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Home , Eotomariidae, Pleurotomaria, Protoconch, Subulitoidea

N. Jb. Geol. Paläont. Mh. 2004 (3) 135-150 Stuttgart, März2O04

Sasakiela, a new Early Garboniferous porcelliid genus (Porcellioidea, ) with an unusual shell ontogeny

Klaus Bandel, Hamburg and Jiii Fryda, Prague With 3 figures

porcelliid BeNoEL, K. & Fnioe, J. (2004): Sasakiela, a new Early shell ontogeny' N' Jb' Geol' lenus llo.cellioidea, Gastiopoda) with an unusual Paläont. Mh., 2004: 135 150; Stuttgart. from Abstract: A new porcelliid gastropod genus,,sasakiela gen. nov., is described the Lower Carboniferous of e.tgir-. It is based on Pleurotomaria ryckholtiana KoNrNt.r, 1843, and it is placedlnto the subfamily Agnesiinae^of the.Porcelliidae of the teleoconch of Sasakiela are openly 1Ärchaeogastropoda). The first two whorls juveniles S. (KoNtNcr' o:na pfunilpi.utty coitea which suggests that of ryckholtiana thickets or reef debris like manv f Sa:jl*"ä porilUty within the in-tärstices of algal sasakiela ,p".i., of tire moäern caecidae. In contrast to the juveniles the adult among had a tightly coiled trochosRrral shell and lived more exposed öriiit,irri openly coiled shells tile organisms of the ..äf .nri.or,rnent. The distribution of among"st Paleozoic gastropods is briefly discussed'

Zusammenfassung:§,asakielaste|lteineneueGatfungderporcelliidenGastro- Die Gattung basiert poJ.n Ju. *a wirJaus ä.. Ünt..turbon Belgiens beschrieben. wird in die Unterfamilie Agne- 'uifiUurotr*orio ry"kioltlona KortNcr, 1843 und eingestuft- Die. beiden ersten siinae der Familie porcelliidae (Archaeogastropoda) und aufgewunden Windungen a., f.f"o.on.i.tl oi Sorokiäo sinä offen Leben des Jungtieres hinweist, was auf ein zwischen eig"n und Geröll verborgenes heutiger Caecidae. Im Gegensatz il;*. u.igl.l.tUu. -lt-ä..Lebensweise vieGr rvckholtiana mit eng gewundener zu den Jungtieren lebte ä. ..*""r,r."'i. -cim.n.n e Sasakiela den anderen organismen des trochospiraler s.rlur. ,iäi, zwischen bei paläozoischen Schnecken Riffmilieus. pa, errt eie"närri. g.;.aener Gehäuse wird angesProchen'

0028-3630/04/2004-01 35 $ 4'00 76 Stuttgart Verlagsbuchhandlung' D-701 O 2004 E. Schweizerbad'sche 136 K. Bandel and J. Fryda

lntroduction

Gastropods belonging to the extinct superfamily porcellioidea represent paleozoic relatively rare elements within marinl communities. Here an unusual change in shell coiling from dextral juvenile teleoconch to sinistral or planispiral later teleoconch represents a character, which facilitates their recognition in the record. BaNopr- (1993) anralyzed the distribution of such unusual reversal in the mode of shell .oilirg ämongst some paleo- zoic and Mesozoic archaeogastropods. He, thereforä, unitJcl the Mesozoic Cirridae porcelliidae with the Paleozoic suggesting that they reprlsent one natural group. Accordingry members of the iamily Forcelliidäe bäaring a srit during the evolved into members of the cirridae that lacked a slit. The oldest representatives of the slit bearing porcelliidae have since been reported from strata (Fn?oa lgga, lggT). But also paleozoic non-slit bearing species have since been discov"."i. Th" Early (Emsian) Alaskacirrus banderi Fntoa & Bloocerr, r99g has been sug- gested to represent the oldest known member of the cirridae, extending thelr time range considerabry (Fnioa & Bloocerr r 99g). The stratigraphical range of the Porcellioidea is, thus, extended from ai least the Sirurian the to Late with the last occurrence of the genus Hamusina GEvvr'Lr-eRo, 1878 (!11 BanoBr ,a 2oo2). The superfariilf rorcettoidea, thus, spans an interval of about 350 million years. Further research dealing with Paleozoic gastropods has revealed a ielativery high ;;;;ologicar diversity of porcelliidae. the Paleozoic Here we report the occurrence of an.unusual, new porcelliid genus that is distinguished uy rruuing u, openry coiled juvenile shell. -carboni-ferous It lived in the tropical seiat Early time in the area, which lies norvadays in southern Belgium.ilso the distrruution of openly coiled sheils paleozoiclastropods found among i, h;;; briefly discussed.

