Steiner, 2002

copy The Norwegian Academy of Science and Letters bull Zoologica Scripta 32 4 July 2003 pp343ndash356 343

Steiner G amp Dreyer H (2003) Molecular phylogeny of Scaphopoda (Mollusca) inferredfrom 18S rDNA sequences support for a ScaphopodandashCephalopoda clade mdash Zoologica Scripta32 343ndash356The phylogenetic relationships of the Scaphopoda one of the lsquolesserrsquo molluscan classes withthe other conchiferan taxa are far from clear They appear either as the sister-group to theBivalvia (Diasoma concept) or to a GastropodandashCephalopoda clade or to the Cephalopodaalone (helcionellid concept) We compiled a 18S rDNA sequence dataset of 48 molluscan spe-cies containing 17 scaphopods to test these hypotheses and to address questions regardinghigh-level relationships with the Scaphopoda Both parsimony and maximum likelihood treesshow low branch support at the base of the Conchifera except for the robust clade unitingScaphopoda and Cephalopoda This result is corroborated by spectral analysis and likelihoodmapping We also tested alternative topologies which scored significantly worse both in treelength and in likelihood The 18S rDNA data thus reject the Diasoma in favour of a ScaphopodandashCephalopoda clade as proposed in the helcionellid concept When plotted on the molec-ular tree the pivotal morphological characters associated with the burrowing life style of theBivalvia and Scaphopoda ie mantleshell enclosure of the body and the burrowing foot withtrue pedal ganglia appear convergent in these groups In contrast the prominent and tilteddorsoventral body axes multiple cephalic tentacles and a ring-shaped muscle attachment onthe shell are potential synapomorphies of Scaphopoda and Cephalopoda Most of the highertaxa within the Scaphopoda are supported by the molecular data However there is no supportfor the families Dentaliidae and Gadilidae The basal position of the Fustiariidae within theDentaliida is confirmedGerhard Steiner amp Hermann Dreyer Institute of Zoology University of Vienna Althanstr 14A-1090 Vienna Austria E-mail gerhardsteinerunivieacat

Blackwell Publishing LtdMolecular phylogeny of Scaphopoda (Mollusca) inferred from 18S rDNA sequences support for a ScaphopodandashCephalopoda cladeGERHARD STEINER amp HERMANN DREYER

Accepted 15 September 2002

IntroductionScaphopoda is one of the less diverse major groups of con-chiferan molluscs with about 520 Recent species (Steiner ampKabat 2001 Steiner amp Kabat 2001) living in all types ofunconsolidated marine sediments (Shimek amp Steiner 1997)Scaphopoda are adapted to their infaunal habit by a tubularmantleshell open at both ends and a burrowing foot thereare no gills or osphradia (Steiner 1992 Shimek amp Steiner1997) They are generally considered to be microcarnivorescollecting their prey items (mainly foraminifers) with numer-ous captacula mdash cerebrally innervated cephalic appendagesmdash and processing them with a large radula apparatus(Shimek 1988 1990 Palmer amp Steiner 1998)

The phylogenetic relationships of Scaphopoda with theother conchiferan taxa are far from settled There are twocompeting basic concepts (1) the DiasomandashCyrtosoma

(Runnegar amp Pojeta 1974 Pojeta amp Runnegar 1976) orLoboconchandashVisceroconcha (Salvini-Plawen 1980) conceptproposing a ScaphopodandashBivalvia vs GastropodandashCephalopoda clade and (2) the lsquohelcionellidrsquo concept (Peel1991) placing Scaphopoda closer to or within the GastropodandashCephalopoda lineage (Fig 1AB) Neither concept wasfundamentally new at the time of proposal The idea thatScaphopoda and Bivalvia are closely related was introduced byLacaze-Duthiers (1857minus58) who emphasized the similaritiesin the weakly developed head pedal morphology and in theformation of mantle and shell This was further developed byRunnegar amp Pojeta (1974 Pojeta amp Runnegar 1976 1979 1985)proposing the Rostroconchia a palaeozoic group of laterallycompressed pseudo-bivalved molluscs as the common stemgroup of Bivalvia and Scaphopoda and coining the term Dia-soma for this lineage The concept was widely accepted (eg

Molecular phylogeny of Scaphopoda bull G Steiner amp H Dreyer

344 Zoologica Scripta 32 4 July 2003 pp343ndash356 bull copy The Norwegian Academy of Science and Letters

Engeser amp Riedel 1996 Ponder amp Lindberg 1997 Reynoldsamp Okusu 1999 Salvini-Plawen 1980 1990 Salvini-Plawen ampSteiner 1996 Wagner 1997) although Steiner (1992 1996)pointed out discrepancies in the development of body axesbetween Rostroconchia and Scaphopoda

Connecting Scaphopoda to the GastropodandashCephalopodaline has a similarly long tradition A close relationship ofScaphopoda and Gastropoda based on the similarities ofbranched head tentacles prominent dorsoventral body axesand the occurrence of shell slits was proposed by Plate (1892)and Simroth (1894) (Fig 1D) The common derivation ofScaphopoda and Cephalopoda was favoured by Grobben(1886) using similar arguments These hypotheses haverecently gained new support Waller (1998) elaborated onand modified the helcionellid concept of Peel (1991) byderiving the ScaphopodandashCephalopoda line from helcionel-lid monoplacophorans as the sister-group of Gastropoda Ina recent cladistic analysis of morphological data Haszprunar(2000) proposed Scaphopoda as the sister taxon of Gastrop-oda and Cephalopoda (Fig 1C) The alternative to identify-ing any of the extant classes of Conchifera as sister-groupsand deriving Scaphopoda directly from an unknown inde-pendent lsquomonoplacophoranrsquo stock was suggested by Edlinger(1991) while Starobogatov (1974) and Chistikov (1979)identified the palaeozoic Xenoconchia as the closest relativesof Scaphopoda Yochelson (1978 1979) even considered thederivation of an un-shelled ancestor

This variety of competing phylogenetic hypotheses ispartly due to the lack of information provided by the fossilrecord Scaphopoda are the latest to appear in the fossil

record among all conchiferan classes and there are no obvi-ous transitional forms connecting them to other molluscsThe oldest scaphopod reported is the Ordovician Rhytioden-talium kentuckyesnis Pojeta amp Runnegar 1979 although itsscaphopod nature has been questioned by Engeser amp Riedel(1996) as has that of several Devonian and Carboniferousscaphopods (Yochelson 1999 Yochelson amp Goodison 1999Palmer 2001)

It is evident from the competing hypotheses that wehave to deal with convergent morphologies in several organsystems The pivotal characters involved (discussed inHaszprunar 2000 Reynolds amp Okusu 1999 Steiner 1992 19981999a Waller 1998) are listed in Table 1 Depending on thetopology of the conchiferan phylogenetic tree at least one ofthe sets of similarities must have arisen convergently If theDiasomandashCyrtosomaLoboconchandashVisceroconcha conceptis favoured elongation of the dorsoventral body axis (mul-tiple) cephalic tentacles and the ring-shaped attachment ofthe dorsoventral body muscles (Mutvei 1964 Yochelson et al1973) must have evolved convergently in Scaphopoda and theCyrtosomaVisceroconcha If however the lsquohelicionellidrsquoconcept is assumed the lsquoventralrsquo mantleshell extension withsimilar innervation of the anterior mantle regions epiatroidnervous system with fully concentrated pedal ganglia andburrowing foot evolved convergently in the Scaphopodaand Bivalvia When faced with a tie like that a morphology-independent dataset such as that provided by DNA sequencesmay help in addressing this question

The relationships of the higher taxa within Scaphopodaare only partly resolved Cladistic analysis of morphological

