P.S. Ro 682 no . 1 56 UI nc < = — co 03 T— 1 -1^— — CM 5^ E ,_ -i ^m = o n = co s-— — -^ O^ — ° E= ^= y— 1 < — CD K Z^^ ^^ 1 o= — *~ 1 _i= = CO < >■ O^^ oc^— ROYAL ONTARIO MUSEUM LIFE SCIENCES CONTRIBUTIONS CONODONTS OF THE LOWER BORDER GROUP AND EQUIVALENT STRATA (LOWER CARBONIFEROUS) IN NORTHERN CUMBRIA AND THE SCOTTISH BORDERS, U.K. Mark A. Purnell W ROM Digitized by the Internet Archive in 2011 with funding from Royal Ontario Museum http://www.archive.org/details/conodontsoflowerOOpurn ROYAL ONTARIO MUSEUM LIFE SCIENCES CONTRIBUTIONS 156 CONODONTS OF THE LOWER BORDER GROUP AND EQUIVALENT STRATA (LOWER CARBONIFEROUS) IN NORTHERN CUMBRIA AND THE SCOTTISH BORDERS, U.K. Mark A. Purnell Ct> ROM © 1992 Royal Ontario Museum All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or data base, or transmitted, in any form or by any means, electronic, mechanical, photocopying, or otherwise, without the prior written consent of the publisher. First published in 1992 by the Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario M5S 2C6. Publication date: 1 December 1992 ISBN: 0-88854^05-7 ISSN: 0384-8159 Canadian Cataloguing in Publication Data Purnell, Mark A., 1964- Conodonts of the Lower Border Group and equivalent strata (Lower Carboniferous) in Northern Cumbria and the Scottish Borders, U.K. (Life Sciences Contribution ; no. 156) Includes bibliographical references. ISBN 0-88854-405-7 I . Conodonts - Cumbria (England). 2. Conodonts - England, Northern. 3. Paleontology - Carboniferous. 4. Paleontology - Cumbria. 5. Paleontology - England, Northern. I. Royal Ontario Museum. II. Title. III. Series. QE899.2.C65P87 1992 562.2094278 C92-095152-X ROYAL ONTARIO MUSEUM PUBLICATIONS IN LIFE SCIENCES The Royal Ontario Museum publishes books on a variety of topics in the life sciences, including Life Sciences Contributions, a numbered series of original scientific publications. All manuscripts considered for publication are subject to the scrutiny and editorial policies of the Life Sciences Editorial Board, and to independent refereeing by two or more persons, other than Museum staff, who are authorities in the particular field involved. Life Sciences Editorial Board Senior Editor: J. H. McAndrews Editor: M. D. Engstrom Editor: G. B. Wiggins External Editor: C. S. Churcher Manuscript Editor: M. D. Engstrom Production Editor: K. Mototsune Mark A. Purnell received his Ph.D. (Geology) from the University of Newcastle upon Tyne, U. K., and has been postdoctoral research fellow in the Department of Invertebrate Palaeontology, Royal Ontario Museum, and in the Department of Geology, University of Toronto. He is currently postdoctoral research fellow in the Department of Geology, the University of Leicester, U. K. The Royal Ontario Museum is an agency of the Ontario Ministry of Culture and Communications. Printed and bound in Canada CONTENTS Abstract 1 Introduction 1 Geological Setting: the Northumberland Trough 1 Stratigraphic Framework 1 Conodont Fauna 3 Materials and Methods 4 Systematic Palaeontology 6 Hindeodus Rexroad and Furnish, 1964 6 Hindeodus crassidentatus (Branson and Mehl, 1934b)? 6 Cavusgnathus Harris and Hollingsworth, 1933 7 Cavusgnathus hudsoni (Metcalfe, 1981) 7 Cavusgnathus unicornis Youngquist and Miller, 1949 10 Cavusgnathus cf. hudsoni (Metcalfe, 1981) 11 Cavusgnathus cf. unicornis Youngquist and Miller, 1949 11 Cavusgnathus? sp. a 12 Clydagnathus Rhodes, Austin, and Druce, 1969 12 Clydagnathus windsorensis (Globensky, 1967) 13 Patrognathus Rhodes, Austin, and Druce, 1969 14 Patrognathus capricornis (Druce, 1970) 15 Taphrognathus Branson and Mehl, 1941 17 Taphrognathus carinatus (Higgins and Varker, 1982) 19 Taphrognathus varians Branson and Mehl, 1941 20 Taphrognathus cf. varians 27 Taphrognathus sp. a 28 Taphrognathus? transatlanticus (von Bitter and Austin, 1984)? 30 Gnathodus Pander, 1856 30 Gnathodus cuneiformis Mehl and Thomas, 1947 30 Gnathodus? simplicatus (Rhodes, Austin, and Druce, 1969) 31 Mestognathus Bischoff, 1957 31 Mestognathus beckmanni Bischoff, 1957 31 Mestognathus praebeckmanni Sandberg, Johnston, Orchard, and von Bitter, 1986 33 Mestognathus praebeckmanni-M. beckmanni intermediates 33 Polygnathus Hinde, 1879 34 Polygnathus bischoffi Rhodes, Austin, and Druce, 1969 34 Polygnathus mehli Thompson, 1967 34 Lochriea Scott, 1942 36 Lochriea scotiaensis (Globensky, 1967) 36 Lochriea sp. indet. 37 Vogelgnathus Norby and Rexroad, 1985 37 Vogelgnathus gladiolus Purnell and von Bitter, 1992 37 Vogelgnathus kyphus Purnell and von Bitter, 1992 38 Vogelgnathus pesaquidi Purnell and von Bitter, 1992 38 Vogelgnathus cf. pesaquidi 38 Kladognathus Rexroad, 1958 39 Kladognathus tenuis (Branson and Mehl, 1941a) 39 " Apatognathus" 40 " Apatognathus" cuspidatus Varker, 1967 41 "Apatognathus" sp. a 42 "Apatognathus" sp. indet. 