All figured specimen of ,\as6pi"1o deposited ..Institute _ure in the coilection of the Royal des Sciences Naturelle de Belgique,; in grussets.

Systematic paleontology Subclass Archaeogastropoda THru_n, I 925 Order Sarvrur-praweN, I 9g0

Remarks: Amongst modern marine gastropods only the Archaeogastropoda have no planktorrophic larvae 18,+Noi. iSä2i*A therefore. they never.produce true tarval sher. Archaeogastropoda a .un u. oirriää i;'il'r"är.*rJ patero_ gastropoda ( = Docoglossi) and'V.tigrrtropoJ, i_ nfripiaoglossa1. They are nected ro each orher by rheir .urty o"nro!.lväuring ;liil;;tü.,p.äo.or.r, con_ r (primary shell of BeNoet 1982) is formed. To their protoconch no shell is added that täs ueen formed by a plankton feeding . (protoconch II). Undoubted members of the Patellogastropoda are unknown from the Paleozoic (BaNou- & GEI-ovacHen 1996, FnVoe-2001). For this reason, the majority of the Paleozoic representatives of the Archaeogastropoda have tentatively been placed in the Vetigastropoda. Accordirig to the analysis of BaNonL & Fnioe (1996) the family-level classi- fication of Päleozoic slit-bearing archaeogastropods used by KNrcHr et al. (1960) is of little use and may even bJmisleading. In addition, it also has to be taken in consideration that the- diversity of the Paleozoic slit bearing archaeogastropods has been higher than today. Späcies with slit and in their shell probably Paleozoic slirbearing Gastro- included.ury g.oupr,-only which äre now extinct. Among poda there aie not members of the Vetigastropoda but NÜrzEr & RrNosl- Late Paleozoic genera with slit iZOOO; ana BeNoel 1iO0Z; recently described ü"u.ing shell that belong inio the Cäenogastropoda according to the presence of a -shell Late larval in their proioconch. Also PeN & EtwrN (2002) illustrated such they slifbearing gastropods with distinct caenogastropod protoconchs,. but did not recognize tf,al they are not Archaeogastropoda. Similarly NÜrzel & Mape s ofthe iiOOll air.,irsed a slit beäring caenogastropod from the Early Carboniferous presence ÜSe äna placed it in the archäeogastropods and even speculated about the speculations of planktoirophic larvae within thä archäeogastropods of that time' Such are misleading if ontogeny of modern archaeogastropods is taken into consideration 19S;). Exisänce of and archaeogastropodtype- protoconch placed 6oruru,- 1994), but the Porcellioidea clearly into the Archaeogastropoda (BeNor,l 1993;Yoo in.f pfu..-"nt within the Vetigastropoda has to be considered as tentative even though it is likely.

Superfamily PorcellioideaKorEN,l895 and Diagnosis: Gastropoda with dextral coiling in the early teleoconch-whorls and characteristic or planispirai .oitlng in the later whoJs ofthe teleoconch, sinis[.at (1982, pioto.on.t of the subclasri...hu.ogurtropoda as documented by BeNo[ l 9e3). to BANDEL Remarks: Members of the Paleozoic family Porcelliidae according of the iisglj *... interpretei to have evolved during the Triassic into members Cirridae.ForthisreasonBaNoEl-(1993)unitedbothlatterfamiliesinthesuper- by Fni»a--(1997' 1999)' family Cirroidea. This -ytt.-"tit approäctr was accepted and Hrtor'reEncsR. Fn?on & Br_oocErr (iqss), Broocerr & Fni.oe (1999), phillipe (Paris) that Ko«eN (1895, in (2001). Recently, *" *ä*uäed by BoucuEr Porcelliidae and.not BnotLI ),iriil rr"t to tä .orriä.ted as the author of the family (1960) Thlrefore, the Porcelliidae have (1924) as had been ,tat.[üy f.rrcrri et al. toberegardedastheolder'validfamilynamepredatingtheerectionofthefamily nomenclature determine that cirridae cossvnNN, l;iä. i;;; ;;i;s of zoological froä the oldest family name available the name of the superf#ily il; b; ierived following BoucHer's advice. replace th. öäiä; üylt eo.".uioidea, we have to " 138 K. Bandel and J. Frirda

