Latest Albian (Vraconian) brachiopod fauna from North Dobrogea (Romania): taxonomy, palaeoecology and palaeobiogeography

Acta Geologica Polonica, Vol. 56 (2006), No.1, pp. 67- 88

Latest Albian (Vraconian) brachiopod fauna from North Dobrogea (Romania): taxonomy,

palaeoecology and palaeobiogeography

EUGEN GRADINARU ',AURELIA BARBULESCU ^I & ELLIS FRED ERIC OWEN ²

'Depanment of Geology and Palaeontology, Faculty of Geology and Geophysics, University of Bucharest, Bd. Bdlcescu Nicolae 1, RO-OlO041 Bucharest, Romania.E-mail: egradin @geo.edu.ro

2Departmentof Palaeontology, TheNatural HistoryMuseum, CromwellRoad,London SW7 5BD, GreatBritain

AB STRACT:

GRADINARU, E., BARBULESCU, A. & O WEN, E.F. 2006. Latest Albian (Vrac o nian) brach iopo d fauna from North Do bro gea (Ro ma nia): taxon om y, palae oecology an d palaeobi ogeograph y. Acta Geologica Polonica, S6 (1), 67-88 . War szawa.

Thelat estAlbian (Vrac onian) brach iopod faunafrom Enisala, in NorthDobrogea, inclu des representativesof rhyn- chon e llids and tere brat ul ids. The rhync ho nellids are scarce, represen t ing two fami lies, Cycloth yrid id ae and Tetrarh ynchiidae.The Cyclo thyrididae with thesubfamilyCyclo thyrid inae, and theTetra rhynch iida ewith the subfa mi- ly Cretirhynch iinae, are re prese nted by rare spec ime ns of ? Cyclothyris sp. and Burrirhynchia cf. sigma (SCHWENBACH, 1867), respectively. The terebratulids are very abundant and include representatives of several families, as follows:

Sellit hyrid idae,Capillit hyrididae,Cance llo thyrididae and Terebrataliid ae. The Sellithyrididae,which mak eupthe bulk of the assemblage, are represe nte d by two subfam ilies: Sellithyridinae with Sellithyris up warnesis (WALKER, 1870), Boubeithyris boubei (O'ARCHIAC, 1847) and Ova/athyris cf potteme nsis OWEN, 1988, and Nertheb roch inae with Harmatosia crassa (O'ARCHlAC, 1847). The Capillithyr id idae are represented by the subfami ly Capillithyrid inae with Caplllithyris capillata (O'ARCHlAC, 1847). The Cancellothyrididaeare repre se nte d bythe sub fa mily Can cellothyridinae with numerous specim ens of Terebratulinaprotostriatula OWEN, 1988. The Terebrataliidae are represented by the sub- family Gemma rculinaewith scarce specime ns of Gemm arcula canaliculata (ROEMER, 1840) and Gemma rcula sp.

The abundan ce and diver sity of the terebratul ids in the brachi op od assem blage from Enisal a was relat ed to favourable environm ent alcondition s conn ecte dwiththeonse tof themarine transgression on NorthDo brogea during the lat est Albian.

There is a mark ed str at igr a phic lag with some species which in North Dobrogea occur in the latest Albian appear- ingintheEarl y Ceno ma n ian inCen traland Western Euro pe.This sugges ts that Nort hDob rogeawaslocat ed on the main route of the westward migrati on of the mid -Cr et ace ou s brachiop od faunas.

Key words: Brach iopods, Late st Albian (Vrac onian), Cr et aceous, Roman ia.

INTRODUCTION the north-eastern margin of the Babadag Basin (Text-

fig. 1). Brachiopod-b earing stra ta crop out on the North Dobrogea is a region situated in the south- south-western side of the hill with the ruins of the eastern part of Romania, on the western shore of the Heraclea Citadel. The age of this previously unde- Black Sea.In this region, Cretaceousbrachiopods are scribed brachiopodfaun ahas been thesubject of some known from a single locality near Enisala village, on controver sy.

68 EUGEN GRADINARU ^{& at.}

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Fig. I. Geologicalmapof the eastern partof the Babadag Basin (North Dobrogea,Romania),redr awn and modified from SZASZ & ION (1988).

Dolojman Formation: 1 and 2 . Coniacian (Jurilofca and Caugagia Memb ers), 3 and 4 ...Turonian (Harada and Jidini Members); Iancila Formation: 5 and 6 . Cenomanian (Golovita and Babadag Members);

7 - Vraconian (Enisala Member); 8 ... Pre-Cretaceous basem ent ; 9 ...Fossiliferous site;10...nor mallithological boundary; 11-diachro nous

lithological boundary; 12 - unconformi ty

Exte nsive sampling mad e during the last years by one of us (E G ) in the loc ality allowed the recovery of rich bivalve and brachi op od faunas .

The brachiopod faun a from Enisala includes a num- ber of new taxa for the Dob rogea area, and for Romania.

The occurrence of the ammo nite genus Lepthoplites in the brachiopod-bearing stra ta establishes a latest Albian (Vraconian) age for the basal deposits of the Babadag Basin (GRADINARU 2004), and allows accurate det ermination of the stra tigra phic position of the bra- chiopo d fauna from Enisa la.

Geographically, the Vraconi an brachiopod faun a from Enisala is of major import ance for the palaeobio- geogra phy of the mid-Cretaceou s br achiopod faunas in Europe. North Dobrogea was a brid ge between the Crimea n and Caucasian region s, on the one side, and theCentra l and Western Europe, on the other, and fills a gap in the knowledge of the geogra phic distributionof mid-Cr et aceou s brachiopods.

PREVIOUS DATA

The first mentions of brachiop od s at Enisala are to be found in the old monographs of PETERS (1867) and ANASTASIU(1898), who assigned them a Middle Jurassic age.

Lat er , POMPECKJ (1897) and SIMIONESCU (1910) argued for a Cenomanian age for the brachiopod-bearing limestones from Enisala. SIMIONESCU (1914) recognized two distinct series in the sedimentary fill of the Babdag

Basin, the lower one named 'Iancila Series ', for the Ce no manian depo sits, and the upper one nam ed 'Dolojman Series', for the Turon ian-Sen onian deposits.

The brachiopod-b earin g stra tafrom Enisalawere located to the 'Iancila Series'. Subsequ ently, SIMIONESCU (1927), MACOVEI & ATANASIU (1934) and MIRAlJlA & MIMUy\.

(1964) accepted a Cenomanian age of the basal deposits of the Babadag Basin.

MUTIHAC & al. (1972) claimed a Late Aptian-Albian age for the brachiopod-bearin g limestones from Enisala , based only on generic assignm ents of poorl y preserved specime ns of brachiopods, and from the study of the bry - ozoans , calcareou s algae an d foramin ife r a . More recently , DRAGASTAN (in BANClLA & al. 1997) reconsid- ered the biostratigraphic significance of the bryozoans, calca reous algae and the foraminifera from this locality and assigned a Late Albian age for the Enisala Limestone.

