Life Sciences Contributions Royal Ontario Museum 1 26 Upper Cambrian to Lower Ordovician Conodont Biostratigraphy and Biofacies, Rabbitkettle Formation, District of Mackenzie Ed Landing Rolf Ludvigsen Peter H. von Bitter M ROYAL ONTARIO MUSEUM LIFE SCIENCES PUBLICATIONS INSTRUCTIONS TO AUTHORS Authors are to prepare their manuscripts carefully according to the following instructions. Failure to do so will result in the manuscript’s being returned to the author for revision. All manuscripts are considered on the understanding that if accepted they will not be offered for publication elsewhere. is GENERAL Papers for publication are accepted from ROM staff members, Research Associates, or from researchers reporting on work done with ROM collections. In exceptional cases,monographic works on the flora and/or fauna of Ontario will be considered for publication by authors not affiliated with the ROM. 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LIFE SCIENCES CONTRIBUTIONS ROYAL ONTARIO MUSEUM NUMBER 126 Sse Upper Cambrian to ROLF LUDVIGSEN ane PETER H. von BITTER) Lower Ordovician Conodont Biostratigraphy and Biofacies, Rabbitkettle Formation, District of Mackenzie ROM ROYAL ONTARIO MUSEUM PUBLICATIONS IN LIFE SCIENCES The Royal Ontario Museum publishes three series in the Life Sciences: LIFE SCIENCES CONTRIBUTIONS, a numbered series of original scientific publications including monographic works. LIFE SCIENCES OCCASIONAL PAPERS, a numbered series of original scientific publications, primarily short and usually of taxonomic significance. LIFE SCIENCES MISCELLANEOUS PUBLICATIONS, an unnumbered series of publications of varied subject mat- ter and format. All manuscripts considered for publication are subject to the scrutiny and editorial policies of the Life Sciences Editorial Board, and to review by persons outside the Museum staff who are authorities in the particular field involved. LIFE SCIENCES EDITORIAL BOARD Senior Editor: J. H. MCANDREWS Editor: R. D. JAMES Editor: C. MCGOWAN ED LANDING was a post-doctoral fellow of the Department of Earth Sciences, University of Waterloo, Wa- terloo, Ontario, and is with the United States Geological Survey, Paleontology and Stratigraphy Branch, Mail Stop 919, Denver Federal Center, Denver, Colorado 80225, USA. ROLF LUDVIGSEN is Associate Professor in the Department of Geology, University of Toronto, and Research Associate, Department of Invertebrate Palaeontology, Royal Ontario Museum. PETER H. von BITTER is Associate Curator-in-charge in the Department of Invertebrate Palaeontology, Royal Ontario Museum, and Associate Professor, Department of Geology, University of Toronto. Canadian Cataloguing in Publication Data Landing, Ed. Upper Cambrian to Lower Ordovician conodont biostratigraphy and biofacies, Rabbit- kettle Formation, District of Mackenzie (Life sciences contributions; no. 126 ISSN 0384-8159) Bibliography: p. ISBN 0-88854-265-8 pa. 1. Conodonts. 2. Paleontology—Cambrian. 3. Paleontology—Ordovician. 4. Paleon- tology—Northwest Territories—Mackenzie. I. Ludvigsen, Rolf, 1944- II. Von Bitter, Peter H., 1942- III. Royal Ontario Museum. IV. Title V. Series. QE899.L36 562’ .2’097193 C80-094632-4 Publication date: 10 October 1980 ISBN 0-88854-265-8 ISSN 0384-8159 © The Royal Ontario Museum, 1980 100 Queen’s Park, Toronto, Canada M5S 2C6 PRINTED AND BOUND IN CANADA BY DEYELL Upper Cambrian to Lower Ordovician Conodont Biostratigraphy and Biofacies, Rabbitkettle Formation, District of Mackenzie Abstract Conodonts have been recovered from two sections through the Cam- brian-Ordovician boundary beds of the upper Rabbitkettle Formation, near the headwaters of the Broken Skull River, western Mackenzie Mountains. The two sections are separated by a thrust fault. The se- quence of trilobite faunas from the low-energy outer shelf facies of the Rabbitkettle is equivalent to the Saukiella junia through Symphysurina brevispicata subzones from the inner carbonate platform in Oklahoma and Texas. Significant differences in trilobite faunas between the Mackenzie Mountains and United States sequences represent contrast- ing biofacies developments. Similarly, the sparse and low diversity conodont faunas of the Rabbitkettle resemble coeval Appalachian con- tinental slope and outer shelf faunas rather than those reported from the inner carbonate platform in Texas and Utah. The Proconodontus and Cordylodus oklahomensis (new name) zones can be recognized in the Rabbitkettle but cannot be divided into the subzones established in Utah. These data suggest that lithofacies associations and biofacies de- velopments in conodont distribution may prohibit detailed conodont- based correlations of Cambrian-Ordovician boundary beds. Introduction Uppermost Cambrian and lowest Ordovician conodonts are known from sections in the western United States (Miller, 1969, 1970, 1975, 1977, 1978; Kurtz, 1976), Al- berta (Derby et al., 1972), Iran (Miiller, 1973), and Australia (Druce and Jones, 1971). The similarities of conodont faunal sequences in these widely separated areas have been interpreted to reflect a lack of or weak development of conodont biofacies or provincialism in Cambrian-Ordovician boundary beds (Barnes et al., 1973). Land- l ing et al. (1978) suggested that conodont faunas bridge the biofacies differences shown by trilobites. Consequently, conodonts have received considerable discussion in intercontinental correlation of Cambrian-Ordovician boundary beds (Jones et al., 1971; Miller, 1977, 1978: Landing et al., 1978). Available lithologic information indicates that the North American, Iranian, and Australian conodont successions listed above were derived from intertidal or very shallow sublittoral, inner carbonate platform sequences. Similarities of the faunal successions may reflect the appearance of comparable conodont assemblages (‘‘com- munities’’) in similar but geographically separated environments. Based on studies of continental slope deposits in the northern Appalachians, Land- ing (1978, 1979) proposed that major conodont biofacies differences existed during the uppermost Cambrian and lowest Ordovician. Faunas from inner carbonate plat- form sequences appear to differ from those in sequences deposited in environments with unrestricted access to the open ocean. The upper Rabbitkettle Formation in the western Mackenzie Mountains (Fig. 1) has lithologic and faunal features representative of an open shelf facies. 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DD. | WA > D. | > Ds | DD. | DD. > D. | DD. | »D.| > D.