Fig 1 AndashD Competing hypotheses on thephylogeny of extant conchiferan classes testedin this study mdashA DiasomandashCyrtosoma (afterPojeta amp Runnegar 1976) or LoboconchandashVisceroconcha (Salvini-Plawen 1980 1990)with fossil Rostroconchia as stemgroup ofScaphopoda and Bivalvia mdashB Helcionellidconcept (Waller 1998) with fossil Helcione-llida as stemgroup of Scaphopoda and Cephalo-poda ScaphopodandashCephalopoda clade alsoaccording to Grobben (1886) mdashC ModifiedVisceroconcha concept (Haszprunar 2000)mdashD ScaphopodandashGastropoda clade accordingto Plate (1892) and Simroth (1894)

G Steiner amp H Dreyer bull Molecular phylogeny of Scaphopoda


data (Reynolds 1997 Reynolds amp Okusu 1999 Steiner 19921998 1999a) has supported the basic dichotomy separatingthe monophyletic Dentaliida and Gadilida and returnedidentical topologies within the Gadilida (Entalinidae(Pulsellidae (Wemersoniellidae Gadilidae))) (Fig 2) In con-trast relationships of the dentaliid family taxa are less cleardue to the lack of reliable morphological characters for thissystematic level and to uncertain monophyly of certainfamilies and genera (Reynolds amp Okusu 1999 Steiner 19981999a) There is agreement on the basal position of theGadilinidae but the position of the Fustiariidae is controver-sial Reynolds amp Okusu (1999) placed it in a derived positionas the sister-group of the Dentaliidae whereas Steiner (19981999a) recovered it either as a sister-group to the Gadilinidaeor in a position between Gadilinidae and the other dentaliidfamilies In addition to these uncertainties the relationshipsof the families Laevidentaliidae Calliodentaliidae and Rhab-didae are completely unresolved

Having been used only as outgroup taxa in molecularanalyses of other molluscan groups Scaphopoda are ratherunder-represented in molecular data sets There are threepartial cytochrome-oxidase-I sequences (Hoeh et al 1998Giribet amp Wheeler 2002) two partial engrailed sequences(Wray et al 1995) three partial 28S rDNA sequences(Rosenberg et al 1997 Giribet amp Wheeler 2002) and fivenear-complete 18S rDNA sequences (Winnepenninckx et al1996 Giribet et al 2000 Steiner amp Hammer 2000) availablein GenBank Inadequate representation of the crown-groupconchiferan taxa at least of Scaphopoda and Cephalopodaandor the use of inadequate molecular markers for resolvingconchiferan relationships (eg Rosenberg et al 1997)accounts for the lack of information on this question from themolecular side

In order to test the morphological data against an inde-pendent data set we obtained near-complete 18S rDNAsequences of 12 scaphopod species from five families andaligned them to the existing ones and to a selected set ofgastropods bivalves and cephalopods using the availablepolyplacophorans as outgroup The resulting trees providea guideline for interpreting the patterns of homology of thedisputed morphological characters and for assessing thesister-group of the Scaphopoda Although some of the scapho-pod family group taxa especially those of the Dentaliida arenot represented in the present data set we are able to addressalso some of their high-rank internal relationships

Materials and methodsMost of the specimens were collected by dredging in theNorth Atlantic off Trondheim Norway and south of IcelandDentalium austini was collected from western Australia andFustiaria rubescens from Greece (Table 2)

DNA extraction amplification and sequencingLiving specimens were fixed in ethanol (96) or frozen inliquid nitrogen at minus70 degC Total DNA was isolated from theentire soft body (small specimens) or pieces of tissue (largerspecimens) of 12 scaphopods (eight Gadilida and four Den-taliida) with the lsquoDNeasy Tissue Kitrsquo (Qiagen) or with CTAB(Winnepenninckx et al 1993a)

Scaphopod character states Bivalvia Gastropoda Cephalopoda

1 Lateroventral extension of mantle-shell enclosing body + ndash ndash2 Burrowing foot with functionally hydraulic component + ndash ndash3 Epiatroid nervous system with true pedal ganglia + ndash 4 Visceral connectives lateral of dorsoventral muscles + ndash ndash5 Prominent dorsoventral body axis with resulting ndash + +

U-shaped gut6 More than two cephalic tentacles ndash ndash +7 Ring-shaped attachment of dorsoventral muscles ndash ndash +

Table 1 Potential synapomorphies of Scaphopoda with Bivalvia Gastropoda and Cephalopoda Scoring refers to the presumed ancestral states for each class Numbering of characters corresponds to that of Fig 7

Fig 2 Phylogenetic relationships of scaphopod family group taxafrom morphological data after Steiner (1998 1999a) Taxa inboldface are represented in the present molecular dataset



Table 2 Species used in the phylogenetic analysis arranged systematically with GenBank accession numbers sources and sampling location for those sequenced in this study

Systematic position Species GenBank no Authors Sampling locality

ScaphopodaDentaliida

Dentaliidae Antalis pilsbry (Rehder 1942) AF120522 Giribet et al (2000)Antalis inaequicostata (Dautzenberg 1891) AJ389660 Steiner amp Hammer (2000)Antalis vulgaris (Da Costa 1778) X91980 Winnepenninckx et al (1996)Antalis perinvoluta (Boissevain 1906) AJ389663 Steiner amp Hammer (2000)Dentalium austini (Lamprell amp Healy 1998) AF490594 this study Watering Cove Burrup

Dampier NW AustraliaPeninsula

Fissidentalium capillosum (Jeffreys 1877) AF490596 this study BIOICE st 3188 62deg0915primendash62deg0873prime N27deg0032primeminus27deg0131prime W 1339ndash1338 m

Fissidentalium candidum (Jeffreys 1877) AF490595 this study BIOICE st 3172 60deg0542primendash60deg0568prime N

20deg5130primeminus20deg4976prime W 2709 mRhabdidae Rhabdus rectius (Carpenter 1864) AF120523 Giribet et al (2000) Fustiariidae Fustiaria rubescens (Deshayes 1825) AF490597 this study Near Athens Greece

GadilidaEntalimorpha

EntalinidaeEntalininae Entalina tetragona (Brocchi 1814) AF490598 this study Trondheim Fjord NorwayHetero- Heteroschismoides subterfissum (Jeffreys 1877) AF490599 this study schismoidinae BIOICE st 3167 60deg5488primendash

60deg5528prime N 22deg4726primeminus22deg4762prime W 1897ndash1899 m

GadilimorphaPulsellidae Pulsellum affine (M Sars 1865) AF490600 this study BIOICE st 3167 60deg5488primendash

60deg5528prime N22deg4726primeminus22deg4762prime W 1897ndash1899 m

GadilidaeSiphono- Siphonodentalium lobatum (Sowerby 1860)dentaliinae AF490601 this study BIOICE st 3161 62deg3708primendash


Polyschides olivi (Scacchi 1835) AF490602 this study BIOICE st 3187 62deg0904primendash62deg0867prime N 27deg0074primeminus27deg0123prime W 1327ndash1326 m

Gadilinae Cadulus subfusiformis (M Sars 1865) AF490603 this study Trondheim Fjord NorwayCadulus sp A AF490604 this study BIOICE st 3181 60deg5286primendash


Cadulus sp B AF490605 this study BIOICE st 3173 60deg0538primendash60deg0559prime N20deg5123primeminus20deg5211prime W 2709ndash2710 m

BivalviaProtobranchiaSolemyida

Solemyidae Solemya reidi (Bernard 1980) AF117737 Distel (2000)Solemya togata (Poli 1795) AJ389658 Steiner amp Hammer (2000)



NuculidaNuculanoideaNuculanidae Nuculana minuta (O F Muumlller 1776) AF120529 Giribet amp Wheeler (2002)

Nuculana pella (Linneacute 1767) Solemyida AJ389665 Steiner amp Hammer (2000)Yoldiella nana (M Sars 1865) AJ389659 Steiner amp Hammer (2000)