PATR ULI US (1974) emphasized that brachiopods simi- lar to those from Enisala occurre d in the East Carp athians in the Vraconian-Ce nomanian time interval, and reck- oned that the brachiop od-bearing strata from Enisala are not older than the Late Albian.

SZASZ & ION (1988) formally described the brachio- pod-b earing strata from Enisala as a distinct member in the Iancila Formation, nam ed Enisala Member. These aut hors agreed to an Early Cenomania n (pro pa11e) age, eventua lly also Vraconian, for the Enisala Member, hav- ing in view that the conformably overlying Babadag Memb er yielded belemn ites, inocer amid s and fora- minifer a of Early (pro partev and Middle Ceno manian age.

Buc u x & BALTRE') (2002) assigned an Early Ceno- manian age, based on the study of foraminifera and red calcareous algae, to the bioclastic limestones from the basal part of the sedimentary fill cored in two wells drilled in the north-eastern part of the Babadag Basin.

Inconclusion, the age of the Enisala Limestone and its brachiopod fauna was widely disputed. While most autho rs supported a Cenoma nian or an Early Ceno- manian age, eventually including also the Vraconian, a few agree d that the Enisala Limestone might be of Late Albian age.

GEO LO G IC AND STRATIGRAPHI C DATA

The Enisala Member, situated in the basal part of the Ian cila Formation, unconformabl y overli es the Triassic Wetter stein- type thick-bed ded grayish lime- sto nes which cropout mainlyin thehillbellowthe ruins of the Heraclea Citad el (Text-fig. 2). Here, on the south-weste rn side of the hill, the Enisala Member is

Her

N

estimate of whitis limeston grained bryozoan mollusca sented m the most some lev specimen teeth , we The Member rich crin Member typical f Basin.

The the brae genus Le of the Lepthopli Zone of HORGUE colloqui this zan Vraconi ing the consider BREISTR publicati 1996; A both in Vraconi marine t

i

69

5

VRACONIAN BRACH IO POD FAUNA FROM NORTH DOBROGEA, ROMANIA

Ifor the

I named

Heraclea C itadel

eposits.

!located

N

i(1927),

~IRAtJTA

~epos its

I-Albian Enisala,

~se rve d

~he bry-

i More

!consid- pzoans,

Triassic ..

. -

..

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!locality Fig. 2.Panoram ic viewof the westernside of theHeracleaHill at Enisala (North Dobrogea,Rom ania ),showingthestratigraphic relatio nshipsofthe

~nisala latest Albian Enisala Memb e r; X - occurre nce point of the descr ibed brachio pod faun a

~ s simi- estimat ed to be less than 20 meters thick . It is made up

~ a t h i a n s of whitish or rosy, massive, poorly bedded biocla stic

Id reck- limeston es. Micr ofacially, the lime stones are coarse-

~ala ^are gra ine d grain stones to pack stones, made up mainly of

bryozoan , red calcareo us algae, echinoid debris and

~ r a chi o ­ mollu scan she ll fragm ents. The macrofossils are repre-

fn ber in sented mainl y by bivalves, amo ng which the oysters are

f These the most abunda nt gro up, and by brachiopods, which in

~e ) age, som e levels ar e the most common fossils. Only a few

~ r, hav- specimen s of echinoids, and rar e ammonites and fish

labadag teeth, wer e recover ed.

~ fora- Th e massive biocl astic limestones of the Enisala rnanian Member grad e upw ards to the well-bedded quartz-

rich crinoid al calca re nites of th e overlyin g Babadag

f Ceno- Member in the Ian cila Formati on , which represent the

~ nd red typical facie s of the Cenomani an in the Babadag

pm the Basin .

~ drilled The recovery of th e first ammo ni te specimen from the brach iop od-bearing stra ta , which is ascribed to the

fand its genus Lepthop/ites (G RADI NA RU 2004), clarifies the age

e

most of the En isal a Member. In West ern Europe Ceno- Lepthop/ites occur s mainly in the Stoliczkaia (5.) dispar lnian, a Zon e of the topm ost Albi an (O WEN 1989; WPEZ-

b f

Late HORGUE & al. 1999; WIEDMANN & OWEN 2001). At the colloqui um on the Lower Cre tace ous in Lyon in 1963 this zone was con sid ered as the equivalent of the Vraconi an (COLLI GNON 1965). Th e discu ssions regard- ing the chro nos tra tigra phic sta tus of the Vraconian , con sid ered as a sub sta ge at the top of the Albi an by rart of BREISTROFFER (1936, 1940), are resumed in recent les the publi cati on s (GALE & al. 1996; MARCINOWSKJ & al.

t lime- 1996; AMBD RO 2002; HANCOCK 2003). In Romania, e ruins both in the Ca rpa th ians and in North Dobrogea , the

bn the Vracon ian sedimenta tio n marked the onset of the

~b e r is marine transgr ession .

MATERIAL, PRESERVATION A ND TAXONOMI C COMPOSITION OF THE STUDIED BRACHIO- POD FAUNA

In the brachiopod material from En isala , which includes more than 214 complete spe cime ns, seve ra l taxonomic groups are represented by numerous speci- mens at different stages of ontogen eti c developm ent, and which show pronounced intraspeci fic morpholo- gies. In addition to the complete spec ime ns, there are numerous incomplete specimens damaged by crus hing during extraction from the host rock.

The preservation of the brachiopod mat eri al is vari- able for the different taxa, being dependent on their onto- genetic development, sizes, etc. Only a few specime ns with separated shells were found. During the extra ction of the brachiopods from the host rock, some parts of their shells, either the umbo or the anterior margin,wer edam- aged. Also, most brachiopods have decorticated shells.

However, many specimens show areas on which the fine details of ornamentation or its inne r structure are visible.

Few specimens naturally released by weathering of the rock preserve shell ornament at ion .

The frequency, distribution and position of the speci- mens in the rock was investig ated . In some stra ta the specimens are abundant, sometimes closely packed, but in other strata there are only a few specime ns. Ther e is nosorting of the specimens by theirsizes or ontoge ne tic development with young specime ns and gero ntic speci- mens found together.Nosor ting eithe rby distincttaxaor by a preferred position was observed. Many spec imens were buried with their she lls either parti ally or com- pletelyvoid of sedime nt,showing no crushing.The inte- riors of some hollowshe llsare filled with calcite crystals, looking like mini-geod es. For the shells filled with sed i-

I

I

,

70 EUGEN GRADINARU & at.

ment, a graded structure can frequently be observed.

The coarser sediment is followed by finer sediment and finally by sparry calcite. Similar filling aspects were described for Cretaceous brachiopods from Algeria, France and Spain by GASPARD (1988, 1996).