Family Porcelliidae KorpN, 1895

Subfamily Agnesiinae KNrcHl 1956

Diagnosis: Porcelliidae with a sinistrally coiled, trochiform teleoconch and with initial portion of shell coiling inward; selenizone narrow situated low on whorls; ornament composed of collabral and,/or spiral elements.

Discussion: KNrcsr (1956) established the subfamily Agnesiinae with no dia- gnosis or list of included_genera. KNlcnr et al. (1960) ptäceo the latter subfamily in the family Eotomariidae weNz, 1938, and characterizeä its membe.. as ."p.er"niing eotomariids with sinistral or hyperstrophic coiling. Besides the type gengs Agnesiä KoNrNc«, 1883, they placed the genera Hesperiella HorzeprEr_, i'ssi ana Enantio- stoma KorcpN, 1896 in this subfamily. weNz (193g) had considered these genera to belong to his Gosseletininae weNz, 193g, of the . KNrcsr et al. ( 1 960) described the presence of a sinistral protoconch in some species of Agnesia; however, the protoconch of the type species is still unknown (KNränr 1941: ,3). on the other hand they described the protoconchof Hesperiel/a as coiling inwards, and they interpreted this character as suggesting hypersträphy. yoo ( I gg4idescribed and figured a juvenile shell of lgzes ia from it e Lo*er'Cärboniferous oi Australia as being dextrally coiled and.thus having the same shape as in Hesperiel/a. BaNoEr_ (1993) assigned the Agnesiinae to the family porcelliidae and also added the genus Antitrochus wuroeonNe, r891 in this subfamily. Earlier, waNz (r93g) questioiably hadplaced Antitrochus in the family TrochoneÄatidae, because no sllioi selenizone was observed in the type species.l. g9l arietinus by wnroeorNe ( I ). KNrcHr (rg4r), who reexamined the coarsely silicified type specimens or Äis species,--notea dso no slit and selenizone. BaN»Er- (1993) suggested that the Middle D.uoniun gastro- pods described as Pleurotomaria nodulorä sa*ou"*cen, 1g42, and pleurotomaria elegans AncHrac & vEnNeurl, 1g42, are very similar to A.ntitrochus arietinus wHroeonNe, 1891 and probably represent the same species. The tereoconch of Antitrochus n_odulosus (saNonencen) is sinistral with ä narrow selenizone at the lower edge of each whorr with_ a dextralry .and coiled first rei*o;,- iqs:l ura thus, it resembles Agnesia,and Hesperiel/a. Recently, uu,ou.u*ä"* .on_ firmed the presence iZbOf ) of a slit in newiy analyzed, specimens of the Middre Devonian Ant ilro chus n odu los us (SeNoaencen', lg42i. The oldest member of the Agnesi inae, Fernericirrus sinistors,s (ponNen, 1907) was reported from early Late Silurian of the prague Basin (Fni,oa Fnioa t9öZl. tn'aAairion, & Bloocprr (r99g) described the unisuar earry she,,orptoiogy genus Alaskiella Fpvoe.