Records of the Western Australian Museum 21: 157-165 (2002).

The asterostomatid echinoid Antillaster from the Paradash Group(Middle Eocene) of the Nakhichevan Region of Azerbaijan

Kenneth J. McNamaral and Oktay H. Melikov2

I Department of Earth and Planetary Sciences, Western Australian Museum, Francis Street,Perth, Western Australia 6000, Australia

2 Azerbaijan State Oil Academy, 370102 Azadlik pr. 20, Baku, Azerbaijan

Abstract - The asterostomatid echinoid Antillaster has previously beenrecorded only from the Caribbean region and northeastern South America.Here we report the first occurrence of this genus from outside the Americas,in the Lesser Caucasus, where it has been found in Middle Eocene sedimentsof the Paradash Group in the Nakhichevan region of Azerbaijan. The materialis described as Antillaster bagmanovi sp. novo It is the earliest knownoccurrence of the genus. Its presence in the Paratethys, in a region farremoved from previous known occurrences, has significantpalaeobiogeographic implications. Its disappearance from the LesserCaucasus, but persistence in the Caribbean, may be linked to the contractionof the Tethys during the Cenozoic.

INTRODUCTION

Eocene sediments in the Nakhichevan region ofAzerbaijan have long attracted the attention ofmany investigators, due to their good exposure andextensive foraminiferal and molluscan fauna. Thedating of the predominantly clay-sand facies asbeing Eocene is based on this rich foraminiferal andmolluscan fauna (Azizbekov 1961; Bagmanov 1966,1980; Paffengoltc 1979). The presence of an Eoceneechinoid fauna in the Nakhichevan region remainedunknown until 1958 when, in addition to theforaminifers and molluscs from sections in Juga,Daralik, Ilandag and Bilav, M.A. Bagmanovcollected a rich fauna of echinoids from theParadash Group. Unfortunately, this faunaremained unstudied for many years. However, in1984 Bagmanov kindly passed his echinoidcollection over to one of us (O.H.M). During 1985­87 Melikov, to supplement this collection, collectedadditional material from Bagmanov's sections.These collections from the Paradash Group haveyielded a rich echinoid fauna, comprising 25 species(Melikov in prep.). Current work by Melikovsuggests that these species can be assigned to 14genera in 11 families, and 5 orders. It is interestingthat this species richness is in strong contrast to afauna of equivalent age occurring in sediments inthe neighbouring territory of Armenia, a mere 40­50 km away. Here only six species are known.

One of the more surprising echinoid finds fromthese sediments were large specimens of Antillaster.The asterostomatid echinoid Antillaster haspreviously been described only from the Caribbeanregion and northern South America, specifically

from Eocene to Miocene sediments in Venezuela,Cuba, Jamaica, Bonaire, Antigua, Puerto Rico andMexico (ICier 1984). Here we report the first recordof this genus from outside the Caribbean region, inMiddle Eocene sediments of the Lesser Caucasusregion in Azerbaijan. This provides the earliestrecord of asterostomatid echinoids in the Paratethysregion.

GEOLOGICAL SETTING ANDBIOSTRATIGRAPHY

Middle Eocene sediments are are widespread inthe southwestern part of the Nakhichevan region ofAzerbaijan, extending to the Arax River, whichmarks the border with Iran. These sediments areseparated by a pronounced unconformity fromunderlying Triassic sediments. This boundary ismarked by a thick basal conglomerate. The MiddleEocene sediments are divided into three groups,which extend through six foraminiferal zones(Figure 1).

Daralik Group

Lower subgroupAlong the south-west limb of the Nakhichevan

synclinal basin, particularly at Daralik (on the rightbank of the Alinjachai River), this basal unit of theMiddle Eocene sequence encompasses theNummulites laevigatus zone and is representedmainly by conglomerates containing a series ofisolated packets and lenses of limestones, clay-shaleand sandstones. It is characterised by its reddish-

158 K.}. McNamara, O.H. Melikov

Upper Globerigina corpulentaEocene zone :>

0c: cca Truncorotaloides rohri Q.