The Vraconian brachiopod fauna from Enisala, list- ed in taxonomic order, is as follows:

RHYNCHONELLIDA (Order) Cyclothyrididae (Family) Cyclothyridinae (Subfamily)

? Cyclothyris sp.

Tetrarhynchiidae (Family) Cretirhynchiinae (Subfamily)

Burrirhynchia cf. sigma (SCHLOENBACH, 1867) TEREBRATULIDA (Order)

Sellithyrididae (Family) Sellithyridinae (Subfamily)

Sellithyris upwamensis (WALKER, 1870) Boubeithyris boubei (O'ARCHIAC, 1847) Ovatathyris d. pottemensis OWEN, 1988 Nerthebrochinae (Subfamily)

Harmatosia crassa (O'ARCHIAC, 1847) Capillilhyrididae (Family)

Capillithyridinae (Subfamily)

Capillithyris capillata D' ARCHIAC, 1847) Cancellolhyrididae (Family)

Cancellothyridinae (Subfamily)

Terebratulina protostriatula OWEN, 1988 Terebralaliidae (Family)

Gemmarculinae (Subfamily)

Gemmarcula canaliculata (ROEMER, 1840) Gemmarcula sp.

As shown in Text-fig. 3, the Vraconian brachiopod fauna from Enisala includes representatives of Rhynchonellida and Terebratulida, representing 6.5 % and 93.5 % of the assemblage, respectively.

The rhynchonellids are rare, with two families, Cyclothyrididae and Tetrarhynchiidae, making up 4.5 % and 1.3 % of the assemblage, respectively.

Cyclothyrididae (subfamily Cyclothyridinae) and Tetrarhynchiidae (subfamily Cretirhynchiinae) are represented by rare specimens of ? Cyclothyris sp.

and Burrirhynchia d. sigma (SCHLOENBACH, 1867), respectively.

In contrast, terebratulids are abundant, and include representatives of several families, as follows:

Sellithyrididae, Capillithyrididae, Cancellothyrididae and Terebrataliidae. The Sellithyrididae, which make up 40 % of the assemblage are represented by two subfamilies: Sellithyridinae with Sellithyris upwamen- sis (WALKER, 1870), Boubeithyris boubei (O'ARCHIAC,

1847), and Ovatathyris cf. potternensis OWEN, 1988, and Nerthebrochinae with Harmatosia crassa (O'ARCHIAC, 1847). The Capillithyrididae, making up 11 % of the assemblage, are represented by subfami- ly Capillithyridinae with Capillithyris capillata (O'ARCHIAC, 1847). The Cancellothyrididae, 34 % of the assemblage, are represented by the subfamily Cancellothyridinae, with numerous specimens of Terebratulina protostriatula OWEN, 1988. The Terebrataliidae, forming 9 % of the assemblage, are represented by the subfamily Gemmarculinae with scarce specimens of Gemmarcula canaliculata (ROE- MER, 1840) and Gemmarcula sp.

Taxonomically, Sellithyrididae, which are represent- ed by four genera, are the main group in the brachio- pod fauna studied. The Cyclothyrididae are represent- ed by two genera while Capillithyrididae, Cancello-

Terebratulida 93.5 %

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6,5 %

Terebrataliidae --' 9.2%

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b) 40% 1.3%

Terebratulina

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Ovalalhyris 6.3%

c) 19%

Gemmarcula

! I /9.4%

?Cyclothyris .--4.9%

Fig. 3. Taxonomic diversity and abundance of the latest Albian brachio- pod fauna from Enisala (North Dobrogea, Romania), by orders (a),

families (b) and genera (c)

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thyridida one genu Num the most (19 %), from

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The Dobroge regionall mental c developrf

In some region.

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and cycl most im ment, flo than 25- 1972).

T~

VRACONIAN BRACHIOPOD FAUNA FROM NORTH DOBROGEA, ROMANIA 71

~, 1988, a) ic macrofauna including serpulids, bivalves, articulat -

crassa ed brachiopods and echinoderms. The oyst ers, which

~king up

E are known as a high opportunist bivalve group during

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the marine transgressions, were by far the most domi-

rapillata _'0^OJ _'C :E s, _}§ nant group in the benthic macrofauna, in abundance

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and diversity. The sea bottom, paved with abu nda nt

.0 "0 _-E ~ ^.0

~bfam i ly z ^E::l ^{U u} >- ;§~ ~ ~ coarser biogenic detritus, was also populat ed by a rich

rens of brachiopod fauna. Besides the robust terebr atulids

~. ^The (Ovatathyris, Harmatosia) , which dominat ed the br a-

[age, are ch iopod assemblage and may have be en detach ed

iae with Rhynch on ell id a Ter ebra tu li da from the substrate in matur ity, the ter ebratu linids,

fa

^(ROE- wit h sma ll-sized, thin and fine ly-orname n te d she lls,

80

b) had a perman ently sessile life-style attache d to other

70 CIl

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_o c: _.!!! s, ^.!!! >. biogen ic rem ains.

[brachio- ^{c 60}

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'iii It is known that the brachi op od s are sensitive to

'u ^{E u} ~ c;; .0 '0.

~re sen t­ ^<J) _c. 50 _U >-

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^{::l the nature of the sub} stratum. Every type of lithol ogy

::l Ul o

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~ance lJo- _{'0 40} ^CIl su p po r te d a dominant brachi op od com mu ni ty to

.0Q; which some species with a lon g ran ge an d ada p te d to

E ³⁰ vario us ecologies were associated (AGER1965; OWEN

::l Z 20

1988). The terrigen ou s sed ime nts that were favou-

10 rabl e for rhynch on ellid s, were not well tol erat ed by

O-ll-..,-.J.,.L,.-~=r"""""-r---4J--r....L.L..-..r...J..,J....,~,J.-,..-J.,.L-,-J-. the terebratuJid s which preferr ed the calca reo us and

Rhynchonell id a Ter ebratulid a

marly or chalky sedime nts. This is well illust rat ed by

Fig.4.Histo gram s showing the abundance of genera by families(a) and the rhynchonellid-rich brachi op od assemb lages from

number ofspecime nsby gen e ra (b) in the lates t Albian brac hiopod the Cracow region,in Pol and (PoPIEL-BARCZYK 1972,

faun a from Enisala (North Dobr ogea, Romani a) 1977), which settled in a terri gen ou s enviro nme nt. In

~a North Dobrogea, the ter eb r atulids, which were the

thyridi dae and Tereb rataliidae are each represented by dominant group in the latest Albian brachiopo d fauna

one genus. from Enisala, disappear ed dur ing the Early Ceno-

Numer ically (Text-figs 3-4), Terebratulina with 34 % is manian due to lithofacies chan ges. The Early Ceno- the most abundant taxon. It is followed by Ovatathyris manian Babadag Member of the Ian cila Formation (19 %), Harmatosia (14 %), and Capillithyris (11 %), consists exclusively of quartz-rich crino ida Jcalcarenites.

from the Sellithyrididae, Other genera, such as Gemmar- At the onset of the Late Cretaceous, by widening and

~bra ta l i idae cula from the Terebrata liidae, Boubeithyris from the deepening of the sea, the brachiopods wer e replaced by

! 9.2%

Sellithyrididae , ? Cyclothyris and Burri rhynchia from the other groups of macrofauna, the ammonoids and the Cyclothyrididae, and Sellithyris from the Seilithyrididae, inoceramids, much better adapted to the new enviro n-

~d ida e

have a decreas inglysma ller number of specimens. mental condition s.

