THE CONODONTA G- lesources,and Morphology,Taxonomy, Paleoecology, andEvolutionary History of a Long-ExtinctAnimal Phylum 3 azI High-pressure WALTERC.SWEEL EE: TheOhio State University fIt;:t F by the -i-:ztlog' fr, :.1 a olution- b.-;:n- New York . Oxford CLARENDON PRESS. OXFORD . 1988 PREFACE Conodonts are common fossils.Almost anyone portant group, I ofer my account of the who dealson a regularbasis with Paleozoicand Conodonta. Triassic marine rocks has probably seena few For their "witting" or unwitting contribu- of them. Through the last 30 yedrs conodonts tions to what I believe I know about the fasci- have come to be of exceptionalvalue in bio- nating gtoup of extinct animals described on stratigraphy, and they now have pride of place the following pages,I am gateful to a long list as index fossils in many parts of the geologic of my students and faculty colleaguesat The column. But conodonts are extinct and are un- Ohio StateUniversity, especiallyStig M. Bergs- knowo to most neontologists. The sketchiness trijm, and to members of the Pander Society, ofinformation about them in most texts on in- an intemational group of exceptionally good- vertebrate paleontology may result either fiom natured "conodontologists"that has met fre- the fact that they are microfossils that haye quently and infomally thougl the last 20 only lately come to be important as strati- years to share infomation about conodonts, graphic tools, or from the fact that nothing argueconclusions, and correct the misappre- quite like them exists today, so their zoologic hensionsof its seniormembers. relations axeuncertain. Karen Tyler, faculty illustrator at The Ohio In this monograph, I provide a summary of State University, drafted nea y all the figures information about a group with which I have from my very crude copy and assistedwith la- worked all my adult life. Charts that name con- beling others. Dr. Jerzy Dzik, of the Polish odont-based biozones and show stratigraphic Acaderny of Sciences, Warszawa, provided rangeofselected conodont speciesare included about half the stippled drawings of conodonts as Appendix B. However, I have purposely that gace various figuresin Chapter 5- The an- avoided a recap of conodont biostratigtaphy istry of tlrese two good friends is plainly evi- becauseit is constantly changing and cunent dent in their work and is warmlY views are readily available in various other acknowledged. places.Instead, I focus here on the conodonts I am also grateful to Sue Shipley and David as a group of extinct animals, about which it is Little, of The Ohio State University, for their important to know as much as possible be- help in completing various parts of the manu- fore assessing their distribution biostrati- script and illustrations, and to Mark Klefner, graphically. who graciously cornpiled information on the Of course, one takes considerablerisk in at- ranges of Silurian conodonts and assembled tempting such a summary, particularly of a the Silurian chart in Appendix B. The Depart- group of animals known only from its fossil re- ment of Geology and Mineralology generously cord, becausemost of what I think I know assumedmuch of the expenseof drafting and about conodontsas animals is either conjecture photogaphy. or a highly personalinterpretation