42 Genus Indeterminate 42 Gen. a sp. a 42 Acknowledgments 43 Appendices 44 Appendix I: Locality Details 44 Appendix II: Conodont Elements Recovered 46 Literature Cited 56 Plates 63 Conodonts of the Lower Border Group and Equivalent Strata (Lower Carboniferous) in Northern Cumbria and the Scottish Borders, U.K. Abstract The shallow-shelf carbonates of the Lower Border Group and equivalent strata of the Northumberland trough have yielded conodont elements belonging to 28 multielement species. Study of these cavusgnathid-dominated faunas highlights the need for major revi- sion of the Cavusgnathidae. Cloghergnathus globenskii Austin is an ecophenotype of Taphrognathus varians Branson and Mehl; Cloghergnathus Austin is a junior synonym of Taphrognathus Branson and Mehl. Capricornognathus Austin appears to be a junior syn- onym of Patro gnat hus Rhodes, Austin, and Druce. The apparatuses of Cavusgnathus hudsoni (Metcalfe), Taphrognathus varians. Polyg- nathus mehli Thompson, and "Apatognathus" cuspidatus Varker are described for the first time. Patrognathus capricornis (Druce), Mestognathus beckmanni Bischoff, Polygnathus bischoffi Rhodes, Austin, and Druce, and "Apatognathus" sp. a are partially recon- structed. The assignment of C. hudsoni to Cavusgnathus extends the range of the genus into the Tournaisian Series in Britain. Introduction GEOLOGICAL SETTING: THE NORTHUMBERLAND TROUGH During the late Paleozoic, crustal extension associated with subduction-collision processes led to the formation of a number of sedimentary basins in what is now northern Britain (Johnson, 1981; Bott, 1987; Leeder, 1988; cf. Has- zeldine, 1984, 1988). The Northumberland trough, com- prising the Northumberland and Solway basins (Leeder, 1971, 1974a), developed during the Carboniferous as a half-graben structure between the Southern Uplands to the north and the Alston block to the south (Text-Fig. 1). Rapid, fault-controlled subsidence of the Northumberland trough took place during the early Dinantian (Johnson, 1984; Kimbell et al., 1989). At that time, the emergent margins of the trough were sources of clastic sediment (Leeder, 1974b). Marginal clastic deposition persisted in the Solway basin (Ord, Clemmey, and Leeder, 1988), but in the Northumberland basin axial drainage systems were dominant for most of the Dinantian. These drainage sys- tems were sourced in the north and east (Robson, 1956; Frost, 1969; Leeder, 1974b) and flowed towards the shal- low, gulflike sea in the west. Marine influence in the trough, therefore, decreased eastwards (Garwood, 1931; Day, 1970; Johnson, 1984) and marine strata have not been recorded east or north of the Rothbury area (Text- Fig. 2). The character of Dinantian sediments in the trough reflects the interplay of fluviodeltaic and shallow marine depositional systems (Leeder, 1974a, b, 1975a, b; John- son, 1984). Sedimentation kept pace with subsidence (Johnson, 1984), and water depth in the trough probably never exceeded 50 m (Leeder and McMahon, 1988). STRATIGRAPHIC FRAMEWORK The outcrop of the Cementstone Group and Lower Border Group in the Northumberland basin, and the equivalent strata in the Solway basin is shown in Text-Fig. 2. With the exception of coastal sections on the Solway Firth, exposure is limited to isolated stream sections and rare quarries. There is considerable variation in the sediment characteristics and in the lithostratigraphic terminology applied to these strata in different areas of the Northum- berland trough. Throughout this work the following strati- graphic schemes are followed: Fowler (1936, 1966) for sections located in the Rothbury and North Tyne areas; Leeder (1974b) for the Newcastleton-Langholm area; Day (1970) for the Bewcastle area; Craig (1956) for the Kirk- bean ouUier; Deegan (1973) and Ord, Clemmey, and Leeder (1988) for the Rerrick outlier (see Text-Fig. 2 for locations). Where appropriate, lithostratigraphic terms are modified according to Holland et al. (1978), although the term "band" is replaced by "Member." Biostratigraphic terminology also follows Holland et al. (1978). Locality details are included as Appendix I. Stratigraphic relation- ships between Lower Border Group sections and equiva- lent strata within the Northumberland trough are shown in Text-Fig. 3. The Cementstone Group in the Rothbury area comprises a generally thinly-bedded sequence of alternating sandstones, shales, and lime mudstones (Fowler, 1936). The lime mudstones are commonly sandy or dolomitic (Fowler, 1936), and the limestone members towards the top of the group are dominated by calcareous algae, chiefly in the form of oncoids. Deposition of these sediments took place in a shallow, restricted intertidal setting or a coastal plain environment with periodic marine influence (Belt, Freshney, and Read, 1967). The algal members were deposited in a shallow, restricted shelf/ lagoon environment. TEXT-FIG. 1. Location and palaeogeographic setting of the Northumberland trough. In the "North Tyne basin" (Fowler, 1966), the Cementstone Group is probably not more than 180 m thick (Fowler, 1966) and consists of sandstones, shales, and limestones. Some of the limestones contain marine fauna] components such as crinoid ossicles and brachiopods (Fowler, 1966; pers. obs.). The character of the sequence reflects the interaction of fluviodeltaic and marine depositional systems (cf. Fowler, 1966). The sediments of the Lower Border Group in the Bewcastle area were deposited in a variety of environments reflecting periodic delta progradation into a shallow marine gulf (Leeder, 1974b, 1975a, b). Leeder (1974b) discussed the detailed sedimentology of the clastic deltaic facies. Carbonate depositional environments ranged from intertidal to shallow subtidal marine (see Leeder, 1975a, b). In the Newcastleton-Langholm area, the Whita Formation is more than 500 m thick near Langholm and is composed mainly of sandstones deposited in a fluvial environment (Leeder, 1974b). The Black Burn Formation comprises