Neionellidae Neilonella subovata (Verrill amp Bush 1897) AF207645 Giribet amp Wheeler (2002)PteriomorphaArcoidea

Arcidae Arca noae (Linneacute 1758) X90960 Steiner amp Muumlller (1996)Acar plicata (Dillwyn 1817) AJ389630 Steiner amp Hammer (2000)

MytiloideaModiolinae Modiolus auriculatus (Krauss 1848) AJ389644Mytilinae Mytilus edulis (Linneacute 1758) L33448 Kenchington et al (1995)

PterioideaPinnidae Pinna muricata (Linneacute 1758) AJ389636 Steiner amp Hammer (2000)

Atrina pectiniata (Linneacute 1767) X90961 Steiner amp Muumlller (1996)HeteroconchiaUnionida

Unionidae Elliptio complanata (Lightfoot 1786) AF117738 Distel (2000)Carditoidea

Carditidae Carditamera floridana (Conrad 1838) AF229617 Campbell (2000)Solenoidea

Pharidae Ensiculus cultellus (Linneacute 1758) AF229614 Campbell (2000)Veneroidea

Ungulinidae Diplodonta subrotundata (Issel 1869) AJ389654 Steiner amp Hammer (2000)Cyamioidea

Sportellidae Basterotia elliptica (Reacutecluz 1850) AF229616 Campbell (2000)Gastropoda

NeritopsinaNeritidae Nerita albicilla (Linneacute 1758)

VetigastropodaTrochidae Monodonta labio (Linneacute 1758) X94271 Winnepenninckx et al (1998)Fissurellidae Diodora graeca (Linneacute 1758) AF120513 Giribet et al (2000)

CaenogastropodaNassariidae Zeuxis siquijorensis (A Adams 1852) X94273 Winnepenninckx et al (1998)Bursidae Bursa rana (Linneacute 1758) X94269 Winnepenninckx et al (1998)Calyptraeidae Crepidula adunca (Sowerby 1825) X94277 Winnepenninckx et al (1998)

CephalopodaNautiloidea

Nautilidae Nautilus macromphalus (Sowerby 1848) AJ301606 Bonnaud amp Boucher-Rodoni (unpublished)Nautilus scrobiculatus (Lightfoot 1786) AF120504 Giribet amp Wheeler (2002)

ColeoideaLoliginidae Loligo pealei (Lesueur 1821) AF120505 Giribet amp Wheeler (2002)Sepiidae Sepia elegans (Blainville 1827) AF120506 Giribet amp Wheeler (2002)

PolyplacophoraIschnochitonina

Chitonidae Liolophura japonica (Lischke 1873) X70210 Winnepenninckx et al (1993b)Acanthochitonina

Acanthochitonidae Acanthochitona crinita (Pennant 1777) AF120503 Giribet et al (2000)Lepidopleurina

Lepidopleuridae Lepidopleurus cajetanus (Poli 1791) AF120502 Giribet et al (2000)


Table 2 continued



The complete 18S rRNA gene was amplified in over-lapping fragments using the primer pairs 18A1600r NS31800r NS31400r and NS51800r (Table 3) The PCRwas performed on a Robocycler 96 (Stratagene) in a 30-microLreaction mix containing 15 mM MgCl2 each dNTP at250 microM each primer at 05 microM 06 units Taq polymerase(Biotaq Red Bioline) and the supplied reaction buffer at1 times concentration The PCR cycle conditions were as fol-lows initial denaturation step of 2 min at 94 degC 36 cycles of30 s denaturation at 94 degC 45 s annealing at 50 degC and 2 minprimer extension at a 72 degC followed by a final primer exten-sion step of 10 min at 72 degC PCR products were purifiedwith the Concert Rapid PCR Purification System (Life Tech-nologies) and sequenced automatically with a range ofprimers (Table 3) on an ABI 3700 at VBC-Genomics BioscienceResearch GmbH Vienna

Choice of taxa alignment and phylogenetic analysisIn addition to the five published sequences we obtained 18SrDNA sequences of 12 species of Scaphopoda resulting in 17ingroup taxa of a sufficiently wide systematic range to addressmajor phylogenetic relationships within the group For theassessment of the conchiferan relationships we selected 17bivalve species (six each of the Protobranchia Pteriomorphaand five of the Heteroconchia) seven streptoneuran gastro-pods the four available cephalopod species and rooted thetrees with three polyplacophoran species

Sequences were aligned with CLUSTALX 18 (Thompsonet al 1997) applying several combinations of gap penalties(opening penalty 10ndash20 extension penalty 5ndash12) and sub-sequent manual corrections The strategy we used was to alignthe species of each class first in the lsquomultiple alignment modersquoand united these in the lsquoprofile alignment modersquo The align-ment is available upon request from the correspondingauthor (GS)

Phylogenetic analyses were performed with PAUP 40b8aand 40b10 (Swofford 1998) on a PC and on the Schroumldinger1 Linux-Cluster at the Central Informatics Service

University of Vienna Unweighted heuristic maximumparsimony (MP) searches were made with 50 random additionsequences and TBR branch swapping Bootstrap support(BS) was assessed by 1000 replicates each with three randomsequence additions and number of trees limited to 200 perreplicate Decay indices (DI) (Bremer 1988 1994) werecalculated using a batch file produced by TREEROT (Sorensen1996) with 10 random addition sequences keeping 100 treesper replicate for each search

For maximum-likelihood analyses (ML) the most parsi-monious trees (MPTs) were used as starting trees for thecalculation of the model parameters and subsequent branchswapping Empirical nucleotide frequencies and the para-meters for the transitiontransversion ratio proportion of invar-iable sites and the gamma shape value were estimated underthe HKY85 model with rate heterogeneity and four catego-ries of substitution rates following a gamma distribution(HKY85 + I + Γ model) The resulting values were then setfor subtree-pruning-regrafting (SPR) branch swapping withrearrangements limited to cross four branches We tested thesignal in and the robustness of the ML tree with the quartet-puzzling program TREE-PUZZLE 50 (Schmidt et al 2000)under the same model as the ML analysis and parametersestimated by the program and with 100000 puzzling stepsFour-cluster likelihood-mapping (Strimmer amp Haeseler1997) implemented in TREE-PUZZLE 50 was performed with10 000 randomly chosen quartets to test the relationships ofthe four conchiferan classes Resulting trees were visualizedwith TREEVIEW 161 (Page 1996) Competing alternativephylogenies were obtained by searching under topologicalconstraints and subsequently compared with the KH(Kishino amp Hasegawa 1989) and Templeton tests for MP andthe SH (Shimodaira amp Hasegawa 1999) test for ML as imple-mented in PAUP under the RELL option

The programs PREPARE and HADTREE (Hendy amp Penny1993) were used for spectral analysis using the options forrecoding the data to two-state characters and lsquosum-of-7rsquo asin Steiner (1999b) and Steiner amp Hammer (2000) As thenumber of species is limited to 20 in these programs wecreated two data sets one for the Scaphopoda only and onewith selected molluscan species to address the sisterg-rouprelationships of the Scaphopoda

ResultsThe 18S rDNA sequences of scaphopods obtained in thisstudy range in length from 1808 to 1854 basepairs in theDentaliida and from 1915 to 1991 basepairs in the GadilidaThe increased sequence lengths of the Gadilida are due toinserts in helices E23_1 and E23_2 to E23_5 of the V4 region(Table 4) according to the secondary structure model inWuyts et al (2002) Sequence similarity of these inserts ishigh and suggests homology The alignment has 2500

Table 3 PCR and sequencing primers used in this study The NS primers were designed by White et al 1990 All other primers were designed for this project