Q) enc: zone 'S

C 0 Paradash 0t c:

Group ~

Q) ca Acarinina rotundomarginata tm() zone

~

0 .mGloberiginatheka subconglobata (/)

~

LU zone ~c: c:q;:ca

Q) .- Nummulites atacicus Bilav+-'

Group- CD zone'"C +-'

'"C ::J Morozovella aragonensis...J zone Daralik.-

~ Nummulites laevigatusGroup

zone

Figure 1 Biostratigraphic chart showing the foraminiferal zonation, stratigraphic groups and range of Antillasterbagmanovi in the Nakhichevan region of Azerbaijan Republic.

brown colouring. The thickness of the subgroupvaries between 5-10 m to 120-150 m. This subgroupcontains abundant Nummulites of Middle Eoceneage, notably N. laevigatus (Brug.), N. laevigatus var.lantaensis Lerisch (B) and the echinoids Porosomalamberti Checcia-Rispoli, Triplacidia veronensisBittner, Echinolampas daralagesensis Poretzkaja, E.blaviensis Cotteau, Echinanthus cf. issyaviensis (Klein)and Cyclaster subquadratus (Desor). The presence ofN. laevigatus indicates a Lower Lutetian age,forarniniferal zone PlO.

Upper subgroupThis encompasses the Morozovella aragonensis

zone. Up the section this predominantlyconglomerate subgroup is intermixed with layers ofshelly-sandstone, argillites and rarely limestones,containing abundant Nummulites. Within thissubgroup in the Julfa region, occur lenses ofgypsumised shale and aleurolites, 150 m thick.These sharply decrease in thickness along bothlimbs of the Bilav fold. The most commonforaminifers in the zone are Nummulites laemgatus(Brug.) and N. uranensis Heim. Other foraminifersinclude Acarinina bulbrooki Bolli and Globigerina

postiloculinoides Chalilov. Acarinina bulbrooki occursin the Lower Lutetian, P9 and PlO. N. uranensisoccurs in PlO. Echinoids occurring in this uppersubgroup are 5chizaster (5chizaster) rindensisPoretzkaia, 5.(5.) sp. nov., Maretia hoffmani Goldfussand M. sp. novo

Bilav GroupThis is represented by tuffaceous conglomerate,

tuff, tuffite of andesite to andesite-dacitecomposition and lenses of sandy shale. The totalthickness of this group is 875 m. Bagrnanov (1966)identified Nummulites laemgatus (Brug) within thisgroup. Highly developed olistolites of verydifferent-sizes is a characteristic feature of thisgroup.

Paradash GroupPalaeontologically this group is divided into four

biostratigraphical zones from the lowestGlobigerinatheka subconglobata zone up through theAcarinina rotundomarginata zone, the Truncorotaloidesrohri zone to the Globigerina corpulenta zone. Thelower three are included within the Middle Eocene,the Globigerina corpulenta zone being Upper Eocene.

Asterostomatid echinoid Antillaster from Azerbaijan

Globigerinatheka subconglobata zoneThis overlies the tuffaceous conglomerate of the

Bilava Group and is represented in its lower part byrepeated beds of argillites, sandstones and clay /shales, having a total thickness of 126 m. Theserocks are overlain by 70 m of repeated beds of darkred clay/shale, argillites and subordinateinterbedded sandstones. Over these lie a 100 mthick sequence of greyish clay. This lowestsubgroup is capped by a sequence of repeatedsandstone and clay / shale 55 m thick, with a 4 mthick conglomerate at its base. The beds of thissubgroup extend along the southern limb of IlandagMountain.

Clay/ shale of all packets contain a foraminiferalassemblage containing Acarinina bulbrooki (Bolli),which ranges from P9-PlO, A. punctocarinata Fleish,Morozovella spinulosa Cushman, which ranges fromP1Q-P14, Globigerina boweri Bolli and Nummuliteslaevigatus Brug., which occurs in PlO, and anechinoid fauna of Schizaster (Schizaster) rindensisPoretzkaia, Linthia (Linthia) soudanensis Bather,Gualtieria (Gualtieria) damesi Koch, Eupatagus(Eupatagus) formosus Loriol and Maretia hoffmaniGoldfuss. G. subconglobata occurs in Pll. Thus thissequence is probably near the Lower-MiddleLutetian boundary.

Acarinina rotundomarginata zoneThis is represented by repeated beds of clay,

sandstone and argillites having a total thickness of391 m. Foraminifers present include Subbotinafrontosa Subbotina (Pll-P14), Acarinina vievensisMorozova, Morozovella lelmeri Cushman (P12-P13),Hantkenina alabamensis CuShmfu'l (P12), Nummulitesacutus (Sowerby) and N. striatus (Brug.). The speciesof echinoids recovered from this zone are:Antillaster sp. nov., Gualtieria (Gualtieria) damesiKoch, Triplacidia veronensis Bittner, Schizaster(Schizaster) sp. nov., Schizaster (Paraster) rimosus L.Agassiz, Conoclypus conoideus Leske, and C. leymerieiCotteau. The planktic forams indicate aforaminiferal zone of P12, which is Upper Lutetianto early Lower Bartonian.