more than 150 m of sandstones, shales, and limestones deposited in coastal plain, marginal marine, and deltaic environments (Leeder, 1974b). The Amton Fell Formation is more than 200 m thick and is made up of sandstones and shales with rare thin beds of limestone. The sequence reflects deposition in a fluvial setting with ephemeral lake development (Leeder, 1974b). A section exposed in Black Burn (G.R. NY 47878880 to 48768869; section 11 of Leeder, 1972, 1974b; locality 18 on Text-Fig. 2) was considered to be part of the Arnton Fell Formation by Leeder (1972). This section was included in the formation in figure 1 of Leeder (1974b) but not in the details of sections (1974b: 175); its stratigraphic position is uncertain. More than 250 m of alternating beds of sandstone, shale, and limestone make up the Liddel Formation. Clastic strata were deposited in deltaic environments (Leeder, 1974b); carbonate beds in a range of shallow subtidal and probable intertidal marine environments (Leeder, 1975a, b). The Harden Member is distinguished by its distinctive fauna, which includes abundant Syringothyris cf. cuspidata (J. Sowerby) (Lumsden et al., 1967). It was deposited in a shallow subtidal marine environment. The Basal Cementstone Formation of the Cementstone Group in the Kirkbean outlier is composed of shales and lime mudstones. Some of the latter are dolomitic and occasionally contain ostracodes, bivalves, or vermiform gastropods (Craig, 1956; Leeder, 1974b; pers. obs.). Deposition probably took place in a shallow, very restricted marine or coastal plain environment, similar to that discussed by Belt et al. (1967). The Southemess Formation comprises approximately 140 m of alternating shales and fossiliferous limestones, containing a fauna dominated by brachiopods and molluscs (Craig, 1956; TEXT-FIG. 2. Outcrop of the Lower Border and Cementstone groups in the Northumberland basin, and equivalent strata in the Solway basin, showing localities and geographic subdivisions used in the text. For locality details see Appendix I. pers. obs.). These strata were probably deposited in a shallow open marine or slightly restricted subtidal environment. The Gillfoot Formation is dominantly composed of reddish-brown conglomerates and sandstones (Craig, 1956). Occasional thin limestones and some of the sandstone beds contain a fauna that includes brachiopods and corals (Craig, 1956; pers. obs.). The depositional environment was, therefore, at least periodically marine. In the Rerrick outlier, the Wall Hill Sandstone and Orroland groups together represent the approximate lateral equivalents of the Lower Border Group (Deegan, 1973). The Wall Hill Sandstone Group is 360 m thick and comprises the White Port, Sheep Bught, and Abbey Head formations, each composed of different proportions of conglomerates, sandstones, siltstones, and shales (Deegan, 1973). These strata were deposited in a variety of fluvial environments (Deegan, 1973) and have not been sampled for conodonts. Strata of the Orroland Group reflect deposition under a range of dominantly fluvial and alluvial conditions. Of the seven formations of the group (see Deegan, 1973), only the Barlacco Heugh and Orroland Lodge formations contain marginal marine strata. CONODONT FAUNA Previous work on British Dinantian conodonts was reviewed by Varker and Sevastopulo (1985). Few studies have dealt with shallow-shelf conodont faunas of Dinan- tian age; Rhodes, Austin, and Druce (1969) is the most recent major systematic work to do so. Since that publica- tion, there has been a major shift away from traditional "form taxonomy" towards a more biologically sound, mul- tielement concept of conodont species. The systematic palaeontology of shallow-shelf faunas is, therefore, in need of thorough revision. Conodont faunas from shallow restricted environments are usually limited in their diversity (e.g., von Bitter and Plint-Geberl, 1982; Higgins and Varker, 1982; Austin and Davies, 1984). This may limit their biostratigraphic utility, but such faunas provide good evidence for the multielement composition of conodont species (von Bitter, 1976; Kozur, 1976). Study of the low-diversity faunas recovered from restricted facies of the Northumberland trough sequence has enabled reconstruction of the apparatuses of several species of conodonts. Series, Stage and Blozone z < < Q UJ Z > rx < Bewcestle Rothbury Langholm-Newcastlelon ■ Annan North Tyne Fell Sst Klrkbean ,HAM "SLM BPSM LAM Fell Sst Gp Sst j Basal Cem'stone Fm Black Liddel Fm Whita Fm Arnton Burn Fm Fell Fm Birrenswark f Lavas *r-rg F BNF SH7 BHF CLF DCF Correlation tentative or uncertain. Precise position ol correlated horizon uncertain. TEXT-FIG. 3. Stratigraphic framework of the Lower Border and Cementstone groups and equivalent strata in the Northumberland trough. Conodont biozonation and correlation from Purnell (1989); local correlation in the Langholm-Newcastleton area follows Leeder (1974b). Sections are not arranged geographically. MBG = Middle Border Group; ESLM = Ellery Sike Limestone Member; RLM = Rawney Limestone Member; CFLM = Common Flat Limestone Member; BLM = Bogside Limestone Member; MA 1 = Main Algal Member One; LAM = Lower Antiquatonia Member; BPSM = Barron's Pike Sandstone Member; SLM = Syringothyris Limestone Member; HAM = Hillend Algal Member; GLM = Glebe Limestone Member; BHLM = Birky Hill Limestone Member; HM = Harden