Name Position on D austini Sequence

18A1 minus20ndash0 5prime-CCT ACC TGG TTG ATC CTG CCA G-3primeNS3 580ndash600 5prime-GCA AGT CTG GTG CCA GCA GCC-3prime600 r 669ndash650 5prime-CCG AGA TCC AAC TAC GAG CT-3primeNS4 r 1203ndash1184 5prime-CTT CCG TCA ATT CCT TTA AG-3primeNS5 1182ndash1203 5prime-AAC TTA AAG GAA TTG ACG GAA G-3prime1400 f 1473ndash1495 5prime-GAG CAA TAA CAG GTC TGT GAT GC-3prime1400 r 1495ndash1473 5prime-GCA TCA CAG ACC TGT TAT TGC TC-3prime1800 r 1843minus1865 5prime-ATG ATC CTT CCG CAG GTT CAC C-3prime



characters of which 948 are parsimony-informative Parsimonyanalysis returns three MPTs of 3206 steps (CI = 0522RC = 03935) (parsimony-uninformative characters excluded)The strict consensus tree (Fig 3A and B) is 3220 steps longThe single ML tree (Fig 4) has a minusln L = 20050762 (transi-tiontransversion ratio = 1338 proportion of invariable sites= 018 gamma shape parameter = 05) Likelihood-mapping(Fig 5A) associates 911 of all quartets with areas of well-resolved topologies (tips of the triangle) and 51 with thearea of unresolved or star topologies (centre of the triangle)This indicates a strong phylogenetic signal in the datasetalthough some parts of the trees can be expected to show lowresolution andor support

Class relationshipsScaphopoda is a well-supported monophylum in all analyseswith BS of 92 DI of 9 and quartet-puzzling support (QP) of74 (Figs 3A 4 and 6A) There is also high support for themonophyly of Polyplacophora (BS = 100 QP = 83 DI = 25)and Cephalopoda (BS = 100 QP = 87 DI = 53) Mono-phyletic Gastropoda are not supported by MP (BS = 29) asthe Nerita sequence renders them paraphyletic with regardto the Cephalopoda and Scaphopoda However ML findsGastropoda monophyletic with moderate puzzling support(QP = 63) although the clade appears as sister taxon to thesolemyid bivalves None of the analyses supports mono-phyly of the Bivalvia which appears as a set of paraphyleticbranches at the base of the conchiferan tree In general

branch support and phylogenetic signals in the deep parts ofthe tree is low In contrast to this the only supported sister-group relationship of molluscan classes is that of Scaphopodaand Cephalopoda (BS = 86 QP = 51 DI = 10) Parsimonyplaces Gastropoda as the sister-group of the ScaphopodandashCephalopoda clade but with low support (BS = 38 DI = 5)This topology is not represented in the ML tree where Gas-tropoda root within the Bivalvia However puzzling support(QP = 33) for this topology indicates that the signal is alsodetected by ML Spectral analysis results (Fig 6A) corrobo-rate the (Gastropoda (Scaphopoda Cephalopoda)) topologyThe six top-ranked splits are those of the four cephalopodspecies the scaphopod orders Dentaliida and Gadilida andthe Polyplacophora The seventh split unites Cephalopodaand Scaphopoda whereas the scaphopod split ranks 10thTwo splits ranking immediately before that of the Scaphop-oda is the first lsquononsense-splitrsquo uniting the vetigastropodMonodonta labio with the two coleolids Loligo pealei and Sepiaelegans (split 8) and a split within the Scaphopoda (split 9)The 49th split is that uniting the Gastropoda with Cephalo-poda and Scaphopoda There is also signal for a Gastropodaand Cephalopoda split which ranks 60th

The comparison of alternative competing topologiesagainst the MP and ML trees shows that trees with all con-chiferan classes being constrained as monophyletic is not sig-nificantly worse (Table 5) The latter tree also features aScaphopodandashCephalopoda clade like the unconstrained treesbut with monophyletic Bivalvia The other trees tested differ

Species Length

E23_1 E23_2 to E23_5

BndashE Length Dr BndashE Length Dr

ReferenceLimicolaria kambeul (Gastropoda) 1839 662ndash713 51 mdash 714ndash773 59 mdash

DentaliidaDentalium austini 1842 669ndash716 47 minus4 717ndash785 68 9Fissidentalium candidum 1808 649ndash695 46 minus5 696ndash755 59 0Fissidentalium capillosum 1812 651ndash697 46 minus5 698ndash757 59 0Antalis vulgaris 1865 683ndash730 47 minus4 731ndash792 61 2Antalis inaequicostata 1762 635ndash682 47 minus4 683ndash744 61 2Antalis perinvoluta 1744 621ndash668 47 minus5 669ndash727 58 minus1Antalis pilsbryi 1804 648ndash694 46 minus5 695ndash754 59 0Rhabdus rectius 1810 649ndash695 46 minus5 696ndash758 62 3Fustiaria rubescens 1854 681ndash727 46 minus5 728ndash793 65 6

GadilidaEntalina tetragona 1915 675ndash757 82 31 758ndash847 89 30Heteroschismoides subterfissum 1915 675ndash758 83 32 759ndash847 88 29Pulsellum affine 1974 682ndash774 92 41 775ndash902 127 68Siphonodentalium lobatum 1926 677ndash763 86 35 764ndash857 93 34Polyschides olivi 1926 677ndash763 86 35 764ndash857 93 34Cadulus subfusiformis 1986 684ndash772 88 37 773ndash915 142 83Cadulus sp A 1991 684ndash776 92 41 777ndash921 144 85Cadulus sp B 1991 685ndash754 69 18 755ndash921 166 107

Table 4 Comparison of 18S rDNA sequence lengths of Scaphopoda with the gastropod Limicolaria kambeul as reference for the secondary structure elements The representatives of the scaphopod order Gadilida show extensions in the helices E23_1 and E23_2 to E23_5 of the V4 region Abbreviations BndashE beginningminusend Dr difference to reference



in the sister-group relationship of the Scaphopoda and aresignificantly worse (P lt 005) both than the unconstrainedtrees and the monophyletic classes trees both in terms oftree length and likelihood The tree with the DiasomandashCyrtosoma topology is the least parsimonious and least likely ofthose tested The likelihood-mapping with four clusters rep-resented by Scaphopoda Bivalvia Gastropoda and Cephalo-poda (Fig 5B) returns the highest support 516 to the(Scaphopoda + Cephalopoda) topology The topologies with

(Scaphopoda + Bivalvia) and (Scaphopoda + Gastropoda)have 195 and 23 support respectively

Relationships within ScaphopodaThe two ordinal taxa Dentaliida and Gadilida are robustlysupported by all analyses (Figs 3A and B 4 5B) The mono-phyly of the Gadilida is further corroborated by thehomologous extensions in the helices E23_1 and E23_2 toE23_5 the topology within it is identical in MP and ML treesalthough the internal branches have only moderate to lowsupport Note that the puzzling values exceed the bootstrapvalues for these branches indicating the ML method beingmore efficient in assessing the phylogenetic signal The basaldichotomy separating Entalimorpha from Gadilimorpha haslow BS and QP support (Fig 3B) but takes fifth rank of allscaphopod splits in the spectral analyses (Fig 5B) Mono-phyly of the Entalinidae and Siphonodentaliidae is fullysupported whereas the robustness of the Gadilidae is low Thethree Cadulus sequences representing the Gadilidae are setoff together with the single pulsellid species from the Sipho-nodentaliidae by a better supported branch (QP = 76) ThusGadilidae and Siphonodentaliidae are not sister taxa

As in the Gadilida the dentaliid topology is consistentbetween the analyses However branch support is consider-ably higher for most clades and bootstrap values tend to behigher than puzzling values in this subtree Fustiaria appearsas the first offshoot within the Dentaliida The monophyly ofthe Dentaliidae receives no support with Rhabdus rectius(Rhabdidae) emerging from among the dentaliid speciesFurthermore the genus Antalis represented by four species ispolyphyletic with only A inaequicostata and A vulgaris form-ing a clade Antalis pilsbryi appears closer related to the twoFissidentalium species than to its congeners