PALAEOECOLO GY PALAEOBIOGEO GRAPHY

The marin e tran sgression which covere d North In the Dob ro gea area , as a whol e, any repr esenta-

lemmarcula Dobr ogea during the latest Albian , altho ug h not tives of the Vraconi an brachiop od faun a from North V^{9 4%}

regio na lly extensive, gave rise to favourable enviro n- Dob ro gea are also found in South Dobrogea, where menta lcond it ions,whic hallowe d the sett le me n tand numerous Earlyand Lat e Cretaceo usbrachiopods have

~Cydothy ris devel opment of a very diversified marine benthic life been inves tiga ted (BARBULESCU & al. 1975, 1979;

~ 4.9%

urrirhynchia in some areas, as illus tra te d now in the Enisal a NEAGU & BARBULESCU 1979; BARBULESCU & NEAGU

t-1.3%

region.The rich assembl age of calca reous red algae 1988).It proves that im por ta ntpalaeogeogra phic modi -

1

and cyclosto ma te bryozo an s, wh ich are among the ficati on s happen ed during the mid-Cre taceou s in the most impor ta nt cont ributor s to the calcareou s sed i- weste rn part of the Black Sea, including also the

Ianbrachia- ment, flo urished in calm and sha llow wat ers, no more Dob rogea area, which con tro lled the distr ibu tion and

larders (a), than 25-30 m in depth (DRAGASTAN in MUTIHAC & al. patt ern ofsedime ntaryenviro nme ntsand the associa ted

1972). The sea bo ttom was in ha bite d by a rich benth- bioti c com mu nities.

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72 EUGEN GRAo lNA R U & al.

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Fig, 5. Palaeogeograph ic map oftheLateAlbia n (redrawnandsimplifiedfrom GOLONKA2004) showi ng thema in occur re ncesofspe cies represe nt ed in Cenom

the Vraco nian brachiopo d fauna from Enisala, and the inferred rou te for the dispersal of some or the Mid- C re ta ceou s brachiopod s, as discu ssed in the

1984

a-~

text ofpaper.1 - South Great Britain; 2 - Belgium (Tourt iaofTournai)and France(Normandy);3 - SouthGermany; 4-Poland (Cracowand Annopol The

regions) andUkraine(Podo lia region); 5 - Rom ani a (North Dobrogea);6 - CentralAsia (GissarRidge); J -"Mountains"lH ighlands (active tectonical- strate t

ly); 2 - Topogr aph ic highs (inactive tectonically); 3- Topographic medium-low (inactive tectonically, non-depositional); 4- Terrestrialund ifferentiated; Europe

5 - Fluvio-Iacustrine; 6 - Coastal, transiti on al, margin al marine; 7 - Shallow marine, she lf; 8 - Slope; 9 - Deep ocean basin with sedime nts (continental, Eastern

tra nsitio nal,orocea nic crust);10-Deepocean basin with little to nosedime nts (primarily oce a nic crust) crassa ( (Gissar occurs i

Regional

(Belgiu

Location Local stratigraphic range

stratigraphic range

in the count

South North

I

^{Belgiu m}

I

^North

I

^South

I

^Poland

I

^Ukraine

I

^{Gissar W~s t Central}

I

^{Cen tral}

Britain France (Tournai) Germany Germany Ridge Europe Europe Asia (D'ARC

Taxons

I

~.

-b-I· I -,I .. I- ,I .. I-, I .. I

^C,

I

^\"1'

I

^C1

L.:.J

^C,

I

^VI'

I

^C,

I

^VI'

I

^{C, VI'I ('I Late A}

describe Bunirh ynclua cf, sigma

importa

Boubeithyris boubei _{fauna (}

Ovatathyris cf.pottern ensis ltel

.~,- ----~--- --

. _. . . .-

located Harmatosia crassa

Cretace Capillithyris capillata

--. ---.. .. " --- '- ' - '- ~ ' " ' -- -' - -._--- -'- ---- '.--- Western

T~~·~bra tli lina protostriutula geograp

the very Gemmarcula canaliculata

the bra

Table 1. Stra tigr aphi c range and geographi c dist r ibu tion of the most representative brach iopod species from Enisala (N orth Dobrogea, Romania). stratigr

Vr - Vraconi a n (upperm ost Albian ); C • Lower Ceno ma nia n in NOr!

1

--

--

- -

--

VRACONIANBRACHIOPOD FAUNAFROM NORTH DOBROGEA,ROMA1"lIA 73

i D

resented in

~e d ^{in the}

~ ^Annopol

!teclonical-

~ren t ia ted;

~ntinenta l,

al range

Central Asia Vr c,

_ .-

-

,...

-

-

-

ornania).

With regard to the occurrence of some brachiopod species in the Vraconian deposits from North Dobrogea, there appea rs to be an appreciable stratigraphic lag in comparison with faun as from Central and Western Europe. In the brachiopod assemblage from Enisala some species occur almost exclusively in the basal Cenomanian from some regions in Central and Western Europe (Tab . 1). The species that also occur in the Albian, such as Boubeithyris boubei (D'ARcHIAC, 1847) and Capi llithyris capillata (D'ARCHIAC, 1847), belong to gener a that show an extended stratigraphic range and wider geog raphic distribution.

The geographic distribution of the species identi- fied in the Vraco nian brachiopod faun a from Enisala is mark edly uneven. Most of the brachiopod species are described from Western Europe, whilst in Cen tra l Europe, only Capiliithyns capillata (D'A RCHIAC, 1847) and Boubeithyris sigma (0' ARCHIAC, 1847) are record ed from southe rn Poland and Podolia (Ukr aine ).

The stra tigraphic lag and the uneven geographic dis- tribution of some brachiopod species from Enisala, as compare d with their occur rence in Western and Cen tra l Europe, can be related to the major palaeogeograph ic events that took place during the Late Albian-Early Cenomani an time. The mid-Cretaceous transgressing sea dete rmined the migration and the re-establishment of the brachiopod fau nas espec ially during the Ceno ma nian, as alrea dy shown by MIDDLEMISS (1981, 1984 a-b), OWEN (1978, 1988) and GASPARD (1997).