Member; WPF = White Port Formation; SBF = Sheep Bught Formation; HM/SDF = Hanged Man and Spouty Dennans formations; DCF = Dropping Craig Formation; BHF = Barlacco Heugh Formation; OLF = Orroland Lodge Formation; SHF = Scar Heugh Forma- tion; BNF = Black Neuk Formation. Materials and Methods One hundred and ninety-five samples from the Lower Bor- der Group and equivalent strata were processed for con- odonts using standard recovery techniques (Austin, 1987). Most samples were taken from the Lower Border Group in its type area (Text-Fig. 4). Samples were selected to maxi- mize yield and stratigraphic coverage, but also to represent the broad range of carbonate facies encountered. Almost 5000 conodont elements were recovered, most of which were assigned to one of 28 species of 12 genera. With a few exceptions, the suprageneric classification of Sweet (1988) is followed herein. The Conodonta, however, are referred to the phylum Chordata (Aldridge et al., 1986; see Smith, 1990, for discussion). Wherever possible, synonymy lists are abbreviated to give the original species designation, important taxonomic changes, and the most recent reference containing a more complete list. All synonymy lists are annotated using the symbols recommended by Matthews (1973, after Richter, 1948; Rabien, 1954). To avoid confusion, these symbols are enclosed in square brackets and appear to the left of taxonomic names. Element notation and, except where indicated other- wise, morphological terminology follows Sweet (1981a, b); symmetry classification follows Lane (1968); and heterochronic terminology follows Alberch et al. (1979). Open nomenclature and the signs for taxonomic uncer- tainty follow Bengtson (1988). The use of quotation marks to indicate invalid or obsolete taxonomic names follows Jeppsson and Merrill (1982). The terms dextral and sinistral are used to describe curvature of elements (contra Sweet, 1981b:W63, W67). In upper view, dextral elements are convex towards the right, sinistral elements are convex towards the left. Under "Material Studied" (and in Appendix II), numbers in parentheses refer to additional, poorly preserved, usually fragmentary specimens and to questionably assigned specimens. All figured material is deposited in the Department of Invertebrate Palaeontology, Royal Ontario Museum. TEXT-FIG. 4. Generalized vertical section through the Lower Border Group in the Bewcastle area showing sample distribu- tion and lithostratigraphic terminology (based on Day, 1970; and measured sections of die author). For locality details see Appendix I. Cambeck Formation Main Algal Formation Bewcastle Formation Lynebank Formation Whitberry Mbr Hillend Algal Mbr Syringothyns Ls. Mbr Whiterlgg Serpula Mbr Butt Ls Mbr Maidenway Ls Mbr Upper Antiquatonia Mbr Barrons Pike Ss Mbr Lower Antiquatonia Mbr MA 13- MA 12 MA 11- MA 10 MA 9 MA 8 Birky Cleugh Ls Mbr MA 4 MA 2 Main Algal Mbr 1 - I I i — r Junction Ls Peel Ls Stack Cleugh Oolite Rigghead Ls Ashy Cleugh Ls Mbr, Mbr- Mbr Mbr Mbr New House Ls Mbr Upper Holmhead Lower Holmhead Kitty Beck Ls Mbr Mbr Mbr Bogside Ls Mbr Common Flat Ls. Mbr Rawney Ls Mbr Ellery Sike Ls Mbr J_l I ! I l l l I I I I I I I I 1111 I I I I I I I 1111 I I I I I I I I l l l l m i i r -108707 108705 108704 108702 108701 88776 88773 i i -i — r I i i I I/LA6 KLA5 ,LA 1 '- 88747 -88744 88743 88740 -88735 -88732 88729 88721 88727 88720 -88718 88715.88717 ^88704,88713 88702 88701 Metres 300 / 1988610 188868 188865 168861.168863 . 78866 Is" 78864 58861 ,58862 117861 h 87865 87862 . 278626 ^ 278622 278619 278614 3068610 306868 h 256866 256862 1411851-1768640 4.- 108774 V 108773 r- 108770 108769 -108768 -108767 108794 VTY\ Limestone/ U-LJ Dolomite ] Sandstone -108729 -108724 108722 -108719 108714 108712 88768 h 88763 88755-88761 88754 88748-51 Systematic Palaeontology Phylum Chordata Bateson, 1886 Class Conodonta Pander, 1856 Subclass Conodonti Branson, 1938 Order Ozarkodinida Dzik, 1976 Family Anchignathodontidae Clark, 1972 Genus Hindeodus Rexroad and Furnish, 1964 Hindeodus Rexroad and Furnish, 1964:671. Anchignathodus Sweet, 1970:7. DIAGNOSIS See Sweet (in Ziegler, 1977:203^1). TYPE SPECIES Trichonodella imperfecta Rexroad, 1957, by original des- ignation (= Sa element of Hindeodus cristula (Youngquist and Miller, 1949)). Hindeodus crassidentatus (Branson and Mehl, 1934b)? Plate l.Figs. la, b Bispathodus stabilis (Branson and Mehl) — Armstrong and Purnell, 1987, pi. l,fig.5. MATERIAL STUDIED Pa elements, 3(4) from the Cambeck and BewcasUe for- mations, Lower Border Group, and the Southemess For- mation, Cementstone Group. DESCRD7TION Apparatus unknown. See Branson and Mehl (1934b:276) under Spathodus crassidentatus for a description of Pa ele- ments. DISCUSSION These specimens are indistinguishable from "Spathogna- thodus crassidentatus" sensu Klapper (1966), assigned by Sweet (1988) to Hindeodus. Their occurrence in rocks of Chadian and Arundian age is considerably above the range indicated for the species by Klapper (1966) and by Rexroad and Thompson (1979). This apparent anomaly suggests that the range of the species is greater than previ- ously thought, or that these specimens are reworked. Alternatively, they may represent a younger homeomorph of H. crassidentatus. Considering their simple carminate morphology, the latter possibility is the most likely. With- out additional information, such as ontogeny or apparatus