DiscussionClass relationshipsScaphopoda and Cephalopoda are robustly monophyletic inall analyses Gastropoda appear as a clade only in the MLtree which is likely due to the long branch of the Neritasequence and the greater sensitivity to long branch attractioneffects of the MP method As in previous analyses (Steiner ampMuumlller 1996 Giribet amp Carranza 1999 Steiner 1999bSteiner amp Hammer 2000) the Bivalvia clade is difficult todetect and here they are always paraphyletic at the base ofthe conchiferan clade A likely explanation (see Steiner ampMueller 1996) posits their low average substitution ratescompared to the other conchiferans However the MP andML trees found under the constraint for all classes beingmonophyletic are insignificantly longer or less likely than theoptimal trees allowing for assessing their phylogenetic rela-tionships Although there are several long-branch taxa mdash egthe Vetigastropoda (Monodonta labio and Diodora graeca) the

Fig 3 A B Strict consensus tree (L = 3220 CI = 05199 RC = 03906)of three MPT (L = 3206 CI = 05221 RC = 03935) with supportindices Bootstrap and puzzling values are above and decay indexbelow branches mdashA Subtree showing relationships of Scaphopodawith the other molluscan taxa mdashB Subtree of Scaphopoda



heterodont Bivalvia (except for Carditamera floridana) thegadilid Scaphopoda and all four cephalopods mdash they do notseem to seriously affect the results as these long branchesdo not come together in the trees and do not cluster near theroot All analyses of the present dataset strongly support thesister-group relationship of Scaphopoda and Cephalopodawhereas there is no apparent signal for a ScaphopodandashBivalvia clade Spectral analysis and likelihood-mappingusing clusters also detect the signal for a CephalopodandashGastropoda clade It is however much weaker in both casesThis result is further corroborated by the comparison of thealternative tree topologies (Table 5) showing that they are allsignificantly worse than both the best trees and the trees forc-ing all classes to be monophyletic Thus there is no supportfor the DiasomaLoboconcha concept its respective topo-logy being the worst of all alternative trees tested

In the light of these results the helcionellid concept asproposed by Waller (1998) gains considerable support Whenplotted on the topology with monophyletic Bivalvia the

morphological similarities of Scaphopoda and Cephalopodaie multiple cephalic tentacles and a ring-shaped dorsoven-tral muscle attachment (see Table 1) can be interpreted assynapomorphies (Fig 7) The pronounced dorsoventral axisis already developed in the Gastropoda and thereforeplesiomorphic for this clade Consequently the similarities of

Fig 4 Maximum likelihood tree of ndashln L = 200507621 under theHKY85 + I + Γ model with transitiontransversion ratio = 13proportion of invariable sites = 017217 gamma shape parameter =04632 and four categories of substitution rates

Fig 5 A B Maximum likelihood mapping using TREE-PUZZLE50 Areas at the corners of the triangle represent one of the threepossible fully resolved four-taxon (quartet) topologies those alongthe edges partly resolved quartets for which it is not possible todecide between two possible topologies The central area representsunresolved quartets Figures give percentages of 10 000 randomlychosen quartets in each area mdashA General likelihood mappingshowing 911 of all quartets being fully resolved and only 51unresolved This indicates high phylogenetic information content ofthe 18S rDNA data mdashB Four-cluster likelihood mapping of theconchiferan classes testing their phylogenetic relationships Thecorners of the triangle are labelled with the corresponding unrootedtree topology The ScaphopodandashCephalopoda topology receivesgreatest support with 516 of all quartets compared to 195 and23 for the competing topologies Note that the topology at the topcorner does not necessarily represent the DiasomandashCyrtosoma conceptbecause the root can also be placed at the Bivalvia branch resultingin the modified Visceroconcha concept of Haszprunar (2000)



Scaphopoda and Bivalvia emphasized by the DiasomaLobo-concha concept must have arisen convergently The charac-ters associated with the burrowing infaunal habit of thesetwo groups ie the enclosure of the body by the mantleshelland the burrowing foot innervated by fully concentratedpedal ganglia are certainly good candidates for convergentevolution

More difficult to explain is the derived position of the vis-ceral connectives median to the dorsoventral muscles sharedby Cephalopoda and Gastropoda as this is unlikely to be theresult of a similar life-style However the shift of nerve posi-tion is not necessarily homologous when the highly concen-trated central nervous system of Cephalopoda is consideredWhile the shift in Gastropoda is apparently a result of a

Fig 6 A B Spectral analysis Histogram of signal (positive values on ordinate) and normalized conflict (negative values on ordinate) for thetop 60 splits (abscissa) in the alignment ranked by net signal (signal minus conflict) mdashA Analysis of 20 selected molluscan taxa assessing sister-group relationships of Scaphopoda (Polyplacophora Lepidopleurus cajetanus Acanthochitona critina Bivalvia Solemya togata Yoldiella nana Arcanoae Ensiculus cultellus Elliptio complanata Gastropoda Nerita albicilla Monodonta labio Zeuxis siquijorensis Cephaolopoda Nautilusmacromphalus N scrobiculatus Loligo pealei Sepia elegans Scaphopoda Antalis perinvoluta A pilsbryi Rhabdus rectius Entalina tetragonaSiphonodentalium lobatum Cadulus subfusiformis) Solid bars represent nodes present in the strict consensus tree The split uniting Scaphopodaand Cephalopoda ranks seventh whereas the split uniting Cephalopoda and Gastropoda ranks 60th mdashB Analysis of all scaphopodspecies Solid bars represent nodes present in the unrooted topology of the ML subtree (inset) numbers at branches indicate their rank inthe spectrum



change in developmental timing of muscle and neuronal dif-ferentiation there are no data on this process for Cephalop-oda (Haszprunar amp Wanninger 2000)

The differentiation of a distinct head is yet another prob-lematic issue We have not included this character in Table 1because delimiting character states and subsequent charactercoding are not as straightforward as in the other charactersThe head of Scaphopoda consisting of a movable buccal tube

and a pair of shields from which the captacula arise (Shimekamp Steiner 1997) is clearly separated from foot but not fromthe visceral sac or the mantle It does not protrude from theshell or directly contact the substratum Scaphopoda arethus intermediate between the lsquoheadlessrsquo Bivalvia and theGastropoda and Cephalopoda with their well-developed headsThey are at a similar level of head differentiation as theTryblidia (Recent monoplacophorans) (Haszprunar amp Schaefer1997) with the significant difference that they have preoralcephalic tentacles like Gastropoda and Cephalopoda Theassumption of a ScaphopodandashCephalopoda clade requires ade-differentiation of the head region in Scaphopoda and thecomplete reduction of the (cerebral) eyes which are considereda potential synapomorphy of Gastropoda and Cephalo-poda The latter argument is however weakened by thepresence of cerebrally innervated eyes on the first ctenidialfilaments of several pteriomorph Bivalvia (eg Rosen et al1978) Such a de-differentiation of the head and loss ofphotoreceptors can again be correlated with the acquisitionof an infaunal life style and the anterior elongation of themantleshell However as the de-differentiation of the headregion can occur from any level this character is not veryinformative

Relationships within ScaphopodaThe taxon sampling of the Scaphopoda in this study is notsufficient to allow definitive conclusions to be drawn on allrelationships of its higher taxa We have no molecular dataon the dentaliid families Calliodentaliidae GadilinidaeLaevidentaliidae and Omniglyptidae or on the gadilid deep-seafamily Wemersoniellidae Moreover some of the family taxaare represented by a single species only Nevertheless it ispossible to address several important questions and demon-strate problematic points

The monophyletic status of the orders Dentaliida andGadilida is fully supported as is that of the Entalimorpha andGadilimorpha in the latter taxon The diphyletic origin of the

