TAXONOMY AND ZOOGEOGRAPHY OF THE

MESOZOIC CYTHERURID OSTRACODA FROM

WEST-CENTRAL ARGENTINA

by SARA C. BALLENT* and ROBIN C. WHATLEY�
*División Paleontologı́a Invertebrados, Museo de Ciencias Naturales de La Plata, Paseo del Bosque s ⁄ n, 1900 La Plata, Argentina;

e-mail: sballent@fcnym.unlp.edu.ar

�Micropalaeontology Research Group, Institute of Earth Studies, University of Wales, Aberystwyth, Dyfed, SY23 3DB, UK

Typescript received 28 September 2007; accepted in revised form 4 June 2008

Abstract: The status of thirty four species of the cytheroi-

dean ostracod family Cytheruridae from the Neuquén Basin,

west-central Argentina is reviewed. These species belong to

the following nine genera: Eucytherura Müller, ranging in

this study from Pliensbachian to Valanginian and

represented by fourteen species; Kangarina Coryell and

Fields, Aalenian–Bajocian, with a single species; Acrocythere

Neale, Hauterivian, one species; Paranotacythere Bassiouni,

Berriasian, two species; Procytherura Whatley, Pliensba-

chian to Hauterivian, twelve species; Cytheropteron Sars,

Aalenian–Bajocian, one species: Eocytheropteron Alexander,

Hauterivian, one species; Paradoxorhyncha Chapman, Aale-

nian–Bajocian, one species; and Paracytheridea Müller,

Berriasian, one species. Of the three subfamilies of the

Cytheruridae, the Cytherurinae, with thirty species are by

far the most numerous and abundant throughout the study.

The other two subfamilies, the Cytheropterinae are repre-

sented by three species and the Paracytherideinae by a single

species of the nominative genus. Several of the species

are very widely distributed geographically and have, for

example, also been recorded from Europe; others indicate

close links with South Africa and Australia. The stratigraphical

ranges of certain genera have been extended as a result of

this study. For example, Kangarina has not previously been

recorded below the Cretaceous. The Cytheruridae are clearly

the most diverse cytheroidean ostracodes in the Mesozoic of

the Neuquén Basin and are more diverse than all other

groups of ostracodes combined. Four new species, Eucyther-

ura tessae, Eucytherura yunga, Procytherura amygdala and

Eocytheropteron immodicus are described. Eucytherura

guillaumeae nom. nov. for Eucytherura tuberculata Brenner

and Oertli and Eucytherura paranuda nom. nov. for

Eucytherura nuda (Brand) are proposed.

Key words: Ostracoda, Cytheruridae, Mesozoic, Argentina,

systematics.

The Family Cytheruridae Müller, 1894 is one of the

most diverse extant families of cytheroidean ostracodes

with a fossil record extending back to the early Mesozoic

or possibly the latest Permian (Whatley and Boomer

2000). During the Cenozoic the family was almost equally

diverse in shelf and deep-sea environments whereas

Mesozoic cytherurids seem to have been confined to shelf

depths, with many species also in marginal marine habi-

tats. They are and were small crawling forms dwelling on

and in soft relatively fine-grained substrates (silt and fine

sand). Their typical carapace with flattened ventral surface

may have acted to facilitate locomotion and prevent them

from sinking into the sediment.

This paper constitutes the first work on cytherurids

from the entire Jurassic and Lower Cretaceous of the

Neuquén Basin, in west-central Argentina. It comprises a

systematic review of thirty four species, including the

description of four new species.

In Argentina, particularly around the Aalenian–Bajo-

cian boundary, Cytheruridae are dominant representing

almost 95 per cent of the total species (Ballent and What-

ley 2000a). Their carapaces are small, delicate and pre-

served white opaque. They indicate essentially shallow

marine conditions with clear and well oxygenated waters.

Some species of the family are very widespread geographi-

cally and Boomer and Ballent (1996) and Ballent and

Whatley (2000b) have demonstrated their usefulness in

palaeogeographical reconstruction.

LOCATION OF THE NEUQUÉN BASIN

The Neuquén Basin is located in west-central Argentina

and eastern Chile, between latitudes 34�S and 41�S. It is

developed in Argentine territory in the provinces of Neu-

quén (from which takes its name), Mendoza, Rı́o Negro

[Palaeontology, Vol. 52, Part 1, 2009, pp. 193–218]

ª The Palaeontological Association doi: 10.1111/j.1475-4983.2008.00827.x 193



and La Pampa (Text-fig. 1). The succession exceeds

5000 m of marine and continental sedimentary rocks

which range from late Triassic to Palaeocene in age. The

nature of its lithology, exposure and fossil content, its mi-

crofaunas associated with well-known ammonite zones,

and the eventual discovery of oil in the region are strong

incentives for the further development of research and

hydrocarbon exploration.

Sampling localities. Text-figure 1 shows the position of

fossiliferous localities and the onshore boreholes which

have been drilled in the course of hydrocarbon explora-

tion. Greenish, greyish and brownish siltstones and grey

calcareous siltstones and shales are the most common

lithologies, and many of these yield microfossils.

Brief comments on the fossiliferous localities (from

south to north) are as follows:

Neuquén Province

1: Cerrito Roth sur (40�08¢S, 70�16¢W) section. It is situ-

ated directly to the south of Cerro Roth, about 500 m

from it. Is is a classical early Jurassic locality. The section

consists of almost 100 m of grey fine-medium sandstones

interbedded with limestones and shales. Bivalves, brachio-

pods and corals are frequent. Contemporary ammonoids

indicate a late Pliensbachian age (cf. Riccardi et al. 1999).

A detailed description of this section is given in Ballent

(1987).

2: 8 km south of Estancia Santa Isabel (39�58¢S,

70�28¢W). This locality comprises isolated outcrops of

grey and yellowish brown tuffaceous siltstones. Fossil

invertebrates are abundant. Contemporary ammonoids

indicate a late Pliensbachian age.

3: Barda Cerro Marucho (Puesto Jara) (39�26¢S,

70�13W) and 4: Cerro Birrete (39�16¢S, 70�05¢W) sections.

These are exposed about 60 km south of the town of Za-

pala and comprise Valanginian–Hauterivian marls and

calcareous shales with intercalated coquinas. Lithological

description, sampling and a detailed nannofossil biostra-

tigraphy are given in Bown and Concheyro (2004).

5: Northern slope of Cerro Trapial Mahuida (39�00¢S,

69�50¢W). This comprises grey and brown limestones of

late Pliensbachian age.

6: Picún Leufú (39�10¢S, 69�50¢W). This section com-

prises some 80 m of brown and yellowish grey siltstones

with ammonoids of late Pliensbachain age, overlain by

about 220 m of greenish and greyish siltstones with spo-

radic intercalated sandstones whose ammonoids indicate

a late Aalenian to early Bajocian age (Riccardi et al.

1999). A detailed description and a palaeoenvironmental

analisis have been made by Ballent (2004). Samples of

mid Callovian and probable Berriasian age from this

locality are also referred to in the present paper.

7: Marı́a Rosa Curicó (38�40¢S, 70�00¢W). This section

comprises some 40 m of greenish and brownish siltstones

with sporadic intercalated sandtones. Contemporary

ammonoids indicate a mid Callovian age (Riccardi et al.

1999). Stratigraphical profile and sampling details are

described in Ballent (2004).

8: Manzano Guacho, Sierra de la Vaca Muerta area

(38�40¢S, 70�10¢W) and 9: Cerro Negro de Covun-có

(38�46¢S, 69�59¢W). These localities are situated about

20 km north of Zapala, on the flanks of the Sierra de la

Vaca Muerta. The exposed succession encompasses the

Callovian-Neocomian interval. The samples with ostra-

codes were from greenish grey limestones and intercalated

sandstones, whose ammonoids indicate a Hauterivian age.

10: Bajada del Agrio section (38�25¢S, 70�00¢W). This is

located about 60 km north of Zapala. The exposed suc-

cession consists of shales, sandstones and limestones

which encompasses the late Valanginian–late Hauterivian

interval. A micropalaeontological study of this locality is

TEXT -F IG . 1 . Base map showing Argentinian part of the

Neuquén Basin outline (thick dashed line, after Legarreta and

Uliana 1996) and position of sampling fossiliferous localities (*).

1: Cerrito Roth sur, 2: 8 km south of Estancia Santa Isabel, 3:

Barda Cerro Marucho (Puesto Jara), 4: Cerro Birrete, 5:

Northern slope of Cerro Trapial Mahuida, 6: Picún Leufú, 7:

Marı́a Rosa Curicó, 8: Manzano Guacho, Sierra de la Vaca

Muerta area, 9: Cerro Negro de Covun-có, 10: Bajada del Agrio,

11: Entre Lomas area, 12: Cuesta del Chihuido.

194 P A L A E O N T O L O G Y , V O L U M E 5 2



in progress. Samples with ostracodes are of late Hauteri-

vian age.

11: Entre Lomas area. This is a petroleum exploration

area located between 37�50¢, 38�15¢S and 68�00¢, 68�30¢W,

in the eastern Neuquén Basin.

Mendoza Province

12: Cuesta del Chihuido section (35�45¢S, 69�34¢W),

southern Mendoza Province. This section consists of 205 m

of black mudstones, marls and micritic limestones. A bio-

stratigraphical and palaeoenvironmental analisis was car-

ried out by Ballent et al. (2006). Nannofossils association

indicates a late Valanginian–Hauterivian age.

SYSTEMATIC PALAEONTOLOGY

The suprageneric classification adopted is that proposed by

Moore and Pitrat (1961); for genera within the family, we follow

the systematic review of early Cytheruridae by Whatley and

Boomer (2000). In the systematic descriptions, synonymies used

follow the symbols listed in Matthews (1973), and the following

conventions are employed: L = length, H = height, W = width;

very small (<0.400 mm), small (0.400–0.500 mm), medium

(0.510–0.700 mm), large (0.710–0.900 mm), very large

(>0.900 mm). Within each genus, new species are described first.

Type and figured specimens are deposited in the collections of

the Museo de Ciencias Naturales de La Plata, Argentina-Sección

Micropaleontologı́a (MLP-Mi) under their respective catalogue

numbers.

PODOCOPIDA Müller, 1894

PODOCOPINA Sars, 1866

CYTHEROIDEA Baird, 1850

CYTHERURIDAE Müller, 1894

CYTHERURINAE Sars, 1925

Genus EUCYTHERURA Müller, 1894

Type species. Cythere complanata Brady, 1867 (by subsequent

designation: Alexander, 1936) from the Recent sediments in the

Gulf of Naples, Italy.

Diagnosis. A genus with a small carapace of subrectangu-

lar, quadrate or subtriangular lateral outline. Eye tubercle

present or absent. Surface very ornate with reticulation,

tubercles or ridges. For other characteristics see emended

diagnosis in Ayress et al. (1995).

Eucytherura tessae sp. nov.

Plate 1, figures 1–4

v.1987 Rutlandella? sp. B Ballent, p. 109, pl. 6, figs 2, 3.

v.1991 Rutlandella? sp. B Ballent, p. 40, pl. 3, figs 5a, b.

Repository. MLP-Mi 581, 582, 583, 1593, 1594, 1595, 1596.

Studied material. Ten carapaces.

Derivation of name. (Latin) Named in honour of Tessa Briggs

neé Evershed, a great friend of the second author, in recognition

of all her help and her exceptional editorial skills.

Type specimens. Holotype MLP-Mi 582, male carapace illustrated

in Plate 1, figure 1, from Cerrito Roth sur section, level 101b,

Neuquén Basin, west-central Argentina.

Paratypes. MLP-Mi 581, female carapace; MLP-Mi 1593, female

carapace; MLP-Mi 1594, juvenile carapace; MLP-Mi 1595, female

carapace; MLP-Mi 1596, juvenile carapace; all from Cerrito Roth

sur section, Neuquén Basin, west-central Argentina.

Type locality and type level. Cerrito Roth sur section (40�08¢S,

70�16¢W), Neuquén Basin, west-central Argentina, level 101b,

late Pliensbachian.

Diagnosis. A very small, elegant, subrectangular species of

Eucytherura, acuminate posteriorly at mid-height and

with three longitudinal ribs. Dorsal and median ribs con-

vex upwards, ventral rib shorter and concave; intercostal

areas smooth. Normal pores with circular conuli, ranging

in size from very small to large and bulbous.

Description. Carapace very small, but rather robust. Subrectangu-

lar in lateral view, acuminate posteriorly with dorsal and ventral

margins slightly convergent posteriorly. Anterior margin obliquely

rounded with apex below mid-height. Posterior margin angular

with a short, posteriorly pointing caudal process at mid-height.