structure, the assignment of these and similar specimens remains problematical (see Rexroad and Thompson, 1979; discussion of Gen. a sp. a). Family Cavusgnathidae Austin and Rhodes, in Robison, 1981 DISCUSSION The family Cavusgnathidae as defined by Austin and Rhodes (in Robison, 1981) contains seven genera. Of these, Capricornognathus Austin (in Austin and Mitchell, 1975) and Cloghergnathus Austin (in Austin and Mitchell, 1975) are herein considered junior synonyms of Patrog- nathus Rhodes, Austin, and Druce, 1969, and of Taphrog- nathus Branson and Mehl, 1941, respectively. The apparatuses of the remaining five genera are, as far as they are known, similar, and the genera are differentiated on Pa element morphology (Table 1). Considering the similarities between these genera and the rather minor differences that divide them, compared with their intra- and interspecific variability, the separate generic status of each is perhaps unjustified (cf. Sweet, 1988). A major revision of the systematics of the Cavusgnathidae based on apparatus structure and phylogenetic information is required but is beyond the scope of this study. TABLE 1. Pa element characteristics important in differentiating genera of Cavusgnathidae. Cavusgnathus Taphrognalhus Adetognathus Clydagnathus Patrognathus Harris and Branson and Mehl Lane 1967 Rhodes, Austin, Rhodes, Austin, Hollingsworth 1933 1941c and Druce 1969 and Druce 1969 Right lateral Right, left, or Right or left Right lateral Medial anterior anterior blade medial anterior blade lateral anterior blade anterior blade blade Ridged platform Nodose, ridged, or Ridged platform Discrete nodose Nodose and/or ornament smooth platform ornament ornament platform ornament ridged platform ornament Class Ilia Class II or ITJ Class II or DIb Class !!Ia Class Ilia symmetry symmetry symmetry symmetry symmetry Blade profile Blade profile Blade profile Blade usually Blade highest variable variable variable highest posteriorly posteriorly Genus Cavusgnathus Harris and Hollingsworth, 1933 Cavusgnathus Harris and Hollingsworth, 1933:200. Lewistownella Scott, 1942:299. Windsorgnathus Austin, in Austin and Mitchell, 1975:53. REVISED DIAGNOSIS Apparatus seximembrate when fully developed: Pa ele- ments carminiscaphate to anguliscaphate with conspicu- ous central trough; anterior blade attached to right side of platform; parapets transversely ridged; basal cavity bilat- erally subsymmetrical to asymmetrically flared. Pb ele- ments angulate; M elements dolabrate; Sa element alate; Sb and Sc elements bipennate. Pa elements paired with Class Ilia symmetry; all other elements, apart from the Sa, symmetrically paired. TYPE SPECIES Cavusgnathus alta Harris and Hollingsworth, 1933, by original designation. DISCUSSION This concept of Cavusgnathus is essentially the same as that of Norby (1976) and Rexroad (1981). Nonplatform elements of various Cavusgnathus species are similar, and generally they can be specifically assigned only in samples that contain Pa elements of just one Cavusgnathus species. Cavusgnathus hudsoni (Metcalfe, 1981) Plate 1, Figs. 2-14 [v.] Cavusgnathus charactus Rexroad — Rhodes, Austin, and Druce, 1969:79-80, pi. 13, figs. 6, 7, 13 [Pa elements]. [v ]Taphrognathus varians Branson and Mehl — Rhodes, Austin, and Druce, 1969:241, 242, pi. 13, figs. 4, 5 [Pa elements]. Cavusgnathus unicornis! Youngquist and Miller — Druce, 1969:48, 49, pi. 3, figs. 1, 2 [Pa elements]. [v.]Taphrognathus varians — Austin, 1973, figs. 1.20, 1.21 [cop. Rhodes, Austin, and Druce, 1969, pi. 13, figs. 4a, 6a] [Pa elements], [v] Windsorgnathus windsorensis (Globensky) — Austin in Austin and Mitchell, 1975:53, pi. 1, figs. 20, 23, 25 [Pa elements], [v.] Hibbardella parva Rhodes, Austin, and Druce — Austin in Austin and Mitchell, 1975:45, table 2 [Sa element] [not figured]. [non]Clydagnathusl hudsoni Metcalfe, 1980:176, pi. 13, figs. 8, 9. [v*] Clydagnathusl hudsoni Metcalfe, 1981:19, pi. 1, fig. 5 [Pa element], [v.] Taphrognalhus varians — Austin and Rhodes in Robison, 1981, fig. 108,1 [cop. Rhodes, Austin, and Druce, 1969, pi. 13, figs. 5a-c] [Pa element]. Taphrognalhus sp. Austin and Davies, 1984, pi. 2, figs. 2, 3,9 [Pa elements]. Cloghergnathus sp. Austin and Davies, 1984, pi. 2, figs. 4, 6, 27 [Pa elements]. Cavusgnathus sp. Austin and Davies, 1984, pi. 2, figs. 5, 7, 8 [Pa elements]. [(?)] Cavusgnathus unicornis — Austin and Davies, 1984, pi. 2, figs. 25, 26 [Pa elements]. [v] Cavusgnathus charactus — Varker and Sevastopulo, 1985, pi. 5.6, figs. 14, 15 [cop. Rhodes, Austin, and Druce, 1969, pi. 13, figs. 7c, 7a] [Pa element]. REVISED DIAGNOSIS Pa element diagnostic: anterior blade higher than long, fixed for up to approximately half its length, higher than parapets; central trough may be closed by the anterior end of the left parapet; parapets convex upwards; basal cavity bears a medial groove for its entire length. HOLOTYPE British Geological Survey, MPK 1907 (Metcalfe, 1981, pi. l,fig.5). TYPE HORIZON AND LOCALITY Haw Bank Limestone sample 272 of Metcalfe (1981), Haw Bank Quarry, North Yorkshire, U.K. (G.R. SE 015532). MATERIAL STUDffiD Pa elements, 259(65) [a blade, 47(1); p blade 65; y blade 12; intermediate blade 107; indeterminable blade mor- phology 28(64). 