| > D. | WA (z ‘BIg 99S) YY UONDIIS Jo [JEM SuIsueYy ay} WoIy Sajdures Ul sUEpUNQe JUOpOUOD = Z [GBI Table 3 Conodont abundance in productive composite samples from the foot and hanging walls of Section KK (see Fig. 2) KK* KK* KK* KK* 135-150 45-54 27-42 0-12 Cordylodus oklahomensis cordylodiform element | 2 cyrtoniodiform element l 3 “‘Oneotodus’’ nakamurai 1 ‘“‘Proconodontus’’ carinatus drepanodiform element scandodiform element 1 Proconodontus serratus s.f. | Protoconodont sp. indet. s/f. 2 Phosphannulus universalis ] one-half to 2 kg of each sample were dissolved in acetic acid to recover conodonts; the remainder was dissolved in hydrochloric acid in the search for silicified trilobites. The samples are identified by a letter/number combination (e.g., KK 50) indicating the distance in metres below top of the Rabbitkettle Formation. In addition, a suite of hand samples, identified in the form of KK* 0-12 to indicate the stratigraphic interval represented by these composite samples, was processed to recover conodonts. Examination of the sequence of silicified trilobites in Section KK led to the recog- nition that a 58 m interval in the upper Rabbitkettle Formation is repeated by a thrust fault which is located 102 m below the top of the formation (Fig. 2). The interval KK 44 to KK 102 of the hanging wall corresponds to the interval KK 102 to KK 160 of the foot wall of the thrust. The repeated interval includes the Cambrian-Ordovician boundary. The resulting composite Section KK (Fig. 3) shows the true stratigraphic thickness of the interval from KK 220 to the top of the Rabbitkettle to be about 160 m. In this paper, levels within the upper Rabbitkettle are cited as distances in metres below the top of the formation in the composite section. Previous Investigations Tipnis et al. (1979) outlined a conodont succession for Section K (Fig. 2). Biostrati- graphically nondiagnostic Upper Cambrian conodonts were recovered from samples K 270 and K 390 (249 m and 213 m below the top of the Rabbitkettle Formation). Proconodontus muelleri Miller s.f. (= sensu formo) in K 525 (172 m below top of Rabbitkettle) represents some portion of Miller’s (1975, 1977) Proconodontus Zone and suggests a possible early or middle Trempealeauan age. Similarly, their report of ‘‘Oneotodus’’ nakamurai Nogami, ‘‘O. cf. O. datsonensis’’ Druce and Jones and ‘*‘O. simplex’’ (Furnish) (here regarded as ‘‘O.’’ nakamurai), Oistodus cf. cambricus 7 COMPOSITE SECTION KK = BIOSTRATIGRAPHY 2 CONODONT TRILOBITE ‘ me 0. — Fauna B? 0 KK*0-12 KK20 o4 Symphysurina 20m brevispicata KK 25 0 Subzone © KK 33 40m Cordylodus KK 43 oklahomensis [ kk 106 e{Apoplanias Fauna Zone KK 109 ° (Undivided) 5 Rese od Missisquoia Ze 0 KK 113 0 depressa O 0 KK 116 © Subzone = © KK 119.5 © te o KK 56 = ° KK 124 ° KK 64 GE Parabolina O aS Fauna LL KK 133 © KK 75 KK 77 KK 141 © KK 143 © 80 m Bowmania © KK146 © americana Lu © KK 86.5 ° Fauna = KK 90 fre KK 156 © LU KK 96 wa _ 100 m aa KK 166 © ral < oO 0 KK177 0 Proconodontus KK 180 Zone (Undivided) 120m KK 189 © Yukonaspis kindlei Fauna "KK 201 140 m KK 208 © KK 211 KK 595 © a 160 m CONODONT TRILOBITE COLLECTIONS COLLECTIONS Figs 3 Composite Section KK showing restored stratigraphic position of samples from the foot and hanging walls of the thrust fault. Productive conodont and trilobite samples are indicated, as are the stratal limits for the conodont and trilobite biostratigraphic units that are discussed in the text. Miller s.f. and Proconodontus spp. s.f. in K 715 (112 m below top of Rabbitkettle) represents Miller’s (1975, 1978) Proconodontus notchpeakensis or Oistodus minutus subzones of the Proconodontus Zone. This fauna indicates an equivalency with the upper Saukiella junia or S. serotina subzones of the Saukia Zone in Utah (Miller, 1978). Cordylodus spp. s.f. in association with Missisquoia Zone trilobites from K 880 (57 m below top of Rabbitkettle) represents the lowest Ordovician portion of Miller’s (1975) Cordylodus proavus Zone. An illustrated drepanodiform element, Drepanodus cf. D. simplex Furnish s.f., with ‘‘Oneotodus’’ spp. from K 995 and unfigured platform elements from-K 1150 (60 m and 25 m below top of Rabbitkettle) were respectively referred to Ethington and Clark’s (1971) Fauna B (K 995) and the middle or upper Tremadocian (K 1150). The occurrence of North Atlantic lower Arenigian (K 1900), middle Arenigian (K 2020-K 2145), and upper Arenigian or Llanvirnian (K 2375) conodonts from the Road River Formation suggests that no significant unconformity is present above the Rabbitkettle Formation (Tipnis et al., 1979). Trilobite Sequence The lower 76 m of the composite section (KK 166 to KK 211 and K 510 to K 595 in the foot wall) is assigned to the Yukonaspis kindlei Fauna and is considered correla- tive to the Saukiella junia Subzone of Texas and Oklahoma. This correlation is based on the presence of Euptychaspis typicalis Ulrich, Triarthropsis limbata Rasetti, He- terocaryon tuberculatum Rasetti, Rhaptagnostus clarki (Kobayashi), and Calvinella cf. prethoparia Longacre as well as stratigraphic position below the superjacent bio- stratigraphic unit. This interval also includes species of Richardsonella (?), Eurekia, Tatonaspis, and a saukiid, as well as Yukonaspis kindlei. The next 22 m in the composite section (KK 141 to KK 156 in the foot wall and KK 75 to KK 156 in the hanging wall) is assigned to the Bowmania americana Fauna. Yukonaspis, Richardsonella (?), Idiomesus, Eurekia, Heterocaryon, Liostra- cinoides, Bowmania americana (Walcott), and two new genera also occur in this fauna. Overlying the Bowmania americana Fauna in the composite section is a 9 m inter- val assigned to the Parabolina Fauna (KK 124 to KK 133 in the foot wall and KK 64 in the hanging wall). This fauna includes Parabolina sp. nov., Richardsonella (?) cf. quadrispinosa Palmer, Bienvillia cf. corax (Billings), and ‘‘Leiobienvillia’’ leonensis Winston and Nicholls, in addition to species of Yukonaspis, Geragnostus, Idiomesus, Eurekia, and Plethometopus. A single specimen of Missisquoia occurs in KK 133. This fauna is correlated with the Corbinia apopsis Subzone of Texas and Okla- homa. A narrow stratigraphic interval above the Parabolina Fauna in the foot wall (KK 122.5 and KK 123) contains a low diversity assemblage of Missisquoia sp. nov., Parabolinella, Geragnostus, and Plethometopus. This is named the Missis- quoia sp. nov. Fauna. It is not certain whether this represents an older level than the base of the Missisquoia Zone in Oklahoma. The next 12 m of the composite section (KK 109 to KK 119.5 in the foot wall and 9 KK 48 to KK 56 in the hanging wall) is confidently assigned to the Missisquoia de- pressa Subzone. This interval is very fossiliferous and contains Parabolinella sp. nov., Parabolinella hecuba (Walcott), Missisquoia depressa Stitt, Ptychopleurites brevifrons (Kobayashi), Geragnostus, Levisaspis glabrus (Shaw), and Plethome- topus. Overlying the Missisquoia depressa Subzone in the composite section is an interval (KK 106 in the foot wall and KK 43 in the hanging wall) dominated by