Table 5 Comparison of MP and ML trees with those of competing hypotheses obtained by heuristic searches with topological constraints enforced The unconstrained MP and ML trees and the tree with all classes were constrained as monophyletic showing Scaphopoda and Cephalopoda as sister-groups For the MP criterion tree lengths were tested with KH for the ML criterion with SH (see text) the probability of the null hypothesis (P ) is listed indicates significant differences (P lt 005) Note that with reference to the Bivalvia the best trees with all classes monophyletic are not significantly worse All trees showing Scaphopoda as not being the sister-group of Cephalopoda are significantly worse than both the unconstrained and monophyletic trees

Constraint Tree length Diff KH-Test (P) ndashln L Diff SH-Test (P)

No [Scaphopoda + Cephalopoda] 3206 mdash mdash 20050762 mdash mdashMonophyletic classes[Scaphopoda + Cephalopoda] 3213 7 03624 20058367 7605 04328Scaphopoda + Bivalvia (Diasoma) 3246 40 00006 20078994 28228 00289Scaphopoda + Gastropoda 3236 30 00019 20077761 26999 00452Cephalopoda + Gastropoda 3232 26 00079 20076278 25516 00452

Fig 7 Character-state transitions of characters from Table 1 plottedon the topology supported by 18S rDNA Solid bars indicatenonhomoplastic empty bars homoplastic characters 1 lateroventralextension of mantle-shell enclosing body 2 burrowing foot 3 epiatroidnervous system with true pedal ganglia 4 visceral connectives lateralof dorsoventral muscles (change to median of dorsoventral musclesindicated) 5 prominent dorsoventral body axis with resultingU-shaped gut 6 more than 2 cephalic tentacles 7 ring-shapedattachment of dorsoventral muscles Note that the homoplasticcharacters 1ndash3 are associated with infaunal burrowing life style andthus prone to convergent evolution Scaphopoda and Cephalopodaare linked by synapomorphic multiple cephalic tentacles and thering-shaped muscle attachment Both share the prominentdorsoventral body axis and the U-shaped gut with Gastropoda



Gadilidae was unexpected but is consistent with the analysesand comparatively well supported The morphologicalcharacter setting Siphonodentaliinae and Gadilinae apart fromall other scaphopods is the anterior constriction of the shellSteiner (1992 1998) noted that not all species of Siphonoden-talium show this constriction In the light of the presentresults the possibility that this trait evolved independently inthe two groups becomes likely

The internal branches of the dentaliid clade are generallyshorter than those of the Gadilida but show a similar level ofsupport Together with the short-terminal branches in thissubtree this indicates low substitution rates andor a recentseries of cladogenetic events For further phylogeneticstudies on lower systematic levels it seems appropriate to usefaster evolving markers since the genetic distances in the 18SrDNA become too small within the Dentaliidae Dentaliidaeitself is at least paraphyletic with Rhabdus rectius (Rhabdidae)being part of the quite recent radiation mentioned aboveThe addition of more species of the smooth-shelled taxa likeLaevidentaliidae or Calliodentaliidae is likely to make thiseven more apparent The only morphological synapomorphyof the Dentaliidae is the longitudinally ribbed shell butseveral species of the genus Antalis show this feature transientlyin the juvenile shell only Moreover Lamprell amp Healy(1998) demonstrated longitudinal sculpture also in someLaevidentaliidae The rather clear separation of Antalisvulgaris and A inaequicostata from the other dentaliids couldpoint to multiple development andor reduction of shell rib-bing The present results on dentaliid molecular phylogenyclearly demonstrate the urgent need of a revision of thisgroup based on additional morphological and moleculardata

The position of Fustiaria rubescens (Fustiariidae) at the baseof the Dentaliida is in accordance with the morphologicalanalyses in Steiner (1998 1999a) Fustiariidae and Gadilinidaeshare a simple anatomy of the posterior mantle edge comparedto the other Dentaliida (Steiner 1991 1998) However con-firmation of this character state being plesiomorphic dependson future analyses including species of the Gadilinidae

AcknowledgementsWe are greatly indebted to the institutions involved in theBIOICE program the University of Iceland the IcelandicMarine Research Institute and the Icelandic Institute ofNatural History and Jon-Arne Sneli (Trondheim BiologicalStation Norway) and Torleiv Brattegard (University of BergenNorway) for the opportunity to join the summer 2000 cruisewhere most of the species for this study were collected Wealso wish to thank John Taylor and Emily Glover (NaturalHistory Museum London) and Kurt Schaefer and ChristianeTodt (University of Vienna) for providing us with specimensWe are grateful for the discussions with Luitfried Salvini-Plawen

(University of Vienna) and his comments on the manuscriptThe study was partly funded by the Austrian Science Foun-dation (FWF) projects P11846-GEN and P14356-BIO

ReferencesBremer K (1988) The limits of amino acid sequence data in

angiosperm phylogenetic reconstruction Evolution 42 795ndash803Bremer K (1994) Branch support and tree stability Cladistics 10

295ndash304Campbell D C (2000) Molecular evidence on the evolution of the

Bivalvia In E M Harper J D Taylor amp J A Crame (Eds) TheEvolutionary Biology of the Bivalvia (pp 31ndash46) London Geo-logical Society of London Special Publications 77

Chistikov S D (1979) Phylogenetic relations of the ScaphopodaIn I M Likharev (Ed) Molluscs Main Results of their Study(pp 20ndash23) Leningrad Academy of Sciences [in Russian]

Distel D L (2000) Phylogenetic relationships among Mytilidae(Bivalvia) 18S rDNA data suggest convergence in mytilid bodyplans Molecular Phylogenetics and Evolution 15 25ndash33

Edlinger K (1991) Zur Evolution der Scaphopoden-KonstruktionNatur und Museum (Frankfurt) 121 116ndash122

Engeser T amp Riedel F (1996) The evolution of the Scaphopodaand its implication for the systematics of the Rostroconchia(Mollusca) Mitteilungen des Geologisch-Palaumlontologischen Instituts derUniversitaumlt Hamburg 79 117ndash138

Giribet G amp Carranza S (1999) Point counter point What can18S rDNA do for bivalve phylogeny Journal of Molecular Evolu-tion 48 256ndash258

Giribet G Distel D L Polz M Sterrer W amp Wheeler W C(2000) Triploblastic relationships with emphasis on the acoel-omates and the position of Gnathostomulida Cycliophora Plathel-minthes and Chaetognatha a combined approach of 18S rDNAsequences and morphology Systematic Biology 49 539ndash562

Giribet G amp Wheeler W C (2002) On bivalve phylogeny ahigh-level analysis of the Bivalvia (Mollusca) based on combinedmorphology and DNA sequence data Invertebrate Biology 212271ndash324

Grobben C (1886) Zur Kenntnis und Morphologie und derVerwandtschaftsverhaumlltnisse der Cephalopoda Arbeiten desZoologischen Instituts Wien VI 1ndash22

Haszprunar G (2000) Is the Aplacophora monophyletic A cladis-tic point of view American Malacological Bulletin 15 115ndash130

Haszprunar G amp Schaefer K (1997) Monoplacophora InF W Harrison amp A J Kohn (Eds) Microscopic Anatomy of Inver-tebrates Vol 6B (pp 415ndash457) New York Wiley-Liss Inc

Haszprunar G amp Wanninger A (2000) Molluscan muscle systemsin development and evolution Journal of Zoological Systematics andEvolutionary Research 38 157ndash163

Hendy M D amp Penny D (1993) Spectral analysis of phylogeneticdata Journal of Classification 10 5ndash24

Hoeh W R Black M B Gustafson R Bogan A E Lutz R Aamp Vrijenhoek R C (1998) Testing alternative hypotheses ofNeotrigonia (Bivalvia Trigonioida) phylogenetic relationshipsusing cytochrome c oxidase subunit I DNA sequences Malacologia40 267ndash278