The brachiopod s from North Dobrogea dem on- strate that many species, which are known in Western Europ e in the Early Cenomanian, occur red earlier in Eastern Euro pe . For instan ce, the species Harmatosia crassa (D'ARCHIAC, 1847), which occurs in Central Asia (Gissar Ridge) in the Late Albian, in North Dobrogea occurs in the latest Albian , whilst in Western Europ e (Belgiu m and Germ any) the sam e spec ies occur s only in the Early Cen om ani an. Following the spec imen count mad e by MICHALIK (1992), Harmatosia crassa (D'ARCHIAC, 1847) comp rises more than 90 % of the Late Albian brachiop od fauna from Gissar Ridge described by LoBACH EVA (1983). The same spec ies is important in North Dobr ogea , making up 14 % of the fauna (Text-fig. 3).

It clearly demonstr ates that North Dobrogea was locat ed on the main migration route of the mid- Cret aceou s brachiopod faunas , from Centr al Asia to Western Europe (Text-fig. 5). It fits well the palaeobio- geographic maps drawn up by MICHALI K (1992). Both the very lon g migration route and the sho rt life-time of the brachiop od larvae could explain the much earlie r stra tigraphic occurren ce of the brachiop od s identified in North Dobrogea (latest Albian), as compared with

their occurren ces in Western Eur ope (Early Ceno- man ian).

The mid-Cr et aceous sea that extende d from south- ern Central Asia across Eastern and Centra l Euro pe toward s Western Eur ope creat ed diversified enviro n- ments, which favour ed the brachiopod migration and specia tion and thus controlled the stratigraphic and geogra phic distribution of the mid-Cretaceou s bra- chiopo ds.

BRACHIOPOD SYST E MAT IC S AND CONV E N- TIONS

The two volumes of Par t H. Brachi opoda in MOORE'S edition of the Treati se on Invert ebrate Paleontology, published by WILLI AMS & at. (1965), have been for a lon g time the basic refere nce for brachiopod systematics. The huge amountof new data,which start- ed to accumulate just after the printing of MOORE'S1965 edition , required the revision of the systematics of the group. Conseque nt ly, in KAESLER'S edition of the Trea tise on Invertebrate Paleontology, no less than six volumes are sche duled to revise the brachiopod system- atics. Four volumes are already published and the other two are in press.

Fo r the Rhynch on ellida we refer to vo lume 4 (SAV-

AGE & at. 2002), while for the Terebratul ida we have

ben efitted of the revised systematics in the volume 5 (LEE & aZ. 2006), which is in press (DE LEE & T.N.

SMIRNOVA for the supe rfamily Terebratuloidea; D.E. LEE, T.N. SMIRNOVA & SUNDONG-LI for the superfami- ly Cancellothyridoi dea ; DJ. MACKiNNON & D.E. LEE for the superfamily Laqueoidea). For the supra-ordinal classification of the Brachiop oda, the classifications given by WILLIAMS & at. (1996) and MANCENIDO &

OWEN (2001) are here in followed.

In describing the shell morph ology and internal char acters, the morphological and anatomical terms applied to brachiop ods given by WILLIAi\o1S & al. (1997) and WILLIAMS & BRUNTON (1997) are used.

Location of specimens: The following abbreviation is used to indicate the repository of specime ns mentioned in the text: LPB.IILB. - Laboratory of Pale ontology, Univer sity of Buch arest, Cata log ue Rom ani a - Brachiopoda.

Other abbreviations: L - length of she ll; W - width of she ll; T - thickness of she ll; W/L - width/length ratio;

TIL-thickn ess/len gth rati o.All dimen sion sare givenin millimetres. Nearly all measurements are approximate owing to poor preservation of the material.

!

j

i

I

I

74 EUOEN ORAD INARU & al.

SYSTEMATI C PALAEONT OLO GY

Orde r Rhynchon ell ida KUHN, 1949

Super fam ily Hemithiridoid ea RZHONSNITSKAYA, 1956 Family Cyclot hyrididae MAKRIDIN, 1955 Subfa mily Cyclothyridinae MAKRIDIN, 1955

Genus Cyclothyris M'Cov, 1844

TYPE SPECI ES: Terebratula latissima J. de C. SOWER.

BY, 1840

? Cyclo thyris sp.

(PI. 1, Fig. 1; Text-fig. 6)

MATERIAL: Eleven specim en s (LPB.III.B.0289), in variou s state of preservation.

DIMEN SI ON S (in mm):

Specimen L W WIL T TIL

LPB.rrLB.0289/1 12.8 14.5 1.13 8.6 0.67 0289/2 15.5 15.8 1.01 10.5 0.67

L= 15.5

o

^5mm

W = 15.8

LJ

T = 10.5

3.4

6 b

~

J>

0289/3 16.0 16.3 1.01 10.8 0.67 0289/4 16.3 17.2 1.05 11.0 0.67 0289/5 17.2 18.0 1.05 11.5 0.66

EXT ERNAL CHARACTERS: She ll slightly bro ader than lon g, biconvex, with short massive umbo. Beak suberect , pointe d; small foram en, deltidial plates con- junct. Anterior commissure uniplicate, symmetrical.

Dorsal valve convex, median fold moderately devel- oped. The orna me nt is composed of numerou s fine ly rounde d costae, rar ely interrupted by grow th lines.

Some of the costa e are bifurcat ed but discern ible only on the well-prese rved specimen s.

INTERNAL CH A RACTE RS: The low and slen der dental lam ell ae are nearly paralle l and per sist ent (Text-fig. 6, sect. 0.7-3.4). The hinge-teeth are thick, quadrat e and deep , nearl y vertica lly inserted . The hinge-pl at es are sle nder, gently arc he d ven tra lly. Well defin ed inner and outer socket -ri dge. The media n sep- tum is very shor t and does not suppo rt the hinge

<::rob

~

)

plates.

parts of shaped

REMAj are sim internal poorly ~

investigi dence, 1 specime Cyclothj and wit]

plates. I ial secti 'Cycloth the pap

oceu

the Ap BILINKE

D EKOY

The sp Cycloth of the I~

4.6 4.9 5.3 5.4

Fig.6.Tran sversese rial sectionsthroughthe umbo of ? Cyclothyris sp.,LPB.IIIB.0289/2:L, 15.5mm;W,15.8mm; 1; 10.5mm.Distance fromtheventral Fig. 7.Tr umbo given in mm

VRACONlAN BRACHIOPOD FAUNA FROM NORTH DOBROGEA, ROMANIA 75

0.67 0.67 0.66

roader . Beak es con- etrical.

devel- s finely

lines.

Ie only

slender rsistent thick, d. The y. Well an sep-

hinge

plat es. Cana lifor m crura originate from the distal parts of the hinge plates and each is terminated in a Y- shaped fork.

