Geologisch-Palaontologisches Institut und Museum, University of Hamburg (AGH), Germany, nos. G161-1
( 9 LV: PI. 24, 18, fig. 1; PI. 24, 22, fig. 3; PL 24, 24, fig. 5), G161-2 ( 9 RV: PI. 24, 18, fig. 2; PI. 24, 22, fig. 4; PL 24, 24, fig. 4), G161-3
(tecnomorphic LV: PL 24, 20, fig. 1; PL 24, 22, fig. 1), G161-4 (tecnomorphic RV: PL 24, 20, fig. 2; PL 24, 22, fig. 2), G161-5
(tecnomorphic LV: PL 24, 24, fig. 1), G161-6 (tecnomorphic RV: PL 24, 24, fig. 6), G161-7 (tecnomorphic car.: PL 24, 24, figs. 2, 3), and
G161-8 (silcoset cast of external mould of holotype, 9 RV: PL 24, 22, fig. 5).

Explanation of Plate 24, 20

Fig. 1, tecnomorphic LV, ext. lat. (AGH G161-3, 1.73 mm long). Fig. 2, tecnomorphic RV, ext. lat. (AGH G161-4, 1.72 mm long).
Scale A (250 pm; X56), figs. 1 , 2.

Stereo-Atlas of Ostracod Shells 24, 21

Severobolbina elliptica (5 of 8)

0.9

mm

0,5

0.9

L

1.1

1.3

1.5

1.9

mm

1.7

0.9

L

Text-fig. 1. Ontogeny of Severobolbina elliptica. A, Length:height (L:H) diagram; B, Length:shape (gestalt, L:H ratio) diagram. Based on 21 female (open circles)
and 60 tecnomorphic (dots) specimens from 1 4 Backsteinkalk erratic boulders from N Germany and N Poland; Caradoc Series, Ordovician. The domicilium is
measured from its inner side to the inner side of the contact margin or hinge margin respectively.

Explanation of Plate 24, 22

Fig. 1, tecnomorphic LV, ext. vent. obi. (AGH G161-3). Fig. 2, tecnomorphic RV, ext. vent. obi. (AGH G161-4). Fig. 3, 9 LV, ext. vent. obi.
(AGH G161-1). Fig. 4. 9 RV, ext. vent. obi. (AGH G161-2). Fig. 5, 9 RV, posterolat. obi., cast (AGH G161-8. 1.78 mm long) of the external
mould of the holotype (UGIGP 114/60).

Scale A (250 pm; X40), figs. 1, 2; scale B (250 pm; X36), figs. 3, 4; scale C (250 pm; X29), fig. 5.

Stereo-Atlas of Ostracod Shells 24, 23 Severobolbina elliptica (7 of 8)

All specimens except the holotype are from Backsteinkalk geschiebes; Idavere “stage” (C3) or Johvi “stage” (Dl), Caradoc Series, Ordovi-
cian. G161-1 to G161-4 are from geschiebe Gis30 from Gislovshammar, Scania, approximately lat. 55° 29' N, long. 14° 18' E; the others are
from geschiebe G29 from the Isle of Gotland, Sweden (cf. Schallreuter 1983, 1 65—6), approximately lat. 57° 18' N, long. 18° 8' E.

Remarks: According to Schallreuter (1964, op. cit.) Strepula elliptica Steusloff, 1895 is a senior synonym of Carinobolbina severa Sarv, 1959. Jaanusson
(1966, op. cit.) considered the designation of the latter as the type-species of the genus as unfortunate because this “poorly known species” came
“from an erratic boulder” of northern Germany, and because the author “overlooked the fact that, according to the Article 23b of the Interna-
tional Code of Zoological Nomenclature (1961), a name that has remained unused as a senior synonym in the primary zoological literature for
more than fifty years is to be considered a forgotten name”. In my opinion Jaanusson interpreted the article incorrectly: the earliest the name
elliptica would have been an nomen oblitum would be in the year 2009, fifty years after the introduction of the name severa, and only if the
senior synonym elliptica had not been used in those fifty years (Schallreuter, 1967, op. cit.). The ICZN article in question is now defunct.