192 Pa elements complete enough for curvature determination: 104 sinistral, 68 dextral, and 20 straight]. Pb elements, 47(15); M elements, 23(1); Sa ele- ments, 6(2); Sb elements, 3; Sc elements, 5(1). All mate- rial from the Liddel and Lynebank Formations, Lower Border Group. DESCRIPTION Pa elements. The anterior blade is between one-quarter and two-fifths of total element length. It is composed of three to five, rarely six, laterally compressed denticles, fused apart from their tips, and is always developed on the right side of the element. A notch is commonly developed between the blade and the right parapet, occasionally with some medial displacement of the blade. The shape of the blade in lateral view is comparable to that of C. unicornis sensu Rexroad (1981) and may be of a, P , y, or intermedi- ate form (see Text-Fig. 5). a-P intermediate blades are particularly common, denticles increasing in size and height posteriorly, but lacking a conspicuously larger pos- terior denticle. The posteriormost blade denticle is often reclined and is always higher than the anterior end of the right parapet Blade height is greater than or equal to length; the fixed blade is usually between one-fifth and one-half of total blade length but may be slightly more or less. The platform height is greater than or, less commonly, equal to width, decreasing slightly in the posterior half. The platform may be straight but usually exhibits some lateral curvature with the outer margin convex and the inner margin convex, straight, or concave. In some specimens, the interplay of arching and lateral curvature give a twisted appearance to the posterior end of the platform. The length of the platform, measured from the anterior end of the left parapet to the posterior tip, is a a-p P-y TEXT-FIG. 5. Blade form in Cavusgnathus hudsoni. Blade type indicated by Greek letters. generally between four and six times the width, occasionally as much as seven times or as little as three times. Maximum platform width is attained either around midlength, gradually tapering to the posterior, or in the posterior third, tapering more rapidly. The parapets are ornamented by weak transverse ridges which may be more strongly developed in larger specimens. The ridges extend up to the parapet crests and create a serrated profile, the strength of which depends on the development of the ridges. The medial trough becomes shallower anteriorly and posteriorly according to the downward curvature of the parapets. In most specimens, the trough remains open at the anterior end but the left parapet may converge with the blade to more or less close the gap. Two or three nodes may be present in the posterior part of the trough forming a short carina of variable strength. The posterior tip of the platform is generally sharply pointed and the carina, if present, may extend posteriorly as a short blade. The lower profile of the platform in lateral view is concave, generally not strongly so, but this is more evident when viewed from the right. In some specimens, the lower margin of the blade is slightly upturned relative to the platform. 8 The basal cavity is lanceolate, tapering anteriorly and posteriorly. It is widest and deepest just anterior of element midlength and comes to a point at, or very close to, the posterior tip of the element A medial groove is present along the entire length of the cavity; on either side of this groove, both sides of the cavity extend an approximately equal distance anteriorly. The generally slight asymmetry of the cavity increases in some larger specimens with greater lateral flaring. Pb elements. See Rexroad (1957:36) under Ozarkodina compressa. These elements are variable; some specimens (e.g., PI. 1, Fig. 10) have a relatively large basal cavity, widest beneath the cusp, and a strongly reclined cusp and denticles. Such specimens approach the morphology of "Subbryantodus stipans" sensu Rexroad (1957). Norby (1976) noted the similarity between "S. stipans" and the Pb elements of Cavusgnalhus. Strati graphically younger specimens are like "O. compressa" but tend to have more discrete, elongate denticles and cusp. M elements. See Rexroad (1957:34) under Neo- prioniodus loxus. Some M elements of C. hudsoni (e.g., PI. 1, Fig. 14) show less downward deflection of the posterior process than "N. loxus" and approach "Neoprioniodus varians (Branson and Mehl)" in form. The discreteness of major denticles and the development of minor denticles also vary. Sa elements. See Rexroad (1958a: 18) under Hibbardella ortha. Sb elements. The anterior process is incomplete in all specimens but is at least as long as the posterior process. It is laterally compressed and bears five discrete thin denticles, subcircular in cross-section, with one or two minor denticles occasionally developed between them. The denticles are erect at the anterior end but are increasingly reclined towards the cusp. The cusp itself is reclined; it is slightly larger than the anterior process denticles but is otherwise similar. The posterior process is slightly higher and thicker and is deflected slightly downwards relative to the anterior. The denticulation is similar to that of the anterior process but the five major denticles increase in size, height, and reclination, posteriorly. The figured specimen (PI. 1, Fig. 13) has two minor denticles on the posterobasal edge of the last major denticle. The lower edge has a sharp downward deflection at the posterior end of some specimens. The basal cavity is developed obliquely beneath the cusp, aligned with its