REMARKS: By its external characters our specimens are similar to Cyclothyris M'Cov, 1844, however the intern al charac te rs are differ ent. The small number of poorly preserved specime ns does not permit adequate investigation of the internal characte rs. In correspon- dence, Dr. Svetlana LoBACHEVA suggested that these spec ime ns could be referred to a new genus of Cyclothyrididae with slim subparallel dent al lamellae and with characte ristic construction of sharpened hinge plate s. In her opinion, the diagram of the transverse ser- ial sections of our specimens is near to the diagram of 'Cyclothyris' globata (ARNAUD, 1877) (non Cyclothyrisy in the paper of MOTCH UROVA-DEKOVA (1995).

OCCURREN CE: Cyclothyris has been mentioned from the Aptian-Maas trichtian across Europe (OWEN 1962;

BILINKEVICII & POPIEL-BARCZYK 1979; MOTCHUROVA- DEKOVA1995; BITNER & MOTCHUROVA-DEKOVA 2005).

The specimens from North Dobrogea assigned to ? Cyclothyris are from the latest Albian Enisala Memb er of the Iancila For mation.

FamilyTet rarh ynchiidae AGER, 1965 Subfamily Cre tirhynchiinae KATS, 1974

L = 14.0 0 5 mm

W r- 12.8 ^{, - - -I} ---L.----'---'----.L.-.J

T = 11.0

oo~~

0.7 0.9 1.3 1.5

Ge nus Burrirhynchia OWEN, 1962

TYPE SPE CIE S: Rhyn chonella leightonensis LAMPLUGH

& WALKER, 1903

Burrirhynchia ct. sigma (SCHLOENBACH, 1867) (PI. 1, Fig. 2; Text-fig. 7)

1969.Rhynchonella sigm a S CHLOE NBACH; P ANOW, p. 578, pI.

110, fig. 2.

1974 .Lep idorynchia sigm a (SC HLOENBACH) ; MARCINOWSKl , p.

123, pI. 20, fig. 7.

1977. Burrirhyn chia sigma (SCHLOENBACH); POPJEL-B ARCZYK,

p. 43, pI. 4, figs 6-8, figs 16-17.

1988. Burrirhynch ia cf. sigma (SCHLOENBACH); OWEN, p. 83, pI.

I, figs 25-27.

MATERIAL: Three specime ns (LPB. IILB.0297), med ium sized, undeformed, nearl y complete.

DIM EN SION S (in mm):

Specim en L W

LPB.III.B.0297/ 1 14.0 12.8

W/L T TIL

0.91 11.0 0.78

EXTERNAL CHA RACT E RS: Shell dor sibiconvex, of medium size, pentago nal in outline, widest ncar anterior mar gin, at 0.56 its length. Umbo narrows pos- te riorly,beak slightly incurved.Pedicleforamen round and small, hypoth yrid , delt idi al plates disjun ct.

00 _~ ^{i ;}

1.9 2.3

e ventral Fig. 7. Transve rse serial sections throu gh the umbo of Bu rrirhynchia cf. sigma (S CHLOENBACH) figured on PI. I,Fig.2,LPB.IIIB.0297/I: L, 14.00mm;

W, 12.8 mm; 1; 11.0 mm. Distance from the ventral umbo given in mm

i

]

i

76 EUGEN GRADINARU & at.

Interare a long, distinctly concave. Later al commis- sure, viewed in profile, has a zigzag fashion. Anterior commissure with su lciplicate sigmo ida l asp ect. There is a tend en cy to an accentuate d asym me try of the anterio r commissure. The shell has an orna me n t of 31 to 32 fine and rounded costae on each valve.

Dichotomous costae are very rare. Owing to the poor preserv at ion of the she ll, the charact er istic lamellar grow th-lines are not visible.

INTERNAL CHARACTERS: As shown in Text-fig. 7, the dental plates are thin and parallel to each other.

Hinge plate narrow, slight ly concave in the posterior part, dental socke t slightly cre nu late d, hinge-t eeth moderat ely developed, medi an sep tum low, rudimen- tary .

REMARKS: The specimen from Enisala resembles those from the Albian-Ce noma n ian of Poland, but the latter ones are subtriangular in outline , with a rounde d anterior margin, umbo more elonga te d and the maxi- mum width about midlength. By its pentagon al outline, the maximum width near the anterior mar gin, roun d foramen and anterior zigzag-shap ed sulciplicat e com- missur e, our figur ed speci me n is much near er to Butrirhyn chia sigm a (SCHLOENBACH, 1867) figure d by POPIEL-BARCZYK(1977,p. 43, pI. 4, figs6-8 and figs16- 17). B. leighton ensis (LAMPLUGH & WALKER, 1903) from the Lower Albian of England, figured by OWEN(1988, pI. 1, figs 28-30) has a much fine r costation and the width exceeds the len gth. B. devoniana OWEN, 1988, from England (OWEN 1988, p. 89, pI. 1, figs 22-24) has comparat ively fewer costae, 20-25, more deepl y incised ribs, and a trapezoidal and high linguiform extension.

OCCURREN C E: Burrirhync hia sigm a has a wide geo- graphic dist ribut ion inEuro pe.InWeste rnEuro pe this species occurs in the Lower Ceno manian of South Germany, Belgium and Fran ce. In Central Europe this species is comm onin the Lower Cenomanianof Pol and (POPIEL-BARCZYK 1977) .

Order Ter ebratulid a WAAGEN, 1883 Suborder Terebratulidina WAAGEN, 1883 Superfamily Terebratul oidea GRAY, 1840 Family Sellithyrididae MUIR-WOOD, 1965 Subfamily Sellithyridinae MUI R-WOOD, 1965

Ge nus Sellithyris MIDDLEMISS, 1959

TY PE SPECIES: Terebratula sella J. de C. SOWERBY, 1823

Sellithyris upwarn ensis (WALKER, 1870) (P I. 1, Fig. 3)

1959. Sellithyris upwarnensis (WALKER) ; M ID DLEM ISS, p. 1I8, pI. 16, fig. 7.

1988. Sellithyris upwamensis (WALKER) ; G ASPARD, p. 105, pI. 3, figs 1-6.

MATERIAL: A single specimen (LPB.I1I.B.0363), nea rly complet e .

DIMENSIO NS (in mm):

Specime n L W W/L T TIL

LPB.III.B.0363/1 27.7 22.7 0.83 18.2 0.66

EXTER NAL CHARACTE RS: Small shell (length less than 30 mm) , globu lose in shape (thickness about 0.64 of len gth ), rhomboid al ventral profile, maximum wide slightly anterior mid line. PIA ratio 1.5, maximum con- vexity of ventral valve near the umbo, of dorsal valve abo ut the mid line. Umbo shor t, straight, beak ridges round,for am en mesoth yrid, symphytiumsho rt, bord er ed . Ante rior commissure very characteristic: lateral sinusses are abru pt, angular and deep; long median sinus angular and deep; lateral plica angular, the median plica of ven- tral valve are lon g and angulate (PI. 1, Figs 3 a-b, d).