ofa still-irn- perfect fossil record. So, with the caveal that Columbus, Ohio w.c.s. whal followsis only one way of viewingan im- February 1988 CONTENTS l. Inhoduction l.l History ofdiscovery and study 3 1.2 Achievements 7 1.3 Pending problems 8 2. Skeletal anatomy 11 2.1 Composition of conodont elements ll 2.2 Structure of skeletalelements t2 2.3 Shapesof element crowns t4 2.3.1 Coniform crowns l5 2.3.2 Ramiform crowns t6 2.3.3 Rastratecrowns l8 2.3.4 Pectiniformcrowns t9 2.4 Symmetry- and curvature-transitionseries 22 2.5 Skeletalapparatuses 2.6 Symmetry of elements,element pairs, and apparatuses 25 J. Whole-animal anatomy 28 3.1 The Scottish Carboniferousspecimens 28 3.2 The Waukeshaspecimen 3Z 3.3 Histology of demineralizedtissues 33 3.4 Summary JJ 4. Taxonomy 35 4.1 Form taxonomy J) 4.2 Multielementtaxonomy 36 4.2.1 Multielementmethodology 4-3 Multielement classifications 4l 4.4 A revised multielement classification 41 5. The major conodontgroups 45 5.1 Introduction 45 5.2 Cavidonti and Conodonti 45 5.3 The Proconodontida (Cavidonti) and its families (Fig. 5.1) 45 5.4 The Belodellida and its families (Fig. 5.1) 49 5.5 OrderProtopanderodontida, new 5l 5.5.1 Family ProtopanderodontidaeLindstrtim, 1970 52 5.5.2 Family ClavohamulidaeLindstrdm, 1970 53 5.5.3 Family AcanthodontidaeLindstritm, 1970 54 5.5.4 Family DrepanoistodontidaeFihraeus and Nowlan, 1978 54 t vtl III eIc,(Ju?rrr^opro ele-I pue opprw z.€.9 B €€l II pue I selci(c I'9 9 B €[l selc,brsplo-puoces t.g ) r'8 ztr selc^crurel-?uo'I Z'2 9 t ztr uroll?dIpre^O lZ'9 I 0€r surened./hrsJe^r( Z'g I 6ZI uorpnporlul I'9 ) €'8 s z'8 6Zl suraDEd.tftuopnlo^fi v r'8 'lqeN pu? uosuerge"p4uopoeloJ qal oql '8 tzr ??6I I.0l.s tzr u,l^Irrrrs{ ou)lun JspJO 0I'S zzl 196l 'sapoqupue u4snv a?pqleuaolse^flurq €1.6.s 'sepoqupu? u48nv e"pqleuEsn^?Jr{lrureJ L 0zl I86I zl.6.s 'reulu e"pqleuEolee^\s,{Iulec L Ltl 9g6l I I.6's SII 'IJelJ eap4uopoqpuftqruvi(Iu"c {. 9'L 7,L61 01.6.s €II 'quoiasauuloHpu? srxeH eeprluopoql"u8orpl L e€6I 6.6's III snqQuSpSoApue DaUqroT^lrtued g'6 L S ll\au.eep4uopoqleuc dlrued L 60r L.6.s 'sepoqupu? urlsnv eepqleuSolcrla L 90r Ig6I 9.6.9 ,reu.e?prdelolerul?d^lluleg^lrued I SL z0l 5.6.5 .relssegesprqlsuai(lod flruleg L 66 sz6l ,.6.s 'redooJeup4uopornBdsoreld ]{lrurEJ L 86 LL6l E 6.s Ltt 'reddelxeeprTlele{co) {[u]BJ L Ig6I 2.6.5 s ?'r 06 6S6l 'sseHe"p4uopoqleu8oqteds I.6.s 68 'Irzq ?prurpolrBzo^IruBJ eqJ L 916l 6's L8 'uro.4spurla?prTlelopuoc /(Iuleg L 016I s.g.s g tL s8 zL6l'TrelJeuprruoslllg/([rrrEg t.g.s .ur-o.4spur.Ie"pr-rlleuEorlceg I zL €8 016l r{lrureJ €.9.s I8 :relssege"puporuogd /{lrluec q IL 9Z6l z.g.s OL tt6l 'Iqew pue uosu?rge?prqleutorqc {IIu"c I.g's FOslEd '' 8L ,{\ou'eprurporuoFd aql g s 9L 016I'ruo4spur-IsBprluopouod,(lruJel zI. L's SL 016I 'urgrtspur.I*pqtsuEoprdrqu ll' L.s s 8'9 NL 6S6l 'ss?Hosprluoporuo!^J ,tllru?