long axis. It is narrow, shallow and elongate, rather conical in one small specimen, and tapers anteriorly and posteriorly. The cavity does not appear to continue as a groove along the process, but a thin zone of recessive basal margin is developed along the lower edge of the posterior process. Sc elements. See Hass (1953:81) under Hindeodella ensis and Clarke (1960:8) under H. tenuis. DISCUSSION The Pa elements of C. hudsoni exhibit considerable varia- tion in many aspects of their morphology. Individual char- acters vary continuously and in discord with other characters; no consistently recognizable relationship between different characters has been observed. The arbi- trary choice of a single character to subdivide this plexus into a number of more convenient "species" would be a backward step taxonomically. Rather, these variable ele- ments are interpreted as members of a single species with considerable plasticity in Pa element development Clydagnathus! hudsoni Metcalfe, 1981, falls com- fortably within the range of variation described above. The original concept of the species (Metcalfe, 1981) was more restricted, almost certainly due to the small sample size of 10 Pa elements. The assignment to Clydagnathus! based on anterior closure of the trough has been emended: firstly because of the variability of the character, and secondly because anterior trough closure is no longer considered diagnostic of Clydagnathus (Nicoll and Druce, 1979; contra Rhodes, Austin, and Druce, 1969). The posterior blade denticle is broken in the holotype of Cavusgnalhus hudsoni; originally the blade probably had an a a-p* intermediate form. The specimens from the Main Algal "series" (= Liddel Formation) of Harden Burn, Roxburghshire, figured by Rhodes, Austin, and Druce (1969) as Cavusgnathus charactus Rexroad and Taphrognathus varians Branson and Mehl, are referred to C. hudsoni. One of these specimens was subsequently figured as T. varians in the Treatise on Invertebrate Paleontology (Austin and Rhodes in Robison, 1981). Nicoll and Druce (1979) included within their concept of Clydagnathus cavusformis specimens figured by Druce (1969) as Cavusgnathus! unicornis. These specimens appear to have ridged platform ornament rather than the nodose ornament characteristic of Clydagnathus and are herein considered to belong to C. hudsoni. Austin (in Austin and Mitchell, 1975) distinguished his new genus Windsor gnat hus from Cavusgnathus on stratigraphic evidence alone. Austin and Rhodes (in Robison, 1981) placed Cavusgnathus and Windsorgnathus in synonymy. Windsor gnathus windsorensis sensu Austin (in Austin and Mitchell, 1975) is distinct from Clydagnathus windsorensis (Globensky) (von Bitter and Austin, 1984) and is identical to Cavusgnathus hudsoni from the Lynebank Formation of the Northumberland trough. C. hudsoni also occurs in Tournaisian strata of the Irish Republic, variously reported as species of Cavusgnathus, Clydagnathus, and Taphrognathus (Johnston, 1976; Marchant, 1978; Rees, 1987). Variation in C. hudsoni Pa elements appears to have decreased through time. Specimens of upper Tournaisian age from Ireland, from the Craven basin (Metcalfe, 1981), TABLE 2. Distinguishing characteristics of Cavusgnathus charactus Rexroad, C. hudsoni (Metcalfe), and C. unicornis Youngquist and Miller. Characteristics of C. charactus based on Rexroad (1957); those of C. hudsoni on personal observation; those of C. unicornis on Youngquist and Miller (1949), Rexroad (1957), Rexroad (1981), and various published plates. Cavusgnathus charactus Cavusgnathus hudsoni Cavusgnathus unicornis "Attachment scar" anterior No "attachment scar" No "attachment scar" of basal cavity 6-8 blade denticles 3-5 blade denticles 5-8 blade denticles Blade < 1/3 free Blade > 1/2 free Blade < 1/2 free Blade slightly > 1/3 Blade usually < 1/3 of Blade commonly > 1/3 of of element length element length element length Inner parapet nearly Inner parapet convex. Both parapets convex straight, convex at tip straight, or concave outwards Trough always open Trough may be closed Trough always open at anterior end at anterior end at anterior end Parapet notch Parapet notch Parapet notch diagnostic common rare Blade slightly convex a, (3, y, and intermediate a, P, y, and intermediate blade morphologies blade morphologies Blade height > length Blade height < length Platform widest at Platform widest near midlength or in posterior 1/3 apical denude and from the Liddel Formation (Rhodes, Austin, and Druce, 1969; Austin and Davies, 1984; this study) exhibit greater morphological plasticity than specimens of Chadian age from Northern Ireland (Austin in Austin and Mitchell, 1975), and from the Lynebank Formation (this study). This apparent trend may prove spurious given that, at present, many more specimens are known from Tournaisian strata. In the Cavusgnathidae, genera and species within a genus are mainly distinguished on Pa element morphol- ogy. Although certain Pa element specimens within the range of variation of Cavusgnathus hudsoni approach the morphology of C. charactus and C. unicornis, they can be differentiated on the basis of the characters in Table 2. Cavusgnathus altus differs in the shape and proportions of the irregular cockscomblike blade and in the termination of the basal cavity one-quarter to one-fifth of the platform length from the posterior end. The platform ornament, blade