Jaanusson also thought that “the synonymy of these two species has not been proved beyond doubt”. He cited Kummerow (1924, op. cit.),
who considered the holotype of S. elliptica to be an unidentifiable steinkern and that, in contrast to its generic features, its specific characters
were poorly discernible. He argued that the holotype of elliptica (length 1.78 mm) is considerably smaller than any female of S. severa which
he examined and in this respect is more similar to S. kuckersiana. He concluded that “without additional material it is impossible to confirm if
S. elliptica is conspecific with S. kuckersiana, whether it represents an aberrant specimen of S. severa, or belongs to a third species”.

The two female specimens of S. severa measured by Sarv (1959, op. cit., 138) are 2.00-2.20 mm long. Females from several Backsteinkalk
geschiebes of northern Germany range from 1.74-2,14 mm in length (Text-fig. 1).

Distribution: Ordovician of Europe.

N Estonia: Idavere (C3) and Johvi stages (Dl) (Sarv, 1959, op. cit ). SW Estonia: ? lower Keila “stage” (Martnil, 1966, op. cit., 69). Latvia:
Eastern facies zone: Shventupys-Viluchiai (-C3-D2) (Gailite, 1982, op. cit.). Lithuania: id, jh, and kl (Idavere-Keila “stages”) of several
boreholes (Sidaravichiene, 1992, op. cit.). Byelorussia: D1-D2 ofVangishki 205 borehole (Ropot & Pushkin, 1987, op. cit.).

Podolia: perevidkladeni vapnyaki (Krandievsky, 1969, I. c.). Eastern Poland: lithuanian facies zone of borehole Mielnik IG 1;
Idavere-Oandu/Rakvere “stages”.

Isles of Gotland, Gotska Sandon and Saaremaa (Osel): Johvi-lower Keila “stages” (Mannil, 1966, op. cit., 68).

Geschiebe: occurs in many Backsteinkalk geschiebes (Baltic and Intermediate types) of northern Central and southern N Europe: Nien-
hagen, Schleswig-Holstein; Neubrandenburg, Mecklenburg; Isle of Hiddensee, Peninsula Kleiner Zicker, Isle of Riigen, Mockowberg; Rixhoft,
Pommerellen; Gislovshammar, Scania; NW coast, Isle of Gotland.

Explanation of Plate 24, 24

Fig. 1, tecnomorphic LV, ext. lat. (AGH 161-5, 1.54 mm long). Figs. 2, 3, tecnomorphic car. (AGH G161-7, 1.49 mm long); fig.2, ext. vent.;
fig. 3, detail of the sculptures at the free margin. Fig. 4, 9 RV, ext. anterovent. obi. (AGH G161-2). Fig. 5, 9 LV, ext. anterovent. obi. (AGH
G161-1). Fig. 6, tecnomorphic RV, ext. lat. (AGH G161-6, 1.61 mm long).

Scale A (250 pm; X45), fig. 1 ; scale B (250 pm; X47), fig. 2; scale C (25 pm; X 195), fig. 3; scale D (250 pm; X30), fig. 4; scale E (250 pm;
X32), fig. 5; scale F (250 pm; X37), fig. 6.

Stereo-Atlas of Ostracod Shells 24, 22 Severobolbina elliptica (6 of 8)

Stereo-Atlas of Ostracod Shells 24 (5) 25-32 (1998) Scrobisylthis reticulatus (1 of 8)

595.336.13 (1 13.31) (430:161.008.54): 551.351 + 552.55

ON SCROBISYLTHIS RETICULATUS (SARV)

by Roger E. L. Schallreuter
(University of Hamburg, Germany)

Genus SCROBISYLTHIS Schallreuter, 1982
Type-species (by original designation): Sigmobolbina quanta var. reticulata Sarv, 1959

Diagnosis: Small, unisulcate Scrobisylthis sp.; adults less than 1 mm long. Valves rather flat. Sulcus (S2) is a broad, shallow pit. Lobes not
distinctly developed. Velum occurs as a keel-like ridge in males; as a narrow flange forming a flat admarginal antrum anteriorly and
ventrally in females; is often lacking in larvae. Histium occurs as a small ridge close to the velum; ends posteriorly as a short spine
(and is reminescent of a spine on a posteroventral lobe); though essentially non-dimorphic, is often not so strongly developed in
males as in the females; sometimes lacking in both dimorphs. No distinct marginal sculpture. Most of valve lateral surface is
reticulate or punctate; smooth adjacent to the dorsal margin.