Distinct rounded eye tubercle, with short ocular rib extending

towards mid anterior margin. Valves subequal. Greatest length at

mid-height; greatest height at anterior third of valve length. In

dorsal view the carapace is ovate with greatest width at mid-

length. Lateral surface with three longitudinal ribs. The dorsal rib

is convex upwards and extends along the homonymous margin

from the posterior margin to the mid-anterior area, close to the

edge of the dorsal margin and, in both valves, dorsal to the eye

tubercle. Median rib also convex, slightly sinuous and extending

from the posterior apex to the anterior margin at mid-height.

Ventral rib concave, shorter than the others and extends from the

postero-ventral margin to the mid antero-ventral area. Intercostal

areas smooth. Normal pores with circular conuli, ranging in size

from very small to large and bulbous. Internal features not seen.

Dimensions (mm). Figured specimens:

MLP-Mi 582, Holotype, L = 0.370, H = 0.190, W = 0.150 (Pl.1,

fig.1), MLP-Mi 1593, Paratype, L = 0.370, H = 0.170, W = 0.150

(Pl.1, fig.2), MLP-Mi 581, Paratype, L = 0.350, H = 0.180,

W = 0.150 (Pl.1, fig.3), MLP-Mi 1594, Paratype, L = 0.345,

H = 0.160, W = 0.140 (Pl.1, fig.4).

Age and distribution. Late Pliensbachian, Cerrito Roth sur and

8 km south of Estancia Santa Isabel sections; this new species is

BALLENT AND WHATLEY: TAXONOMY AND ZOOGEOGRAPHY OF THE MESOZOIC CYTHERURID OSTRACODA 195



also possibly represented by juvenile and fragmentary carapaces

in the late Aalenian-early Bajocian (Picún Leufú section), Neu-

quén Basin, west-central Argentina.

Remarks. The lateral outline of the carapace and the pat-

tern of the longitudinal ribs of this elegant species are

somewhat similar to those of Eucytherura fissicostata

(Herrig, 1969, p. 1088, text-fig. 11; pl. III, figs 5–6) from

the Upper Pliensbachian of Germany; however, the new

species lacks the rhomboid figure at the posterior end of

the median rib which characterizes the German species.

This new species also resembles Eucytherura yunga sp.

nov. of this study from the late Aalenian–early Bajocian

of the Picún Leufú section (see below), but is distinguish-

able by its somewhat more robust carapace, different rib

features and the possession of a caudal process at mid-

height. Eucytherura tessae is a little similar to Eucytherura

sp. A of Boomer and Ballent (1996, pl. I, fig. 6) from the

Sinemurian and Pliensbachian of the Mochras Borehole

(Wales).

Eucytherura yunga sp. nov.

Plate 1, figures 5–9

v.1991 Ostrácodo A Ballent, p. 44, pl. 4, figs 6, 7, 8.

Repository. MLP-Mi 690, 694, 695, 696, 1597, 1598, 1599.

Studied material. Five carapaces, five left valves, two right valves.

Derivation of name. From the aboriginal Mapuche word yung

meaning sharp. With reference to the sharp ribs on the lateral

surface that characterizes this species.

Type specimens. Holotype MLP-Mi 694, male left valve, illus-

trated in Plate 1, figures 5–6, from Picún Leufú section, level

1685, Neuquén Basin, west-central Argentina.

Paratypes. MLP-Mi 690, female left valve; MLP-Mi 695, juvenile

right valve; MLP-Mi 696, juvenile right valve; MLP-Mi 1597,

juvenile left valve; MLP-Mi 1598, juvenile left valve; MLP-Mi

1599, female left valve; all from Picún Leufú section, Neuquén

Basin, west-central Argentina.

Type locality and type level. Picún Leufú section (39�10¢S-

69�50¢W), Neuquén Basin, west-central Argentina, level 1685,

late Aalenian–early Bajocian.

Diagnosis. Very small, subrectangular species of Eucyther-

ura, acuminate posteriorly with subdorsal caudal process,

prominent round eye tubercle and three sharp longitudi-

nal ribs on the lateral surface. Intercostal areas smooth

medianly but with rather weak, open reticulation anteri-

EXPLANATION OF PLATE 1

Figs 1–4. Eucytherura tessae sp. nov. 1, MLP-Mi 582, holotype, male carapace, right lateral view. 2, 3, 4, paratypes. 2, MLP-Mi 1593,

female carapace, left lateral view. 3, MLP-Mi 581, female carapace, right lateral view. 4, MLP-Mi 1594, juvenile carapace, left

lateral view, late Pliensbachian, Cerrito Roth sur section, level 101b.

Figs 5–9. Eucytherura yunga sp. nov. 5, 6, MLP-Mi 694, holotype, male left valve. 5, external lateral view, and 6, internal lateral view,

Picún Leufú section, level 1685. 7, 8, 9, paratypes, 7, MLP-Mi 690, female left valve. 8, MLP-Mi 1597, juvenile left valve. 9, MLP-

Mi 1598, juvenile left valve, all external lateral views, late Aalenian–early Bajocian, Picún Leufú section, level 1676.

Figs 10–11. Eucytherura argentina Ballent, 1991. 10, MLP-Mi 654, carapace, left lateral view. 11, MLP-Mi 1600, left valve, external

lateral view, late Aalenian–early Bajocian, Picún Leufú section, levels 1681 and 1684, respectively.

Figs 12–13. Eucytherura gassumensis (Michelsen, 1975). 12, MLP-Mi 691, juvenile carapace, right lateral view, late Aalenian-early

Bajocian, Picún Leufú section, level 1683. 13, MLP-Mi 1602, carapace, left lateral view, late Pliensbachian, Cerrito Roth sur

section, level 101b.

Fig. 14. Eucytherura isabelensis Ballent, 1987, MLP-Mi 576 ⁄ 1, carapace, left lateral view, late Pliensbachian, locality 8 km south of

Estancia Santa Isabel.

Fig. 15. Eucytherura leufuensis Musacchio, 1979b, MLP-Mi 727, carapace, left lateral view, mid-late Callovian, Picún Leufú section,

level 2.

Figs 16–17. Eucytherura michelseni (Finger, 1983). 16, MLP-Mi 666, female right valve, external lateral view. 17, MLP-Mi 665, female,

left valve, external lateral view, late Aalenian–early Bajocian, Picún Leufú section, level 1680.

Fig. 18. Eucytherura paranuda nom. nov., MLP-Mi 1073, carapace, left lateral view, mid Callovian, Maria Rosa Curicó section, level

1159.

Fig. 19. Eucytherura oeresundensis (Michelsen, 1975), MLP-Mi 1603, carapace, left lateral view, late Pliensbachian, Cerrito Roth sur

section, level 101b.

Figs 20–21. Eucytherura pichia (Ballent, 1991). 20, MLP-Mi 645 ⁄ 1, female left valve, external lateral view. 21, MLP-Mi 645 ⁄ 8, male

carapace, right lateral view, late Aalenian-early Bajocian, Picún Leufú section, levels 1153 and 1686, respectively.

All scale bars represent 0.050 mm.

196 P A L A E O N T O L O G Y , V O L U M E 5 2



PLATE 1

BALLENT and WHATLEY, Mesozoic ostracods

1 2 3 

4 5 6 

7 8 9 

10 11 12 

13 14 15 

16 17 18 

19 20 21 



orly and posteriorly. Normal pore canals either emerging

with a smooth lip or as bulbous pore conuli.

Description. Carapace very small, subrectangular, acuminate

posteriorly in lateral view. Strongly dimorphic. Males more

subrectagular and more elongate in lateral view. Anterior mar-

gin bluntly rounded; posterior margin compressed, obliquely

truncated below and with asymmetrical caudal process in the

upper half of the valve. Dorsal margin straight with distinct

cardinal angles. Ventral margin, slightly concave medianly and

well developed postero-ventral keel. Females, less subrectangu-

lar in lateral view, shorter than males. Anterior margin

squarely truncated, posterior margin with a blunt subdorsal

caudal process. Dorsal margin straight to slightly sinuous

medianly; ventral margin convex and obliquely compressed

posteroventrally. In both sexes, left valve larger than right.

The greatest length is above mid-height, coincident with the

extremity of caudal process. Greatest height at mid-length. In

dorsal view the carapace is subovate with the greatest width

at mid-length. The lateral surface with three sharp longitudi-

nal ribs. The dorsal rib extends in a gentle arc directly adja-

cent to the dorsal margin, passing above the eye tubercle. The

median rib extends posteriorly from the mid-anterior area,

but terminates short of the caudal process and being concave

in its anterior and convex in its posterior halves. The ventral

rib is convex and extends along the homonymous margin. In

males this rib forms a postero-ventral keel. Prominent round

eye tubercle with a short oblique ocular rib that bifurcates

anteriorly. Intercostal areas smooth centrally but with a weak,

open reticulum towards anterior and posterior margins. Nor-

mal pore canals either emergent as large open normal pores,

surrounded by a lip or as rather bulbous pore conuli. Internal

characters as for genus with small vestibula at either free

margin.

Dimensions (mm). Figured specimens:

MLP-Mi 694, Holotype, L = 0.340, H = 0.160 (Pl.1, figs 5–6),

MLP-Mi 690, Paratype, L = 0.300, H = 0.165 (Pl.1, fig. 7), MLP-

Mi 1597, Paratype, L = 0.280, H = 0.130 (Pl.1, fig. 8), MLP-Mi

1598, Paratype, L = 0.280, H = 0.140 (Pl.1, fig. 9).

Age and distribution. Late Aalenian–early Bajocian, Picún Leufú

section, Neuquén Basin, west-central Argentina.

Remarks. Eucytherura yunga in lateral outline and

pattern of ornamentation resembles Movschovitschia

schulzi (Kozur) (in Gründel 1980, fig. 4). This Triassic

genus, however, is regarded as a junior synonym of Eu-

cytherura by Whatley and Boomer (2000). The new spe-

cies is similar to Eucytherura tessae described in the

present study, but differs in the possession of a subdor-

sal caudal process, sharper ribs and a well developed

postero-ventral keel in males. Eucytherura pichia (Bal-

lent) from the same levels, is also similar, but is more

delicate, subquadrate (females) and subrectangular

(males) in lateral outline and with the median rib inter-

rupted (or weakened) at subcentral tubercle region.

Eucytherura argentina Ballent, 1991

Plate 1, figures 10–11

v*1991 Eucytherura argentina Ballent, p. 34, pl. 2, only

fig. 1.

Repository. MLP-Mi 654, 1600.

Studied material. Five carapaces, one left valve.

Complementary description. A very small, delicate species, subqua-

drate to subrectangular in lateral view. Dorsal and ventral margins

nearly straight, almost parallel; anterior margin bluntly rounded

to truncate and posterior margin compressed with a short caudal

process in the upper half of the valve pointing posteriorly. Orna-

ment fairly coarsely reticulate in two generations. Primary reticu-

lae generally subquadrate, radiating from the subcentral tubercle

area and showing some cellation, coarsest dorsally and ventrolater-

ally on sub-alar protuberance. Some intermural nodes developed.

Secondary reticulation more subrounded. Prominent eye-tubercle

below anterior cardinal angle, having a short ocular rib extending

antero-ventrally. An ill-defined, blunt antero-ventral rib enhances

junction between the lateral and ventral surfaces. Hinge loph-

odont. Narrow vestibula occur at the end margins.

Dimensions (mm). Figured specimens: MLP-Mi 654, carapace,

L = 0.300, H = 0.150, W = 0.180 (Pl.1, fig. 10); MLP-Mi 1600,

left valve, L = 0.290, H = 0.150 (Pl.1, fig.11).

Age and distribution: Late Aalenian–early Bajocian, Picún Leufú

section, Neuquén Basin, west-central Argentina.

Remarks. Eucytherura batei (Ainsworth, 1986) from the late

Toarcian–Aalenian offshore south-west Ireland is a similar

species, but can be distinguished by its subrectangular out-

line in lateral view and in details of the reticulate ornamen-

tation. The specimen MLP-Mi 666, assigned to Eucytherura

argentina (see Ballent 1991, pl. 2, figs 2, 3), now is accom-

modated in E. michelseni (Finger, 1983) (see below) due to

the presence of a distinct irregular median rib.

Eucytherura gassumensis (Michelsen, 1975)

Plate 1, figures 12–13

*1975 Acrocythere gassumensis Michelsen, p. 153, pl. 7,

figs 97–100; pl. 8, figs 117–119.

v.1991 Acrocythere sp.; Ballent, p. 43, pl. 4, figs 1–2.

Repository. MLP-Mi 691, 692, 1601, 1602.

Studied material. Four carapaces.

Dimensions (mm). Figured specimens: MLP-Mi 691, juvenile

carapace, L = 0.325, H = 0.170, W = 0.140, Pl. 1, fig. 12); MLP-

Mi 1602, carapace, L = 0.370, H = 0.180 (Pl. 1, fig. 13).

