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Chapter 60. Ostracoda of the early Jurassic Tethyan Ocean

Chapter 60. Ostracoda of the early Jurassic Tethyan Ocean

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4



Ostracoda of Early Jurassic Tethyan Ocean 851



also colonised the new shelf sea bottom, developed rapidly in diversity and density and appear to

have been well able in the early Toarcian to occupy the habitats left by the extinction of the healdiids. This biostratigraphical pattern was set against a background of fluctuating sea level (Vail,

Hardenbol and Todd, 1984; Van Harten and Van Hinte, 1984: fig. 3) and bottom water anoxia,

especially during the early Toarcian when benthonic organisms were rare or absent over much

of the area. This general pattern of events is well known, but should be borne in mind when

considering areas away from the north-west European shelf. It is also important to note that thanks

to the work of, amongst others, Bolz, Gramm, Kollmann, Kristan-Tollmann, Kozur, Sohn and

Urlichs, the hitherto poorly known ostracod faunas of the Triassic are now more familiar than

those of the extra-European Lower Jurassic.



THENATURE

OF TETHYS

During the Jurassic the area to the south of the north-west European shelf sea was occupied by a

major east-west marine feature: Tethys. The name was first used by Eduard Suess in 1893 for a

pre-Mediterranean seaway which connected the Alpine and Mediterranean areas with the Himalayas. The concept was originally that of Melchior Neumayr who had mapped a Jurassic ‘Zentrales

Mittelmeer’ extending latitudinally from Central America through the Mediterranean to Iran and

the Himalayas (Jenkyns, 1980: 109-1 10). During the last century ideas about what Tethys may have

been and its geographical extent have varied with the geological age and author (see Adams and

Ager (Editors), 1967), so much so that the very imprecision was the main linking theme of a vague

palaeogeographical idea (see Sengor, 1985: 3-5). Even with palaeomagnetic-based continental

reconstructions, plate-tectonic theory and modern understanding of tectonic terrains it is still

possible for there to be major differences in interpretation of temporal and spatial relationships.

Sengor (1985, and Sengor, Yilmaz and Sungurlu, 1984) recognises a Permian ‘Palaeo-Tethys’ which

preceded the real Tethys of Neumayr and Suess (or ‘Neo-Tethys’). Sengor (1985: fig. 6B) shows Palaeotethys closing during the Rhaetian as Neotethys opens. A good discussion of Palaetotethys,

Neotethys and Pangaea in the context of the evolution of the eastern Mediterranean is given by

Robertson and Dixon (1984). In the present work, Tethys (=Neotethys) is a biogeographical as

much as an oceanographical feature. In early Jurassic times the Atlantic was no more than appendix,

an embayment between north-west Africa and eastern North America (Text-figs. 1,2). Rifting preceding the opening phase was in progress during the late Triassic and early Jurassic, but there is no

palaeontological evidence for full marine connections between the Atlantic and the Gulf of Mexico

prior to the Callovian (Scott, 1984: 51). For our time period then, Tethys was linked northwards to

Siberia via the north-west European shelf but had no westerly outlet to the area of the modern

Pacific. Eastwards it widened rapidly, presumably to the point where genuine oceanic conditions

obtained. The sedimentary sequences of Jurassic Tethys are interpreted (Jenkyns, 1980: 115) as having been deposited in intra-continental basins and continental margins around Gondwanaland.

Pelagic sediments which accumulated in deep oceanic conditions are not at present recognised.

There is considerable uncertainty about the palaeocontinental position of certain areas of southeast Asia during the Jurassic. Smith, in various reconstructions, places Sumatra and other islands

on the northern margin of Tethys with New Guinea adjacent to Australia on the southern margin.

A recent reconstruction places Sumatra, parts of Borneo, Sulawesi, etc. together with much of Malaysia, Thailand and Burma close to Australia on the southern margin of Tethys (Audley-Charles,

in press: fig. 4). This latter pattern is followed here for the material from Timor and the island is

placed, palaeogeographically, just off the north-west margin of Australia. The dramatic differences

in the palaeocontinental reconstructions reflect the relative scarcity of palaeomagnetic data.