Parabolin- ella, Apoplanias, and Geragnostus. This is named the Apoplanias Fauna and is tenta- tively correlated with the Missisquoia typicalis Subzone of Oklahoma. The highest trilobite-bearing interval in the Rabbitkettle Formation is a narrow in- terval (KK 20 and KK 25 in the hanging wall) with Apoplanias, Symphysurina cf. brevispicata Hintze, and Geragnostus. These collections are correlated with the S. brevispicata Subzone of the Symphysurina Zone in Oklahoma. Considerable problems are encountered in correlating the trilobite succession in the upper Rabbitkettle Formation at Section KK with coeval successions in central Texas (Winston and Nicholls, 1967; Longacre, 1970) and the Arbuckle and Wichita Moun- tains of Oklahoma (Stitt, 1971, 1977). Saukiid trilobites, the prime biostratigraphic indices of the Trempealeauan zonation established in Texas by Winston and Nicholls (1976) and Longacre (1970), are uncommon in the Rabbitkettle Formation. Calvin- ella is the only well-represented member of this family in Section KK and it only occurs in a single collection. Other important genera of the latest Cambrian zonation in Texas and Oklahoma, such as Acheliops, Bayfieldia, Rasettia, Stenopilus, Theo- denisia, Briscoia, Keithiella, Bynumina, Bynumiella, and Corbinia have not been re- covered from the Rabbitkettle Formation. One of the few firm correlation tie-points between the Northwest Territories and Oklahoma (Fig. 4) is the 12 m thick Missisquoia depressa Subzone in the Rabbit- kettle which undoubtedly is correlative with the 6 m thick M. depressa Subzone in the Signal Mountain Limestone in Oklahoma (Stitt, 1977). The substantial difference in generic composition within this subzone suggests the influence of environmental factors. The M. depressa Subzone in Oklahoma is strongly dominated by Plethopeltis (about 85% of 260 specimens). This genus does not occur in Section KK where the subzone is dominated by Parabolinella (about 65% of 760 specimens). Geragnostus is also much more abundant in the M. depressa Subzone in Section KK than in Okla- homa. Each of the 14 trilobite collections from the base of the Missisquoia sp. nov. Fauna to the Symphysurina Zone at Section KK is dominated by olenid and agnostid trilo- bites. In addition, two olenids and one agnostid occur in the Parabolina Fauna. Thus, the upper part of Section KK is numerically dominated by trilobites characteristic of Slope and outer shelf facies in the Lower Palaeozoic (Lochman-Balk and Wilson, 1958; Fortey, 1975; Taylor, 1977; Ludvigsen, 1979a). The evidence for the lower part of Section KK is less clear, but it is not inconsistent with a similar outer shelf po- sition (Taylor, 1977:table 3). Section KK, therefore, records a sequence of trilobite faunas which, in comparison with coeval inner shelf sequences in Texas and Okla- homa, appears to represent an unrestricted open marine sequence deposited in an outer shelf setting. 10 QIdSVHOALd «CIYNOILSAH:;, SausSWOIE ‘BUIOYP|YO UI SauOzZqns puke souoZ d}IQO[IN JO sduanbas YM YY UOTDIS Je UOTBULIOJ aPWexIQqGey Joddn ay) Jo spoq Arepunoq UPIDIAOPIO-UPLIQUIeD oY) UT s}IUN dIYdeIZeNSOIg 9}1QO]IN puke S9UOZ JUOPOUOD Jo UOT}e[ALIOD p ‘3l4 (9 6Z6L) NASDIAGM YAdVd SIHL (2261) LLILS eubew eijjasey Bune /o/puly sidseuoyn, ejunf ejjalynes SN]UOPOUdIOlg euney euegwaewe ejuewMOg BUIJOIAS B//alyneS euney eul/ogeled sisdode ejuiquog euney ‘Aou ‘ds B/onbsissip QUOZqNS essa/dap ejonbsissiw siSuawoye)/yo snpojApsog essaidap elonbsissipy $1/20IdA] eionbsissipy S = 2 =. Q S S =. euney sejue/dody ejeoidsinasq eulinskydws -9uOzZgNS eB}Jea/dsinasq eulinsAydwhks esogjng eutnskydwhs eUlINS -Aydwiks AHdV¥DILVYeLSOIE SLIGOTNYL SANOZ LNOGONOO SANOZENS SSNOZ SNIVLNNOW AIZNAMOVAN VNOHV 1X0 NVIHENVO NVIDIAOQGHO 11 Depositional Setting Dark grey, thinly bedded, more-or-less silty lime mudstone and fossiliferous lime wackestone that regularly alternate with finely laminated, thinner calcareous silt- stones dominate the section. Thin oolitic and granule intraclastic lime wackestones and packstones appear in the Yukonaspis kindlei Fauna and the Bowmania americana Fauna. Bedding surfaces are typically planar with sedimentary boundinage appearing with the Parabolina Fauna and through higher strata. Bioturbation and light grey lime wackestones and mudstones are present only in the Bowmania americana Fauna in- terval. Trilobite remains observed on bedding surfaces and in etched residues are typ- ically disarticulated but are neither abraded nor severely broken. The regular alternations of fine-grained silty, dark limestones and thinner cal- careous siltstones with occasional well-sorted and winnowed allochem limestones suggest episodic deposition generally below effective wave base. The absence of fea- tures such as penecontemporaneously contorted and folded beds, slumps, mass movement deposits occupying channels, and carbonate flyschoid beds with erosional bases precludes deposition on or at the foot of a steep submarine slope. Such features appear in coeval fine-grained clastics of the Road River Formation in the Selwyn Basin to the northwest of Section K (Cecile, 1978). Similarly, a restricted marine, very shallow or intertidal, inner shelf depositional environment is not indicated because of the absence of fenestral fabric, flat pebbles, channels and scour and fill structures, early dolomitized lime mudstone, prominent bioturbation, algalaminates and stromatolites, wave or tidally produced sedimentary structures, evaporites, and light coloration (Roehl, 1967; Shinn, 1968; Wilson, 1970, 1974.Cook, 1972). The upper Rabbitkettle Formation of Section KK contains few lithologic features which can be assigned to a unique depositional environment. However, it is probable that these beds were deposited under low energy open shelf or very low angle muddy slope conditions. It is questionable whether Wilson’s (1969) association of the type of sedimentary boudinage present within the Lower Ordovician of Section KK with shallow subtidal shelf deposition below effective wave base is appropriate. The pres- ence of intercalated oolitic, intraclastic, and fossiliferous (trilobite and **pelmato- zoan’’) grainstones and packstones low in the sequence suggests that lime mud and silt deposition was punctuated by the transport of allochthonous carbonate debris by nonturbid bottom traction currents or nonturbid sand sheet flows. The source of this debris quite likely lay to the east in the area of platform deposition of the Broken Skull Formation. A two-fold division is apparent in the rocks of Section KK: 1) a lower sequence of planar bedded, medium to light grey and silty lime mudstones, wackestones, and grainstones, which locally are bioturbed, and 2) an upper sequence of wavy bedded, dark grey and silty lime mudstones which lack bioturbation. This lithologic division also coincides with a pronounced fanual division. The lower sequence (Yukonaspis kindlei Fauna and Bowmania americana Fauna) contains typical Saukia Zone trilo- bites and the upper sequence (Parabolina Fauna to Symphysurina brevispicata Sub- zone) is dominated by olenids, agnostids, and trilobites of probable extra-North American origin. The base of the Parabolina Fauna thus coincides with a significant environmental change and this level was interpreted by Ludvigsen (1979b) as a bio- mere boundary. 