&_Bloocerl rn tr.," 199g, which is based on Alaskiella med_ fraensis from the late Earry Devonian oietasta representing the only known species of this genus.In this species the axis of the dextraily coiteaTnitiaiü;;;ä. sheil is not parallel with the axis^of the teleoconch, but forms an angle of about r40" with it (Fni'oa & BroocErr lggg, pr. l). Incrineä trlierost.opny was, thus, documented occur within representative: to of r!: Agnesiinae. ir," iira ain from that of the Heterostropha (:1.t.-ui"r.rriuj*h... "i'rr"i..Lroäp'rry the early ontogenetic shell,^ usually representing the embryoni. ura ru.rui-irrell are coiled'r;i;;i"ily and the change into dextral coiling of the teleoconch occurs just before metamorphosis or some time before it. The recent revision of the Middle Devonian gastropod fauna of Germany has revealed two additional new genera of the Agnesünae, Paragnesia Br-oocErr & Fnipa, 1999, and Trochagneiia HeroEI-sE,ncEn,200l. But up to now their first needs to whorls are not well knownänd their placement in the Agnesiinae, therefore, from be confirmed. wENz (1938) consideied the genvs Enantiosloza KorpN, 1896 the Triassic to be closely..lut.d to Agnesia, and this position was,also accepted by KNrcHr et al. (1960). But also in Enintiostoma the morphology of the early whorls in needs to be restudied. on the other han4 protoconch morphology is known the Triassic genus Kokenella Knrr ,l8gl, coming from Anisian to Rhaetian strata of the Alps (BeNoel 1991), Timor (Knuvnecr 1924), and Iran (NÜrzer & coiled (see S'NoweeRr-DanveN 1999). ihe early shell of Kokenel/a is planispirally Bo*ouL 1991, pl. 2, figs. s-z;, in contrast to distinct dextral coiling in the Paleozoic diagnostic Porcelliinae. The lattei shell character has been considered to be one of is_ a strong shell features of the Porcelliidae (BenoEr- 1993). Even though there simitarlty in teleoconch features between Triassic Kokenella and Late Paleozoic Porcellia, the taxonomic position of Kokenella with the Pleurotomariidae as since the insertion of srrggested by BaNoeL (lgg1) is considered the most likely one, position reflects thJielenizone and its subsequent migration from apical to latera-l as member Jextral coiling in the planispiral shell. Until Enantiostoma rs confirmed oiifr. ng".riinae theä is nä undoubted evidence that the members of the subfamily survived the Permian/Triassic mass extinction' Included genera: Pernericirrus Fnioa, 1997 - Silurian; KonepruselliaFp7oe" 1SSS Ear[ Devonian; Alaskiella Fnioe & Bt-oocer-r' 1998 - Early Devonian' Trochagnesia Hr'toel- Paragnesia brooo.r, & f*V,o, 1999 - Middle Devonian; De- 2001 _ Middle Devonian; Antitrochus wHroeonNe, 1891 - Middle HoLza'eFeL' "i*o'.^,änian; ,lgn"sia oe KoNtNcr, 1883 - Devonian - Permian; Hesperiella nov. - Early carboniferous; ?Enantio- 1889 - Devonian - Permian; Sasakiela gen. s/oza KorEN, 1896 - Triassic.