858 A.R.LoRD



TETHYAN

LOWERJURASSICOSTRACOD

ASSEMBLAGES

Available data from the author’s collection and the literature are reviewed, from the area of the

‘Proto-Atlantic’ in the west to Indonesia in the east.



Deep Sea Drilling Project Site 547B,Leg 79.

The site is important as it provides a marine Lower Jurassic sequence (dated by the ostracods

plus calcareous nannofossils) from within the incipient Atlantic Ocean. The ostracods listed and

figured by Bate, Lord and Riegraf (1984) are revised and summarised in Table 1, but are the subject

of continuing study by the author. Many elements are common to north-west Europe; healdiid

genera (Ogmoconcha, Ogmoconchella, Ledahia) occur with cytheraceans, especially small cythe-



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S



P



‘Limnocythere’ (= Lutkevichinella

of Bate et at.)

Darwinula

Gen. et sp. D Bate et al.

Ektyphocythere cf. E. luxuriosa

Ogmoconchellajuv.

BairGa spp.

tsobythocypris spp.

small cytherwids

Ogmoconcha cf. 0. contractula

Ogmoconchajuv.

Monoceratina scrobiculata

?Gramannicytheresp.

Polycope cf. P. pelta

Ektyphocythere sp. juv.

Paracypris

Acrocythere michelseni

?Ogmoconchellasp.

Paracypris redcarensis

Polycope

‘Cytheropteron’spp.

Bairdia guttulae

B. molesta

B. cf. B. carinata

Ptychobairdia hahni

Pt. aselfngenensis

Cytherelloidea sp.

Ledahia cf. L. septenaria

Bairdiacypris

Stages (tentative assignments

based on ostracods)



Ostracoda of EarIy Jurassic Tethyan Ocean 859



rurid forms, while the larger cytheracean genera common in the north are restricted to single

species of Ektyphocythere and Monoceratina. Other elements, e.g. Ptychobairdia hahni Lord and

Moorley are apparently Tethyan (see below) but vallate healdiids (Hermiella) were not observed.



Portugal

Range data for the Pliensbachian-Toarcian sections at Zambujal (Exton, 1979) and Peniche

(Lord, 1982: 270-71) have recently been supplemented by Exton and Gradstein (1984) in a valuable

comparative discussion of the Lower Jurassic sequences of Portugal and the Grand Banks off eastern Canada. The two areas were adjacent during the Lower Jurassic (Text-fig. 2) and a comparison of the ostracod assemblages is therefore of interest, although the material is not abundant. In

both Portugal and the Grand Banks no microfossils older than late Sinemurian (Raricostatum

Zone) are recognised. In the Portuguese Lower Pliensbachian Gammacythere ubiquita Malz and

Lord occurs, a form widespread at this time in north-west Europe (Malz and Lord, 1976: fig, 1).

In the Upper Pliensbachian (Spinatum Zone) Ogmoconcha species (including 0 . cf. 0. amalthei

(Quenstedt)) occur with the vallate healdiid Hermiella cf. H. ambo (Lord and Moorley) and are

succeeded in the Lower Toarcian by assemblages dominated by ‘Bairdiacypris’ with the cytheraceans Ektyphocythere debilis Bate and Coleman and Kinkelinella sermoisensis Apostolescu. The

Ektyphocythere and Kinkelinella forms were described from Britain and France respectively; K.

sermoisensis is particularly widespread, while a number of species closely resembling E. debilis

occur throughout Europe and also in North Africa (Table 3). Middle to Upper Toarcian assemblges contain Kinkelinella costata Knitter and Cytherella toarcensis Bizon from the Paris Basin,

Rutlandella transversiplicata Bate and Coleman from Britain, Polycope pelta Fischer and Cytheropteron alafastigatum Fischer from south Germany, Monoceratina scrobiculata Triebel and Bartenstein and Praeschuleridea spp.