{^lrru?d 0I.L.s 9 ct ,r\eu'eeprurpopald ,qFued 6'L'g 9 ZL tg6l 'slrrsH e"p4uopolsro4lnll g.t.s rruorlstrege"pql"utoceld^lod^llure{ x L9 IL Ig6l ^Irue{ L.L-9 9 69 ts6l 'rellnn pu? relml I e?pnuopoucl.,(Iuleg g L.s 9 /o Ig6I 'redd"Dl eepquopouolsr(IJ{lruleg S-L-S 9 s9 1l\eu'eepqlepoucl/(IIuIug v'L's f. 9'9 t9 6S6l 'sseHe"pqleuEopg ,{IurBJ E L.s rI s'9 z9 9z6l 'r3lss?ge?pquoporuoud {lrrrrBJ z.L's a v9 09 016l 'ur-o.4spur.Ie"puuopolsro lL.s 9 6S 9L6I'I:IZ(, sprluoporuoud^lruru eqJ ,'s r 9 9S 0t6I'rrrojtspur.I e?prluopolepued^lrruBJ I.9.S v 9 ss spquoporepuedeql 9'9 hl SJNAINOC IITA L \,,, CONTENTS lx 55 6.3.3 Siluriancycles r34 fb 6.3.4 Devonian and Carboniferouscycles 135 59 6.3.5 Permian and Triassic cycles r37 60 6.4 Extinction 138 62 6.5 Iterativeevolutionarypatterns 140 63 6.6 Evolutionary trends t42 65 6.6.1 Apparatuselaboration t42 67 6.6.2 Apparatusreduction 143 69 6.6.3 Elaboration of elementsin P positions 144 7l 6.7 Developmentalslralegies 145 72 6.7.1 Recapitulation 145 6.7.2 Paedomorphosrs t46 74 6.8 Summary t46 75 76 78 7. Paleoecologyand paleobiogeography 149 79 8l 7.1 Introduction 149 83 7.2 Mode of life, or habit, of conodonts 149 7.3 Ecologicmodels 6) 150 87 1.3.1 Thedepth-stratificationmodel l5l 89 1.3.2 The lateral-segegationmodel 152 90 7.4 Selectedstudies of conodont ecology 152 9'7 7.4.1 Ordovician paleoecologyof Cincinnati Region t52 98 7.4.2 Mississippianpaleoecology, western United States 157 99 7.4.3 Paleoecologyof Pennsylvanianconodonts 160 t02 7.5 Ecologicgeneralizations 164 r06 7.5.1 Depth as a factor 165 109 7.5.2 Ternperutureas a factor 165 tlt 7.5.3 Nearshoreand ofshore faunas 165 7.5.4 Phyletic changesin ecologicaldistribution l_ - ::l 113 t66 115 7.6 Paleobiogeography 166 |7 7.6.1 Late Cambrian and Ordovician paleobiogeography t67 t20 7.6.2 l-ater Paleozoicand Triassic paleobiogeography 167 122 123 8, The phylum Conodonta 170 t23 8.1 A personalbias 170 t29 8.2 Summary of conodont characters 170 8.3 Conodonts as invertebrates t7l r29 8.3.1 Arthropod and annelid connections t7l r30 8.3.2 Molluscanconnections 172 132 8.3.3 Connectionswith other invertebrates 173 132 8.4 Conodonts as chordates 175 133 8.4.1 The opinions of Pander 175 133 8.4.2 Newberry, Hinde, Huxley and Myxine r75 t34 8.4.3 Macfarlane and the nemertineanconnection 176 s07 XAPUI 68r sueqc e?uerrrqder8uats g xrpuaddv s8l etuopouoJ eql Jo uo4?cgrsselctuputuns v v xpuoddv z8l ro^ug..I g.g I8I seuru{geol?pJoqc ?urlecrpur sernlee3 Jo fu?ruruns 6.t.g 6LI auxftl,tJ1o snteredd?pnAuq eqJ g.r.g suourceds LLI snolgJruoqJ?Jqsr ors eqlJo suorlelsrfualuy 4.7.g LLI slualuoleJo qyro:8 pue uoqrsodruoJ 9.t.9 9LI IBllaletu ,{uoq pseq Jo uorl"laJfuelur pue fus^ocsrq S.r'g 9LI relsssgpu? qslrlnJoJerTeq eqL n.v.g troJ eqJ SJ-NETNOi) The Conodonta 176 t76 t77 t77 t79 181 t82 185 189 lu) sr Jl ? -ro j I SUOIlqer ,i(qroN h or e,ia ',(e^rnslmrEoloaC srourlll ,{q peqsruJnJ,tlpuDl se^ntsod -EIp Jolo3 uro+ apeIII quud 'snpoqwug ^oupoU P SJTUEe_I elrq^\ pue \Jelg Jo seroads_ed^lpel?u8rsap ,{lluacor s?^{ rr qcrgA '(,(punou) snpaultrq snpoqpug slueseJderpue eueluol uI $lcoJ snoJeJruoqffCrando-I t FxuJs .srourll I , il sruoq uro{ sr e8elqueswurouog ur $IcoJ(u"unossrl I) ueru?Al^suusdruo{ ,(sepoql{)snrld,t mqpuSo .gtx ,slueuale |$O-XJ Jq us Jo ed,tloloqsr dol tp atelqruassv luopouocJosaEelqruesie prnlep F suopo r {qr uI 'tuJsard + m uJrq F J{OZOel lfuL\los le lxxroJ Jql q leql lnq cfed srql D :{IO lsEAI lE-fueduroJ slrsso_I qer naql :qr:roru b ;mssed ?rI _to fg G rGololq hs Eruoq |D 'ulued r|e F:ujeal ppol-t ou1 r -iqdB-6'u Fdar rsot! &1u.uo5 x sdno-6 IP|:-j llJto lEseq lual lsqf, ale.$ t D Jrqde6 3122\ $.el e lEi sFsso_I FB PaESU lsso_loDlur lla-rur luJn FisE lsour P IJOJ Juu r ls.n! 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