198 P A L A E O N T O L O G Y , V O L U M E 5 2



Age and distribution. Late Sinemurian–early Pliensbachian, Danish

Embayment (Michelsen 1975) and Skåne, Sweden (Sivhed 1980);

early Sinemurian, offshore southwest Ireland (Ainsworth 1989); late

Pliensbachian, Cerrito Roth sur section and late Aalenian–early

Bajocian, Picún Leufú section, Neuquén Basin, west-central Argentina.

Brief description. This is a very small species, subrectangular in

lateral view, with the greatest height at the anterior cardinal

angle. It is characterized by a very strong, broad ventro-lateral

rib with terminal elevations and two distinct sub-alar protuber-

ances postero-ventrolaterally. The entire surface is rough and

irregular, comprising many structural elements, including a

coarse and imperfect reticulation.

Eucytherura isabelensis Ballent, 1987

Plate 1, figure 14

v*1987 Eucytherura? isabelensis Ballent, p. 105, pl. 6, figs 4–8.

Repository. MLP-Mi 576 ⁄ 1-576 ⁄ 11, 722.

Studied material. Eleven carapaces.

Dimensions (mm). Figured specimen: MLP-Mi 576 ⁄ 1, female

carapace, L = 0.320, H = 0.175, W = 0.170 (Pl. 1, fig. 14).

Age and distribution: Late Pliensbachian, locality 8 km south of

Estancia Santa Isabel, Neuquén Basin, west-central Argentina.

Brief description. Very small with subquadrate carapace,

strongly dimorphic, with a moderately depressed subcentral-

anterior area. Surface of tubercles and a secondary ornament

of delicate reticular and occasional small papillae. Generally

there are five large tubercles: one, on the eye tubercle; another

postero-dorsal and three rather smaller tubercles along the

ventro-lateral margin.

Remarks. These above mentioned characteristics distin-

guish E. isabelensis from all other Jurassic species of the

genus. Arias (2006, p. 20) considered that some of the

specimens of this species illustrated by Ballent (1987, pl.

5, figs 4–8) could possibly be reassigned to Trachycythere

tubulosa (Triebel and Klingler, 1959), which is considered

to be indicative of the Upper Pliensbachian–Toarcian of

Central Europe. The very small size of the carapace and

its external features suggest that this species is clearly

accommodated within Eucytherura.

Eucytherura leufuensis Musacchio, 1979b

Plate 1, figure 15

v*1979b Eucytherura? leufuensis Musacchio, p. 502, pl. 2,

figs 8–12.

v. 2004 Eucytherura leufuensis Musacchio; Ballent, fig. 6.O.

Repository. MLP-Mi 727.

Studied material. Five carapaces.

Dimensions (mm). Figured specimen: MLP-Mi 727, carapace,

L = 0.360, H = 0.190, W = 0.180 (Pl. 1, fig. 15).

Age and distribution. Mid–late Callovian, Picún Leufú section,

Neuquén Basin, west-central Argentina.

Brief description. Very small, elongate subtriangular to subrect-

angular in lateral view, with distinct ocular, postero-dorsal and

postero-ventral nodes; entire surface ornamented with a subpo-

lygonal reticulum.

Eucytherura michelseni (Finger, 1983)

Plate 1, figures 16–17

1975 Acrocythere tricostata Michelsen, p. 158, pl. 9, figs

131–142; pl. 11, figs 157– 158; text-fig. 26 (pre-

occupied binomius).

*1983 Acrocythere michelseni Finger, p. 110. (nom. nov. for

A. tricostata)

v.1991 Eucytherura argentina Ballent, p. 34, pl. 2, figs 2–3.

Repository. MLP-Mi 665, 666, 667.

Studied material. Four carapaces, four valves.

Dimensions (mm). Figured specimens: MLP-Mi 666, female right

valve, L = 0.345, H = 0.175 (Pl. 1, fig. 16); MLP-Mi 665, female,

left valve, L = 0.330, H = 0.175 (Pl. 1, fig. 17).

Age and distribution. Late Pliensbachian, Danish Embayment

(Michelsen 1975); also, Pliensbachian, southern Sweden (Sivhed

1980) and southwest Germany (Harloff 1993); late Aalenian–

early Bajocian, Picún Leufú section, Neuquén Basin, west-central

Argentina. It is possible that this species occurs (as Renicytherura

sp. A and sp. B) in the lower Jurassic ⁄ Aalenian of Australia

(Lord et al. 1993) but further study is required to determine

this.

Brief description. This is a very small species, subquadrate to

subractangular in lateral view, with distinct eye tubercle and

the posteroventral part of the lateral surface inflated with a

weak alate extension. It is ornamented with three distinct lon-

gitudinal ribs and the intercostal areas have a polygonal pat-

tern of low ribs. Hinge antimerodont which, in the right

valve, consists of small but prominent ovate anterior and pos-

terior teeth with a very narrow and delicately locellate median

groove.

Remarks. The specimen MLP-Mi 666 (see Ballent 1991,

pl. 2, figs 2, 3) there assigned to E. argentina, is herein

accommodated in E. michelseni, because of its delicate

dorsal and ventral ribs and distinct irregular median

BALLENT AND WHATLEY: TAXONOMY AND ZOOGEOGRAPHY OF THE MESOZOIC CYTHERURID OSTRACODA 199



ridge. Eucytherura oxfordiana Rosenfeld and Honigstein

(in Rosenfeld et al. 1987, p. 239), a minute species from

the Oxfordian of the Golan Heights, Israel, could be con-

specific with the present species.

Eucytherura paranuda nom. nov. for Eucytherura nuda

(Brand, 1990)

Plate 1, figure 18

*1990 Tethysia nuda Brand, p.169, pl. 5, figs 3–7.

v.2004 Eucytherura sp. Ballent, fig. 6.M.

Repository. MLP-Mi 1073.

Studied material. One carapace.

Derivation of name. With reference to its similarity to Eucyther-

ura nuda (Brand).

Dimensions (mm). Figured specimen: MLP-Mi 1073, carapace,

L = 0.290, H = 0.160, W = 0.120 (Pl. 1, fig. 18).

Age and distribution. Late Bathonian, northwest Germany

(Brand 1990); mid Callovian, Marı́a Rosa Curicó section,

Neuquén Basin, west-central Argentina.

Brief description. Species with very small and delicate carapace,

subrectangular, slightly acuminate posteriorly with a blunt

caudal process at mid-height and ornamented with three dis-

tinct but rather fine longitudinal ribs. Distinct eye tubercle

with a short oblique ocular rib produced anteriorly. Lateral

surface smooth, except for primary polygonal reticulation and

second-order punctae anteroventrally and on the caudal pro-

cess area.

Remarks. Brand (1990) included this species in Tethysia

Donze, but we have no doubts in including it within Eu-

cytherura. Eucytherura nuda (Brand) is a junior secondary

homonym of Eucytherura nuda Kaye, 1964 (p. 99, pl. IV,

figs 13–15) from the Lower Barremian at Speeton (UK)

and should be renamed. It is proposed herein that the

new name Eucytherura paranuda replace the preoccupied

binomius Eucytherura nuda (Brand).

Eucytherura oeresundensis (Michelsen, 1975)

Plate 1, figure 19

*1975 Acrocythere oeresundensis Michelsen, p. 155, pl. 7,

figs 101–104; pl. 8, figs 120–124.

Repository. MLP-Mi 1603.

Studied material. Three carapaces.

Dimensions (mm). Figured specimen: MLP-Mi 1603, carapace,

L = 0.400, H = 0.170, W = 0.180 (Pl. 1, fig. 19).

Age and distribution. Late Sinemurian–early Pliensbachian, Dan-

ish Embayment (Michelsen 1975), late Sinemurian–early Toar-

cian, southwest Germany (Herrig 1981; Harloff 1993); late

Pliensbachian, Cerrito Roth sur section, Neuquén Basin, west-

central Argentina.

Brief description. Small, elongate subrectangular and subalate in

lateral view, with a ‘wrinkled’ carapace surface brought about by

an irregular, rather weak reticulation and with a strong longitu-

dinal rib ventrolaterally terminating in an alar boss and a short

rib below posterior cardinal angle.

Remarks. The small size and external features suggest that

this species is better accommodated within Eucytherura.

Eucytherura pichia (Ballent, 1991)

Plate 1, figures 20–21

v*1991 Acrocythere pichia Ballent, p. 41, pl. 3, figs 7–11.

v.2000a Eucytherura pichia (Ballent); Ballent and Whatley,

fig. 15.5.

Repository. MLP-Mi 645 ⁄ 1-645 ⁄ 8.

Studied material. Four carapaces, twenty valves.

Dimensions (in mm). Figured specimens: MLP-Mi 645 ⁄ 1, female

left valve, L = 0.265, H = 0.145 (Pl. 1, fig. 20); MLP-Mi 645 ⁄ 8, male

carapace, L = 0.310, H = 0.150, W = 0.150 (Pl. 1, fig. 21).

Age and distribution. Late Aalenian–early Bajocian, Picún Leufú

section, Neuquén Basin, west-central Argentina.

Brief description. A very small, strongly dimorphic species with

subquadrate (females) to subrectangular (males) carapace in lat-

eral view. Characteristic features are the very distinct longitudi-

nal ventro-lateral, median and dorsal ribs. The median rib is

interrupted (or subdued) in the subcentral tubercle region and a

prominent eye tubercle with a short, oblique ocular rib pro-

duced anteriorly. Intercostal regions smooth or weakly punctate.

Remarks. Eucytherura sp. A of Boomer and Ballent (1996,

pl. I, only fig. 4) from the Sinemurian and Pliensbachian

of the Mochras Borehole (Wales) is possibly conspecific

with the Argentinian species.

Eucytherura transversiplicata (Bate and Coleman, 1975)

Plate 2, figures 1–2

*1975 Rutlandella transversiplicata Bate and Coleman,

p. 34, pl. 13.7, 13.10, 13.12; figs 14a, b, 15, 16.

200 P A L A E O N T O L O G Y , V O L U M E 5 2



v.1987 Rutlandella? sp. A Ballent, p. 108, pl. 5, fig. 11;

pl. 6, fig. 1.

v.1991 Rutlandella cf. transversiplicata Bate and Coleman;

Ballent, p. 38, pl.2, figs 1, 2.

v.1991 Rutlandella sp. A Ballent, p. 39, pl. 3, figs 3, 4.

v. 1996b Eucytherura transversiplicata (Bate and Coleman);

Ballent and Whatley, p. 148, pl. 1, fig. 15.

Repository. MLP-Mi 579, 580, 586, 622, 656, 687.

Studied material. Twelve carapaces, three valves.

Dimensions (mm). Figured specimens: MLP-Mi 579, female cara-

pace, L = 0.330, H = 0.155, W = 0.150 (Pl. 2; fig. 1); MLP-Mi

687, female carapace, L = 0.370, H = 0.175, W = 0.170 (Pl. 2,

fig. 2).

Age and distribution. Lower and Middle Toarcian of Leicester-

shire and Cambridgeshire (Bate and Coleman 1975). Also,

Toarcian and Aalenian, west-central Europe (see Ainsworth

1986); Pliensbachian from D.S.D.P. (Deep Sea Drilling Project)

Site 547 off North Africa (Bate et al. 1984); Bajocian, Sinai,

Egypt (Rosenfeld et al. 1987); late Pliensbachian, Picún Leufú

and Cerrito Roth sur, sections and late Aalenian-early

Bajocian, Picún Leufú section, Neuquén Basin, west-central

Argentina.

Brief description. Very small, dimorphic, subrectangular to sub-

triangular in lateral outline, tapering posteriorly, with prominent

eye tubercle. Valve surface coarsely reticulate and with three ribs;

the dorsal rib is largely eroded by the reticulation resulting in an

irregular dorsal margin; the median rib is very strong and tra-

verses the valve obliquely from a complex postero-dorsal loop to

the anterior margin at about mid-height; the ventro-lateral rib is

complex being subalate postero-ventrally, with an overlap at

mid-length and as inverted chevron in its anterior third. The eye

tubercle is hemispherical, very prominent and bearing an ocular

rib that extends vertically downwards to the median rib. Argen-

tinian specimens possess a polygonal (mainly pentagonal) reticu-

lum; second-order reticulation occurs in the solum of primary

reticula, but is best developed towards the central area of the

valve.

Remarks. Whatley and Boomer (2000, p. 140) consider

Rutlandella as one of the many junior synonyms of

Eucytherura. Arias and Lord (1999) considered

E. transversiplicata as a junior synonym of E. michelseni

(Finger). However, while the two species are similar,

the latter possess three distinct longitudinal ribs and is

subquadrate in lateral outline (the dorsal and ventral

margins only converge slightly posteriorly) rather than

subrectangular as in E. transversiplicata. Arias (2006,

table 3b) considered Rutlandella? sp. A of Ballent, 1987

as a junior synonym of E. oeresundensis (Michelsen,

1975), from the Lower Pliensbachian of Denmark. We

dispute this as the two species differ considerably in

the nature of their costae.