12 EEO EEE LD Conodont Sequence General Ten multi-element and form species are represented among the 202 specimens recov- ered from 23 of 45 samples. Conodont elements have a thermal colour alteration index of 4.5 to 5 (Epstein et al., 1977) and slightly corroded surfaces. The sparse, low diversity conodont faunas from Section KK can be compared with Miller’s (1975, 1977, 1978) conodont zonation of the western USA. Proconodontus Zone Conodonts from the upper Yukonaspis kindlei Fauna and Bowmania americana Fauna intervals of Section KK include multi-element ‘‘Proconodontus’’ carinatus Miller (= Proconodontus carinatus s.f. and P. notchpeakensis Miller s.f.), P. serratus Miller s.f., ‘‘Oneotodus’’ nakamurai Nogami, ‘‘Prooneotodus’’ tenuis (Muller), and Furnishina asymmetrica Muller. Miller (1978) has equated the upper Saukiella junia Subzone and lowest S. serotina Subzone with the Proconodontus notchpeakensis Subzone of the Proconodontus Zone. The first appearance of Oistodus minutus Miller s.f. in the lower S. serotina Subzone and its persistence to the top of that trilobite subzone defines the Oistodus minutus Subzone of the upper Proconodontus Zone. Oistodus minutus s.f. was not recovered in this study. Consequently, the faunally similar Proconodontus notchpeakensis and O. minutus subzones cannot be differen- tiated in Section KK. ‘“‘Oneotodus’’ nakamurai appears in the Bowmania americana Fauna in Section KK. The species has its lowest occurrence in the Corbinia apopsis Subzone in the western United States where it regularly appears along with the first Cordylodus form species (Miller, 1975, 1977, 1978; Kurtz, 1976). However, ‘‘O.’’ nakamurai occurs in rocks older than those bearing Cordylodus in the People’s Republic of China (No- gami, 1967), Alberta (Derby et al., 1972), Appalachian North America (Landing, 1977, 1979), Korea (Lee, 1975), and Australia (Druce and Jones, 1971). A single element representing Fryxellodontus? sp. nov. from the Bowmania ameri- cana Fauna is a possible Upper Cambrian representative of the genus. Fryxellodontus lineatus Miller and F.. inornatus Miller first appear at the base of the Lower Ordovi- cian Missisquoia typicalis Subzone in the western United States (Miller, 1977, 1978). Tipnis et al. (1979) report an anomalous occurrence of Clavohamulus cf. C. bul- bousus (Miller) from K 390 (213 m below the top of the Rabbitkettle). The species is known from the upper Missisquoia typicalis Subzone and lower Symphysurina Zone in the western USA (Miller, 1978). The occurrence of the species below the lowest studied trilobites in Section KK (Yukonaspis kindlei Fauna) suggests that the Clavo- hamulus lineage originated considerably before the Lower Ordovician. 13 Cordylodus oklahomensis Zone The disappearance of several conodont species and the appearance of Cordylodus proavus Millers.f., C. oklahomensis Muller s.f., ‘‘Oneotodus’’ nakamurai, and Hir- sutodontus at the base of the Corbinia apopsis Subzone define the base of Miller’s (1975, 1977, 1978) Cordylodus proavus Zone. Miller (1975, 1977, 1978) has di- vided the latest Cambrian through lowest Ordovician Cordylodus proavus Zone (= Corbinia apopsis Subzone— lower Symphysurina Zone) into five subzones. Cordylodus proavus s.f. is part of multi-element C. oklahomensis (see Systematic Palaeontology) and the designation “‘Cordylodus oklahomensis Zone’’ is here substi- tuted for ‘‘C. proavus Zone’’. Cordylodus oklahomensis Zone faunas from Section KK are sparse and of low di- versity. The eponymous species first appears in uppermost Cambrian strata equiva- lent to the Corbinia apopsis Subzone although the species was not recovered in this study from the base of the Parabolina Fauna. However, the Proconodontus and C. oklahomensis Zone faunas are not as strongly differentiated as they are in Texas, Utah, and Wyoming (Miller, 1975, 1977, 1978; Kurtz, 1976). As noted above, ““On- eotodus’’ nakamurai first appears in the Proconodontus Zone in the Rabbitkettle. In addition, Tipnis et al. (1979) note the co-occurrence of Proconodontus muelleri Miller s.f. with Cordylodus proavus s.f. and Missisquoia in K 880 (57 m below top of Rabbitkettle Formation). The persistence of P. muelleri into the Lower Ordovician contrasts with the species’ disappearance just below the Corbinia apopsis Subzone in the western USA (Miller, 1975, 1977, 1978; Kurtz, 1976). Proconodontus Zone spe- cies also persist into the local range zone of Cordylodus oklahomensis in Vermont (Landing, 1979). Miller’s subzonal sequence of the Cordylodus oklahomensis Zone is based on the range zones of species of Hirsutodontus, Clavohamulus , and Fryxellodontus. The ab- sence of these forms precludes division of the zone in Section KK. A single element of Fryxellodontus inornatus from KK 43 supports the tentative correlation of the Apo- planias Fauna with the Missisquoia typicalis Subzone. Miller (1978) documents the occurrence of F. inornatus through the Fryxellodontus inornatus and lower Clavo- hamulus subzones (middle Cordylodus oklahomensis Zone) and equates these with the Missisquoia typicalis Subzone. The youngest conodont collection (KK* 0-12) consists of one element of ‘‘Pro- conodontus’’ carinatus. This composite sample was collected above the highest trilo- bite collection (KK 20) and could represent either the upper Cordylodus oklaho- mensis Zone or Ethington and Clark’s (1971) Fauna B. This uncertain correlation is due to the absence of associated Cordylodus form species. Fauna B is recognized by the appearance of advanced form species of Cordylodus, including Cordylodus lind- stromi Druce and Jones, 1971, and C. intermedius Furnish, 1938 (Miller, 1975). However, 1) the recovery of C. intermedius from the Cordylodus oklahomensis Zone (Miller, 1978; Landing, 1979; this report), 2) the probability that ‘‘C. lindstromi’’ is an ontogenetic variant with supernumerary basal tips that appears in all Cordylodus elements (Landing, 1979), and 3) the persistence of upper Cordylodus oklahomensis Zone species into Fauna B (Miller, 1970; Landing, 1979) make the differentiation of Fauna B unclear at present. 