Remarks: Sylthis Schallreuter, 1982 is distinguished from Scrobisylthis by having S2 developed as a cavum and by the occurrence of a poster-
ventral lobe (L3) and a fissum-like furrow behind and sometimes anteroventrally of that lobe (Schallreuter, R.E.L., N. Jb. Geol.
Palao. Mh., 1982 (9), fig. 1.5-6). Disulcinoides Schallreuter, 1982 differs by having a long and sigmoidal S2 and a crista parallel to
the posterior margin of the valve (loc. cit., fig. 1 .2—4).

Adults of Scrobisylthis have a dimorphic velum and a more or less distinct, torus-like, essentially non-dimorphic histial ridge
ending posteriorly as a weak spine. Such a distinct histium is rare among unisulcate Sylthinae (Tetradellidae); it indicates that Scro-
bisylthis probably had its origin in quadrilobate forms such as Consonopsis Schallreuter, 1967.

The Sylthinae are small tetradellids (adults are typically less than 1 mm long), characterized by having a velum which in females
forms are anteriorly closed, admarginal botulate antrum. A non-dimorphic histium may be present, forming a ridge-like bend near
the velum in some taxa ( Scrobisylthis ), or together with a rudimentary L4 forming a crista in posterior part of the valve (Disulci-
noides), or is fused totally with the velum to form a histiovelum (Sylthis). A non-dimorphic histium is also present in the

Explanation of Plate 24, 26

Figs. 1-5, 9 RV (AGH G159-1, 618 pm long): fig. 1, ext. lat.; fig. 2, ext. ant.; fig. 3, ext. dors.; fig. 4, ext. vent, obi.: fig. 5, lat. detail of
reticulation. Figs. 6-8, 9 RV (AGH G159-2, 655 pm long): fig. 6, ext. lat.; fig. 7, ext. post.; fig. 8. lat. detail of reticulation.

Scale A ( 100 pm; X 1 15), figs. 1, 4, 6; scale B ( 100 pm; X95), figs. 2, 3, 7; scale C (25 pm; X335), figs. 5, 8.

Stereo- Atlas of Ostracod Shells 24, 27

Scrobisylthis reticulatus (3 of 8)

tetradellines; some of their quadrilobate or rudimentary quadrilobate members, for example Consonopsis, possibly more
appropriately belong in the Sylthinae.

Scrobisylthis reticulatus (Sarv, 1959)

1959 Sigmobolbina quanta var. reticulata sp. et var. n. L.I. Sarv, Eesti NSV Teaduste Akad. Geol Inst. Uurimused. 4, 132, 193, table 2 (189), pi. 23, figs. 20, 21 .

1962 Sigmobolbina quanta var. reticulata Sarv, 1959; S.A. Levinson, Micropaleo.. 8(1), 100.

1970 Hesslandella auricularis reticulata (Sarv); A. Roomusoks, Stratigrafija viruskoj i char'yuskoj serij (ordovik) Severnoj Estonii, 1, table 13 (246).

1974 Sigmobolbina quanta reticulata ; V. Nestor, Cat. paleont. Coll., 76

1976 Henningsmoenia ? reticulata (Sarv); V. Jaanusson, in M.G. Bassett (ed.), The Ordovician System: proc. Palaeo. Assoc, symp. Birmingham , figs. 10A, 1 1 (faunal logs).

1982 Scrobisylthis reticulatus (Sarv, 1959); R.E.L. Schallreuter, N. Jb. Geol. Palao. Abh., 1982 (9), 553, 554, 557, fig. 1.1.

1983 Scrobisylthis reticularis (Sarv, 1959); R.E.L. Schallreuter, Palaeontographica A, 180 (4/6), 161, 162, pi. 28 (14), fig. 4.