Eucytherura guillaumeae nom. nov. for Eucytherura

tuberculata Brenner and Oertli, 1976

Plate 2, figure 3

*1976 Eucytherura (Vesticytherura) tuberculata Brenner and

Oertli, p. 511, pl. 7, figs 11–14; pl. 8, fig. 10.

Repository. MLP-Mi 1604.

Studied material. Three carapaces.

Derivation of name. In honour of the late Dr. Marie-Claude

Guillaume, in recognition of her important studies on the genus

Leptocythere.

Dimensions (mm). Figured specimen: MLP-Mi 1604, carapace,

L = 0.250, H = 0.125, W = 0.120 (Pl. 2, fig. 3).

Age and distribution. Late Valanginian–late Hauterivian, Algoa

Basin, South Africa (Brenner and Oertli 1976; Valicenti and Ste-

phens 1984); late Valanginian, Barda Cerro Marucho (Puesto

Jara) section, Neuquén Basin, west-central Argentina.

Brief description. A very small species with a tapering subrectan-

gular outline. Ornament essentially of tubercles, and a network

of first and second-order reticula. Smooth semiglobular eye

tubercle, situated just behind the anterior cardinal angle. The

dorsal margin is overreached by two tubercles: the most anterior

is in the lowest third of the valve and the most posterior lies

close to the postero-ventral border, directly beneath the postero-

drosal cardinal angle. The ventro-lateral ridge is substituted by

five tubercles.

Remarks. Eucytherura tuberculata Brenner and Oertli,

1976 is a junior primary homonym of Eucytherura tuber-

culata Bonnema, 1941 (p. 21, pl.5, figs 52–57, in Howe

and Laurencich 1958, p. 341) from the subsurface Seno-

nian of the northeastern Netherlands. Since the two spe-

cies are distinct in the arrangement and shape of the

tubercles, a replacement name is required for Brenner

and Oertli species. It is proposed herein that the new

name Eucytherura guillaumeae replace the preoccupied bi-

nomius Eucytherura tuberculata Brenner and Oertli, 1976.

Eucytherura sp. B Boomer and Ballent, 1996

Plate 2, figure 4

v.1991 Hemiparacytheridea sp.; Ballent, p. 335, pl. 2,

fig. 4.

v.1996 Eucytherura sp. B; Boomer and Ballent, pl. I,

fig. 14.

Repository. MLP-Mi 655.

Studied material. One right valve.

BALLENT AND WHATLEY: TAXONOMY AND ZOOGEOGRAPHY OF THE MESOZOIC CYTHERURID OSTRACODA 201



Dimensions (mm). Figured specimen: MLP-Mi 655, right valve,

L = 0.330, H = 0.160 (Pl. 2, fig. 4).

Age and distribution. Late Pliensbachian–early Toarcian, British

Isles (Mochras Borehole, Boomer and Ballent 1996); late Aale-

nian–early Bajocian, Picún Leufú section, Neuquén Basin, west-

central Argentina.

Brief description. Very small, subrectangular to subtriangular,

with notably cribose intercostal ornament and with very

strong subdorsal caudal process and further distinguished by

strong ocular, postero-dorsal and postero-ventral nodes. The

latter forming the termination of a ventrolaterally alar inflated

rib.

Remarks. The specimen figured by Ballent (1991, pl. 2,

fig. 4) and by Boomer and Ballent (1996, pl. I, fig. 14)

are certainly conspecific and they have been referred to

Group 9, which is recorded in the British Isles and Argen-

tina (Boomer and Ballent 1996).

Eucytherura sp.

Plate 2, figure 5

v.1991 Rutlandella sp. C Ballent, p. 41, pl. 3, fig. 6.

Repository. MLP-Mi 688.

Studied material. One carapace.

Dimensions (mm). Figured specimen: MLP-Mi 688, L = 0.370,

H = 0.175, W = 0.160 (Pl. 2, fig. 5).

Age and distribution. Late Aalenian–early Bajocian, Picún Leufú

section, Neuquén Basin, west-central Argentina.

Remarks. In this species, the intercostal areas are coarsely

punctate, which separates it from Eucytherura transversi-

plicata (Bate and Coleman) in which the intercostal areas

are coarsely reticulate.

Genus KANGARINA Coryell and Fields, 1937

Type species. Kangarina quellita Coryell and Fields, 1937 from

the Miocene of Panama.

Diagnosis. A very small to small, strongly, thick-shelled,

ornate cytherurid genus with strong ribs, deep intercostal

reticulae, a rather narrow and often marginally denticu-

late anterior margin, pronounced caudal process above

EXPLANATION OF PLATE 2

Figs 1–2. Eucytherura transversiplicata (Bate and Coleman, 1975). 1, MLP-Mi 579, female carapace, left lateral view, late Pliensbachian,

Picún Leufú, level 1145. 2, MLP-Mi 687, female carapace, right lateral view, late Aalenian–early Bajocian, Picún Leufú section,

level 1676.

Fig. 3. Eucytherura guillaeumeae nom. nov., 1976, MLP-Mi 1604, carapace, right lateral view, late Valanginian, Barda Cerro Marucho

(Puesto Jara) section, level MARJ11, Bco 15.

Fig. 4. Eucytherura sp. B Boomer and Ballent, 1996, MLP-Mi 655, right valve, external view, late Aalenian–early Bajocian, Picún Leufú

section, level 1681.

Fig. 5. Eucytherura sp., MLP-Mi 688, carapace, right lateral view, late Aalenian–early Bajocian, Picún Leufú section, level 1676.

Figs 6–7. Kangarina sp., MLP-Mi 1605, right valve. 6, external view. 7, internal view, late Aalenian–early Bajocian, Picún Leufú

section, level 1676.

Figs 8–10. Acrocythere sp. 8, MLP-Mi 1606, male carapace, left lateral view. 9, MLP-Mi 1607, male carapace, left lateral view. 10,

MLP-Mi 1608, juvenile carapace, left lateral view, late Hauterivian, Bajada del Agrio section, level AG 18a.

Fig. 11. Paranotacythere sp., MLP-Mi 1609, carapace, right lateral view, late Tithonian, Entre Lomas area (YPF.PC.Nq.EL-10, 1870 m

below surface).

Fig. 12. Paranotacythere? sp., MLP-Mi 1610, carapace, left lateral view, Berriasian?, Entre Lomas area (YPF.PC.Nq.EC-24, 1930–1940 m

below surface).

Figs 13–17. Procytherura amygdala sp. nov. 13, MLP-Mi 1434, holotype, carapace, right lateral view. 14, 15, 16, 17, paratypes. 14,

MLP-Mi 1437, carapace, dorsal view. 15, MLP-Mi 1435, carapace, left lateral view. 16, MLP-Mi 1436, carapace, right lateral view.

17, MLP-Mi 1439, carapace, left lateral view, late Valanginian, Cuesta del Chihuido section, level CH6.

Figs 18–19. Procytherura bispinata Ballent, 1991. 18, MLP-Mi 1611, carapace, right lateral view. 19, MLP-Mi 678 ⁄ 2, carapace, right

lateral view, late Aalenian–early Bajocian, Picún Leufú section, levels 1675 and 1676, respectively.

Fig. 20. Procytherura brenneri Valicenti and Stephens, 1984, MLP-Mi 1612, caparace, left lateral view, late Valanginian, Barda Cerro

Marucho (Puesto Jara) section, level MARJ11, Bco 15.

Scale bars represent 0.050 mm in figs 1, 2, 3, 4, 5, 6, 7, 10, 13, 14, 15, 16, 17, 18, 19, 20 and 0.100 mm in figs 8, 9, 11, 12.

202 P A L A E O N T O L O G Y , V O L U M E 5 2



PLATE 2

BALLENT and WHATLEY, Mesozoic ostracods

1 2 3 

4 5 6 

7 8 9 

10 11 12 

13 

14 

15 

16 17 

18 19 20 



mid-height, and particularly strong dorsal and ventro-lat-

eral ribs, the latter being alate. Eye tubercle prominent;

hinge antimerodont.

The genus is worldwide in both deep and shallow mar-

ine environments and usually ranges from the mid Creta-

ceous to the Recent.

Kangarina sp.

Plate 2, figures 6–7

Repository. MLP-Mi 1605.

Studied material. A single right valve.

Description. Very small, thick-shelled, subrhomboidal. Dorsal

margin very slightly convex and partly obscured posteriorly by

dorsal rib; anterior cardinal angle more strongly marked than pos-

terior. Ventral margin with slight median incurvature but over-

hung in lateral view by strong ventro-lateral alar rib. Anterior

margin only rounded medianly and with straight antero-dorsal

and antero-ventral slopes; medianly denticulate and with extrem-

ity near mid-height. Posterior margin with a compressed, slightly

upturned caudal process in the upper half of the valve. Eye tuber-

cle and internal ocular sinus present but not strongly developed.

Valve surface costate and coarsely reticulate, especially centrally. A

dorsal rib bearing a number of excavations and isolated pits, paral-

lels the dorsal and posterior margins. A strong alar rib extends

across the ventro-lateral surface. At 1 ⁄ 3 length of the valve, it

bifurcates with a short ramus continuing along the ventro-lateral

surface and another, broader and somewhat interrupted by coarse,

deep puncta bearing large solate normal pores, extends to an ante-

ro-median complex and then extends to the anterior margin at

mid-height and is responsible for the marginal denticulation.

Another, weaker rib also extends from the alar process, obliquely

anteriorly at 45� to an elevated complex of strongly reticulate

anastomosing ribs that extend horizontally forwards to the previ-

ously-mentioned antero-median complex. Smaller ribs extend

down towards this complex from the area of the eye tubercle. All

intercostal areas and many of the ribs are coarsely reticulate. Inter-

nal features as for genus. Hinge well developed and antimerodont,

with the posterior terminal hinge element bearing six small teeth

and the anterior three and separated by a deep, locellate median

groove. Adductors an oblique row of four oval scars with a flat-

tened u-shaped frontal scar antero-dorsally.

Dimensions (mm). Figured specimen: MLP-Mi 1605, right valve,

L = 0.360, H = 0.185 (Pl. 2, figs 5–6).

Age and distribution. Late Aalenian–early Bajocian, Picún Leufú

section, Neuquén Basin, west-central Argentina.

Remarks. It is possible that this specimen from the late

Aalenian–early Bajocian represents the earliest record of the

genus. In the general outline of its costation, it resembles

most species of the genus and can, for example, be compared

in this respect with Kangarina abyssicola (Müller, 1894).

The ORTHONOTACYTHERE Group

Three genera, Orthonotacythere Alexander, Paranotacythere

Bassiouni and Acrocythere Neale form a distinct group of costate,

reticulate and tuberculate, with antimerodont hinge ostracodes

within the Cytherurinae, of which the former is late Cretaceous

and Tertiary, while the latter two are Jurassic and Creta-

ceous. Paranotacythere and Acrocythere both occur in this study

but are neither diverse nor numerous; Orthonotacythere does not

occur.

Genus ACROCYTHERE Neale, 1960

Type species. Orthonotacythere hauteriviana Bartenstein, 1956

from the Upper Hauterivian of Lincolnshire, England.

Diagnosis. Medium; subrectangular to elongate-triangular,

with eye tubercle and ornamented by sharp longitudinal

ribs, converging towards end margins with remainder of

valve surface generally reticulate. Hinge and other internal

features as in Orthonotacythere Alexander, 1933.

The genus was first described as a subgenus of Ortho-

notacythere; both have similar hinge and internal features

but differ in shape and ornamentation. The posterior

termination of the carapace is bluntly pointed at about

mid-height and not markedly subdorsally as in Ortho-

notacythere. The ornamentation is dominantly costate

and ⁄ or reticulate, whereas tubercles (reflected as pits in

the inner surface of the valve) are typically present in

Orthonotacythere.

Acrocythere sp.

Plate 2, figures 8–10

Repository. MLP-Mi 1606, 1607, 1608.

Studied material. Fifteen carapaces, mainly juveniles.