Genus Sasakiela gen' nov' Typespecies'.PleurotomariaryckholtianaKoNlNcx'1843'fromtheEarlyCar- boniferous of Belgium. Se'sa'rt' Derivatio nominis: sasakiela,after the Japanese zoologist Dr' Takenori Diagnosis:Slirbearing,lowtrochospiral,sinistralteleoconch'withopenlycoiled of teleoconch openly and plani- initial part of tet"o.oniti; ;l;"; ;" iirst whorls type; selenizone situated low spirally coiled; protoco,,"i' ü"i'g of archaeogastropod of gröwth (lunulae); teleoconch on whorls and uearing ev.nry Ä*ing increments ornament consisting of fine collabral elements' Discussion:Thesinistrallycoiledslit-bearinsteleoconchofsasakie/agen.nov' r;";ralieatures of the shell and thus, was resembles that of th. sä;'i;;;;;;;t known However' Sasakiela differs from all placed here uv ro*'*Jfiliäi, p' iool' 1ß K. Bandel and J. Fryda

members of the Agnesiinae by its openly and planispirally coiled juvenile teleo- conch. In addition, its low trochospiral teleoconch distinguishes Sasakiela from the genera Agnesia, Hesperiella, Koneprusellia, and Alaskiella, ar of which have medium to high-spired trochospiral teleoconchs. But also the Silurian Pernericirrus. and the Devonian Paragnesia have a low trochospiral teleoconch as is present in Sasakiela. Howeveq the juvenile teleoconch of Pernericinus sinistorsus (pnnNrn, 1903) is tightly coiled and has dextral orientation. Also its selenizone has more complex structure that differs from that of Sasakiela. The teleoconch of Paragnesia costata (Goloruss, 1844) has distinctly concave sides contrasting from that of Sasakiela. The placement of sasakiela gen. nov. into the subfamily Agnesiinae is based on the sinistral coiling of the teleoconch, position of selenizöne, whorl shape and its expansion rate which are similar to those of the other members of the subfamily. The dextral coiling ofthe early whorls ofteleoconch is one ofthe diagnostic characters of both subfamilies, Agnesiinae and Porcelliinae and unites them ii the porcelliidae. ln sasakiela the early teleoconch whorls are openly and almost planispirally coiled. The lack ofdistinct dextral coiling in the early sheli whorls of Sisakieiais probably due to the development of open coiling. Thus, the lack of dextral coiling of ihe early shell is considered to represent a derived shell feature and, Sasakielacarinevertheless be placed in the Agnesiinae.

Sasakiela ryckholtiana (KoNrNcr, 1g43) comb. nov. Figs. 1-3 1843 Pleurotomaria ryckholtiana. - Dr KoNrNcr , p. 407 . 1843 Pleurotomaria acuta. oe KoNrNcr, p. 400, pl.34, fig. 6. 1849 Pleurotomaria ryckholtiana. BnoNN, p. l0lg. 1883 Agnesia ryckholtiana. - Dr KoNrNcrc, p. f OO, pl. 34, figs. 14_ 17. The. holotype is the specimen illustrated in Figs. 3.1, 3.5, 3.6 from the limestone of vis6 ("assise vI" of De KoNrNcr lgg3). Itis housed in the Museum of Natural History in Brussels, as are the illustrated paratypes. Description: The sm-all, rorv trochospiral teleoconch is up to l0 mm wide and sinistrally coiled. Slightly less than the two first whoils of teleoconch grew. in opglly and planispirally coiled mode. The apical side of the teleo- conch-is widely concave. Its width is about twice of ihe whorl width on the end of the first teleoconch whorl. The openly coiled initial part of ieieoconch bears the protoconch and extends freelyinto the apicar gupä ir,i, p.otoconch is.of archaeogastropod type, about 0.3 mm wide, and rIi'i"t"J.iärrtiy out of teleoconch axis (Figs. r-3). About the first half of the teleoconfh whorl is more curved than the remaining whorls, having constant translation rate. For this reason the first half of thJ tereoconch reÄained without contact to the later. whorls and is openly coiled for approximately one and tt r"l-qur.t.r, or revolurions' During further growrh thä whorr *u, in contact to inä ir.uior. Sasakle/a, a new Early Carboniferous porcelliid genus 141

1843) from the Early Carbo- Fig. 1. Drawin gs of Sasakiela ryckholtia.na (Kor'rtNcx' of openly of Belgium (at.i tp.cimen figured here on Fig' 2'1)' Detail ;iäil protoconch initial part of rts teleäconch beaiing an archaeogastropodtype. coiled onto length of protoconch about 0'3 mm' On the right an apical^view ileft); hollowt width of teleoconch teleoconch showing its initial p;;tprotruding into apical about 6 mm.

whorlandallsubsequentwhorlsaretightlycoiled.Inapicalviewtheteleo. having an elliptical outline conch shows a deviation from spirar Äiling by juvenile shell crossing a point with the longer u)(l, oi,f'" ()p'ify coiled later shell ontogeny' the where the whorls U.girio io*i eath othe.. buring incräases continually and the rate of whorl transl"ti"" the shelr axis "iä.g to low trochospiral' The growing shell changet il'tl*pt from planisoiral and is covered by the subsequent selenizone is situated i"* ä"-irr. whoris each side and is ornamented by whorl. lt is bordered b;; tfi*i tf"tuO on growth (lunulae) (Figs' 2-3)' The irregularly curving spated increments of numerous' regularly spaced' collabral ornament of the sheli consists of .u.tt other tf,an wide and curve back- threads which are -rgnf,äJi.tu.,tto seleni- inu. with an angle of about 60" with the ward below trre sutureioton collabral is ornamentäd by the same type of zone. The basal part oiit'" *t'o'f threads. 142 K. Bandel and J. Fryda