1984 Scrobisylthis reticulatus (Sarv, 1959); R.E.L. Schallreuter, N. Jb. Geol. Palao. Mh., 1984 (1), 34.

1984 Scrobisylthis reticulatus (Sarv, 1959); R.E.L. Schallreuter, N. Jb. Geol. Palao. Abh., 169 (1), 7, 8.

1985 Scrobisylthis reticulatus (Sarv, 1959); R.E.L. Schallreuter, Fossilien von Sylt, 1, pi. 3 (87), fig.3.

1986-7 Scrobisylthis reticulatus (Sarv, 1959A) of Schallreuter 1982A; Sigmobolbina quanta reticulata of Sarv, 1959A; Sigmobolbina reticulata (Sarv, 1959A) of Schallreuter 1982A;
E.K. Kempf, Geol. Inst. Univ. Kbln Sonderveroeff., 50, 684, 694; 51, 502, 487, 501; 52, 730, 353.

1987 Scrobisylthis reticuesatus (Sarv, 1959), Scobisylthis reticulatus (Sarv, 1959); R.E.L. Schallreuter, N. Jb. Geol. Palao. Abh., 174 (1): 25, table 1 (26).

1988 Scrobisylthis reticulatus (Sarv); L. Polma et al.. Lithology and fauna of the Caradoc Series type sections in North Estonia, 43, 44, 61, figs. 9, 19, 26, 27 (faunal logs).

1990 Scrobisylthis reticulatus (Sarv, 1959); VA. Ivanova in A.F. Abushik et al., Prakticheskoe rukovodstvo po mikrofaune SSSR, 4, 71, 236, pi. 12, fig. 3.

1990 Scrobisylthis reticulatus (Sarv, 1959); R.E.L. Schallreuter, Fossilien von Sylt, 3, 255, tables 2-4.

1993 Scrobisylthis reticulatus (Sarv, 1959); R.E.L. Schallreuter, Geol. Palao. Westfalen, 27, 45.

1996 Scrobisylthis reticulatus (Sarv, 1959); T. Meidla, Late Ordovician Ostracodes of Estonia, 73, fig. 7 (faunal log), table 9 (206), pi. 13, fig. 9.

Holotype:
Type locality:
Diagnosis:
Figured specimens:

Institute of Geology, Tallinn, Estonia, no. Os 2290; female (?) left valve.

Alliku, Estonia; Johvi “stage” ( D 1 ), Caradoc Series, Ordovician.

As for genus, which is currently monotypic.

Archiv fur Geschiebekunde, Geologisch-Palaontologisches Institut und Museum, University of Hamburg (AGH), Germany, nos.
G159-1 ( 9 LV: PI. 24, 26, figs. 1-5). G159-2 (9 RV: PI. 24, 26, figs. 6-8), G159-3 (juv. LV: PI. 24, 28, figs. 1-3), G159-4 (juv.
LV: PI. 24, 32, fig. 6), GI59-5 (o’ LV: PI. 24, 30, figs. 1-3), G159-6 (juv. LV: PI. 24, 30, fig. 4), G159-7 (9 LV: PI. 24, 32,
figs. 1-4), G 159-8 (juv. car.: PI. 24, 30, fig. 5; PI. 24, 32, fig. 5) and G159-9 ( 9 RV: PI. 24, 28, figs. 4-8).

Explanation of Plate 24, 28

Figs. 1-3, juv. LV (AGH G159-3, 543 pm long): fig. 1, ext. lat.; fig. 2, ext. vent.; fig. 3, lat. detail of reticulation. Figs. 4-8, 9 RV (AGH
G159-9, 659 pm long): fig. 4, ext. lat.; fig. 5, ext. vent, obi.; fig. 6, ext. ant.; fig. 7, ext. post, obi.; fig. 8, lat. detail of reticulation.

Scale A (50 pm; X 145), fig. 1 ; scale B (100 pm; X 1 15), fig. 2; scale C (25 pm; X480), fig. 3; scale D (100 pm; X 1 10), fig. 4; scale E (100 pm;
X105), fig. 5; scale F (100 pm; X95), fig. 6; scale G (100 pm; X80), fig. 7; scale H (25 pm; X350), fig. 8.