Description. Small; subrectangular in lateral view, somewhat

inflated ventrally and with caudal process at mid-height. Subdor-

sal anterior area depressed. Dorsal margin straight, slightly sinu-

ose medianly; ventral margin regularly convex. Anterior margin

regularly rounded; posterior margin subangular with posteriorly

pointing caudal process at mid-height. Greatest length at mid-

height; greatest height anteriorly, at anterior cardinal angle area,

in front of the eye tubercle. Subrectangular in dorsal view and

somewhat inflated, with maximum width at mid-length. Orna-

ment of three main sharp ribs. The dorso-marginal, keel-like rib

extends from the posterior margin to the anterior area, where it

extends distal to the eye tubercle before becoming an antero-

marginal fringe-like rib. Median rib sinuous, extending from the

posterior area and bifurcating anterior of mid-point; both rami

reach the anterior margin. The ventral rib extends parallel to

that homonymous margin and bifurcates at about two third of

204 P A L A E O N T O L O G Y , V O L U M E 5 2



length. Eye tubercle conspicuous. A short anterodorsal rib

extends ventrally from the eye tubercle. Intercostal surface punc-

tate. Large pore openings, few in number, occur widely scattered

over the lateral surface of the valve. Sexual dimorphism present;

males more elongate than females. Juveniles are more acuminate

posteriorly, with more subtriangular outline in lateral view, and

with the mid-rib strongly arched in the posterior two-thirds of

its length. Internal features not seen.

Dimensions (mm). Figured specimens: MLP-Mi 1606, male cara-

pace, L = 0.410, H = 0.210, W = 0.170 (Pl. 2, fig. 8); MLP-Mi

1607, male carapace, L = 0.500, H = 0.230, W = 0.170 (Pl. 2,

fig. 9); MLP-Mi 1608, juvenile carapace, L = 0.360, H = 0.175,

W = 0.150 (Pl. 2, fig. 10).

Age and distribution. Early Hauterivian, Barda Cerro Marucho

(Puesto Jara) and Cerro Birrete sections; late Hauterivian, Bajada

del Agrio section, Neuquén Basin, west-central Argentina.

Remarks. Its rib pattern distinguishes this species from

other Acrocythere species. The diagnostic character of the

type species A. hauteriviana Bartenstein is the interrupted

mid-rib which is broken abruptly about one third of

its length. A. costata Brenner and Oertli, 1976 (pl. 4, figs

1–6) from the Hauterivian of the Algoa Basin in South

Africa, possesses a distinct longitudinal ribbing with the

upper lateral rib interrupted al mid-length. In A. cf. ashq-

elonensis (Rosenfeld and Raab) of Bassiouni (2002, pl. 8,

figs 12, 13) from the Albian–Cenomanian of Sinai, Egypt,

the mid-rib bifurcates in front of the centre of the cara-

pace; from these branches the upper one gives rise to a

short dorsal vertical branch.

Genus PARANOTACYTHERE Bassiouni, 1974

Type species. Orthonotacythere diplypta Triebel, 1941 from the

Hauterivian of Germany.

Diagnosis. Medium size. Subrectangular to subtrapezoidal

in lateral view with a subdorsal caudal process. Prominent

eye tubercle and pronounced subcentral vertical subcen-

tral sulcus. Lateral surface with a number of well devel-

oped tubercles disposed along dorsal and ventral margins.

These latter generally form a more or less distinct ventral

ridge. Remainder of surface variously costate, reticulate or

punctate.

Paranotacythere sp.

Plate 2, figure 11

Repository. MLP-Mi 1609.

Studied material. Five carapaces.

Dimensions (mm). Figured specimen: carapace, MLP-Mi 1609,

L = 0.580, H = 0.290, W = 0.250 (Pl. 2, fig. 11).

Age and distribution. Late Tithonian–Berriasian from boreholes,

Entre Lomas area, Neuquén Basin, west-central Argentina. Possi-

bly also Berriasian, outcrops Picún Leufú area, in the Neuquén

Basin.

Brief description. Medium, subrectangular, posteriorly acuminate

with caudal process above mid-height, depressed subdorsally and

inflated ventrolaterally. Lateral surface rough with irregular ribs

and irregularly reticulate intercostal areas with scattered mamil-

lae. Eye tubercle hemispherical.

Remarks. Only few specimens have been recovered. The

species is very similar in shape and ornament to a num-

ber of European late Jurassic and early Cretaceous species

and is possibly conspecific with Paracytheridea sp. 1 of

Musacchio (1979a, pl. 2, figs 13, 14, not described) from

the Berriasian at Picún Leufú area.

Paranotacythere? sp.

Plate 2, figure 12

Repository. MLP-Mi 1610.

Studied material. Three carapaces.

Dimensions (mm). Figured specimen: carapace, MLP-Mi 1610,

L = 0.520, H = 0.290, W = 0.160 (Pl. 2, fig. 12).

Age and distribution. Berriasian? from boreholes of the Entre

Lomas area, Neuquén Basin, west-central, Argentina.

Brief description. The carapace is of medium size and subtrape-

zoidal in lateral view. Anterior margin hight, obliquely rounded

to truncated with extremity just below mid height and posterior

margin with a moderately well-developed, posteriorly directed

caudal process just above mid height. Dorsal and ventral mar-

gins straight, converging posteriorly. Subvertical subcentral sul-

cus fairly well-defined. Distinct rounded, glassy eye tubercle. The

lateral surface of the valves is rough and chaotic with interaction

of numerous short ribs and tubercles and with an anterior,

ventral and posterior submarginal rib. In dorsal view the cara-

pace is compressed and flattened (deformed?).

Remarks. A few, reasonably preserved specimens have

been studied, that are accommodated tentatively within

Paranotacythere.

Genus PROCYTHERURA Whatley, 1970

Type species. Procytherura tenuicostata Whatley, 1970 described

from the top of the Nothe Clay (plicatilis Zone), Corallian of

BALLENT AND WHATLEY: TAXONOMY AND ZOOGEOGRAPHY OF THE MESOZOIC CYTHERURID OSTRACODA 205



the Dorset Coast; widespread throughout the English Oxfor-

dian.

Diagnosis. Small, subtriangular to subovate carapace, with

variable ornamentation from almost smooth to reticulate

or striate ⁄ costate. Lophodont hinge and narrow anterior

and posterior vestibula.

Procytherura amygdala sp. nov.

Plate 2, figures 13–17

.1998 Procytherura cf. maculata Brenner and Oertli;

Simeoni and Musacchio, p. 1412, pl. 2.

v.2006 Procytherura sp. nov.? Ballent (in Ballent et al.),

p. 65, pl. 4, fig. H.

.2008 Procytherura cf. maculata Brenner and Oertli;

Musacchio and Simeoni, pl. 1, fig. 7.

Repository. MLP-Mi 1434–1442.

Studied material. Eleven carapaces.

Derivation of name. (Greek altcdakg) amygdal�e almond.

With reference to the almond-like shape and outline of this

species.

Type specimens. Holotype MLP-Mi 1434, carapace illustrated in

pl. 2 fig. 13, from Cuesta del Chihuido section level CH6, Neu-

quén Basin, west-central Argentina.

Paratypes. MLP-Mi 1435, MLP-Mi 1436, MLP-Mi 1437, MLP-

Mi 1438, MLP-Mi 1439, MLP-Mi 1440, MLP-Mi 1441, MLP-Mi

1442, carapaces, all from Cuesta del Chihuido section (level

Ch6), Neuquén Basin, west-central Argentina.

Type locality and type level. Cuesta del Chichuido section

(35�45¢S-69�34¢W), Neuquén Basin, west-central Argentina, level

CH6, late Valanginian.

Diagnosis. Very small and elongate subrectangular spe-

cies of Procytherura characterized by an almond-like

appearance with well defined ventro-lateral rib, faintly

developed reticulation and fine punctae on the surface

of the valves.

Description. Carapace very small, delicate. Elongate subrectan-

gular in lateral view, acuminate and compressed posteriorly

with a caudal process at mid-height. Greatest length at

mid-height; greatest height in the anterior third of the valve.

Dorsal margin straight and sloping posteriorly. Ventral margin

feebly convex with a well-developed posteroventral keel. Ante-

rior margin broadly and symmetrically rounded. Posterior

margin with a compressed and symmetrical posteriorly

pointed caudal process. Mid-dorsal area somewhat depressed

in both valves. In dorsal view the carapace is subovate in

outline with the greatest width behind mid-length. Ornament

with a faint regular reticulation that is best developed in

ventral area parallel to that margin. Fine puncta and normal

pore canals occur in the solum of the reticula. A well defined

ventro-lateral rib is present. Eye tubercle absent. Lateral

outline and ornamentation of this species is almond-like.

Internal features not seen.

Dimensions (mm). Figured specimens: MLP-Mi 1434, Holotype,

L = 0.375, H = 0.180, W = 0.150 (Pl. 2, fig.13), MLP-Mi 1435,

Paratype, L = 0.380, H = 0.160, W = 0.180 (Pl. 2, fig. 15), MLP-

Mi 1436, Paratype, L = 0.360, H = 0.170, W = 0.180 (Pl. 2, fig.

16), MLP-Mi 1437, Paratype, L = 0.375, H = 0.200, W = 0.150

(Pl. 2, fig. 14), MLP-Mi 1439, Paratype, L = 0.375, H = 0.170,

W = 0.160 (Pl. 2, fig. 17).

Age and distribution. Late Valanginian–late Hauterivian: Cuesta

del Chihuido section; late Valanginian–early Hauterivian: Barda

Cerro Marucho (Puesto Jara) and Cerro Birrete sections, Neu-

quén Basin, west-central Argentina.

Remarks. P. amygdala is closest to P. maculata Brenner

and Oertli, 1976 (see below) from the Hauterivian of

South Africa and Neuquén Basin in Argentina which is

distinguished by a ventro-lateral node present on each

valve at 2 ⁄ 3 length. P. batei Dingle, 1984 (p. 129, fig. 12

B–C, E) from the early–middle Albian of boreholes on

the Falkland Plateau is ovate in lateral outline, lanceolate

in dorsal view and coarsely punctate with a prominent

ventrolateral swelling.

Procytherura bispinata Ballent, 1991

Plate 2, figures 18–19

v*1991 Procytherura bispinata Ballent, p. 37, pl. 2,

figs 8–11.

Repository. MLP-Mi 1611, 578 ⁄ 2.

Studied material. Fifteen carapaces.

Dimensions (mm). Figured specimens: MLP-Mi 1611, carapace,

L = 0.250, H = 0.120, W = 0.100 (Pl. 2, fig. 18); MLP-Mi 678 ⁄ 2,

carapace, L = 0.260, H = 0.125, W = 0.100 (Pl. 2, fig. 19).

Age and distribution. Late Aalenian–early Bajocian, Picún Leufú

section, Neuquén Basin, west-central Argentina.

Brief description. Very small, ovate with a short subdorsal caudal

process in lateral view; punctate surface and with two postero-

ventral spines.

Remarks. Its delicate costate ornament and two postero-

ventral spines distinguish this species from others of the

genus.

206 P A L A E O N T O L O G Y , V O L U M E 5 2



Procytherura brenneri Valicenti and Stephens, 1984

Plate 2, figure 20

*1984 Procytherura brenneri Valicenti and Stephens, p. 192,

pl. 7, figs 9–11; pl. 8, figs 1–2.

.1998 Procytherura cf. brenneri Valicenti and Stephens;

Simeoni and Musacchio, p. 1412, pl. 2.

Repository. MLP-Mi 1612.

Studied material. Two carapaces.

Dimensions (mm). Figured specimen MLP-Mi 1612, carapace,

L = 0.325, H = 0.140, W = 0.150 (Pl. 2, fig. 20).

Age and distribution. Late Valanginian and Hauterivian, Sundays

River Formation, Algoa Basin, South Africa; late Valanginian,

Cerro Birrete and Barda Cerro Marucho (Puesto Jara) sections,

Neuquén Basin, west-central Argentina.

Brief description. Very small, subrectangular to subovate in lateral

view with angular posterior margin with caudal process at or above

mid-height and well-developed postero-ventral keel. Postero-ven-

tral alar process developed; surface ornamented with large puncta.

Remarks. Argentinian specimens have more numerous

and smaller puncta than the types. P. brenneri appears to

be intermediate in shape and ornament between P.

aerodynamica Bate, 1975 (pl. 11, figs 7–15) from the

Middle and Upper Kimmeridgian of Tanzania, with fewer

puncta) and the reticulate P. maculata Brenner and Oertli

(see below).

Procytherura celtica Ainsworth, 1986

Plate 3, figure 1

*1986 Procytherura celtica Ainsworth, p. 303, pl. 4,

figs 8–11.

v.1991 Procytherura cf. celtica Ainsworth; Ballent, p. 36,

pl. 2, figs 7.

Repository. MLP-Mi 1613.

Studied material. Forty carapaces.

Dimensions (mm). Figured specimen: MLP-Mi 1613, carapace,

L = 0.270, H = 0.135, W = 0.120 (Pl. 3, fig. 1).

Age and distribution. Late Toarcian–Aalenian, off southwestern

Ireland (Ainsworth 1986); late Aalenian–early Bajocian, Picún

Leufú section, Neuquén Basin, west-central Argentina.

Brief description. Very small, subtriangular in lateral view, with a

nearly straight dorsal margin, a very subdued costate ornament

with fine secondary punctation.

Remarks. Argentinian specimens are somewhat more pos-

teriorly acuminate than those from offshore Ireland.