Truncorotaloides rohri zoneThis consists of red-brownish (43 m) and greyish

(25 m) clay with interbeds of sandstones containingnummulites. This zone is characterised by thepresence of numerous Truncorotaloides rohriBronnimann and Bermudez (Pll-P14), Globigerinaincretacea Chalilov, G. praebl1110ides Blay.,Nwnmulites brongniarti 0'Archiac and Haime (P12­P14), N. perforatus (Mont.)(P12-P14), N. striatus(Breys.). Echinoids occurring in this zone areConoclypus conoideus Leske and Antillaster sp. novoThe foraminifers indicate a possible UpperBartonian age.

159

Globigerina corpulenta zoneSediments within this zone consist of repeated

beds of nummulitic sandstones, clays andconglomerates, 50 m thick. Foraminifers presentinclude Nummulites striatus (Brug.), N. brongniarti0'Archiac and Haime, N. paradashensis Mamedov,N. fabiani Prever, N. rectus Currey. N. brongniarti isBartonian, and N. fabiani uppermost Bartonian toLower Priabonian.

The Paradash Group would therefore seem torange from near the Lower-Middle Lutianboundary to the Upper Bartonian or earliestPribonian. The sequence at Daralik probablyoccupies the entire Middle Eocene, possiblyextending into the lowest part of the Upper Eocene.

SYSTEMATIC PALAEONTOLOGY

Order Spatangoida CIaus, 1876

Family Asterostomatidae Pictet, 1857

Genus Antillaster Lambert, 1909

Type speciesAsterostoma cubensis Cotteau, 1871; by original

designation of Lambert, 1909, p. 103.

DiagnosisTest large, low to high; apical system ethmolytic

with 3 or 4 genital pores; petals long, wide, open,flush with test, or very slightly depressed; anteriorambulacrum with small pores, in slight groove orflush with test; some plates occluded at ends ofpetals; peristome large; periproct large,inframarginal; tubercles small, no fascioles; plastronmesamphisternous with large labrum, narrowsternal plates, large episternal plates; in somespecies first plate in interambulacrum 1 followed bysingle plate (after Kier 1984:131).

RemarksSpecies of Antillaster are particularly characterised

by their very large test size, typically reaching inexcess of 100 mm test length, but sometimes to over150 mm. Antillaster lacks any evidence of fascioles,hence its assignment to the Asterostomatidae.Antillaster bears a superficial resemblance to thebrissid Pharaonaster, which is known from theEocene of North Africa (Roman and Strougo 1994).However, Antillaster can be distinguished by itsmuch larger test size and absence of fascioles;peripetalous and subanal fascioles are present inPlzaraonaster. Another superficially similar form isHypsopatagus, which is known from the Eocene toOligocene of parts of Europe, Asia and NorthAmerica. However, unlike Antillaster it has aperipetalous fasciole; is smaller; and has closed,rather than open, petals. On account of its large size,

160

absence of fascioles, distally open petals that arealmost flush with the surface of the test, the formdescribed herein from Azerbaijan is considered tobe a species of Antillaster.

Antillaster bagmanovi sp. novoFigures 2-7

DiagnosisSpecies of Antillaster with very slightly sunken

petals; anteriorly divergent petals with very narrowinterporiferous zone; peristome sunken;ambulacrum III deeply sunken orally.

MaterialHolotype WAM 99.428, from Daralik,

Nakhichevan region of Azerbaijan Republic;paratypes WAM 99.429 and 99.432 from the samehorizon and locality; other specimens WAM 99.427,99.430, 99.431 and 99.433 from the same horizonand locality. All specimens collected by O. H.Melikov from the Acarinina rotundamarginata zone,

K.J. McNamara, O.H. Melikov

Paradash Group (Middle Eocene - Upper Lutetianto early Lower Bartonian).

EtymologyNamed in honour of palaeontologist M. A.

Bagmanov.

DescriptionTest very large, reaching up to 154 mm TL;

cupola-shaped, with apex anterior of centre; heightabout 50%TL; test longer than wide, rangingbetween 90-94%TL. Aboral surface declines moresteeply anteriorly; ambitus broadly rounded.Shallow anterior notch present. Apical systemanteriorly eccentric, 41-46%TL from anteriorambitus; ethmolytic, with four genital pores,madreporite extending posteriorly the samedistance again as the distance between the anteriorand posterior pairs of genital pores.

Ambulacrum III very slightly depressed aborally;pore pairs very small. Anterior petals slightlyflexuous, curving anteriorly distally; very slightly

Figure 2 Antil~ster bagr:zanovi sp. ~ov. WAM 99:~28; holotype, aboral view; from Paradash Group (Middle Eocene),Darahk, Nakhlchevan regIOn of Azerbalpn Republic; xl.