Stereo-Atlas of Ostracod Shells 24, 26

Scrobisylthis reticulatus (2 of 8)

Stereo-Atlas of Ostracod Shells 24, 29

Scrobisylthis reticulatus (5 of 8)

1 A

300

pm

H

200

100

200

L

300 400 500 600 pm 700

2,05

1,75

IB

i

'•» ,

•o %

« • •

• s*» »•'

500

600 pm

L

700

Text-fig. 1. Ontogeny of Scrobisylthis reticulatus. A, length:height (L:H) diagram; B, length:shape (gestalt; L:H ratio) diagram. Based on 172 valves (including 35
females and 70 left valves) from 15 erratic boulders (“geschiebes”) from the Isle of Sylt , N Sea. Open circles: females; tecnomorphs: dots. The domicilium is
measured from its inner side to the inner side of the contact margin or hinge margin respectively.

Explanation of Plate 24, 30

Figs. 1-3, 9 LV (AGH G159-5, 618 pm long): fig. 1, ext. lat.; fig. 2, ext. vent, obi.; fig. 3, ext. dors. obi. Fig. 4, juv. LV, ext. lat. (AGH

G159-6, 420 pm long). Fig. 5, juv. car., ext. vent. (AGH G159-8, 470 pm long).

Scale A (100 pm; X 130), figs. 1, 2, 4; scale B (TOO pm; X95), fig. 3; scale C (100 pm; X 145), fig. 5.

Stereo-Atlas of Ostracod Shells 24, 31 Scrobisylthis reticulatus (7 of 8)

The figured specimens are from upper Viruan Hornstein geschiebes (erratic boulders). Isle of Sylt (approximately lat. 54° 46' N,
long. 8° 18' E), Germany; Johvi “stage” [Dl] or Keila “stage” [D2] ); Caradoc Series. G159-1 is from geschiebe no. Sy-52 (Dl);
G159-3 is from geschiebe Sy-68 (Dl ); G159-9 is from geschiebe Sy-55 (Dl); all the others are from geschiebe Sy-108 (D2). The
valves are silicified, and have been recovered using dilute HF.

Remarks: The area of reticulation and the number of luminae it contains increase during ontogeny (see PI. 24. 26, fig. 1, PI. 24. 28, fig. 1,
PI. 24, 30, fig. 4, and PI. 24, 32, fig. 6). This reticulation may represent ornament related to cell development, as in examples
described from post-Palaeozoic ostracodes by Liebau (for example, Geol. Paldo. Westfalen, 13, 1991). In those cases every lumen
of the reticulation is underlain by an epidermal cell, which multiply in numbers during ontogeny.

If the largest tecnomorphs of S. reticulatus are adults (Text-fig. 1 A), then females of the species are larger than the males. During
the ontogeny of S. reticulatus its shape (gestalt, L:H ratio) becomes more elongate (Text-fig. IB).

The present material (—300 specimens), from erratic boulders from the Kaolinsand of the Isle of Sylt, is characterized by relatively
small size valves. The females (35 valves measured) reach only a length of 0.66 mm whereas the type specimens are at least 0.94
mm long. Furthermore, the only specimen known from a Backsteinkalk geschiebe, a tecnomorphic valve, is also larger than the Sylt
material (Schallreuter, 1983, op. cit., 162). The size difference of the Sylt material probably reflects its separate geographical region
of origin, and one which was nearer to a former coastline; this very probably was a region N of Estonia and one formerly covered
by Ordovician beds.

Distribution: Currently known only from the Ordovician of Estonia and geschiebes from northern Germany.

In Estonia the species is rather rare: Sarv (1959) notes only 21 specimens from the Johvi “stage” (Dl ) at Alliku, and Meidla
records (1996) only 12 specimens from the Johvi to Oandu “stages” (D3) of the Orjaku core and outcrops of Saku and Ussimagi.
Polma et al. (1988) mention that the species is rare in the Dl horizon of some borehole cores in N Estonia (Tatruse, Niitvalja, Keila
and Rummu), and is also known from the lower D2 horizon at Rummu. In contrast, the species is rather common in geschiebes of
Johvi and Keila (D2) age from the Isle of Sylt (Schallreuter, 1990). It is also recorded from geschiebes from near Ahlintel, West-
phalia (Schallreuter, 1993). On the other hand. S’, reticulatus has not been found in the S Baltic (e.g. see Sidaraviciene 1992, 1996).
This fact also endorses the notion that the Sylt geschiebes originate from a region further to the north or northeast of Estonia, such
as the southern Bothnia area of Finland.