Discussion: The pseudo-elliptical outline of the teleoconch seen in apical view represents an unusual shell feature of the Archaeogastropoda and Agnesiinae (Fnioa & MaNoa 1997). The longer axis of the outlined "ellipse" in all five studied specimen ..rnt a"ros, the point where the juvenile-whorls join and represent a primary shell charact.r. tt are not a result of postmortem shell deformation. "y

Discussion of openly coiled shells found among paleozoic gastropods

The first teleoconch whorls of the Early carboniferou s sasakiela rvckhol- tiana grew in an open coil and whorls came only into contact with each other after about two whorls had been secreted. öpenly coiled shells are aL unusual character found among modern as well as extinct gastropods. Modern caecidae represent one example of such a group 6eN"o* t-eoe). Here the process of uncoiling can be observed to efrect^the teleoconch as well as the larval shell of the protoconch and it differs from sfecies to species. Also the return to normal coiling from uncoiled anästors is documented among different species of that group. ^ Even though it can be studied in living gasträpods, the development of free. whorls during later shell stages seeris*to be moie .o;;;rii seen in ancient and sometimes even ex;t1n9t yocn.rsJN gastropod groups. ogTr) and PEsr (1.975, 1984) noted a highei frequency of äxa with or openly-ärun coiled uncoiled whorls to occur among paleozoic gastropods u-org modern. ones. They interpreted the äecrease i, deq.r"ä"y-oigurt.opoo. developing free whorls as the resurt of an increasing prJaulioi-p.essure phanerozoic during the (venuer t 79g7, 1993). The ..ärägr"ui .igr'ifi"un". of free whorl paleozoic -was .development in many gastropods diiussed by YocsersoN (.1971), pEu_ (1975, pBei lgg4), A ör"o*o,, unA Fnioa etal. (2002). 1iOSl;,

Fig.2. Sasakiela ryckholtiana (KoNrucr, lg4m Belgium. l' 6 apical - views on tereoconch showing its initial. part protruding hollow: into apical 2 apical view of anorh.r.p..ir.i .f, ornamentation i ,pi.rl views showing collabral of the first tereoconch wtrort ärä,r,,"J,p..i-.;;;r;;i:"d specimen four; 5 detair view view of - showing"irlLl *norr protruding into *i;ih''i''2"ä-ä apicar I,:.,"il'r:%Tää1]Z fl',ü*'h '-' t,s s *Ä; iia-ä; rigu.. Sasakieta, a new Early Carboniferous porcelliid genus 143