Asterostomatid echinoid Antillaster from Azerbaijan

Figure 3 Antillaster bagmanovi sp. novo WAM 99.429;paratype, A, aboral view, B, adoral view;from Paradash Group (Middle Eocene),Daralik, Nakhichevan region of AzerbaijanRepublic; xl.

sunken; width 8-9%TL; diverging anteriorly atabout 140°; long, 43-48%TL, extending to theambitus; distaliy open; with up to 46 pore pairs ineach row; inner pores circular, outer pores slightly

161

elongate, not conjugate; interporiferous zonenarrow, being less than width of pore pairs insmallest specimen (TL 89.5 mm) to slightly greaterin largest specimen. Posterior petals also veryslightly sunken; straight; slightly longer thananterior, being 46-52%TL; with up to 51 pore pairsin each row; nature of pore pairs and width ofinterporiferous zone same as in anterior petals;slightly wider than anterior petals, being 8--10%TL.Terminal ambulacrum plates of petals sometimesoccluded.

Aboral tubercles relatively sparsely distributed;range in diameter from 0.8 to 1.6 mm in largestspecimen. Set in a dense field of miliary tubercles.Fascioles absent.

Oral surface with moderately convexinterambulacral areas and sunken ambulacra. Theseare very weakly sunken ambitally, increasing indepth to relatively deeply sunken peristome.Ambulacrum III deeply sunken throughout.Peristome width 11%TL; moderately crescentic;posterior of peristome situated 30-35%TL fromanterior ambitus. Labrum strongly arcuateanteriorly. Plastron length 24-34%TL, beingrelatively longer in smaller specimens; width 17­21%TL; gently convex. Episternal plates about halfthe length of sternal plates, but episternal andpreanal plates combined are longer than sternalplates. Periproct inframarginal, transversely oval,width 12-13%TL. Adoral tuberculation slightlymore dense than on aboral surface; primarytubercles of more even diameter; up to 1.5 mm;slightly smaller on plastron than on lateralinterambulacra; set in field of dense miliarytubercles.

Ontogenetic variationWhile the partially weathered and usually

somewhat crushed nature of the specimensprecludes any detailed ontogenetic assessment ofthe species, some differences are apparent betweenthe smallest specimen (WAM 99.429, test length 89mm), compared with the other, larger, individuals(125 to 154 mm). The plastron in the smallerindividual is distinctly narrower, with a length towidth ratio of 1:1.77, compared with 1:1.27 - 1:1.40(n=5) in the larger ones. Furthermore, the petals areslighty more sunken in larger individuals, as is theanterior ambulacrum on the oral surface. Theinterporiferous zone increases slightly in relativewidth during ontogeny, being slightly narrowerthan the width of the pore pairs in the smallestspecimen, becoming wider than pore pair width inthe largest specimens.

RemarksKier (1984) considered that there were two species

groups of Antillaster present in the Caribbeanregion. One he characterised by its possession of a

162 K.]. McNamara, O.H. Melikov

Figure 4 Antillaster bagmanovi sp. novo WAM 99.432; paratype, adoral view; from Paradash Group (Middle Eocene),Daralik, Nakhichevan region of Azerbaijan Republic; xl.

large, very high, steep-sided test, with a flat ventralsurface and very wide petals. Species within thisgroup range in age from the Oligocene to Miocene.Kier characterised the second group (whichcomprises species ranging in age from Eocene toMiocene) by the possession of relatively lower,more elongate test, more rounded ventral surfaceand narrower petals. In its possession of narrowpetals and relatively lower test with more roundedventral surface, A. bagmanovi resembles the second,probably more primitive, group.

Antillaster bagmanovi can be readily distinguishedfrom all other described species of Antillaster byvirtue of its slightly sunken petals that have a verynarrow interporiferous zone, and orally possessinga relatively deeply sunken ambulacrum Ill. Theonly other known Eocene species of Antillaster areA. arnoldi Clark in Arnold and Clark, 1927 from the

Eocene of Jamaica and A. albeari Kier, 1984 from theMiddle to Late Eocene of Cuba. The apical systemis less anteriorly situated in A. bagmanovi than inthese two species. Moreover, it has sunken petalsthat are more anteriorly divergent and narrowerinterporiferous zone. Although sharing slightlysunken petals, A. bagmanovi can be distinguishedfrom A. albeari by possessing more anteriorlydivergent petals, very much narrower anterior andposterior petals and interporiferous zone, morevaulted test and deeper anterior ambulacrum on theoral surface.