Explanation of Plate 24, 32

Figs. 1 — 4, 9 LV (AGH G159-7, 610 pm long): fig. 1, ext. lat.; fig. 2, ext. vent, obi.; fig. 3, ext. post.; fig. 4, ext. ant. Fig. 5, juv. car., ext. vent.

(AGH G159-8). Fig. 6, juv. LV, ext. lat. (AGH G159-4, 333 pm long).

Scale A (100 pm; X 1 55), figs. 1, 6; scale B ( 100 pm; X 120), figs. 2-4; scale C ( 100 pm; X 145), fig. 5.

Stereo-Atlas of Ostraeod Shells 24, 30

Scrobisylthis reticulatus (6 of 8)

Stereo-Atlas of Ostraeod Shells 24, 32

Scrobisylthis reticulatus (8 of 8)

Stereo-Atlas of Ostracod Shells 24 (6) 33M0 (1998) Kirkbyrhiza retifera (1 of 8)

595.336. 14 (113.4) (768:162.089.35): 551.351 + 552.52

ON KIRKBYRHIZA RETIFERA (ROTH)

by Gerhard Becker, Lee E. Petersen & Robert F. Lundin
(Senckenberg Museum, Frankfurt am Main, Germany;

Anardako Petroleum Corp., Houston, U.S.A.; & Arizona State University, Tempe, U.S.A.)

Kirkbyrhiza retifera (Roth, 1929)

1929 Amphissites retiferus sp. nov. R. Roth, J. Paleontol., 3, 348, pi. 36, fig. 1 la.

1935 Amphissites retiferus Roth; C.W. Wilson, J. Paleontol., 9, 638.

1935 Amphissites primaevus Roth; C.W. Wilson, J. Paleontol., 9, 638.

1961 Reticestus? retiferus (Roth); I.G. Sohn, Prof. Pap. U. S. geol. Surv., 330-B, 140, pi. 9, figs. 49-51.

1968 Reticestus? retiferus (Roth); R.R Lundin, Bull. Okla. geol. Surv., 108, 47, 48, pi. 5, figs.4a-h.

1972 Reticestus retiferus (Roth); L.E. Petersen, Unpubl. M.S. thesis, Arizona State Univ., 74—78, pi. 3, figs. 8-1 1.

1992 Reticestus retiferus (Roth); L.E. Petersen & R.F. Lundin, Bull. Okla. geol. Surv., 145, pi. 2, fig. 14.

1995 Kirkbyrhiza retifera (Roth); G. Becker, L.E. Petersen & R.F. Lundin, N. Jb. Geol. Palaeont., Abh., 198 (3), 427M28, fig. 1 1 .

Holotype: United States National Museum of Natural History, Washington (USNM) no. 80659H; right valve. This
specimen was illustrated by Roth (1929, op. cit., pi. 36, fig. 11a) and Sohn (1961, op. cit., pi. 9, figs. 49-51).
Type locality: “White Mound,” Section M4 of Lundin (1968, op. cit., 19); Murray County, Oklahoma, U.S.A.; approximately
lat. 34° 32' N, long. 97° 01' W; Haragan Formation, early Early Devonian (Fochkovian).

Explanation of Plate 24, 34

Figs. 1, 2, adult RV (X-269, 1066 pm long): fig. 1, ext. lat.; fig. 2, vent. Fig. 3, adult car., ext. It. lat. (X-166, 957 pm long). Figs. 4, 5, adult LV
(X-272, 1041 pm long): fig. 4, vent.; fig. 5, ext. lat.

Scale A (300 pm; X45), figs. 1, 2; scale B (300 pm; X50), fig. 3; scale C (300 pm; X46), figs. 4, 5.

Stereo-Atlas of Ostracod Shells 24, 35 Kirkbyrhiza retifera (3 of 8)

Figured specimens: Department of Geology, Arizona State University (ASU), nos. X-166 (car.: PL 24, 34, fig. 3; PI. 24, 38, fig.