Procytherura euglyphea Ainsworth, 1986

Plate 3, figure 2

*1986 Procytherura euglyphea Ainsworth, p. 303, pl. 4,

figs 12–15.

v.1991 Procytherura cf. euglyphea Ainsworth; Ballent, p. 35,

pl. 2, fig. 6.

Repository. MLP-Mi 670.

Studied material. Twelve carapaces, three valves.

Dimensions (mm). Figured specimen: MLP-Mi 670, carapace,

L = 0.310, H = 0.150, W = 0.150 (Pl. 3, fig. 2).

Age and distribution. Mid to late Toarcian to Aalenian, British

Isles (Ainsworth 1986; Boomer 1989); late Aalenian–early Bajo-

cian, Picún Leufú section, Neuquén Basin, west-central Argen-

tina.

Brief description. Very small and subtriangular, ornamented with

a strongly developed, slightly oblique longitudinal rib. Antero-

ventrally, weak ribs extend to and beneath ventral inflation.

Valve surface with irregular open polygonal reticulation medi-

anly and posteriorly, with punctation anteriorly.

Remarks. The specimens from Argentina are less ventrally

inflated and less prominently costate than the type mate-

rial from Ireland, though this may be related to preserva-

tional differences. Procytherura sp. A of Ballent and

Whatley (2000b, p. 234, fig. 2. N, MLP-Mi 1082) from

the late Pliensbachian (Cerrito Roth sur section, Neuquén

Basin), which is a very small species with an oblique,

somewhat inflated, lateral rib and an indistinct postero-

ventral spine, is possibly a juvenile of E. euglyphaea Ains-

worth.

Procytherura kroemmelbeini Musacchio, 1979a

Plate 3, figure 3

v*1979a Procytherura kroemmelbeini Musacchio, p. 467,

pl. 2, figs 10–12.

v.2000b Procytherura kroemmelbeini Musacchio; Ballent

and Whatley, p. 233, fig. 2J.

Repository. MLP-Mi 1077.

Studied material. Five carapaces.

Dimensions (mm). Figured specimen: MLP-Mi 1077, carapace,

L = 0.410, H = 0.200, W = 0.170 (Pl. 3, fig. 3).

BALLENT AND WHATLEY: TAXONOMY AND ZOOGEOGRAPHY OF THE MESOZOIC CYTHERURID OSTRACODA 207



Age and distribution. Hauterivian, Cerro Negro de Covun-có

section, Neuquén Basin, west-central Argentina.

Brief description. Small, with a slim elongate-triangular outline

and ornamentation of sinuous and anastomosing longitudinal

ribs subparallel to margins and a ventro-lateral spine on each

valve.

Remarks. This species is closest to P. beerae Brenner and

Oertli, 1976 (pp. 507–508, pl. 8, fig. 9) from the Hauteri-

vian of the Algoa Basin, South Africa. However, they can

be easily distinguished because the South African species

lacks a ventro-lateral spine.

Procytherura maculata Brenner and Oertli, 1976

Plate 3, figures 4–5

*1976 Procytherura maculata Brenner and Oertli, p. 507,

only pl. 8, fig. 8.

v.1979a Procytherura aff. maculata Brenner and Oertli;

Musacchio, pl. 6, fig. 6.

v.2000b Procytherura maculata Brenner and Oertli; Ballent

and Whatley, p. 234, figs 2K–M.

Repository. MLP-Mi 1078, 1614.

Studied material. Ten carapaces.

Dimensions (mm). Figured specimens: MLP-Mi 1078, male cara-

pace, L = 0.350, H = 0.185, W = 0.150 (Pl. 3, fig. 4); MLP-Mi

1614, juvenile, L = 0.280, H = 0.135, W = 0.100 (Pl. 3, fig. 5).

Age and distribution. Hauterivian, Algoa Basin, South Africa

(Brenner and Oertli 1976); Hauterivian, Manzano Guacho sec-

tion, Sierra de la Vaca Muerta area and late Valanginian, Barda

Cerro Marucho (Puesto Jara) section, Neuquén Basin, west-cen-

tral Argentina.

Brief description. Small to very small, elongate subtriangular in

lateral view and with dorsal and ventral margins nearly straight,

EXPLANATION OF PLATE 3

Fig. 1. Procytherura celtica Ainsworth, 1986, MLP-Mi 1613, carapace, right lateral view, late Aalenian–early Bajocian, Picún Leufú

section, level 1676.

Fig. 2. Procytherura euplyphea Ainsworth, 1986, MLP-Mi 670, carapace, left lateral view, late Aalenian–early Bajocian, Picún Leufú

section, level 1676.

Fig. 3. Procytherura kroemmelbeini Musacchio 1979a, MLP-Mi 1077, carapace, right lateral view, Hauterivian, Cerro Negro de Covun-

có section.

Figs 4–5. Procytherura maculata Brenner and Oertli, 1976. 4, MLP-Mi 1078, male carapace, left lateral view, Manzano Guacho section,

Sierra de la Vaca Muerta area. 5, MLP-Mi 1614, juvenile carapace, left lateral view, late Valanginian, Barda Cerro Marucho

(Puesto Jara) section, level MARJ3, Bco 5.

Fig. 6. Procytherura mediocostata Bate and Coleman, 1975, MLP-Mi 1615, carapace, left lateral view, late Pliensbachian (Northern slope

of Cerro Trapial Mahuida), level 1186.

Fig. 7. Procytherura sp. B Ballent and Whatley, 2000b, MLP-Mi 1083, carapace, left lateral view, mid Callovian, Marı́a Rosa Curicó

section, level 1159.

Fig. 8. Procytherura sp. 1, MLP-Mi 1616, carapace, left lateral view, late Aalenian-early Bajocian, Picún Leufú section, level 1685.

Fig. 9. Procytherura sp. 2, MLP-Mi 1617, carapace, left lateral view, late Aalenian-early Bajocian, Picún Leufú section, level 1685.

Fig. 10. Procytherura? sp. Ballent and Whatley, 2000b, MLP-Mi 1084, carapace, left lateral view, late Pliensbachian, Cerrito Roth sur

section, level 101b.

Figs 11–12. Cytheropteron sp., MLP-Mi 1618, right valve. 11, external lateral view. 12, internal lateral view, late Aalenian–early

Bajocian, Picún Leufú section, level 1677.

Figs 13–18. Eocytheropteron immodicus sp. nov. 13, MLP-Mi 1619, holotype, female carapace, left lateral view, ?early Hauterivian, Entre

Lomas area (YPF.PC.Nq.EL. a-9, 1740 m below surface). 14, 15, 16, 17, 18, paratypes. 14, MLP-Mi 1620, male carapace, left

lateral view, ?early Hauterivian, Entre Lomas area (YPF.PC.Nq.EL. a-9, 1740 m below surface). 15, MLP-Mi 1621, female

carapace, right lateral view, ?early Hauterivian, Entre Lomas area (YPF.PC.Nq. PB. a-9, 1754 m below surface). 16, 17, MLP-Mi

1622, juvenile carapace, left lateral and dorsal views, ?early Hauterivian, Entre Lomas area (YPF.PC.Nq. PB. a-9, 1754 m below

surface). 18, MLP-Mi 1623, juvenile carapace, right lateral view, ?early Hauterivian, Entre Lomas area (YPF.PC.Nq. PB. a-9,

1745 m below surface).

Fig. 19. Paradoxorhyncha neuquenensis (Ballent, 1991), MLP-Mi 664 ⁄ 2, male carapace, left lateral view, late Aalenian–early Bajocian,

Picún Leufú section, level 1676.

Fig. 20. Paracytheridea sp. 2 Musacchio, 1979a, MLP-Mi 360, male carapace, right lateral view, ?Berriasian, Picún Leufú section, level

138.

Scale bars represent 0.050 mm in figs 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 19 and 0.100 mm in figs 10, 13, 14, 15, 16, 17, 18, 20.

208 P A L A E O N T O L O G Y , V O L U M E 5 2



PLATE 3

BALLENT and WHATLEY, Mesozoic ostracods

1 2 3 

4 
5 6 

7 8 9 

10 11 12 

13 
14 15 

16 

17 

18 

19 20 



and well-developed posteroventral keel. A ventro-lateral node is

present on each valve at 2 ⁄ 3 length and a shallow, vertical sulcus

extends across the lateral surface from the dorsal margin. Orna-

mentation by a distinctive regular reticulum, disposed concentri-

cally and parallel to margins.

Remarks. Ballent and Whatley (2000b, p. 234) have pro-

vided a complementary description of this species in

order to clarify its confused status (also see P.brenneri

Valicenti and Stephens, this study).

Procytherura mediocostata Bate and Coleman, 1975

Plate 3, figure 6

*1975 Procytherura mediocostata Bate and Coleman,

p. 40, pl. 14.1–14.9, 14.11, 14.12, 14.15; fig. 18a–c.

Repository. MLP-Mi 1615.

Studied material. One carapace.

Dimensions (mm). Figured specimen: MLP-Mi 1615, male cara-

pace, L = 0.310, H = 0.115, W = 0.150 (Pl. 3, fig. 6).

Age and distribution. Lower Toarcian of England; late Pliensba-

chian, northern slope of Cerro Trapial Mahuida, Neuquén Basin,

west-central Argentina.

Brief description. Very small, narrow, elongate carapace taper-

ing posteriorly with distinct sub-dorsal caudal process. Well-

marked diagonal rib crosses a dorso-median sulcus, surface

with irregular reticulation. The only specimen recovered seems

to be male.

Procytherura sp. B Ballent and Whatley, 2000b

Plate 3, figure 7

v.2000b Procytherura sp. B Ballent and Whatley, p. 235,

fig. 2O.

Repository. MLP-Mi 1083.

Studied material. One carapace.

Dimensions (mm). Figured specimen: MLP-Mi 1083, carapace,

L = 0.275, H = 0.130; W = 0.140 (Pl. 3, fig. 7).

Age and distribution. Mid Callovian, Marı́a Rosa Curicó section,

Neuquén Basin, west-central Argentina.

Brief description. Very small and very elongate ovate in lateral

view, with a small postero-ventral keel. Surface smooth except

for feeble anterior ribs and a strong reticulum at the base of

the caudal process. Although probably a new species, with

only a single specimen, it is retained under open nomencla-

ture.

Remarks. Procytherura sp. B is closest to Procytherura sp.

of Dépêche (1985, pl. 31, fig. 29) from the Middle Batho-

nian of the Paris Basin, France, but the latter species has

a more pronounced ventral expansion.

Procytherura sp. 1

Plate 3, figure 8

Repository. MLP-Mi 1616.

Studied material. One carapace.

Description. Very small and delicate species, subrectangular

tapering posteriorly in lateral view. Anterior margin regularly

rounded; posterior margin acute, with a symmetric caudal pro-

cess nearly mid-height. Dorsal margin convex, with well formed

dorsal flange. Ventral margin slightly concave medianly. Greatest

length above mid-height; greatest height at mid-length. In dorsal

view, very compressed, subrhomboidal, with greatest width

behind mid-length at posterior termination of ventro-lateral rib.

Three longitudinal ribs are disposed over the lateral surface of

the valves. The sharp dorsal rib, extends from the antero-dorsal

angle parallel to the dorsal margin; at the postero-dorsal region

turns vertically terminating at postero-ventral angle. The median

rib, somewhat sinuous extends from the mid-anterior margin

terminating against the vertical part of the dorsal rib in a promi-

nent postero-dorsal node. Round, small mid-anterior node is

present. The ventral rib, concave and somewhat sinuous, extends

along a weakly alar inflation terminating in a distinct postero-

ventral node. Round eye tubercle with a fine ocular rib produced

anteriorly. Inter-rib regions with delicate irregular polygonal

reticulation; fine secondary pitting within reticulae. Internal fea-

tures not seen.

Dimensions (mm). Figured specimen: MLP-Mi 1616, carapace,

L = 0.270, H = 0.150; W = 0.100 (Pl. 3, fig. 8).

Age and distribution. Late Aalenian–early Bajocian, Picún Leufú

section, Neuquén Basin, west-central Argentina.

Remarks. The ornamentation distinguishes it from oth-

ers of the genus. Although surely a new species, with

only a single specimen, it is retained under open

nomenclature.

Procytherura sp. 2

Plate 3, figure 9

Repository. MLP-Mi 1617.

Studied material. One carapace.

210 P A L A E O N T O L O G Y , V O L U M E 5 2



Description. Very small, subrectangular tapering posteriorly and

ventrally inflated. Anterior margin slightly asymmetrically

rounded, extremity below mid-height. Posterior margin subtri-

angular, extremity above mid-height. Dorsal margin straight,

tapers towards posterior. Ventral margin slightly convex, tapers

towards posterior. Greatest length above mid-height; greatest

height at mid-length. Valves subequal. In dorsal view, lanceolate

with greatest width in the posterior third at termination of ven-

tro-lateral rim. Weak eye swelling is present. Valve surface punc-

tate and with weak ribs situated mainly in anterior region of the

valve and two irregular ribs extending back from anterior mar-

gin; they fuse at the moderately developed ala to form a single

rib extending back along alar rim and terminating in a postero-

ventral node.