The Grand Banks assemblages are at present sparse, consisting of Ogmoconcha spp., Polycope

spp. (including P. cincinnata Apostolescu and P . decoruta Apostolescu) in the Pliensbachian,

‘Bairdiacypris’in the (?)Lower Toarcian and Kinkelinella sermoisensis, K . costata, Polycope pelta,

C. toarcensis, Praeschuleridea sp. and Monoceratina ungulina Triebel and Bartenstein in the Toarcian-Aalenian. The assemblages, as known so far, consist of large cytheraceans, healdiids and

Polycope, many known from north-west Europe, but with the presumed Tethyan element Hermiella

in Portugal especially. Lithostratigraphically, the Lower Jurassic in the Portuguese Lusitanian Basin is essentially the same as in the Grand Banks Basin, both of which are similar to the Cantabrian

and Aquitaine Basins. These occupy an intermediate position in palaeogeographical and facies

terms between the north-west European basins and the early Jurassic Tethyan carbonate platform

to the south. This pattern is reflected by the ostracod assemblages.



Spain

Upper Pliensbachian assemblages collected by British Petroleum from Rincon del Obispo in

the Sub-Betic zone have been examined.

The samples contain Polycope sp., Ogmoconcha, Ogmoconchella, Hermiella, Paracypris, Isobythocypris, Bairdiacypris, Cardobairdia, Bairdia (including B. rostrata Issler) and Ptychobairdia

forms. The Ptychobairdia are particularly strking; P. sp. A is large, distinctive and resembles P.

kuepperi Kollmann, while ‘P’. sp. B is comparable with Anisobairdia salisburgensis Kollmann

from the Triassic of Austria.

The assemblage composition pattern is a significant one, with dominant healdiid and bairdiid

forms and a lack of Cytheracea. The distinctive Ptychobairdia sp. A also occurs in North Africa.



860 A.



R. LORD



TEXT-FTG.

2-Palaeogeography and generalised lithofacies distribution pattern for the Pliensbachian of western

Tethys (after Tyson unpublished). 1 = marginal marine, 2 = argillaceous shelf, 3 = carbonate platform, 4 =

‘pelagic’ facies.



Morocco

Boutakiout, Donze and Oumalch (1 982) have described 5 cytheracean species from rocks west

of Fez dated as Pliensbachian and Toarcian. The Ektyphocythere and Kinkelinella species could be

of Lower Jurassic age but may be younger, as indicated by the presence of Marslatourella, (not

known below the Middle Jurassic). The assemblages may in fact be Bajocian or even Bathonian.

No associated ostracods are mentioned and the assemblage is anomalous when compared with the

assemblage composition pattern found in Lower Jurassic samples from Algeria and Tunisia; a

younger age for this material is likely.



Algeria

The record for Algeria is fragmentary because much of the Lower Jurassic consists of dolomites

overlain by oolitic limestones, but it is important as, together with Morocco and Tunisia, the area



Ostracoda of Early Jurassic Tethyan Ocean 861



provides information about the southern margin of Tethys, i.e. the coast and shelf of northern

Gondwanaland.

Maupin and Vila (1976) figured poorly preserved material of supposedly Toarcian age from

Djebel Youssef, south of Setif: Cytherella cf. C . toarcensis, ?Liasina lanceolata, ?Isobythocypris,

‘Bythocypris’(?= Bairdiacypris from the Toarcian of Portugal-Exton and Gradstein, 1984: PI. 2,

fig. 5), ?Kinkelinella, ?Monoceratina. The specimens are steinkerns, but the lack of healdiids and

the tentatively identified cytheracens, plus ‘Bairdiacypris’ is not inconsistent with a Toarcian age.