14 RT ee Conodont Biofacies Although conodonts are sparsely represented in samples from Section KK, the faunal sequence has closer similarities with continental slope sequences from the Appala- chians (Landing, 1979) than with inner carbonate platform successions in the western USA (Miller, 1969, 1970, 1975, 1977, 1978; Kurtz, 1976). These differences are most obvious in the generic composition of the euconodont components (Bengtson, 1976) of Cordylodus oklahomensis Zone faunas. Multi-element ‘‘Proconodontus’’ carinatus and Cordylodus oklahomensis and mono-elemental ‘‘Oneotodus’’ nakamurai are dominant species both in continental slope and inner carbonate platform sequences. These three species are represented by 83 per cent of the elements from Miller’s (1978) Lava Dam Five section in the upper Notch Peak Limestone and lower House Limestone, western Utah. Species of Clavo- hamulus, Fryxellodontus, and Hirsutodontus, which are used for the subzonation of the Cordylodus oklahomensis Zone (Miller, 1975), are represented by 7 per cent of the elements at the Lava Dam Five section. Although elements of Clavohamulus, Fryxellodontus, and Hirsutodontus are relatively minor components of Cordylodus oklahomensis Zone faunas in shallow-water sequences, these components are absent or very sparingly represented in continental slope deposits in the Appalachians. Land- ing (1979) recovered only one element of Fryxellodontus lineatus from the Highgate and Gorge formations, northwestern Vermont. Similarly, representatives of the three genera have not been encountered in Cordylodus oklahomensis Zone faunas from the Green Point Group, western Newfoundland (E. Landing, unpublished data). Similar Cordylodus oklahomensis Zone faunas are present in the lower Grove Formation, at Lime Kiln, central Maryland (E. Landing, unpublished data) where the transition from the upper Frederick Limestone to the lower Grove Formation represents a pro- gradation of shallow shelf carbonates over fine-grained carbonates (Reinhardt, 1974). The lower Grove Formation at Lime Kiln consists of festoon bedded, oolite bar de- posits. This shelf margin sequence has yielded low diversity conodont faunas com- prised of Cordylodus, ‘‘Proconodontus’’ , and ‘‘Oneotodus’’ . The reasons for the absence or near absence of Clavohamulus, Fryxellodontus, and Hirsutodontus from the outermost shelf or slope environments listed above and from the Rabbitkettle Formation are unknown. Water depth and energy of the environment do not seem to be common factors which would limit their distribution. It is possible that representatives of the three genera were adapted to variable and/or elevated salin- ities and temperatures of the restricted marine conditions of the inner shelf and were environmentally stenotopic. Cordylodus species and the ancestral ‘“‘Proconodontus’’ carinatus and ‘‘Oneotodus’’ nakamurai are geographically widespread in terms of lithofacies associations and were presumably eurytopic. Biofacies developments in euconodont distributions in Proconodontus Zone faunas are obscure at present. Landing (1979) did not encounter Oistodus minutus Miller s.f. in upper Proconodontus Zone faunas in slope deposits in northwestern Vermont. The form was recovered in turbiditic limestones in the Taconic allochthon (Landing, 1977, 1979) although it is absent in the uppermost Cambrian in the Green Point Group, western Newfoundland (E. Landing, unpublished data). Similarly, deep shelf lithotopes of the uppermost Frederick Limestone, central Maryland, have not yielded the species. It is possible that O. minutus may be found to be more regularly asso- ciated with restricted, marine inner shelf deposits. 15 Discussion Reinvestigation of the lithologic and faunal sequences of Section KK demonstrates the stratigraphic repetition of the section by a thrust fault located 102 m below the top of the Rabbitkettle Formation. Tipnis et al. (1979) recovered lowest Ordovician con- odonts and trilobites at K 880 (Fig. 2). Conodonts from their sample K 995 higher in the section do not represent Ethington and Clark’s (1971) Fauna B and are referable to the preuppermost Cambrian Proconodontus Zone (Saukiella serotina Subzone equivalent). Similarly, the report of middle or upper Tremadocian “‘platform ele- ments’’ from K 1150 (30.4 m below top of Rabbitkettle) (Tipnis et al. 1979) cannot be evaluated because the specimens were not illustrated. However, conodonts recov- ered in this study from KK 33 and KK* 0-12 seem to represent the upper Cordylodus oklahomensis Zone or, possibly, Fauna B, and are of Lower Tremadocian aspect. As discussed above, the Rabbitkettle Formation at Section KK has no lithologic features indicating shallow, inner carbonate platform deposition. The deep, outer shelf or low angle slope depositional environment suggested above is supported by the composition of uppermost Cambrian and lowest Ordovician trilobite faunas. The absence of Clavohamulus and Hirsutodontus and poor representation of Fryx- ellodontus in Cordylodus oklahomensis Zone faunas from the Rabbitkettle Formation at Section KK are considered to be related to unrestricted marine conditions of depo- sition and have parallels in Appalachian outermost shelf and continental slope faunas. Although it is less clear, the absence of Oistodus minutus s.f. in the upper Procon- odontus Zone may also be related to the palaeogeographic setting of Section KK. Miller’s (1975, 1977, 1978) conodont-based subzonation of the uppermost Cam- brian through lowest Ordovician (Saukiella junia Subzone through lower Sym- physurina Zone) provides a biostratigraphic resolution comparable to that provided by trilobite faunas. However, the absence of key conodont species in Cambrian-Or- dovician boundary beds in outer shelf and slope deposits results in recognition only of the Proconodontus and Cordylodus oklahomensis zones and not faunas referable to conodont subzones. This biofacies control of conodonts has probable implications for conodont-based correlations of Cambrian-Ordovician (Olenidian-Tremadocian se- ries) boundary beds of the classic Acado-Baltic biofacies of the Cambrian and Ordo- vician systems. The deposition of the carbonate-poor Acado-Baltic sequences of this age in palaeogeographic settings that had unrestricted access to the open ocean (Ross, 1975) suggests that conodont species required for subzonation of the Proconodontus and Cordylodus oklahomensis zones may not be encountered here with enough regu- larity for precise correlations. Landing et al. (1978) recovered only Proconodontus carinatus s.f. and Cordylodus proavus s.f. in the uppermost Cambrian in the Acado- Baltic sequence on Navy Island, New Brunswick, and did not encounter the Hirsu- todontus species which appear in the lowest Cordylodus oklahomensis Zone in the western USA (see also Miller, 1977, 1978). 