Dimensions (mm). Figured specimen: MLP-Mi 1617, carapace,

L = 0.335, H = 0.150; W = 0.150 (Pl. 3, fig. 9).

Age and distribution. Late Aalenian–early Bajocian, Picún Leufú

section, Neuquén Basin, west-central Argentina.

Remarks. The two irregular ribs extending back from the

anterior margin which then fuse to form a single rib run-

ning along the ala, diagnoses Cytheropteron pulchellum

Bate and Coleman, 1975 (p. 30, pl. 12, figs 10–14) from

the early Toarcian of England, which is, however, more

acuminate posteriorly and has more distinct lateral

expansions.

Procytherura? sp. Ballent and Whatley, 2000b

Plate 3, figure 10

v.2000b Procytherura? sp. Ballent and Whatley, p. 235,

fig. 2P.

Repository. MLP-Mi 1084.

Studied material. One carapace.

Dimensions (in mm). Figured specimen: carapace MLP-Mi 1084

L = 0.420, H = 0.180; W = 0.200 (Pl. 3, fig. 10).

Age and distribution. Late Pliensbachian, Cerrito Roth sur sec-

tion, Neuquén Basin, west-central Argentina.

Brief description. Small, elongate subrectangular, tapering poste-

riorly. Anterior margin rounded; posterior produced into a cau-

dal process with blunt apex almost coincident with mid-height.

The surface of the valves is finely reticulate with muri preferen-

tially aligned parallel to margins.

Remarks. This species is only tentatively assigned to

Procytherura due to differences in lateral outline and lack

of internal details.

CYTHEROPTERINAE Hanai, 1957

Genus CYTHEROPTERON Sars, 1866

Type species. Cytheropteron latissimum (Norman) (by subsequent

designation: Alexander, 1933) from the Recent sediments in the

North Atlantic.

Diagnosis. A genus with a small carapace of subcircular,

subovate or subrhomboidal lateral outline. With or with-

out caudal process. Alate or, alternatively, very tumid

ventrolaterally. Smooth, punctate, rarely reticulate or deli-

cately ribbed. Blind. Median element of hinge crenulate.

Radial pores relatively few, well spaced, straight and

simple.

Cytheropteron sp.

Plate 3, figures 11–12

Repository. MLP-Mi 1618.

Studied material. One right valve.

Dimensions (mm). Figured specimen: right valve MLP-Mi 1618

L = 0.235, H = 0.140 (Pl. 3, figs 11–12).

Age and distribution. Late Aalenian–early Bajocian, Picún Leufú

section, Neuquén Basin, west-central Argentina.

Brief description. Very small, delicate species, subovate in lateral

view with dorsally directed caudal process at mid-height. Moder-

ately alate ventrolaterally and with weak dorsal and median ribs

and delicate intercostal punctation. Hinge merodont, inner

lamella of moderate width; vestibula not seen.

Remarks. Cytheropteron sp. A of Boomer and Ballent

1996 from the Late Pliensbachian–Toarcian at Mochras

(British Isles) and North Africa is more elongate in lateral

view and more strongly alate than the present species.

Genus EOCYTHEROPTERON Alexander, 1933

Type species. Cytheropteron bilobatum Alexander, 1929 from the

Lower Cretaceous of Texas.

Diagnosis. Carapace subtrapezoidal in lateral view, egg-

shaped in dorsal view, short caudal process, without trace

of wing-like lateral expansions. Left valve overhanging right

valve conspicuously along the dorsal margin. The right

valve bears small teeth on short, ridge-like elevations at

each end of the hinge margin, with corresponding notched

sockets in the left valve. The hinge margin of each valve,

BALLENT AND WHATLEY: TAXONOMY AND ZOOGEOGRAPHY OF THE MESOZOIC CYTHERURID OSTRACODA 211



between the terminal series of teeth of the right, and the

terminal sockets of the left valve, is finely denticulate.

Eocytheropteron immodicus sp. nov.

Plate 3, figures 13–18

Repository. MLP-Mi 1619, 1620, 1621, 1622, 1623, 1624, 1625,

1626, 1627.

Studied material. Fifteen carapaces.

Derivation of name. Latin immodicus = excessive, extravagant.

With reference to the very strongly expressed sexual dimorphism

of this species.

Type specimens. Holotype MLP-Mi 1619, female carapace illustrated

in pl. 3 fig. 13, from borehole YPF.PC.Nq.EL.a-9 (Entre Lomas),

Neuquén Basin, west-central Argentina, 1740 m below surface.

Paratypes. MLP-Mi 1620, male carapace, YPF.PC.Nq.EL.a-9 (Entre

Lomas), 1740 m below surface; MLP-Mi 1621, female carapace,

YPF.PC.Nq.PB.a-99 (Piedras Blancas), 1754 m below surface; MLP-

MLP-Mi 1622, juvenile carapace, YPF.PC.Nq.PB.a-99 (Piedras

Blancas), 1754 m below surface; MLP-Mi 1623, juvenile carapace,

YPF.PC.Nq.PB.a-99 (Piedras Blancas), 1745 m below surface; MLP-

Mi 1624, female carapace, YPF.PC.Nq.PB.a-99 (Piedras Blancas),

1772 m below surface; MLP-Mi 1625, juvenile carapace,

YPF.PC.Nq.PB.a-99 (Piedras Blancas), 1772 m below surface; MLP-

Mi 1626, male carapace, YPF.PC.Nq.EL.a-9 (Entre Lomas), 1740 m

below surface; MLP-Mi 1627, male carapace, YPF.PC.Nq.PB.a-99

(Piedras Blancas), 1871 m below surface, all from the Entre Lomas

area, Neuquén Basin, west-central Argentina.

Type locality and type level. Borehole YPF.PC.Nq.EL.a-9 (Entre

Lomas), Entre Lomas area (between 37º50¢–38�15¢S and 68�00¢–
68º30¢W) Neuquén Basin, west-central Argentina, 1740 m below

surface, ?early Hauterivian.

Diagnosis. A medium, very strongly inflated species of

Eocytheropteron, with marked sexual dimorphism.

Description. Medium, strongly dimorphic. Female, ovate and

strongly inflated in lateral view, with a short upturned caudal

process below mid-height. Dorsal margin regularly and strongly

convex; ventral margin markedly convex in lateral view with

apex at mid-length. Anterior margin obliquely rounded; poster-

ior margin, with a short, narrow, upturned caudal process below

mid-height. Greatest length below mid-height; greatest height at

about mid-length. The H ⁄ L ratio is nearly 2 ⁄ 3. Males, subovate,

more elongate than females in lateral view with the short caudal

process at mid-height. In both sexes, in dorsal view the carapace

is subovate with maximum width at mid-length and the left

valve, larger than right, overlaps along the dorsal margin. Lateral

surface finely punctate. Ventral surface with weak ribs beneath

and parallel to the line of the prominent ventro-lateral tumidity.

Internal features not seen.

Dimensions (mm). Figured specimens: MLP-Mi 1619, Holotype,

L = 0.510, H = 0.320, W = 0.320 (Pl. 3, fig. 13), MLP-Mi 1620,

Paratype, L = 0.590, H = 0.310, W = 0.300 (Pl. 3, fig. 14), MLP-

Mi 1621, Paratype, L = 0.480, H = 0.300, W = 0.250 (Pl. 3, fig.

15), MLP-Mi 1622, Paratype, L = 0.450, H = 0.280, W = 0.310

(Pl. 3, figs 16–17), MLP-Mi 1623, Paratype, L = 0.430,

H = 0.260, W = 0.250 (Pl. 3, fig. 18).

Age and distribution. ?Early Hauterivian from boreholes of the

Entre Lomas area, Neuquén Basin, west-central Argentina.

Remarks. This new species differs from others with simi-

lar lateral outline, such as E. tumidum (Alexander) and E.

delrioense (Alexander) from the Lower Cretaceous of

Texas (Alexander 1933, pl. 27, figs 13a, b and pl. 25, fig.

12; pl. 26, fig. 9, respectively) in the strength of its sexual

dimorphism and punctate ornament.

Genus PARADOXORHYNCHA Chapman, 1904

Type species. Paradoxorhyncha foveolata Chapman, 1904 from

the Middle Jurassic (Lower Oolite) strata, near Geraldton, in

Western Australia.

Diagnosis. The type species is medium-sized, thick-shelled

and very coarsely ornamented, whereas other species

included in this genus are smaller, thinner-shelled and

much more delicately ornamented, with puncta rather

than reticulae. Hinge hemimerodont.

Paradoxorhyncha neuquenensis (Ballent, 1991)

Plate 3, figure 19

v*1991 Praeschuleridea? neuquenensis Ballent, p. 331, pl. 1,

figs 5–11.

v.1996a Paradoxorhyncha neuquenensis (Ballent); Ballent

and Whatley, Fig. 1: 4–6.

Repository. MLP-Mi 627, 664 ⁄ 1-664 ⁄ 14.

Studied material. Thirty carapaces, twelve valves.

Dimensions (mm). Figured specimen: MLP-Mi 664 ⁄ 2, male cara-

pace, L = 0.360, H = 0.180, W = 0.160 (Pl. 3, fig. 19).

Age and distribution. Late Aalenian–early Bajocian, Picún Leufú

section, Neuquén Basin, west-central Argentina.

Brief description. Paradoxorhyncha neuquenensis is small, subtri-

angular to subovate in lateral view, moderately alate and with a

densely and coarsely punctate ornament. It has a poorly pre-

served hinge, imperfectly described originally because it is only

observed in juveniles (Ballent 1991), which could be interpreted

as lophodont. Lophodont hinges occur in the ontogeny of

212 P A L A E O N T O L O G Y , V O L U M E 5 2



merodont types (for example in species of Galliaecytheridea Oer-

tli); the present species could represent a similar case with juve-

niles bearing lophodont, but adults hemimerodont hingement.

Remarks. Ballent and Whatley (1996a) included in the

genus Paradoxorhyncha five early Middle Jurassic species:

P. foveolata Chapman (the type species), P. jurassica

(Chapman), P. australiense (Chapman) and Paradoxo-

rhyncha sp. (Chapman) from Australia and Paradoxo-

rhyncha neuquenensis (Ballent) from west-central

Argentina. Mette (in Mette and Geiger 2004) recorded the

genus with four species from the Bajocian and middle-

Upper Bathonian of the Morondova Basin, Madagascar.

The systematic status of Australian species of this genus

has been recently discussed by Lord et al. 2006.

P. neuquenensis is extremely similar in shape, outline

and ornamentation to P. australiense, which is, however,

medium in size. Ballent and Whatley (1996a) considered

that the two species shared a common ancestor.

Gen. indet. B of Bate et al. 1984 (pl. 5, figs 12, 14, 15)

from the Pliensbachian of Leg 79, Site 547 (offshore Mor-

occo) strongly resembles species of Paradoxorhyncha.

PARACYTHERIDEINAE Mandelstam in Orlov, 1960

Genus PARACYTHERIDEA Müller, 1894

Type species. Paracytheridea depressa Müller, 1894 from the

Recent sediments in the Gulf of Naples, Italy.

Diagnosis. Subrectangular elongate, moderately to

strongly alate, flattened ventrally and with posterior end

drawn out into a distinct caudal process. In dorsal view

the carapace is arrowhead-shaped. Surface heavily orna-

mented with ridges and ⁄ or tubercles. Ventral rib in pos-

terior end, often terminating in a prominent spine. Hinge

weak and variably crenulate, with faint indications of

sockets in left valve; hinge margin or crenulate bar

between them.

Paracytheridea sp. 2 Musacchio, 1979a

Plate 3, figure 20

v. 1979a Paracytheridea? sp. 2 Musacchio, p. 467, pl. II,

figs 23–25.

Repository. MLP-Mi 360, 361.

Studied material. Two carapaces.

Dimensions (mm). Figured specimen: MLP-Mi 360, male cara-

pace L = 0.500, H = 0.200, W = 0.185 (Pl. 3, fig. 20).

Age and distribution. Berriasian?, Picún Leufú section, Neuquén

Basin, west central Argentina.

Brief description. The studied material consists of two carapaces;

one of them apparently an adult male and the another probably

an A-1 juvenile. The species is of medium length, elongate

subrectangular in lateral view, with a distinct, backward point-

ing, symmetrical caudal process at mid-height. Moderately alate

mid ventrolaterally. Eye tubercle at some distance from the mar-

gin. Longitudinal ribs and coarse punctations ornament the

lateral surface of the valves. The dorsal rib, weak and discontinu-

ous, extends along the dorsal margin, cuts through the eye node

and joins the anterior margin in the lower half of the valve. The

median rib extends obliquely across the valve, and posteriorly, in

front of the caudal process area, it bends ventrally and continues

as a ventro-lateral rib. The median rib is markedly concave

below the position of the adductor scars.