Kenchington E Landry D amp Bird C J (1995) Comparison oftaxa of the mussel Mytilus (Bivalvia) by analysis of the nuclearsmall-subunit rRNA gene sequence Canadian Journal of Fisheriesand Aquatic Sciences 52 2613ndash2620



Kishino H amp Hasegawa M (1989) Evaluation of the maximumlikelihood estimate of the evolutionary tree topologies from DNAsequences data and the branching order in Hominoidea Journalof Molecular Evolution 29 170ndash179

Lacaze-Duthiers H (1857ndash1858) Histoire de lrsquoorganisation et dudeacuteveloppement du Dentale Annales des Sciences Naturelles Zoologie6 225ndash281 7 5ndash51 171ndash255 8 18ndash44

Lamprell K L amp Healy J M (1998) A revision of the Scaphopodafrom Australian waters (Mollusca) Records of the AustralianMuseum Supplement 24 1ndash189

Mutvei H (1964) Remarks on the anatomy of recent and fossilcephalopods with description of the minute shell structure ofbelemnoids Stockholm Contributions to Geology 11 79ndash102

Page R D M (1996) TREEVIEW An application to display phy-logenetic trees on personal computers Computer Applications in theBiosciences 12 357ndash358

Palmer C P (2001) Dentalium giganteum Phillips a serpulid wormtube Proceedings of the Yorkshire Geological Society 53 253ndash255

Palmer C P amp Steiner G (1998) Scaphopoda Introduction InP L Beesley G J P Ross amp A Wells (Eds) Mollusca the SouthernSynthesis Vol 5 (pp 431ndash438) Melbourne CSIRO Publishing

Peel J S (1991) Functional morphology of the class Helcionelloidanov and the early evolution of the Mollusca In A M Simonettaamp S Conway-Morris (Eds) The Early Evolution of Metazoa andthe Significance of Problematic Taxa (pp 157ndash178) CambridgeCambridge University Press

Plate L H (1892) Uumlber den Bau und die Verwandtschaftsbezie-hungen der Solenoconchen Zoologische Jahrbuumlcher der Anatomie 5301ndash386

Pojeta J amp Runnegar B (1976) The paleontology of rostroconchmolluscs and the early history of the phylum Mollusca UnitedStates Geological Survey Professional Papers 968 1ndash86

Pojeta J amp Runnegar B (1979) Rhytiodentalium kentuckyensis a newgenus and new species of Ordovician scaphopodsand the earlyhistory of scaphopod Molluscs Journal of Paleontology 53 530ndash541

Pojeta J amp Runnegar B (1985) The early evolution of diasomemolluscs In E R Trueman amp M R Clarke (Eds) The MolluscaVol 10 Evolution (pp 295ndash336) London Academic Press

Ponder W F amp Lindberg D R (1997) Towards a phylogeny ofgastropod molluscs mdash analysis using morphological charactersZoological Journal of the Linnean Society 119 83ndash265

Reynolds P D (1997) The phylogeny and classification ofScaphopoda (Mollusca) mdash an assessment of current resolution andcladistic reanalysis Zoologica Scripta 26 13ndash21

Reynolds P D amp Okusu A (1999) Phylogenetic relationshipsamong families of the Scaphopoda (Mollusca) Zoological Journal ofthe Linnean Society 126 131ndash154

Rosen M D Stasek C R amp Hermans C O (1978) Theultrastructure and evolutionary significance of the cerebral ocelliof Mytilus edulis the bay mussel Veliger 21 10ndash18

Rosenberg G Tillier S Tillier A Kuncio G S Hanlon R TMasselot M amp Williams C J (1997) Ribosomal RNA phylog-eny of selected major clades in the Mollusca Journal of MolluscanStudies 63 301ndash309

Runnegar B amp Pojeta J (1974) Molluscan phylogeny The pale-ontological viewpoint Science New York 186 (4161) 311ndash317

Salvini-Plawen L (1980) A reconsideration of systematics inMollusca (Phylogeny and higher classification) Malacologia 19247ndash278

Salvini-Plawen L (1990) Origin phylogeny and classification ofthe phylum Mollusca Iberus 9 1ndash33

Salvini-Plawen L amp Steiner G (1996) Synapomorphies and plesi-omorphies in higher classification of Mollusca In J Taylor (Ed)Origin and Evolutionary Radiation of the Mollusca (pp 29ndash52)Oxford Oxford University Press

Schmidt H Strimmer K Vingron M amp von Haeseler A (2000)TREE-PUZZLE 50 Manual Maximum Likelihood Analysis forNucleotide Amino acid and Two-state Data Available via httpwwwtree-puzzledemanualhtml

Shimek R L (1988) The functional morphology of scaphopod cap-tacula Veliger 30 213ndash221

Shimek R L (1990) Diet and habitat utilization in a NortheasternPacific Ocean scaphopod assemblage American MalacologicalBulletin 7 147ndash169

Shimek R L amp Steiner G (1997) Scaphopoda In F W Harrisonamp A J Kohn (Eds) Microscopic Anatomy of Invertebrates Vol 6B(pp 719ndash781) New York Wiley-Liss Inc

Shimodaira H amp Hasegawa M (1999) Multiple comparisonsof log-likelihoods with applications in phylogenetic inferenceMolecular Biology and Evolution 16 1114ndash1116

Simroth H (1894) Dr H G Bronnrsquos Klassen und Ordnungen desThier-Reichs wissenschaftlich dargestellt in Wort und Bild DritterBand Mollusca (Weichthiere) Abteilung I Amphineura ScaphopodaLeipzig C F Winterrsquosche-Verlagshandlung

Sorenson M D (1996) Tree-Rot Ann Arbor University of MichiganStarobogatov Y I (1974) Xenoconchias and their bearing on the

phylogeny and systematics of some molluscan classes Paleontolog-ical Journal of the American Geological Institute 8 1ndash13

Steiner G (1991) Observations on the anatomy of the scaphopodmantle and the description of a new family the FustiariidaeAmerican Malacological Bulletin 9 1ndash20

Steiner G (1992) Phylogeny and classification of ScaphopodaJournal of Molluscan Studies 58 385ndash400

Steiner G (1996) Suprageneric phylogeny in Scaphopoda InJ Taylor (Ed) Origin and Evolutionary Radiation of the Mollusca(pp 329ndash335) Oxford Oxford University Press 29ndash52

Steiner G (1998) Phylogeny of Scaphopoda (Mollusca) in the lightof new anatomical data on the Gadilinidae and some Problemat-ica and a reply to Reynolds Zoologica Scripta 27 73ndash82

Steiner G (1999a) A new genus and species of the family Anuliden-taliidae (Scaphopoda Dentaliida) and its systematic implicationsJournal of Molluscan Studies 65 151ndash161

Steiner G (1999b) Point counter point What can 18S rDNA dofor bivalve phylogeny Response Journal of Molecular Evolution48 258ndash261

Steiner G amp Hammer S (2000) Molecular phylogeny of Bivalvia(Mollusca) inferred from 18S rD N A sequences with particularreference to the Pteriomorphia In E M Harper J D Taylor ampJ A Crame (Eds) The Evolutionary Biology of the Bivalvia (pp 11ndash29) London Geological Society of London Special Publications77

Steiner G amp Kabat A R (2001) Catalogue of supraspecific taxa ofScaphopoda (Mollusca) Zoosystema 23 433ndash460

Steiner G amp Kabat A R (200x) Catalogue of species-groupnames of Recent and fossil Scaphopoda (Mollusca) Zoosystema (inpress)

Steiner G amp Muumlller M (1996) What can 18S rDNA do for bivalvephylogeny Journal of Molecular Evolution 43 58ndash70



Strimmer K S amp Haeseler A (1997) Likelihood-mapping asimple method to visualize phylogenetic content of a sequencealignment Proceedings of the National Academy of Sciences USA 946815ndash6819