16 Systematic Palaeontology Remarks Conodont taxa are listed alphabetically. A suprageneric classification is not applied although the informal designations ‘‘protoconodont’’, ‘‘paraconodont’’, and ‘‘eucon- odont’’ (Bengtson, 1976) are used to summarize the growth modes of conodont ele- ments. Conodont form species are designated in sensu formo (s.f.) when the composi- tion of the apparatus is unknown. The presumed hyolithelminthoid Phosphannulus is listed at the end of the section. Repository Royal Ontario Museum, Toronto (ROM). Figured specimens are stored under ROM numbers 38361 to 38375. Topotype collections from the upper Rabbitkettle Forma- tion are reposited under ROM numbers 38401 to 38444. Phylum uncertain Class uncertain Order Conodontophorida Eichenberg, 1930 Genus Cordylodus Pander, 1856 Type Species Cordylodus angulatus Pander, 1856, s.f. from the Early Ordovician glauconitic sand- stones of Estonia. Emended Diagnosis Euconodonts represented by a bi-elemental apparatus consisting of a numerically pre- dominant cordylodiform element and a subordinate cyrtoniodiform element. Cusp and denticles are albid and the elements lack any surface microsculpture. Discussion Previous reconstructions of the Cordylodus apparatus (Bergstrom and Sweet, 1966; Sweet and Bergstrom, 1972; Barnes and Poplawski, 1973; Nowlan, 1976) are not fol- lowed in this report and J. F. Miller’s (pers. comm. to E. L., 1977) reconstruction is followed. The Cordylodus apparatus is bi-elemental and consists of an element with rounded denticles and cusp and a second element with laterally flattened, basally con- fluent denticles and cusp. The former, termed the ‘‘rounded element’’ by Miller, is here designated the ‘‘cordylodiform element’’ because this plan is shown by the type form species. The second element, Miller’s ‘‘flattened element’’, is termed the ‘‘cyr- toniodiform element’’ because its plan is similar enough to Cyrtoniodus Stauffer sf. that some authors (Miller, 1970; Ethington and Clark, 1971) have referred ‘* flattened elements’’ to that form genus. 17 Cordylodiform elements are generally more abundant in collections than cyrtonio- diform elements. The former are more variable in a large collection than associated cyrtoniodiform elements and show a more-or-less distinctive symmetry transition se- ries (see also Ethington and Clark, 1971 : 68, pl. 1, figs. 15, 16, 20). Cordylodiform elements designated in the literature as 1) Cordylodus proavus Muller s.f., 2) C. in- termedius Furnish s.f., and 3) ‘‘C. lindstromi’’ Druce and Jones s.f. are externally identical. They are separable, respectively, by 1) a convex anterior margin of the basal cavity, 2) a straight to concave anterior margin of the basal cavity, and 3) con- vex to concave anterior profile of the basal cavity and presence of secondary basal tips. The associated cyrtoniodiform elements are 1) C. oklahomensis Muller, s.f., 2) an unnamed element often misidentified as C. oklahomensis or C. prion Lindstrom s.f. and 3) an element included by Druce and Jones (1971) in the definition of “‘C. lindstromv’’ s.f. These cyrtoniodiform elements are distinguished by developments in the anterior profile of the basal cavity which parallel those in the cordylodiform ele- ment. ‘“‘Cordylodus lindstromi’’ elements are not considered to represent a biologic spe- cies. Druce and Jones (1971) illustrated a cyrtoniodiform holotype (pl. 1, figs. 9a, b, text-fig. 23h) and paratype cordylodiform (pl. 1, figs. 7a-8b, pl. 2, figs. 8a—c) ele- ments with secondary basal tips. One paratype (pl. 2, figs. 8a—c) has a convex an- terior margin of the basal cavity and is comparable to C. proavus s.f. with exception of a second basal tip. A second paratype (pl. 1, figs. 7a, b) has the straight anterior margin of the basal cavity which is present in early elements of C. intermedius. Druce and Jones’s (1971) holotype of “‘C. lindstromi’’ is otherwise comparable to the cyr- toniodiform element of Cordylodus intermedius. Miller (1970) illustrated in nomen nudum forms designated Cordylodus insertus sp. nov. s.f. and C. sp. aff. insertus sp. nov. s.f. These elements are closely similar to C. proavus s.f. and C. oklaho- mensis s.f., respectively, but have an additional basal tip. Accessory apices of the basal cavity are regarded in this report as not of signifi- cance in the classification of Cordylodus and are developmental variants. The an- terior profile of the basal cavity is considered to have primary significance in the clas- sification of Cordylodus elements. Although Miller (1975, 1977) has used the first appearance of ‘‘Cordylodus lindstromi’’ in defining Ethington and Clark’s Fauna B, he has illustrated aC. oklahomensis s.f. element from the underlying Cordylodus ok- lahomensis Zone with secondary apices of the basal cavity (Miller, 1969: pl. 65, fig. 53). Nowlan (1976) recovered ‘‘C. lindstromi’’ from sequences older than Fauna B. Advanced Cordylodus intermedius gave rise to multi-element C. angulatus Pander and C. rotundatus Pander of Fauna C. The latter apparatuses have apparently indis- tinguishable cyrtoniodiform elements referable to C. prion Lindstrom sf. (J. F. Miller, pers. comm. to E. L., 1977). The ‘‘phrygian cap’’ anterior profile of the basal cavity of C. angulatus s.f. and C. rotundatus s.f. is a more exaggerated condi- tion than that seen in the concave profile of C. intermedius s_f. Cordylodus is a characteristic latest Cambrian and Tremadocian genus in the North American, Australasian, Siberian, and Acado-Baltic faunal provinces (Muller, 1959, 1973; Miller, 1969; Druce and Jones, 1971; Abaimova and Markov, 1977; Landing, et al., 1978). Van Wamel (1974) reported the genus in the lower Arenigian of Swe- den. Dzik (1976) renamed a Llanvirnian and Llandeilian apparatus containing cordy- lodiform and ramiform elements Spinodus spinatus (Hadding). Cordylodus horridus 18 s.f. of Barnes and Poplawski (1973) from the uppermost Arenigian (Landing, 1976) seems to be part of an undescribed apparatus (R. L. Ethington, pers. comm. to E. L. 1978). The ancestor of the earliest appearing Cordylodus species, Cordylodus oklaho- mensis, appears to have been a middle Trempealeauan species consisting of Procon- odontus carinatus Miller s.f. and P. notchpeakensis Miller s_f. Cordylodus intermedius Furnish, 1938, s.f. Figs. 5E, 6A, B Cordylodus intermedius Furnish, 1938:338, pl. 42, fig. 31, text-fig. 2C. Cordylodus insertus Miller, 1970:88, 89 (nomen nudum) (pars, pl. 1, figs. 37, 38). Cordylodus cf. C. angulatus—Druce and Jones, 1971:67, text-fig. 23c. Cordylodus caseyi Druce and Jones, 1971:67, 68, pl. 2, figs. 9a—12c, text-figs. DOG, e. Cordylodus intermedius—Druce and Jones, 1971:68, pl. 3, figs. la—3b, text-figs. 23, 2. Cordylodus proavus—Druce and Jones, 1971:70, 71, (pars, pl. 1, figs. la, b, 3, 5a-6, text-figs. 23p, q, (non C. proavus Muller, 1959, s.f.). Cordylodus cf. C. proavus—Druce and Jones, 1971:71, (pars, pl. 1, figs. 10a—11b, non C. proavus