3), X-268 (car.: PI. 24, 38, figs. 1, 5), X-269 (RV: PI. 24, 34, figs. 1, 2; PI. 24, 38, fig. 2), X-270 (RV: PI. 24,
36, figs. 3-5), X-271 (RV: PI. 24, 36, figs. 1, 2), X-272 (FV: PI. 24, 34, figs. 4, 5), X-273 (RV: PI. 24, 40, figs.
1-3), X-274 (LV: PI. 24, 40, figs. 4, 5), X-275 (LV: PI. 24, 38, fig. 4).

ASU X-271 is from sample Rl-4, X-269 is from sample Rl-6, X-166 is from sample Rl-1 1, and X-272
and X-274 are from sample R 1 - 1 9; all from section Rl, Rockport Quadrangle, Benton County, Tennessee,
U.S.A.; lat. 35° 55' 15" N, long. 88° 07' 15" W. ASU X-275 is from sampkR4-l; at section R4, Rockport
Quadrangle, Benton County, Tennessee, U.S.A.; lat. 35° 55' 20" N, long. 88° 05' 15" W. ASU X-273 is from
sample J5a-1 1; at section J5, Jeannette Quadrangle, Decatur County, Tennessee, U.S.A.; lat. 35° 41' N, long.
88° 06' W. ASU X-268 and X-270 are from sample J7-8; at section J7, Jeannette Quadrangle, Decatur County,
Tennessee, U.S.A.; lat. 35° 39' 30" N, long. 88° 05' 30" W. All specimens are from the Birdsong Formation,
lowermost Early Devonian (Lochkovian).

Diagnosis: Kirkbyrhiza species with obsolete sulcal depression; lateral lobes, if developed, diffuse. Dorsal surface
epicline. Admarginal carina (outer carina) narrow, delicate, best developed ventrally; very fine marginal ridge
on both valves. Valves subequal; right valve with contact groove, slightly larger than left; hinge structure
straight, not known in detail (probably anterior cardinal projection in left valve). Adductor muscle pit distinct,
bordered, located subcentrally; corresponding adductorial boss on interior surface prominent. Valve surface
reticulate, with small to large pits, generally arranged in rows concentric around the adductorial pit, but more
closely spaced in dorsomedian area.

Remarks: In the closely related Kirkbyrhiza primaeva (Roth, 1929), from the late Silurian (Ludlow-Pridoli series) of
south-central Oklahoma and western Tennessee, the sulcal depression is distinct and two, more-or-less
conspicuous lateral lobes are developed near the sulcal depression (Becker, G. & Lundin, R.F., Stereo-Atlas

Explanation of Plate 24, 36

Figs. 1, 2, adult RV (X-271, 1226 pm long): fig. 1, ext. lat.; fig. 2, vent. Figs. 3-5, adult RV (X-270, 1026 pm long): fig. 3, ext. lat.; fig. 4, dors;
fig. 5, int. lat.

Scale A (300 pm; X39), figs. 1, 2; scale B (300 pm; X47), figs. 3-5.

Stereo-Atlas of Ostracod Shells 24, 34

Kirkbyrhiza retifera (2 of 8)

Stereo-Atlas of Ostracod Shells 24, 36

Kirkbyrhiza retifera (4 of 8)

Stereo-Atlas of Ostracod Shells 24, 37 Kirkbyrhiza retifera (5 of 8)

Ostracod Shells , 22, 96-103, 1995). Furthermore, the reticula are arranged in dorsoventral rows roughly
parallelling the free margin. In Kirkbyrhiza retifera, the sulcal depression has become obsolete; surface
convexity and ornamentation, however, are variable. Lateral lobes are either obscured or, if developed, the
posterior lobe is more conspicuous. The question whether this variability reflects a kind of domiciliar dimor-
phism is not in consideration with the Superfamily Kirkbyacea. Surface ornamentation is also highly variable,
varying from small to large reticula, generally arranged in rows concentric around the adductorial pit. By
means of these characters, the obsolete lobation and the concentric surface ornament, K. retifera is clearly
distinguished from the older, markedly primitive K. primaeva which is considered to be the late Silurian
precursor.