Like A. elegans Jackson, 1922 from the Miocene ofPuerto Rico, A. bagmanovi has an apical system in asimilar relative position, a little anterior of central,and slightly anteriorly divergent petals. However,the Azerbaijan species has slightly sunken petals,narrower interporiferous zone, deeper anterior

Asterostomatid echinoid Antillaster from Azerbaijan 163

A

B

Figure 5 Antillaster bagmanovi sp. novo WAM 99.432; paratype, A, partial adoral plating, B, lateral profile; fromParadash Group (Middle Eocene), Daralik, Nakhichevan region of Azerbaijan Republic; xO.9.

164

Figure 6 Antillaster bagmanovi sp. novo WAM 99.429;paratype, partial adoral plating; fromParadash Group (Middle Eocene), Daralik,Nakhichevan region of Azerbaijan Republic;xl.

ambulacrum orally and narrower labrum. Anotherspecies to possess a narrow interporiferous zone isA. jernandezi (Sanchez Roig, 1952) from theOligocene-Miocene of Cuba (Kier 1984). However,A. bagmanovi has narrower petals that are anteriorlymore divergent, a less vaulted test and four, notthree, gonopores.

AntilIaster bagmanovi can also be distinguishedfrom A. vaughani (Jackson, 1922) from theOligocene-Miocene of Antigua, Mexico and Cuba(Kier 1984) by its narrower interporiferous zone,sunken petals, deeper anterior ambulacrum orally,narrower peristome and narrower plastron. A.sanchezi Lambert in Lambert and Thiery, 1924 fromthe Early - Middle Miocene of Cuba (Kier 1984)has, like A. bagmanovi, a very narrowinterporiferous zone and slightly sunken petals, butthe Azerbaijan species has a more central apicalsystem, more anteriorly divergent petals that arenot so parallel-sided, and a deeper anteriorambulacrurn orally.

BIOGEOGRAPHIC IMPLICAnONS

The highly disjunct Eocene populations ofAntillaster, with nine Eocene to Miocene species inthe Caribbean and one Middle Eocene record in theLesser Caucasus, suggests an originally widespreaddistribution as far east as the Eastern Paratheys that

K.]. McNamara, O.H. Melikov

contracted rapidly to the west in the Oligocene.Whether Antillaster originated in the west or theeastern parts of the orginal range is hard toestablish. Evidence from other echinoids indicatesthat up until the Early Oligocene there was arelatively free exchange of taxa across the AtlanticOcean, mainly in a westerly direction. For example,Clypeaster appeared earlier in the Tethyan regionthan in the Caribbean (Ali 1983). LikewiseEchinolampas first appeared in the Mediterraneanregion during the Late Paleocene, but did notappear in the Caribbean region until the MiddleEocene (Roman 1977). Similarly Rhyncholampas firstappeared in the Caribbean at this time, although itis found in the Early Eocene in France (Roman1977). Comparable east to west migrations areshown by Eupatagus (Roman 1970) and Maretia(Roman 1977). Perhaps of more interest than thelikelihood of Antillaster forming part of this east towest migration of faunal elements in the MiddleEocene, is the fact that it disappeared from theeastern part of its range so soon after. This may be afunction of its mode of life. Kier (1984) suggeststhat, like living asterostomatids, Antillaster probablylived on the top of the substrate, lacking featuresassociated with a burrowing mode of life, and inrelatively deep water, perhaps up to 800 m deep,like living members of the family. Its disappearancefrom the Lesser Caucasus may have been associatedwith a shallowing of the sea as Tethys contractedthrough the Cenozoic and a separation of the deepbasins of the Eastern Paratethys from deeper basinsto the west.

Figure 7 Antillaster bagmanovi sp. novo WAM 99.431;para type, apical system plating; fromParadash Group (Middle Eocene), Daralik,Nakhichevan region of Azerbaijan Republic;xIS.

Asterostomatid echinoid Antillaster from Azerbaijan

ACKNOWLEDGEMENTS

We thank Or Kevin Kelly, Director of AzerbaijanRelief International, for his assistance; VasifMelikov for helping with computer services; OrAndrew Smith for his constructive comments on themanuscript; Or Stefan Rivets for assistance withforaminiferal biostratigraphy; Kris Brimmell forphotography and Oanielle West for help with theline drawings.

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Roman, J. (1970). Echinides cretaces et eocenes du Bas­Congo et de cabinda (Cote occidentale d'Afrique).Annales du Museum royale Afrique central, Teruuren 68:67-76

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Manuscript received 31 October 2000; accepted 30 November2001.