Maupin (1977) has also figured material of Upper Pliensbachian and Toarcian age from 2 sections

north of Constantine,containingOgmoconcha, Hermiella and Ektyphocythere (Upper Pliensbachian)

and Cytherella toarcensis, K . sermoisensis and Ektyphocythere cf. E. bucki (Bizon) (Toarcian). The

material is not well-preserved. The Hermiella is only weakly vallate and therefore a suspect identification. Age assignments are based in part on the ostracods themselves and the Upper Pliensbachian

assemblage might in fact be early Toarcian.

The most complete survey of Algerian Jurassic Ostracoda is that of Lasnier (1965. MS), who

described and figured Lower Jurassic material from 3 regions (Monts de Hodnor, Djebel Nador and

the Ain Sbfra-MCchCria area) of north-east, north and western Algeria. Upper Pliensbachian assemblages contain a number of Ogmoconcha species, one Ogmoconchella form, Hermilla cf. H.

ambo, Liasina, Bairdia, Zsobythocypris and a small cytherurid (called Orthonotacythere by Lasnier).

At Djebel Nador the large and distinctive Ptychobairdia sp. A occurs, a form also found in Spain

and Tunisia. Toarcian assemblages contain Kinkelinella, Ektyphocythere, and ‘Bythocypris’ (?=

‘Bairdiacypris’?)The occurrence of Ptychobairdia sp. A with Hermiella in the Upper Pliensbachian,

succeeded by cytheraceans and ?‘Bairdiacypris’ in the Toarcian is a pattern observed elsewhere.



Tunisia

Much of the Lower Jurassic is in a massive carbonate facies and the only record of ostracods is

of two assemblages of Upper Pliensbachian age from Djebel Zaghouan, north-east Tunisia (Lord

1982: 271). The ostracuds present are: Ogmoconcha spp., Ogmoconchella spp., Hermiella, ‘Isobythocypris’, Liasina and Ptychobairdia sp. A .The assemblage composition is one recorded elsewhere

in this work; note the absence of cytheraceans.



Italy

a) Sicily



Barbieri (1964) has described Upper Sinemurian to Toarcian ostracods from a borehole at Ragusa. The Pliensbachian material includes Ogmoconcha s p ~ (with

.

‘Hungarella’ hyblea Barbieri

which may be a vallate Hermiella), Bairdia spp., Isobythocypris. Liasina and Polycope cincinnata,

but no cytheraceans. In the Toarcian, sparse assemblages contain single species of Ektyphocythere

and Kinkelinella with Cytherella and Bythocypris (?= Bairdiacypris). These assemblages closely

resemble material from the Apennines and are typical of the general assemblage pattern found

elsewhere. Certain species are forms described from northern Europe (the ornamented K. costata,

P . cincinnata), but with the unornamented forms, e.g. one resembling Bairdia rostrata, it is less easy

to be certain.



b) Apennines

Much of the Lower Jurassic is represented by massive carbonates and the Toarcian by ‘Ammonitico Rosso’ in which ostracods were not found. At Strettura in Umbria, however, a sequence of

argillaceous beds in carbonates has yielded ostracods of Upper Pliensbachian age. Lord (in Farinacci et al., 1979) provides a brief account of the material, which contains Ogmoconcha spp., Ogmo-



862 A.R.LoRD



conchella sp., Hermiella spp., Liasina, Bairdiacypris spp., Bairdia, Paracypris, Ptychobairdia aselfingenensis Lord and Moorley and Polycope cincinnata.



Turkey

A Lower Pliensbachian assemblage from Bilecik, in the north-western corner of Asiatic Turkey,

has been described by Lord (1982 : 276-77). The ostracods include Ogmoconcha spp. (including 0.

amalthei (Quenstedt)), Bairdia, Paracypris, Zsobythocypris and Polycope. The assemblage is too old

to contain Hermiella (late Pliensbachian to earliest Toarcian), but characteristically lacks cytheracean species; in certain respects it is comparable with contemporaneous north-west European

material.