Amphissites planus Wilson, 1935, from the early Early Devonian of western Tennessee, is here considered
to be a distinct species which belongs to Kirkbyrhiza Becker & Lundin, 1 995 and not to Reticestus Kesling &
Weiss (Conti: Mus. Paleont., Univ. Mich., 11 [3], 52, 1953) as suggested by Sohn (op. cit., 140, 1961), Lundin
& Petersen (J. Paleont., 48, pi. 1, fig. 9, 1974) and Petersen & Lundin (op. cit., pi. 2, fig. 13, 1992). This
generic placement is based on the presence of a delicate admarginal carina (outer carina) observed on unpub-
lished material from the Tennessee River valley of western Tennessee (see Text-fig. 1 ). Reticestus has, instead,
a smooth rounded bend. K. plana is distinguished from K. retifera by its generally coarser reticula and in
having the surfaces of both valves flat and parallel to each other (see Wilson, op. cit., 639, 1935, and Petersen,
op. cit., 79, 1972). Variation in these characters has, however, produced a relatively few specimens which are
morphologically intermediate between K. retifera and K. plana.

Distribution: K. retifera is known from lowermost Early Devonian (Lochkovian) strata of south-central Oklahoma (Haragan
Formation) and western Tennessee (Birdsong Formation), and is, like K. primaeva, probably endemic to the
North American Midcontinent region. Kirkbyrhiza species are considered to be neritic, and characteristic of
shallow-water environments below wave base.

Explanation of Plate 24, 38

; ; Figs. 1, 5, adult car. (X-268, 1021 pm long): fig. 1, dors.; fig. 5, vent. Fig. 2, adult RV, dors. (X-269, 1066 pm long). Fig. 3, adult car., vent,
i i ; (X-166, 957 pm long). Fig. 4, LV, vent. (X-275, 922 pm long).

; ; ; Scale A (300 pm; X47), figs. 1, 5; scale B (300 pm; X45), fig 2; scale C (300 pm; X50), fig. 3; scale D (300 pm; X51), fig. 4.

■>•••!••!

Stereo-Atlas of Ostracod Shells 24, 39

Kirkbyrhiza retifera (7 of 8)

E

ri

D)

0

X

500

• ••

•

• ••

• • •

•

•

•

L

400

• • _
• • • •

• • •

300

• • •
•

_i

• •
•

•

•

200

• _

i i i i

500

600 700 800 900

Length, jam

Text-fig. 1 . Ostracod localities, referred to in the text, in the Early Devonian Text-fig. 2. Size dispersion of Kirkbyrhiza retifera from sample ST3-9 (see

(Lochkovian) Birdsong Formation in the Tennessee River valley of western Text-fig. 1), Early Devonian (Lochkovian) Birdsong Formation, Tennessee,

Tennessee, U.S.A. (after Petersen & Lundin 1992, op. cit., text-fig. 1). U.S.A.

Explanation of Plate 24, 40

Figs. 1-3, adult RV (X-273, 937 pm long): fig. 1, ext. lat.; fig. 2, vent.; fig. 3, int. lat. Figs. 4, 5, adult LV (X-274, 1049 pm long): fig. 4, vent.;
fig. 5, int. lat.

Scale A (300 pm; X51), figs. 1-3; scale B (300 pm; X46), figs. 4, 5.

Stereo-Atlas of Ostracod Shells 24, 38

Kirkhyrhiza retifera (6 of 8)

Stereo-Atlas of Ostracod Shells 24, 40

Kirkhyrhiza retifera (8 of 8 )

Stereo-Atlas of Ostracod Shells: Vol. 24, Parts 1 and 2

CONTENTS

24(1)

1-4

24 (2)

5-12

24(3)

13-16

24 (4)

17-24

24(5)

26-33

24 (6)

34-40

24 (7)

41-42

On Cytheropteron crassiscutum Ayress sp. nov.; by M. Ayress.

On Cythere hanaii Tsukagoshi & Ikeya; by A. Tsukagoshi.

On Eodominina ema Schallreuter sp. nov.; by R.E.L Schallreuter.

On Severobolbina elliptica (Steusloff); by R.E.L. Schallreuter.

On Scrobisylthis reticulatus (Sarv); by R.E.L. Schallreuter.

On Kirkbyrhiza retifera (Roth); by G. Becker, L.E. Petersen & R.F. Lundin.
Index for volume 24 (1998 for 1997)

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