Fig.2 (Legend see P' 142) 144 K. Bandel and J. Fryda

Devonian and carboniferous members of the family Euomphalidae (Euomphalomorpha BaNoel & Fn?oa, 1998) such as serpulospira coss- MANN, 1915, Ecculiomphalus PonrLocr, 1843, straparollus (Eleuthero- spira) Broocerr & JonNSoN, 1992, and Lytospira K.KEN, 1g96, represent typical examples of Paleozoic gastropods with free whorls. These gasfropods actually have no modern counterparts since they have become extinct at the end of the Paleozoic (different view see Nürzel 2002). The development of a free gerontic whorl in the Silurian species Crenilunula? markhaensis pr:rlt & GueaNov, 1997, and, in the Devonian genera Barocospira HonNv, 1964, and lbergia BloocBrr & Fni,oe, 1999, documents the occurrence of this shell feature among Paleozoic slit-bearing gastropods which most probably belong to the subclass Archaeogast.opoäa-. For example the - Silurian species of the genus Loxoplocis FrscHEn, lggi have disjunct, later whorls among the trochomorphs which probably also represerf archaeo- gastropods and which detached their latest whorl from the coiled shell. wacNeR (1999) suggested independent derivations of open coiling in several genera within the Lophospiridae. shells developing free wliorls during late shell ontogeny are arso known among paleäzo]c gastropods belonging to the orders cycloneritimorpha and clrtoneritimoriha of the s-ubclass Neritimorpha (BeNoEr- & Fnion, 1999). The same sheli tbature is developed in carboniferous species of Helminthozyga KNrcnl 1930, which belongs to the subclass C_aenogastropoda, order Ctäioglossa 1: pl.roglossa) (Nürzer- 1998, pl. 30H-J). In addition, the developm"-nt orun openly-coileä gerontic whorl is found in s-ome bellerophontiform molluscs (Amphigastro- poda) such as the genera chalarostrep.r,, KNrcnl r94g, and Groämodiscus RgHn & YocueLsoN, 1990. euite unusual development of free gerontic -Fntoe, whorls is known from members of the family säliostomatidae B.oncsrr &LsNz,2002.. rn the latter gastropods, rapid growth oiit rnrr"., and later also of the basal " parts of the af,ertu.ät -u.gi, ainng tt iute ,t ett ontogeny caused twisting of the gerontic whorl bäth outwärds"i, and back_ wards. This type of growth enableä a rotation of the final free whorl in an opposite direction to that of the main shell body. Thus, the g".orti; up..,u.. of these dextrally coiled shells is situated on the left sid"e seen from the . The above-mentioned examples illustrate a development of openly coiled whorls during rater shelr stages. This rype of deviatiän r-r,, iigii-""iling is more common than development of open coiling only in jlvenile strelt stages as in the case of -sasakiera ryckhortiana. Neiertheresr, är"n u,,,ongrt the Paleozoic-gastropods such example may be found. M;;y of the Devonian and Carboniferous #;;;;s memblrs ofine Fuomphaloiä"" fr"J openly coiled initial part of their teleoconchs (yoo r994; BaNoer- apnvon HEronLsERcen 200r) rqqs; in the continuuiion oi tr," d;;;;;rrd lonicalty Sasakiela, a new Early Carboniferous porcelliid genus 1,,L5

I r-

2

E

from the Early Carboniferous of Fig. 3. Sasakiela ryckholtiana (KoNINcr, 1843) Belgium. ^ ornamentation__-^-^_+^+i^- and^-n "alselenizone, 1, _-"pi.ur and lateral views showing collabrat i 6 detail views on apical and lateral views' specimen six; 5' - si*lrr"i iir"',2,4 - proto- äi"riv *ir.a'iniiur pätt oiitt"otonth bearing an archaeogastropod-§pe mm' 3' 4-8 mm; figure width:5-4'2 conch, holotype.teteoconJwidth: 1,3-9 mm,6-3.5 mm. 146 K. Bandel and J. Fryda

rounded embryonic shell. similarly the ordovician-permian gastropods united to the cyrtoneritimorpha BeNopr- & Fn?na, l99g had in opinly coiled first whorl. In contrast to the Euomphaloidea, this openly ioileä protoconch of the cyrtoneritomorpha represented with exception of the small embryonic initial shell cup a true larval shell that probably formed while the veliger larva lived in and from the plankton. openly coiied larval shells are also known in the members of the peruneloidea rn?tn & BaNoor_, 1997, which have been interpreted to represent the basal or ancestral group the of (BaNoer_ I 997; Fn ?on lggg, 1999,200 I ; Fnt-oa & BaNoEl 1997; Fn?oe & MaNoa 1997; Nürzel et al. 2000) or related but independent groups to the caenogastropods (BnNorr- 2002) 'ihus, in the two latter groups, cyrtoneritimorpha and peruneroidea, the openly coiled whorl is_restricted to the protoconch whorl, and does not repiesent the juvenile teleoconch as is the case in Sasakielq ryckholtiana.