Himalayas, Eastern Karakoram

Pant and Gergan (1983) recorded 6 ostracod species from the Burtsa Formation, a unit considered to be about 1,000 m. thick and apparently ranging in age from Jurassic (?Triassic) to

Cretaceous. The ostracods appear to be Lower Jurassic in age and have been compared with European species, viz. the healdiids Ledahia septenaria Griindel, Ogmoconcha intercedens Dreyer, 0.

klingleri Malz, 0. sp., Ogmoconchella cf. Olla propinqua Malz and the cytheracean ?Procytheropteron sp. Although small and isolated, this assemblage is nonetheless an impressive record. Current

interpretation of the structural setting of the Eastern Karakoram places this material on the northern edge of Tethys.



Timor

Samples from the Aitutu (Triassic to (?)Lower Jurassic) and Wai Luli (Lower and Middle

Jurassic) Formations of Timor studied by Mr. D. J. Carter have been made available. The assemblages are summarised on Table 2 and are of particular interest in that they compare in general

composition with samples discussed above from western Tethys. Some species range through the

2 formations, apparently from Triassic to Jurassic. In the palaeocontinental recontruction used

here, Timor is situated on the southern margin of Tethys. Ostracod assemblages from eastern

Tethys are so rare that the Timor data do not influence the argument as to whether the island was

on the northern or southern side, nor do they allow at present any discussion about the

differences in ostracod faunas between the two shores, or of faunal evolution and migration.

From Table 2 should be noted the absence of (a) bairdiids with strong surface morphology

and/or ornamentation, so characteristic of many western Tethys Triassic sites, and (b) cytheracTABLE

2-sPECIES OCCURRENCE LISTFOR TIMOR.

Acratia sp.

7Anisobairdiasalisburgensis Kollmann

Bairdia spp., including

B. cf. B. (Akidobairdia)farinacciae Oertli

B. cf. B. rostrata Issler

Bairdia sp. puncatate surface

Bairdiacypris spp.

‘Bythocypris’ spp.

Fabalicypris sp.

‘Healdia’7 spp.

7Hiatobairdiaarcuata Kristan-Tollnann

Ogmoconchella/Ogmoconcha/Hungarella?

spp.

Polycope cf. P. cerasia Blake

PolvcoDe cincinnata Avostolescu



-



+



Ostracoda of Early Jurassic Tethyan Ocean 863



eans, as in Lower Jurassic Tethys assemblages, but in contrast to the Triassic material from China

described by Kristan-Tollmann (1983).



LOWERJURASSICOSTRACODS FROM



SOUTH



GERMANY

AND FRANCE



Although vallate healdiids (Hermiella) have been recorded from various parts of France (Lord,

1982: fig. 7.2), the assemblages are generally rich with cytheracean species (see review by Dome

1985) and have much in common with Britain, The Netherlands, Denmark and north-west Germany. Material from south Germany is different and is reviewed for comparative purposes.

Vallate forms of Ogmoconcha were first described from south-west Germany and the area provides the best and most varied material available to date (Malz, 1975), but some Cytheracea also

occur in the assemblages(Urlichs, 1977; Riegraf, 1984 -selected species only). Moorley (1974 MS)

records full assemblages from the Upper Pliensbachian containing Polycope species (including P .

cincinnata),Bairdia spp. (including B. rostrata), Ptychobairdia aselfingenensis, P . hahni, Bairdiacypris, Liasina, Isobythocypris, Ogmoconcha spp., Ogmoconchella spp., Hermiella spp. (see Malz op.

cit.) and cytheraceans viz. Bythoceratina seebergensis (Triebel and Bartenstein, Cuneoceratina

amlingstadtensis (T. & B.), Gramannicythere aubachensis Riegraf and Nanacythere persicaeformis

Riegraf, although the cytheraceans are in relatively small numbers. In the Toarcian of southern

Germany the assemblages can be diverse and are closely related to those described from elsewhere

in northern Europe (Knitter, 1983; Knitter and Ohmert, 1983; Knitter and Riegraf, 1984). Thus,

in the Pliensbachian, the area of southern Germany appears to lie in a transitional zone between

Tethys and the north-west Europe shelf.