REM ARKS: The sharpness of the plicae of the anteri - or commissure combine d with gently rounded large lat- era l sinuses is a not able feature of Sellithyris upwarnen- sis. This species differs from Sellithyris sella (1. de C.

SOWERBY, 1823) in being markedly thicke r in relatio n to length, by having a med ian sinus muc h larger than the lat eral sinusses and much less rounded appe arance .

OCCUR R E NCE: Describ ed from Lower Greensand at Upware and Brickhill (England). Men tion ed at Cor- bieres (Fra nce).

Ge nus Boubeiihyris Cox & MIDDLEM ISS, 1978 TYPE SPECIES: Terebratula boubei D'ARCHIAC, 1847

Bou beithyris boubei (D'ARCHIAC, 1847) (PI. 1, Figs 4-6)

1847. Terebratula boubei nov. sp.; D'ARc HlAc, p.320, pI. 19, fig. 11.

1978. Boubeithyris boubei D'ARCHIAC; Cox & M ID DLEMISS, p.

419, pI. 40, figs 1-4; text-f ig. 4.

1988.Boube ithyris boubei D'ARCH IAC; OWEN, p. 112, pI. 7, figs 4-9.

MAT ERIAL: Fourteen comple te specime ns (LPB.III.

B.0296) were recovered in the lim est one s from E nisa la.

DIME

Specime LPB.III.

EXTE

cate co to the aq

REMA size, bu mens fi Lower Tourtia type fig specime

occuB

Tourtia manian Leightor from Le

TYPES

42 '0 38 36 3":

- 32

~ ³⁰

: ; 28

U ²⁶

~ 24 v;

Ql ²² .5 ²⁰

0 18

6- 16 14 12 10

26

Fig. 8. Int Scali,

VRACONlAN BRACHIOPOD FAUNA FROM NORTHDOBROGEA, ROMANIA 77 p. 118,

15, pI. 3,

.0363),

TIL 0.66

:th less 0.64 of

I wide mcon- I valve

ridges rdered.

musses mgular ofve n- p).

lanteri- rgelat- r^amen- I de C.

tionto an the ceo

and at

t Cor-

8 1847

. fig. 11.

IISS, p.

. 7, figs

B.III.

from

DIMENSIONS (in mm):

Specime n L W WIL T TIL

LPB .III .B.0296/1 22.2 17.0 0.76 12.2 0.54 0296/2 24.0 18.4 0.77 14.5 0.60

EXTERN AL CHARACTERS: Oval-pentago nal ou t- line, narrow subere ct umbo and well defined sharp beak ridges . The she llsare moder atelylarge;foramen circu lar;

symphytium short, not well expose d. Maximum width mid-shell. The anter ior margin of the shell is rounded (smallspecimen, PI. 1, Fig. 4) or nearly straight (PI.1,Fig.

5). The ante rior commissure is sulciplicate, the plicae are close set (PI. 1, Fig. 5), relatively narrow and rounde d, resembling the figure presented by OWEN(1988, pl. 7, figs 7-9). The immature individuals have incipiently sulcipli- cate commissures. The folds of dorsal valve are confined to the ante rior third of valve (PI. 1, Figs 5-6).

REMARKS: The spec imens from Enisala are of smal1 size, but close to the W/L and TIL rat io of the speci - mens figured by OWEN (1988, pI. 7, figs 4-9) from the Lower Ceno ma nia nof Le Havre,in No rmandy, and the Tour tia of Tou rn ai, Belgium. As compa red to the holo- type figur ed by D'ARCHIAC (1847, pl. 19, fig. 11), the specimens from Enisa la are less thick.

OCCUR RENCE: Lower Cenoma nia n from the Tourtia of Tournai, in Belgium; Lower Albian -Cen o- manian in United Kingdom (Shen ley Limeston es of Le ighton Buzzard , Bedfordshire), Lower Cenomanian from Le Havre, Norma ndy.

Genu s Ovatathyris OWEN, 1988

TYPE SPECIES: Terebratula ovata J. SOWERBY, 1812

42

38

36

~

34

40

\WfLl

E ³² ₃₀

~ ₂₈ .c D ²⁶

~ ²⁴

m

22

,;z ²⁰

0 \8

& 16 14 12 10

Lenght (mm)

Fig. 8. Intr aspecific varia tion in Ovatathyris ct. pottemensis OWEN.

Scatt e r diagram plotting width/len gth and thickness/length

Ovatathyris cf potternensis OWEN, 1988 (PI. 1, Figs 7-9; PI.2, Figs 1-6;PI.3, Fig. 1;Text-figs 8-10)

1847. Terebratula squam osa MANT ELL; D AVIDSON & M ORRIS ,

p. 254, pI. 18, figs 8 a-b .

1988. Ovatathyris pottem ensis sp. nov.; O WE N , p. 109, text -fig.

16, pI. 7, figs 10-18, pI. 25, figs 1-2.

MATER IAL: Forty-two specimen s and numerous frag- ments (LPB.II1.B.0290).

DIM EN SIONS (in mm):

Specimen L W WIL T TIL

LPB. III. B.0290/l 33.5 24.4 0.72 20.5 0.60 0290/2 34.9 26.6 0.76 18.6 0.53 0290/3 37.0 28.2 0.76 19.7 0.69 0290/4 38.5 29.6 0.76 21.6 0.56 0290/5 39.2 31.2 0.87 26.5 0.67 0290/6 39.3 28.5 0.72 24.3 0.61 0290/7 39.8 30.3 0.77 25.2 0.63 0290/8 40.4 28.6 0.70 24.7 0.61 0290/9 40.6 25.2 0.62 23.6 0.55 0290/10 41.0 28.7 0.70 24.2 0.59 0290/11 50.2 41.0 0.81 31.2 0.62

EXT ER NAL CHARACTERS: Biconvex shell, robust, commo nly obese; fully mature and gero ntic individu als may be larger (over 30 mm lon g). Outline pentagonal- oval to regularly oval (Text-fig. 8). Short, massive, suberect umbo with beak ridges well-de fined. Interarea triang u lar, shor t pentago nal symp hytium with slightly concave base. Mesot hyrid or rarelysubmesothyrid fora- men, usually relatively large, circular, with the margin rarelypreserved .Themaximumwidth of the shell is just posteri orly to the middle of shell, or little mor e posteri- orly placed . The ante rior commissure is usu ally sulcipli- cate to par aplicate. The folding shows a wide range of development,usually being confinedtothe anterior third of the dorsal valve. The ventralvalve maybe gently fold- ed or may not show any fold ing. A shallow sulcus starts about mid length, or little below, on dorsal valve and deepens and wide ns ante riorly, bordered by rounded carina . Owing to the poor state of .preservation, the rugose orna mentof concen tric growth lines and the spin- ules are visible only on small well-preserved shell sur- faces of some specimens.