lnterpretation of the function of uncoaling of the earty shell of Sasakiela ryckholtiana The early teleoconch of the Early carboniferou s sasakiela rvckholtiana is openly coiled similarly to that of many species of the Euompnätoidea. But in contrast to the latter its embryonic shell was twisted into the spiral, as is characteristic yocnsr_soN to archaeogastropods. LrNsley & ( t oz j; analyzed the shell morphology of some Devonian euomphalids from Europe and North America and speculated on their life strategy. They came to the con- clusion that the Middle Devonian euomphalids üä"e teä a sedentary life. Shells of other organisms are often found attached to their shells, anä they may have had limited selection pressures exerted by predators (LrNslev & Y_ocHE'so* 1973)..They arso suggested that the cärrying position of medium-sized, low-spired sheils as that of straparollr, ,ui äifficult to balance on the foot and crawling about seemea tä be improbable and such euomphalids probably mostly rested on the bottom orine sea leading a yocHEr-soN sedentary life (LrNsr-rv-& I973, fig 3). A similar life position of-shells was suggested. by Fn?» r' (1997) inteipreting the ecorogy of the oldest porcelliids which have a large, flattened, discoidäl shell. onihe other hand development of sheils with high and the reduction of the shell size in post-Silurian Agresiinae^*a=s inte.p.eted as reaction to a higher mobility of these forms (Fn?o e 1997). The juvenile teleoconch of sasakiera ryckhortiana with two whorls had a ring-like shape. The inner diameter of th! apicar hollow in sucrr a iuvenile shell is much wider than whorl width (Fig. : i, ä1. §r.rr;;;;;';;,.he early teleoconch had a center of gravity ,.iy iu. from the shett api.tur.. ,t, ,t i, stage of shell growth sasakiera rvckhoitiana probably diJr;;;;;t its shell balanced on the foot but held it up, since it was small and light. The shell of Sasakiela ryckholtiana was relatively small, in contrast to that of adult euomphalids, which had probably their shells mostly rested on the bottom. But juvenile euomphalids may have lives in a rather similar way as sasc- kieli, untll they began coiling tightly or grew to larger size becoming heavier. The opän coiled juvenile shell allows a comparison of the mode of life in sasakiela ryckholtiana wtth that of living caecidae (BeN»el- 1999), which live protected in interstices. As shown by LrNsLsv (1977,1978) the development of openly coiled whorls during iate ontogeny of the gastropod shells is typically connected with a changä from mori mobile to sessile style of life. The change seen in whorls Sasakielq ryckholtiana is from openly to closely coiled teleoco-nch instead. In early life ranging from metamorphosis to more fully grown existence after the embryonic stage to about the time when two whorls of the teleoconch were compleiedn Sasakiela ryckholtiana probably carried its shell upright and lived among algae, or produced thickets, or within the inteÄtices of reef rubbie, quite similar to modern representatives of the Caecidae. Its radial aperture also supports such a interpretation. Subsequent development of the closely coiled trochomorph teleoconch may have enableä to carry the shell in normal gastropod manner. Thus, the adult the Sqsakiela ryckhäkianamay be seen as mobile snail moving about among organisms *itnin the reef änvironment or among the rubble of the reef. The ,oät typ. from which S. ryckholtiana was extracted presents evidence for a life aÄäng coral and bryozoan colonies in tropical shallow water environ- ment. Bui it has to be taken into consideration that the possibilities of interpretation of shell shape and mode and place of life are limite4 as was sea and documented in case of the;odern gastropods that live in the shallow analysis coastal environment of the Caribbian Sea of Columbia. Here the carried out by BANoBr- & wr,olen (1987) indicated that with only few place of its e^ceptions shäll shape appears to be more a matter of systematic gastropod carrier than its ecolögy.'äut commonly juvenile individuals of a shape than species lead a more r6"tuA"a life and have a quite different shell fi,Lly gro*n and larger individuals, as can be noted for example in case of Cypraea and Strombu§ among others.

Acknowledgements WeliketothankANNIEDoNorforthepossibilitytostudytheEarlyCarboniferous in Brussels' JrRi Fnioe gur,.opoat from the cottection of the Royal Belgiän Museum while supported by the was enabled to get engaged with this -ut..iuiin Germany by grant 20510110143 Alexander von Humbo-l'Eiitiftung and was also sponsored to thank Devlo DocrEnv from the Grant Agency of the Czäch Republic' We wish (Mississippi) for his helpful review of this paper' 1218 K. Bandel and J. Frlrda

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Received: February 6th, 2003. Accepted by the Stuttgart editor: April l4rh, 2003. Addresses of the authors: Prof' Dr' Klaus BaNopr-, universität Hamburg, Georogisch-paläontorogisches.- Institut und Museum, Bundesstraße SS;»_ZOli{Ha.Urrg,ö.._*. " E-mai I : _b-andel@geowiss. un i_hamburg.de RNDr' Jrfti Fnioa, Dr, Czech Geologlcal Survey, Krärov 3/t3l; praha Czech Republic. cs-lrg2r l, E-mail: [email protected]