ORNAMENTED

BAIRDIIDOSTRACODS

The most impressive element in Triassic ostracod assemblages is without doubt the range of

genera allied to Bairdia which have strong surface morphology and/or ornamentation. In the past

25 years our knowledge of Triassic faunas has greatly improved but, despite the growing number

of taxa recognised and the special interest of cytheracean forms for postBalaeozoic workers, the

characteristic element of Triassic Tethyan assemblages remains the ornamented bairdiids. These

ostracods are known primarily from the Alps, but recent accounts by Kristan-Tollmann (1980,

1983) describe material from Iran and China. It is easy to overlook the fact that these ostracods

were not necessarily the most important element in the faunas, e.g. summariesof assemblagecontent

for samples from the Zlambach-Schichten (NorianlRhaetian) by Bolz (1974, figs. lc, 2c, 2e) give

a range of 5 to 20 % for ornamented bairdiids, but they were never again so diverse and appear to

be a characteristic Tethyan faunal element.

Ornamented bairdiid ostracods occur only sporadically during the rest of the Mesozoic. It is

tempting to hypothesis that the cryptogenic appearances we encounter in younger levels in

northern Europe are occasional migrants from Tethys ; however, our knowledge of post-Triassic

Tethyan ostracod faunas is very patchy and it is difficult to substantiate the idea. The species

Ptychobairdia sp. A recorded above from eastern Spain, Morocco and Tunisia is not only a

distinctive Pliensbachian marker, but is also morphologically very close to Ptychobairdia kuepperi

Kollmann from the Rhaetian of Austria, an example of iterative evolution but in a purely Tethyan

context.



864 A.R.L.oRD



TABLE

%SUMMARY



DIAGRAM

FOR TETHYAN

A N D MARGINAL

OSTRACOD



ASSEMBLAGES.



I



8



Portugal T



P. cincinnata found

in Grand Banks



0

0



0



P



0



.



P



0



.



Algeria T

P



0



.



0



Tunisia P



0



.



0



0

0



.

0



P



0



.



S



0



S



Spain



0



Also Ptychobairdia sp. B and

unornamented PolvcoDe



0



0



0



0



Italy/Sicily T



P

Italy/Apennines P



0

0

0



0



0



SW Germany T



0



0



.

0



0



0



Cytheracea rare



.

0



~~



Turkey



Karakoram (L.J.)



0



Polycope sp. present

0

~~



Timor (Tr.-L.J.)

0

.

0

0

See Table 2

Key: Tr. = Triassic, L.J. = Lower Jurassic, H = Hettangian, S = Sinemurian, P = Pliensbachian,T =

Toarcian. @ Ogmoconcha. Ogmoconchella, Ledahia, etc. ; @ Hermiella; @ Bairdiacea with surface

morphology and/or ornamentation; @ E. intrepida, E. debilis, E. fwcata, E. bucki. 0 and @

Healdiacea, @ Bairdiacea, @ and @ Cytheracea.



VALLATE

HEALDUD

OSTRACODS

The ‘VallateOgmoconcha’ of Malz (1979, formalised as the genus Hermiella by Kristan-Tollmann (1977), were originally described from south-west Germany where they are a distinctive element in the Upper Pliensbachian. Fortuitously, these forms appear to be most diverse and wellpreserved in the type area, but they seem to be characteristic of the Tethys rather than the northwest European shelf sea. Throughout the area covered by this discussion, from the ‘Proto Atlantic’

in the west (Portugal) to Timor in the east, the vallate forms are a characteristic Tethyan element.



Ostracoda of Early Jurassic Tethyan Ocean 865



Polycope cincinnata

Polycope cincinnata

This ornamentally distinctive species was described from the Paris Basin (Apostolescu, 1959),

but is now known to range in time from the Triassic into the Lower Jurassic (Anisian-Pliensbachian; Urlichs, 1972: 696) and geographically in the Lower Jurassic from the Grand Banks to

Timor. P. cincinnata thus originated in the Triassic in Tethys and became particularly cosmopolitan in the Lower Jurassic, together with the healdiids.