Muller, 1959, s.f.). Cordylodus caseyi—Jones, 1971:46, pl. 2, figs. la-c. Cordylodus intermedius—Jones, 1971:46, pl. 2, figs. 2a—3c. Cordylodus lindstromi—Jones, 1971:47, pl. 2, figs. 4a-c. Cordylodus intermedius—Muller, 1973:30, pl. 10, figs. la—3, text-figs. 2c, 4a, b. Cordylodus lenzi Muller, 1973:31, pl. 10, figs. 5-9, text-figs. 2f, 5a, b. Cordylodus angulatus—Viira, 1974:63, (pars, pl. 1, fig. 8, text-figs. 4a, b, non C. angulatus Pander, 1856, s.f.). Cordylodus angulatus—van Wamel, 1974:58, 59, (pars, pl. 1, figs. 6, 7, non C. an- gulatus Pander, 1856, s.f.). Cordylodus intermedius—Repetski, 1975:44, 45, pl. 1, figs. 11, 12. Cordylodus intermedius—Nowlan, 1976:149, 150, pl. 2, figs. 1, 2. ?Cordylodus cf. C. intermedius—Tipnis et al., 1979:31, pl. 1, fig. 7. Cordylodus intermedius—Landing, 1979:62-64, 133-135, 200-201, pl. II-3, fig. 3, pl. IlI-1, fig. 8, pl. IV—2, fig. 6 (pars, citations listed are only those of C. inter- medius s.f.). Occurrence and Hypotype One element (ROM 38373) from KK 33. The associated conodont fauna represents the upper Cordylodus oklahomensis Zone. Remarks The shape of the basal cavity of Cordylodus intermedius s.f. is intermediate between those of C. proavus s.f. andC. angulatus s.f. as noted by Druce and Jones (1971) and 19 Fig. 5A, D Cordylodus oklahomensis Miller, cordylodiform, ROM 38372, 70, and cyrtoniodiform, ROM 38367, X75, elements, respectively. B Fryxellodontus? sp. nov. Lateral view of serrrated elements with attached pyrite crystals (di- agonal ruling), ROM 38366, X60. C,F ‘‘Proconodontus’’ carinatus Miller, drepanodiform, ROM 38365, 60, and scandodiform, ROM 38362, X150, element, respectively. E Cordylodus intermedius Furnish s.f., ROM38373, 140. G Protoconodont sp. indet. s.f., ROM 38375, X55. Muller (1973). The element (Fig. 6A) has rounded denticles and cusp and has a straight anterior profile of the basal cavity which differs from the convex profile pres- ent in cordylodiform elements of C. oklahomensis. The surface of the element has un- dergone slight dissolution and blocky crystallites are exposed on the surface (Fig. 6B). 20 Cordylodus oklahomensis Miller, 1959 Figs. 5A, D, 6C-E Cordylodiform Element Cordylodus proavus Muller, 1959:448, 449, pl. 15, figs. 11, 12, 18, text-fig. 3B. Cordylodus proavus—Miller, 1969:424-426, pl. 65, figs. 37-45, text-fig. 3D. Cordylodus insertus Miller, 1970:88, 89 (nomen nudum), (pars, pl. 1, fig. 37, text- fig. 11B). Cordylodus proavus—Miller, 1970:89, text-fig. 11D. Cordylodus lindstromi Druce and Jones, 1971:68, 69, pl. 2, figs. 8a—c (pars). Cordylodus proavus—Druce and Jones, 1971:70, 71 (pars, pl. 1, figs. 2a, b, 4a, b, text-fig. 23r). Cordylodus cf. C. proavus—Druce and Jones, 1971:71, (pars, pl. 1, figs. 12a, b, text-fig. 23s). Cordylodus proavus—Ethington and Clark, 1971:71, pl. 1, fig. 19. Cordylodus proavus—Jones, 1971:48, pl. 2, figs. 9a-c. Cordylodus proavus—Miller and Melby, 1971:120, pl. 1, figs. 18, 19. Cordylodus proavus—Miuller, 1973:35, pl. 9, figs. 14, 9, text-figs. 2a, 9a, b. Cordylodus angulatus—van Wamel, 1974:58, 59 (pars, pl. 1, fig. 5, non C. angu- latus Pander, 1856, s.f.). Cordylodus proavus—Abaimova, 1975:109, 110, pl. 10, fig. 16, text-fig. 8 QaR2s). Cordylodus proavus—Nowlan, 1974:15, pl. 1, figs. 9, 10, 14-16. Cordylodus proavus—Abaimova and Markov, 1977:91, pl. 14, fig. 1. Cordylodus proavus—Landing et al., 1978:76, text-fig. 2F. Cordylodus proavus—Fahraeus and Nowlan, 1978:453, pl. 1, figs. 8, 9. Cordylodus proavus—Tipnis et al., 1979:31, pl. 1, figs. 8, 9. ?Cordylodus cf. C. proavus—Tipnis et al., 1979:31, pl. 1, fig. 10. Cordylodus proavus—Landing, 1979:21, 22, pl. I-1, figs. 10, 13. Cordylodus oklahomensis—Landing, 1979:64, 65, 135, 136, 202, 203, pl. II-3, fig. 1, pl. II-1, fig. 11, pl. [V—2, fig. 8 (pars, cited figures only of C. proavus Cy Cyrtoniodiform Element Cordylodus oklahomensis Muller, 1959:447, 448, pl. 15, figs. 15a—16. Cordylodus oklahomensis—Miller, 1969:423, 424, pl. 65, figs. 46-53. Cordylodus sp. aff. C. insertus Miller, 1970:89, pl. 1, fig. 40, text-fig. 11C. Cyrtoniodus oklahomensis—Miller, 1970:90, 91, pl. 1, figs. 35, 36, text-fig. 11F. non Cordylodus oklahomensis—Druce and Jones, 1971:69, pl. 5, figs. 6a—7c, text- fig. 23 (= cyrtoniodiform element of Cordylodus intermedius Furnish apparatus). Cordylodus oklahomensis—Ethington and Clark, 1971:71, pl. 1, fig. 24. Cyrtoniodus prion—Miller and Melby, 1971:120 (pars, pl. 2, fig. 17, non C. prion Lindstrom. 1955, s.f.). ’Cordylodus oklahomensis—Jones, 1971:47, 48, pl. 2, figs. 5a—8b. Cordylodus oklahomensis—Miuller, 1973:33, pl. 9, figs. 12-13b, text-figs. 2B, 1as'D: 21 22 4 é p é % Cordylodus prion prion Nowlan, 1976:154—156, pl. 2, figs. 23-31. Cordylodus oklahomensis—Landing, 1979:64, 65, 135, 136, pl. H-3, fig. 5, pl. IlI-1, fig. 10. Occurrence A total of 105 cordylodiform and 29 cyrtoniodiform elements from the uppermost Cambrian and lowest Ordovician of Section KK (Parabolina Fauna through Apo- planias Fauna). Hypotypes Cordylodiform elements ROM 38371 and ROM 38372 from KK 124 and cyrtoniodi- form element ROM 38367 from KK 122.5. Description The component form species Cordylodus proavus and C. oklahomensis have been ad- equately redescribed by Miller (1969) and only remarks are presented here. Cordylo- diform elements have discrete denticles and cusp which have well rounded to laterally flattened cross sections. A rounded carina may be present on the anterior and poste- rior edges of the cusp (Figs. 6C-G), and the anterior margin may be laterally deflected (Figs. 6F, G). Cyrtoniodiform elements have basally confluent denticles and, gener- ally, a lateral flaring of the base under the cusp (Figs. 6H, I). Crystallites present in Cordylodus elements apparently are oriented radially to the surface of the element. Edges or keels are formed by the elongation of these crystal- lites along the anterior margin of the cusp (Figs. 6C-G). Fig. 6A, B Cordylodus intermedius Furnish s.f., ROM 38373, sample KK 33. A Lateral view, <120. B Detail of slightly etched surface, <602. C-E Cordylodus oklahomensis Miller, cordylodiform element, ROM 38371, sample KK 124. Cc Lateral view, <60. D,E Detail of anterior carina showing orientation of crystallites, 301 and <1204, respec- tively. F,G Cordylodus oklahomensis Miller, cordylodiform element, ROM 38372, sample KK 124. F Lateral view of asymmetrical element, <60. G Detail of slightly etched surface and anterior carina, X301. H,1 Cordylodus oklahomensis Miller, cyrtoniodiform element, ROM 38367, sample KK 122.5. H Inner lateral view of element with attached basal plate, 65. I Detail showing contrasting surface texture of smooth conodont element and porous basal plate, <129. J-L__‘Fryxellodontus? sp. nov., serrated element, ROM 38366, sample KK 146. J,L Lateral views, <52. K Right-lateral view showing denticulated oral edge of broken distal end of posterior process, X103. 