Remarks. Valicenti and Stephens (1984, p. 189) suggested

that the present species, together with Orthonotacythere

(Acrocythere) 129 of Grékoff 1963 (Portlandian of Mada-

gascar), Paracytheridea mandawaensis Bate, 1975 (Middle

to Upper Kimmeridgian of Tanzania) and Paracytheridea?

aranea Valicenti and Stephens, 1984 (Upper Valanginian

of South Africa), all of very small size, may belong to a

new genus of the family Cytheruridae. We consider that

while the three African species, which are very similar,

both in size and general morphology, might constitute a

new taxon, the present species is considerably different

and we prefer to consider it as Paracytheridea.

ZOOGEOGRAPHY

During the Cenozoic the Cytheruridae was almost equally

diverse in shelf and deep-sea environments. During the

Mesozoic, members of the family seem to have been con-

fined to shelf depths, with many species also in marginal

marine habitats.

The distribution of Recent cytherurids from the coast of

northern Rı́o de Janeiro (Brazil) shows that most of the

species have a preference for finer sands and greater depths

offshore, where influence of wave action on the bottom is

diminished. The results show that ostracods are most abun-

dant between 51 and 70 m, where 88 per cent of the total

number of the specimens occurs. Fine sand predominates

in this depth range (Feijo Ramos et al. 1999). Similarly,

Coimbra et al. (1999) concluded that cytherurids from the

Brazilian continental shelf inhabit on a substrate of fine-

grained bioclastic sands between 75 and 100 m depth.

In the present study, early and Middle Jurassic cyther-

urids occur in association with abundant and diverse

lagenid foraminifers, with floods of polymorphinids, spir-

illinids and involutinids, which indicate shallow-marginal

marine restricted environments, with clear and well

BALLENT AND WHATLEY: TAXONOMY AND ZOOGEOGRAPHY OF THE MESOZOIC CYTHERURID OSTRACODA 213



oxygenated waters (Ballent 1987, 2004). Cytherurids from

the late Valanginian–early Hauterivian of the Barda Cerro

Marucho (Puesto Jara) and Cerro Birrete and from the

Hauterivian of the Cerro Negro de Covun-có sections, all

close to the southern border of the Neuquén Basin, occur

associated with species of Platycopina, with a relatively

high ostracod ⁄ foraminiferal ratio with the latter domi-

nated by polymorphinids and spirillinids (Concheyro

et al. 2005). The environment of deposition corresponds

to restricted marginal marine conditions with warm

waters. In both Jurassic and early Cretaceous microfaunas,

the presence of Cytherelloidea, a well-known warm water

indicator (Sohn 1962) militates in favour of inner rather

than outer shelf in a subtropical or warmer environment.

Mesozoic Cytheruridae were marine podocopid

ostracods, which, in common with all contemporary (and

modern) cytheroideans, were incapabable of free swim-

ming and also lacked pelagic larvae. Therefore, their

active migration is confined to the distance where they

could ‘walk’ or be transported by marine agencies. The

dispersion of ostracods in shallow water marine environ-

ments is much more constrained by physical factors than

it is for deep water forms. Only where continuity of con-

tinental shelf occurs latitudinally are conditions likely to

be ideal for the successful migration of such shallow water

faunas (Whatley 1986, 1988). Ostracodes can migrate lati-

tudinally when temperature and other ecological parame-

ters, such as the bathymetry, remain stable within certain

limits and continental margins can function as migration

pathways (Babinot and Colin 1992).

The Tethys, a largely east–west, latitudinally oriented

thermospheric ocean, was a major oceanographic feature

throughout the late Palaeozoic, entire Mesozoic and the

pre-Miocene Cainozoic. It was a major route adopted by

migrant ostracodes during all this time (McKenzie 1967,

1982; Whatley 1988). Given the absence of polar ice dur-

ing the Mesozoic, the depth of Tethys was not a barrier

to migration from one shore to the other (Whatley 1988;

Whatley and Ballent 1994).

The presence in the Neuquén Basin of Eucytherura gas-

sumensis, E. michelseni, E. paranuda [ex Eucytherura nuda

(Brand)], E. oeresundensis, E. transversiplicata, Procyther-

ura celtica and P. mediocostata as well as several cyprid-

oids (Ballent and Whatley 2000a; Arias 2006) all species

known from the well-documented shelf deposits of the

North West European Lias, supports the idea that an ini-

tial migration route may have taken place from European

epicontinental seas, around the southern margin of

Tethys, around western Australia and southern Antarctica

and northwards to the western Argentina. The same route

is known to have been adopted by foraminifers (Ballent

1987) and invertebrates (Riccardi 1991; Damborenea and

Manceñido 1992).

The contemporaneous presence of Paradoxorhyncha in

the early Bajocian of Western Australia (Malz and Oertli

1993; Lord et al. 2006), late Aalenian–early Bajocian of

Western Argentina (Ballent and Whatley 1996a) and

Bajocian of southwest Madagascar (Mette and Geiger

2004) indicates the genus to be apparently restricted to

the Southern Hemisphere. Since it has not been found in

the northern parts of Gondwana and southern Europe, it

is probable that it migrated along the southern shores of

Gondwana from Australia to South America and Mada-

gascar during the early Bajocian (Mette 2004). This allows

us to explain the close similarities between early–mid

Jurassic foraminifers from Australia and Argentina

(Bartenstein and Malz 2001).

Species such as Eucytherura sp. B of Boomer and

Ballent and Procytherura euglyphea, recognized from sites

to the southwest of the British Isles, off Northwest Africa

and in the Neuquén Basin, although not known from

other parts of Britain and Europe (Boomer and Ballent

1996), support the existence of a central Atlantic seaway

which connected the western part of the Tethys with the

eastern Pacific (‘the Hispanic Corridor’) as a migration

route during the early–Middle Jurassic (see discussion in

Ballent and Whatley 2000b).

During the latest Jurassic (Berriasian) the opening of a

shallow intermittent epicontinental seaway between

southern South Africa and southern Argentinian Pata-

gonia favoured faunal interchange. This seaway corre-

sponds to the commencement of the continental

separation between Africa and South America (124 Ma),

which created the South Atlantic and a small ocean basin

off south-east Africa (Natal Valley, see Dingle 1988) pro-

ducing a Valanginian–Hauterivian influx of new species

and an increase in population diversity. The coeval

records of Procytherura brenneri, P. maculata and Eucy-

therura guillaumeae (ex E. tuberculata Brenner and

Oertli), as well as several species of Majungaella and

Rostrocytheridea (Ballent et al. 1998; Ballent and Whatley

2007) and foraminifers (Mcmillan 2003) in the Algoa

Basin in South Africa and in the Neuquén Basin, western

Argentina strongly support the existence of a southern

Gondwana seaway.

CONCLUSIONS

The Cytheruridae were clearly the most abundant and

diverse ostracod family during the studied interval in the

Neuquén Basin, west-central Argentina. No other family

of ostracods can even approach them in these respects.

Table 1 demonstrates the diversity of podocopinid fami-

lies within the Pliensbachian to Tithonian interval in the

Neuquén Basin.

214 P A L A E O N T O L O G Y , V O L U M E 5 2



The Late Pliensbachian is represented by a mixed

fauna of Metacopida, Platycopida and Podocopida with

marine Cypridoidea (four species), Bairdioidea (five

species) and Cytheroidea with ten species, of which the

Cytheruridae are the most abundant family with seven

species.

Around the Aalenian–Bajocian boundary, the fauna is

strongly dominated by Cytheroidea, with the Platycopina,

Cypridoidea and Bairdioidea comprising together only 4.5

per cent of the total number of individuals. The Cytheroi-

dea comprise twenty three species with the Cytheruridae

again being clearly the most abundant group with seven-

teen species. Of these, the three most abundant species

(Procytherura celtica, Eucytherura pichia and Paradox-

orhyncha neuquenensis) make up almost 50 per cent of

the total of specimens.

In the mid–Late Callovian, the dominant Cytheroidea

(84.5 per cent) are mainly represented by the Bythocythe-

ridae followed by the cytherurids. Throughout the Titho-

nian–early Cretaceous interval the Cytheroidea retain

their dominance; however, data on relative abundance of

each family are not yet comprehensive available. Nine

species of Cytheruridae have been recorded in this paper

and five species of Rostrocytheridea (Cytherideidae) have

been described by Ballent and Whatley (2007); studies on

other genera, such as ‘Sondagella’ and allies by the

authors are in progress.

In numerical terms the Cytheruridae are distributed

throughout the strata available for study in the basin as

indicated in Table 2. It demonstrates, as shown by What-

ley and Stephens (1976) and Whatley (1988), the great

expansion of the Cytheroidea, and the Cytheruridae in

particular in the Middle Jurassic, with a further increase

in the marine early Cretaceous.

The most abundant genus, with fourteen species is

Eucytherura, followed closely by Procytherura with twelve

species; these two accounting for 77 per cent of the fauna.

The Cytherurinae are by far the most important of the

three subfamilies of the Cytheruridae. With thirty species

belonging to four genera, they make up 44.4 per cent of

the genera but 86 per cent of the species, while the Cythe-

ropterinae comprise three genera and three species (11

per cent) and the Paracytherideinae with a single genus

and species are very poorly represented.

The fact that several of the species are also known as

far away as Europe, demonstrates the very important

migrationary links that existed between the two areas

during the Mesozoic. Examples are particularly common

among Eucytherura and Procytherura species (Eucyther-

ura gassumensis, E. michelseni, E. paranuda [ex Eucyther-

ura nuda (Brand)], E. oeresundensis, E. transversiplicata,

Procytherura celtica, P. mediocostata). Others, such as

Eucytherura sp. B of Boomer and Ballent and Procyther-

ura euglyphea, recognized from sites to the southwest of

the British Isles, off Northwest Africa and the Neuquén

Basin (although not known from other parts of Britain

and Europe), support the existence of the Hispanic Cor-

ridor as a migration route during the early–Middle

Jurassic. The coeval occurrence of the genus Paradox-

orhyncha in western Australia, southwest Madagascar

and western Argentina indicates that it migrated along

the southern shores of Gondwana during the early

Bajocian. In the early Cretaceous, some species indicate

close links with South Africa (Procytherura brenneri,

TABLE 1 . Diversity of Podocopina throughout the stages of late early Jurassic and late Jurassic of the Neuquén Basin, west-central

Argentina.

Stages Number of species

Cypridoidea Bairdioidea Cytheroidea

Tithonian 0 1 6 (1 Cytheruridae)

Mid-Late Callovian 2 0 16 (5 Bythocytheridae, 3 Cytheruridae)

Bajocian 0 0 1

Aalenian-Bajocian 1 2 23 (17 Cytheruridae)

Late Pliensbachian 4 5 10 (7 Cytheruridae, 3 Bythocytheridae)

TABLE 2 . Distribution of Cytheruridae throughout the Jurassic

and early Cretaceous of the Neuquén Basin, west-central Argen-

tina.

Stage Number

of genera

Number

of species

Cretaceous Hauterivian 3 5

Valanginian 2 3

Berriasian 2 3

Jurassic Tithonian 1 1

Callovian 2 3

Bajocian 1 1

Aalenian-Bajocian 5 17

Pliensbachian 2 7

BALLENT AND WHATLEY: TAXONOMY AND ZOOGEOGRAPHY OF THE MESOZOIC CYTHERURID OSTRACODA 215



P. maculata, Eucytherura guillaumeae [ex E. tuberculata

Brenner and Oertli]) supporting the existence of a

southern Gondwana seaway.

The fact that certain genera, such as Kangarina, hith-

erto not recorded below the Cretaceous, have been

encountered in the late Aalenian–early Bajocian suggests

that southern South America should be considered more

seriously as an important locus of evolution for cytheroi-

dean ostracodes.

With respect to palaeoenvironmental preferences, Juras-

sic and early Cretaceous cytherurids seem to typify a mar-

ginal marine environment, with warm-temperate waters,

normal salinity levels and low energy regime.

Acknowledgements. S. Fontana (Liverpool) and A. Benialgo (La

Plata) helped us in many ways. An anonymous referee informed

us about homonym names. Thanks also to the editor Professor

Paul Smith for his many helpful suggestions. Funding for this

study was provided by Consejo Nacional de Investigaciones

Cientı́ficas y Técnicas (CONICET) and Agencia Nacional de

Promoción Cientı́fica y Tecnológica (PIP 5613 and ANPCYT

14143 ⁄ 03, respectively).

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