CYTHERACEAN

SPECIES

From the site details discussed above (summarised in Table 3) it is clear that members of the

Cytheracea are absent or at best uncertainly present in Hettangian to Pleinsbachian age sediments

of the Tethyan area. In the Toarcian some representatives have been found, essentially only the

widespread Kinkelinella sermoisensis and Ektyphocythere of species morphologically similar to E.

bucki, viz. E. intrepida, E. debilis, E. furcata. Paucity of cytheracean species is thus a characteristic

of Lower Jurassic Tethyan ostracod assemblages.

In marginal areas such as south-west Germany and Portugal, cytheraceans are relatively uncommon as compared with assemblages from north-west Europe. DSDP site 547 contains an

interesting assemblage of species, with some large cytheraceans, small cytheraceans, healdiids and

bairdiids including Ptychobairdia, with species known from north-west Europe, south-west Germany and Tethys (Apennines). The Tethyan element is most apparent at site 547 in the Pliensbachian, represented by healdiids and bairdiids, but is not especially strong.

Whatever the Palaeozoic origins of the Cytheracea may have been, it is clear that they were

well-established and relatively diverse by the early Mesozoic. Kristan-Tollmann (1983) has described an Upper Anisian fauna from China containing 24 cytheracean species and subspecies and, interestingly, few unornamented healdiids and bairdiids. This example, together with other records of Triassic Cytheracea, supports Bate’s (1977, p. 236) comment about the ancestral stock of

new Lower Jurassic cytheracean lineages being introduced into north-west Europe from Tethys

during the Rhaetian transgression. Once in the epicontinental seas of north-west Europe the cytheraceans rapidly diversified and from the early Toarcian onwards, following the extinction of the

healdiids, dominated the ostracod faunas as they have continued to do to the present day. Thus,

the north-west European shelf sea in Lower Jurassic times was the locus of evolution for the Cytheracea leading to the development of a large proportion of later Jurassic and Cretaceous genera and

higher taxa.



CONCLUSIONS

A basic faunal pattern for Lower Jurassic ostracods seems evident, but it is important to remember the limitations of the data, which relate mostly to western Tethys and the north-west European

epicontinental sea. Outside these areas, the faunas available for analysis are so scattered as to make

their interpretation of little value at present. In addition, our knowledge of contemporary conditions is limited. Simulation of past climates is being carried out at present. Current patterns have

been postulated (e.g. Ager, 1975, fig. 1) but are tentative and reconstruct surface currents only. The

major marine feature of the Mesozoic world, ‘eastern’ Tethys, is almost unknown in terms of



866 A. R. LORD



ostracods. We can at present only conjecture that there may have been a 'Pacific' Ostracod Province,

distinct from that of Tethys.



ACKNOWLEDGEMENTS

This paper is based in part on material collected with the support of the University of London

Central Research Fund and of Shell International Petroleum Mj. Specimens from Timor were

kindly provided by Mr. D. J. Carter (formerly Imperial Co lege London). I am also indebted to BP

Petroleum Development for permission to cite material collected in Spain and to Dr. J. Athersuch

(BP Research, Sunbury) for his help and discussion. The palaeogeographical maps were prepared

with the generous help of Dr. R. V. Tyson (UCL). The palaeocontinental reconstructions are the

work of Dr. A. G. Smith (Cambridge) modified in the area of SE Asia-Australia with the aid of

Professor M. G. Audley-Charles (UCL). Miss E. G. Murray kindly prepared the manuscript and

Mrs. J. Baker the maps. Finally, I am as ever indebted to Dr. H. Malz (Frankfurt) and to Dr. H. J.

Oertli (Pau) for their advice and hospitality.

The support of the Organising Committee, 9th International Symposium on Ostracoda, and of

The Royal Society is gratefully acknowledged.



REFERENCES



+



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Chapter 60. Ostracoda of the early Jurassic Tethyan Ocean

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