Swofford D L (1998) PAUP Phylogenetic Analysis Using Parsi-mony (and Other Methods) Version 4 Sunderland MA SinauerAssociates

Thompson J D Gibson T J Plewniak F Jeanmougin F ampHiggins D G (1997) The ClustalX windows interface flexiblestrategies for multiple sequence alignment aided by qualityanalysis tools Nucleic Acids Research 24 4876ndash4882

Wagner P J (1997) Patterns of morphological diversificationamong the Rostroconchia Palaeobiology 23 115ndash150

Waller T R (1998) Origin of the molluscan class Bivalvia and aphylogeny of major groups In P A Johnston amp J W Haggart(Eds) Bivalves an Eon of Evolution mdash Paleobiological Studies Honor-ing Norman D Newell (pp 1ndash47) Calgary University of CalgaryPress

White T J T Bruns S amp Lee amp Taylor J W (1990) Amplifica-tion and direct sequencing of fungal ribosomal RNA genes forphylogenetics In M A Innis D H Gelfand J J Sninsky ampT J White (Eds) PCR Protocols a Guide to Methods and Applications(pp 315ndash322) New York Academic Press

Winnepenninckx B Backeljau T amp De Wachter R (1993a)Extraction of high molecular weight DNA from molluscs Trendsin Genetics 9 407

Winnepenninckx B Backeljau T amp De Wachter R (1993b)Complete small ribosomal subunit RNA sequence of the chiton

Acanthopleura japonica (Lischke 1873) (Mollusca Polyplacophora)Nucleic Acids Research 21 1670

Winnepenninckx B Backeljau T amp De Wachter R (1996) Inves-tigation of molluscan phylogeny on the basis of 18s rRNAsequences Molecular Biology and Evolution 13 1306ndash1317

Winnepenninckx B Steiner G Backeljau T amp De Wachter R(1998) Details of gastropod phylogeny inferred from 18S rDNAsequences Molecular Phylogenetics and Evolution 9 55ndash63

Wray C G Jacobs D K Kostriken R Vogler A P Baker R ampDeSalle R (1995) Homologues of the engrailed gene from fivemolluscan classes FEBS Letters 365 71ndash74

Wuyts J Van de Peer Y Winkelmans T amp De Wachter R(2002) The European database on small subunit ribosomal RNANucleic Acids Research 30 183ndash185

Yochelson E L (1978) An alternative approach to the interpretationof the phylogeny of ancient molluscs Malacologia 17 165ndash191

Yochelson E L (1979) Early radiation of Mollusca and mollusc-like groups In M R House (Ed) The Origin of Major InvertebrateGroups Vol 12 (pp 323ndash358) New York Academic Press

Yochelson E L (1999) Rejection of Carboniferous QuasidentaliumShimansky 1974 from the phylum Mollusca Journal of Paleonto-logy 73 63ndash65

Yochelson E L Flower R H amp Webers G F (1973) The bearingof the new Late Cambrian monoplacophoran genus Knightoconusupon the origin of the Cephalopoda Lethaia 6 (3) 275ndash309

Yochelson E L amp Goodison R (1999) Devonian Dentaliummartini Whitfield 1882 is not a mollusk but a worm Journal ofPaleontology 73 634ndash640



Engeser amp Riedel 1996 Ponder amp Lindberg 1997 Reynoldsamp Okusu 1999 Salvini-Plawen 1980 1990 Salvini-Plawen ampSteiner 1996 Wagner 1997) although Steiner (1992 1996)pointed out discrepancies in the development of body axesbetween Rostroconchia and Scaphopoda

Connecting Scaphopoda to the GastropodandashCephalopodaline has a similarly long tradition A close relationship ofScaphopoda and Gastropoda based on the similarities ofbranched head tentacles prominent dorsoventral body axesand the occurrence of shell slits was proposed by Plate (1892)and Simroth (1894) (Fig 1D) The common derivation ofScaphopoda and Cephalopoda was favoured by Grobben(1886) using similar arguments These hypotheses haverecently gained new support Waller (1998) elaborated onand modified the helcionellid concept of Peel (1991) byderiving the ScaphopodandashCephalopoda line from helcionel-lid monoplacophorans as the sister-group of Gastropoda Ina recent cladistic analysis of morphological data Haszprunar(2000) proposed Scaphopoda as the sister taxon of Gastrop-oda and Cephalopoda (Fig 1C) The alternative to identify-ing any of the extant classes of Conchifera as sister-groupsand deriving Scaphopoda directly from an unknown inde-pendent lsquomonoplacophoranrsquo stock was suggested by Edlinger(1991) while Starobogatov (1974) and Chistikov (1979)identified the palaeozoic Xenoconchia as the closest relativesof Scaphopoda Yochelson (1978 1979) even considered thederivation of an un-shelled ancestor

This variety of competing phylogenetic hypotheses ispartly due to the lack of information provided by the fossilrecord Scaphopoda are the latest to appear in the fossil

record among all conchiferan classes and there are no obvi-ous transitional forms connecting them to other molluscsThe oldest scaphopod reported is the Ordovician Rhytioden-talium kentuckyesnis Pojeta amp Runnegar 1979 although itsscaphopod nature has been questioned by Engeser amp Riedel(1996) as has that of several Devonian and Carboniferousscaphopods (Yochelson 1999 Yochelson amp Goodison 1999Palmer 2001)

It is evident from the competing hypotheses that wehave to deal with convergent morphologies in several organsystems The pivotal characters involved (discussed inHaszprunar 2000 Reynolds amp Okusu 1999 Steiner 1992 19981999a Waller 1998) are listed in Table 1 Depending on thetopology of the conchiferan phylogenetic tree at least one ofthe sets of similarities must have arisen convergently If theDiasomandashCyrtosomaLoboconchandashVisceroconcha conceptis favoured elongation of the dorsoventral body axis (mul-tiple) cephalic tentacles and the ring-shaped attachment ofthe dorsoventral body muscles (Mutvei 1964 Yochelson et al1973) must have evolved convergently in Scaphopoda and theCyrtosomaVisceroconcha If however the lsquohelicionellidrsquoconcept is assumed the lsquoventralrsquo mantleshell extension withsimilar innervation of the anterior mantle regions epiatroidnervous system with fully concentrated pedal ganglia andburrowing foot evolved convergently in the Scaphopodaand Bivalvia When faced with a tie like that a morphology-independent dataset such as that provided by DNA sequencesmay help in addressing this question

The relationships of the higher taxa within Scaphopodaare only partly resolved Cladistic analysis of morphological

Fig 1 AndashD Competing hypotheses on thephylogeny of extant conchiferan classes testedin this study mdashA DiasomandashCyrtosoma (afterPojeta amp Runnegar 1976) or LoboconchandashVisceroconcha (Salvini-Plawen 1980 1990)with fossil Rostroconchia as stemgroup ofScaphopoda and Bivalvia mdashB Helcionellidconcept (Waller 1998) with fossil Helcione-llida as stemgroup of Scaphopoda and Cephalo-poda ScaphopodandashCephalopoda clade alsoaccording to Grobben (1886) mdashC ModifiedVisceroconcha concept (Haszprunar 2000)mdashD ScaphopodandashGastropoda clade accordingto Plate (1892) and Simroth (1894)





























































Table 2 continued




















Species Length

E23_1 E23_2 to E23_5























































































































































































Table 2 continued




















Species Length

E23_1 E23_2 to E23_5











































































































































































Table 2 continued




















Species Length

E23_1 E23_2 to E23_5




















































































































































Table 2 continued




















Species Length

E23_1 E23_2 to E23_5














































































































































Species Length

E23_1 E23_2 to E23_5

































































































































Species Length

E23_1 E23_2 to E23_5











































































































































































































































































































































































































































































































































































































































































































































Documents

Steiner, 2002