INT ERNALCHARACTERS:Tra nsver seserial sectio ns throu gh two large specimens (Text-figs 9-10) display a well develope d pedicle collar, a wide symphytium and a cardinal process with well developed muscle attachment area. The high cardinal process encloses long and slen-

I l

78 EUGEN GRADINARU & al.

o

5mm 26

L = 34.9 I , , , , I

W = 26.6 ²⁴

T = 18.6 ²²

f~O~©~

E^{I 20}

3.8 4.8 5.4 _s:

~ ^:8

vi

Qj 16

s

_u

~Q~~~~0

_{5.6 6.0 6.7} ^{G :4}

~~

12

~~ ~~ r-; _{~ ~} \ f

7.1 8.3 9.1 10.4 Fig. 11. \

~ _~ ^Scat

.r>:>

der _{initi ~}

; ( ) ^{t ,}

^{an acutd}

sive an

11.0 \ 11.3 11 .8

tively s are stro

~ ---

^{process .}

descend high-ar

<>

_13.6 ^{' \}

<>:

_14.0

RE Fig. 9. Transverseserial sections through theumbo of Ova/athyris cf. pottemensis OWEN, LPB.III B.0290/2: L, 34.9 mm; W,26.6 mm;T, 18.6 mm.Distance manyca

from the ventral umbo given in mm and pli

to be Ie L = 39.3

o

5 111m

from.th W = 28.5 ~

T= 24.3 frequenti

species nensis

1 3~(.,,)(r,~:(:r:o~~

~

^5.6

/

^{6.0 6.6}

:.~

^{," 7.5 "\'}

10.X

occursi

) !\Jl ,

_('

11.0 12.7 13.1 S

Fig. 10. Transver se serial sections through the umbo of Ovatathyris cf. potternensis Owr:v, LPB.lllB.0290/6: L, 39.3 mm; W, 28.5 mm; T 24.3 mm.

Distance from the ventral umbo given in mm TYPES

••

---

VRACONlAN BRACHIOPOD FAU NA FROM NORTH OOBROGEA, ROMANIA 79

26 Harmatosia crassa (O'A RCHIAC, 1847)

~

_{(PI. 2, F}igs 7-8; PI. 3, Figs 2-4; Text-figs 11-13)

~

22 1847. Terebratula crassa nov. sp.; O'ARCHIAC, p. 318, pi. 18, figs

E _8-9.

f 20 s:

'Q 18 vi

:s:

. ... ~;:;-:y-: '

~ ¹⁶

-.

.'2 ~ 14

. . .. : - .

....s->:

^---- __V

I I

20 22 2. 26 28 30

Lenght (mm)

Fig. l l. intrasp ecific variat ion in Harmatosia crassa (D'AR CHIAC). Scatter diagram plott ing wid th/le ngthand thickn ess/length

der initial hinge plates with high crural bases att ached at an acute angle to slightly concave hinge plates. The mas- sive and thick hinge teeth with large bases fix into rela- tively shallow rounded sockets. The inner socket ridges are stro ng, the outer socket ridge is very weak. Crural processes are long, slender and inwardly curving. The descending branches of the brachial loop have a broad , high-arched transver se band .

REMARKS: Measurementof 35specimens revealsthat in

Distance many cases there is considerable variation in size, convexity

and plication. In addition, no specimen reveals a tendency to be less biplicate than in 0. pottemensis (OWEN, 1988) from the United Kingdom and the anterior cornmisssure-is frequently more or less asymmetrical. From the congeneric species 0. ovata (J. SOWERBY, 1812), Ovatathyris cf potter- nensis can be distinguished by its consistently acute bicon- vexity and its rugose shell ornam ent Ovatathyris cf,potter- nensis differs internally from 0. ovata (1. SOWERBY, 1812) and 0. pottemensis(OWEN, 1988) which have a low, flatcar- dinal process, acutely ventrally concave hinge plates and strong inner and outer socket ridges. From other species of Terebratulid ae (Omatothyris, Boubeithynss, Ovatathyris cf pottemensis can be distinguished by its intern al characters:

angular shape of hinge-plates and high arched transverse band of the brachial loop.

OCCURRENCE: Ovatathyrispottemensis (O WEN, 1988) occurs in the Lower Cenomanian in the southern British Isles: Upper Greensand from Potterne, Wiltshire and Glauconitic Marl of Compton Bay, Isle of Wight .

Subfamily Nerthebrochinae COOPER, 1983 Ge nus Harmatosia COOPER, 1983

24.3 mm.

TYPE SPECIES: Terebratula crassa O'ARCHlAC, 1847

1983. Harmatosia crassa (O'ARCHIAC); COOPER, p. 196, pi. 19, figs 13-22, pI. 29, figs 8-11; pi. 67, figs 5, 10-11.

1983. Sellithyris crassa (D'ARCHIAC); LOBACHEVA, p. 105, pi. 1, figs 10-15; text-fig. 2.

1988. Harm atosia crassa (O'ARCHIAC); OWEN,p. 127,pi.6,figs 4-6.

MATERIAL: Twenty-two complete and ten incomplete spe cimens (LPB.III.B.0292).

DIMENSIONS (in mm):

Specimen L W WIL T TIL

LPB.III .B.0292/1 20.6 16.8 0.81 14.3 0.69 0292/2 22.6 20.3 0.80 15.4 0.69 0292/4 23.4 20.3 0.86 15.0 0.64 0292/5 24.3 20.0 0.78 16.3 0.64 0292/6 27.2 22.5 0.81 17.7 0.61 0292/7 28.8 24.4 0.85 17.5 0.60

EXTERNAL CHARACTERS: Short she ll acutely con- vex. The outline is fro m pentagonal to subpentago nal (Text-fig.11),with ante rior marginlarge, rounded (PI.3, Fig.4) or straight (PI.2,Fig.8;PI. 3, Figs2-3).Large and shor t umbowith relativelylongbeak, suberect; foramen sma ll to large, circular , submesothyrid, symphytium large. Long beak-ridge well defined, inter area extensive, concave. Maximum width of shell is at the middle of the valve length. Lateral commissure curved toward ventral valve. Two rounded folds originate at about half the valve length; between these folds ther e is a shallow dorsal sul- cus. Ventral valve has a medi an carina in the post er ior half. Anterior commissureis mor eor lessparaplicate.

INTERNAL CHARACTERS: Owing to the rock hard- ness the intern al structur e of the spec imens from Enisala cannot be dissected and thus cannot be com- pared with that of the specimens prepared by COOPER (1983). Instead , we prepared transverse serial section s which show the pattern of the internal morphology (Text-figs 12-13).

A pedicle collar is present. The weJJ-deveJoped car- dinal process encloses the initiallyconcavehingeplates.

The hinge plates are wide, concave, slen der, and are more or lesscurving in a posteriordirection . These are poorl y differ entiated from the laterallydeflected inner socket ridges. The long, strong, nearly vertical hinge teeth are deeply inserted in the brachial valve sockets.