23 Remarks Cordylodus proavus s.f. and C. oklahomensis s.f. are considered to be the component form species of multi-element C. oklahomensis. The two form species have a compa- rable stratigraphic range (Miller, 1969:426). Both elements appear at the same strati- graphic level in Utah (Miller, 1978) and Vermont (Landing, 1979), and co-occur in the same samples in Iran (Muller, 1973). The two form species also have nearly coin- cident ranges in Alberta (Derby et al., 1972) with C. oklahomensis sf. first recovered less than a metre above the lowest occurrence of C. proavus s.f. Similarly, C. proavus s.f. and ‘‘C. prion prion’’ (= C. oklahomensis sf.) of Nowlan (1976) first appear at the same level in the Copes Bay Formation in the Canadian Arctic and have similar stratigraphic ranges. Druce and Jones (1971, see also Druce, 1978) described a stratigraphic overlap of Cordylodus oklahomensis s.f. only in the upper portion of the local range zone of C. proavus s.f. However, this stratigraphic non-concordance is probably related to the small number of specimens recovered. The illustrated specimens of C. oklahomensis s.f. from Australia (Druce and Jones, 1971) are apparently the cyrtoniodiform ele- ments of multi-element C. intermedius. Proconodontus notchpeakensis s.f. and P. carinatus s.f. are the apparent ‘‘ances- tors’’, respectively, of Cordylodus proavus s.f. and C. oklahomensis s.f. (Miller, 1969, 1970). The similarity of the elements in bi-element “‘Proconodontus’’ carin- atus (discussed below) to those of multi-element C. oklahomensis also suggests a comparable apparatus construction in the two species. Cordylodus proavus s.f. appears to have been numerically dominant over C. okla- homensis s.f. in the C. oklahomensis apparatus. Miller (1978) recovered the elements in the ratio 3287:781 at the Lava Dam North section in Utah. A closely similar ratio 105:29 occurs in the Rabbitkettle collection. These data suggest that the elements oc- curred in the ratio 4:1 in aC. oklahomensis apparatus and that a minimum number of 10 elements was present in a bilaterally symmetrical C. oklahomensis animal. Genus Fryxellodontus Miller, 1969 Type Species Fryxellodontus inornatus Miller, 1969, from the Notch Peak Limestone, House Range, west-central Utah. Fryxellodontus inornatus Miller, 1969 Figs. 7C-G Fryxellodontus inornatus Miller, 1969:426, 428, 429, pl. 65, figs. 1-10, 12-16, 23-25, text-figs. 4A, C, D, E (pars). Fryxellodontus inornatus—Miller, 1970:97, text-figs. 1OQ-T. Gen. et sp. indet. B Druce and Jones, 1971:102, pl. 12, figs. 9a, b, text-fig. 33. Fryxellodontus inornatus—Nowlan, 1976:237, pl. 1, figs. 17-19. 24 a Occurrence and Hypotype One symmetricus element (ROM 38368) from the Apoplanias Fauna, sample KK 43. Remarks Miller (1969) has provided a thorough description of the elements of the Fryxello- dontus inornatus apparatus. An additional observation is that the elements lack surfi- cial microsculpture when examined with the scanning electron microscope (Fig. 7C, D, G). The element recovered from Section KK is composed of acicular crystallites oriented perpendicular to the surface of the specimen (Fig. 7E, F). Fryxellodontus? sp. nov. Fig. 5B, 6-L, 7A, B Occurrence and Hypotype One element (ROM 38366) from the Bowmania americana Fauna (KK 146). Description A strongly laterally flattened, completely hollow, sheathlike element with a denti- culated posterior process which is much longer than the blunt cusp. A smooth, open arc is formed by the posterior edge of the cusp and the oral edge. Lateral displace- ment of the anterior keel and slight concavity of the right-lateral surface produce asymmetry in the element. Remarks The element is completely hollow and lacks any surface microsculpture. It has some similarity to the planus and serratus elements of Fryxellodontus inornatus (Miller, 1969) although a long posterior process is present. This posterior process, which was broken in preparation, is distally denticulated (Fig. 6K, L). It is uncertain whether the element actually represents a species of Fryxellodontus because associated elements of the apparatus were not recovered. However, if the el- ement does belong to the genus, it is the only known Upper Cambrian representative of the genus. Genus Furnishina Miller, 1959 Type Species Furnishina furnishi Miller, 1959, s.f. from the Gallatin Limestone, Big Horn Moun- tains, Wyoming. 25 26 Furnishina asymmetrica Miller, 1959 s.f. Figs. 7J-M Furnishina asymmetrica Muller, 1959:451, 452, pl. 11, figs. 16a, b, 19. Furnishina asymmetrica—Nogami, 1966:354, pl. 9, figs. la—2b. Furnishina asymmetrica—Miuller, 1971:8, pl. 1, figs. 13, 16. Furnishina asymmetrica—Miuller, 1973:39, pl. 1, figs. 6, 8, 9. Furnishina asymmetrica—Lee, 1975:79, pl. 1, fig. 1, text-fig. 2A. Furnishina asymmetrica—Miller and Paden, 1976:595, pl. 1, figs. 13, 14. Furnishina asymmetrica—Abaimova, 1978:78, pl. 7, fig. 1. Furnishina asymmetrica—Landing, 1979:22, pl. I-1, fig. 7. Occurrence and Hypotype One element (ROM 38374) from the Cordylodus oklahomensis Zone (KK 33). Trilo- bites of the Apoplanias Fauna and Symphysurina brevispicata Subzone were recov- ered, respectively, below (KK 43) and above (KK 25) sample KK 33. Remarks Furnishina asymmetrica s.f. and F. furnishi Muller are probably asymmetrical and subsymmetrical to symmetrical elements of the F. furnishi apparatus (Landing, 1979). Paraconodont structure, or the aboral addition of growth lamellae which do not en- close the distal portion of the element (Bengtson, 1976), is shown by the detachment of the distal portion of growth lamellae from previously secreted portions of the sclerite (Figs. 7K—M). Fig. 7A, B Fryxellodontus? sp. nov., serrated element, ROM 38366, sample KK 146. A Detail of posterolateral margin of cusp showing prismatic crystallites comprising poste- rior carina (compare Fig. 6L), 269. B Detail of lateral surface of cusp showing slightly corroded surface of originally smooth element (compare Fig. 6J), 269. c-G_ Fryxellodontus inornatus Miller, symmetrical element, ROM 38368, sample KK 43. (© Aboral-lateral view (note broken tip of element, compare Fig. 7D), <215. D Posterior view, X15]. E,F Detail of crystallites oriented normal to wall of element (compare Fig. 7c), *731 and * 1462, respectively. G Detail of corroded outer surface of originally smooth element (compare Fig. 7D), X753. H,1 Protoconodont sp. indet. s.f., ROM 38375, sample KK* 135-150. H Lateral view, X47. I Detail showing lower edges of basally-internally secreted lamellae, < 237. J-M Furnishina asymmetrica Muller, s.f., ROM 38374, sample KK 33. J Posterior view, X99. K-M_ Detail of surface of element showing exfoliation of upper portions of paraconodont growth lamellae, 290, 247,