shape and proportions, and the strong downward deflection of the lower edge of the blade, only rarely developed in C. hudsoni, serve to distinguish C. naviculus. An Sa element occurring with C. hudsoni in the Lower Carboniferous Shale of Northern Ireland was identified by Austin (in Austin and Mitchell, 1975) as Hibbardella parva. This element is very similar to the Sa element figured here (PI. 1, Fig. 11) and probably belongs to C. hudsoni. Sc elements of C. hudsoni show considerable variation, especially in the degree of inward and upward or downward curvature of the anterior process. One of the figured specimens (PI. 1, Fig. 12) has very little inward curvature of the process and may be transitional to an Sb element. The other figured specimen (PI. 1, Fig. 9) shows the abrupt downward curvature of the lower edge developed at the posterior end of some specimens. Cavusgnathus unicornis Youngquist and Miller, 1949 Plate 2, Figs. 1-5, 7 Cavusgnathus unicornis Youngquist and Miller, 1949:619, pi. 101, figs. 18-23 [Pa element, a morphotype]. Cavusgnathus regularis Youngquist and Miller, 1949:619, pi. 101, figs. 24, 25 [Pa element, P morphotype]. [v*] Cavusgnathus convexa Rexroad, 1957:17, pi. 1, figs. 3-6 [Pa element, y morphotype]. Neoprioniodus loxus Rexroad, 1957:34, pi. 2, figs. 8, 9, 14 [M element]. 10 Ozarkodina compressa Rexroad, 1957:36, pi. 2, figs. 1, 2 [Pb element]. llibbardella ortha Rexroad, 1958a: 18, pi. 2, figs. 9-12 [Sa element]. Cavusgnathus unicornis — Rexroad, 1981:8, 9, pi. 1, figs. 17, 22, 26, 27 [Pa element, a morphotype], fig. 21 [Pa element, P morphotype], figs. 18-20, 23 [Pa element, y morphotype], figs. 7, 8 [M element]. Cavusgnathus unicornis — Rexroad and Horowitz, 1990: 499, pi. 1, figs. 12, 13, 16, 17 [Pa element, a morphotype], figs. 11, 14, 15 [Pa element, (3 morphotype], fig. 10 [Pa element, y morphotype], fig. 18 [Pa element, a morphotype?], fig. 19 [Pa element, a - (3 intermediate morphotype] [includes synonymy]. DIAGNOSIS See Rexroad (1981:8). HOLOTYPE State University of Iowa, 4174 (Youngquist and Miller, 1949, pi. 101, figs. 18, 19). TYPE HORIZON AND LOCALITY Pella beds, Chesterian age; Pella South West, Marrion County, Iowa, U.S.A. MATERIAL STUDIED Pa elements, a morphotype, 19(1); p* morphotype, 14(5); y morphotype, 8(1); intermediate morphotype, 14(2); inde- terminate morphotype, 6(26). Pb elements, 10(7); M ele- ments, 24(7); Sa elements, 2(7); Sb elements, (1); Sc elements, 1(1). Material from the Main Algal and Cam- beck formations, Lower Border Group, the Cementstone Group, and the Orroland group. DESCRIPTION Pa elements, a morphotype, see Youngquist and Miller (1949:619) and Rhodes, Austin, and Druce (1969:82) under Cavusgnathus unicornis; P morphotype, see Young- quist and Miller (1949:619) under C. regularise y morpho- type, see Rexroad (1957:17) under C. convexa. Pb elements. See Rexroad (1957:36) under Ozarkodina compressa. M elements. See Branson and Mehl (194 la: 174) under Prioniodus varians and Rexroad (1957:34) under Neoprioniodus loxus. These forms represent end members of the range of variation in C. unicornis M elements. Sa elements. See Rexroad (1958a:18) under Hibbardella ortha. Sc elements. See Hass (1953:81) under Hindeodella ensis, and Clarke (1960:8) under//, tenuis. DISCUSSION The concept of C. unicornis followed herein is essentially the same as that of Rexroad (1981). Pa elements with a low blade, which in some specimens approaches the mor- phology of Cavusgnathus sp. sensu Rexroad (1981), are not uncommon in the Northumberland trough and are herein considered as variants of C. unicornis. Slight lateral offset of the anterior blade, encountered only rarely in the present study, is also considered to represent intraspecific variation (cf. Rexroad and Nicoll, 1965:18, pi. 1, figs. 21- 23). M elements of "N. loxus" and "N. varians" forms differ in little other than the angle of downward deflection of the posterior process (Rexroad, 1958a; Norby, 1976), although "N. varians" may be more robust (Norby, 1976). Both forms were considered by Rexroad and Horowitz (1990) to be morphotypes of M elements shared by C. uni- cornis and C. char actus (contra Rexroad, 1981). Both are included in C. unicornis herein. Some specimens develop an inclined basal cavity, which forms an anticusplike anterobasal termination. Similar anticusps are seen in Cavusgnathus M elements from the Bear Gulch Lime- stone, Montana (Conway Morris, 1990, fig. 7; pers. obs.). A single Sb element in sample 1768701 has been tentatively assigned to C. unicornis. The presence of other cavusgnathid Pa elements with C. unicornis in this sample precludes more certain assignment. Cavusgnathus cf. hudsoni (Metcalfe, 1981) MATERIAL STUDIED A single Pa element from the Bewcastle Formation, Lower Border Group. DESCRIPTION Apparatus unknown. The single sinistral specimen of C. cf. hudsoni (y morphotype) differs from C. hudsoni in hav- ing a higher blade than y morphotypes of the species. It has very weak platform ornament and a lateral ridge along the left side of the blade as an anterior extension of the plat- form. The basal cavity does not reach the posterior end of the element; it bears thickened lips, the outer of which dips downwards. DISCUSSION This element may represent an extreme variant of C. hud- soni. Cavusgnathus cf. unicornis Youngquist and Miller, 1949 Plate 2, Figs. 6a, b MATERIAL STUDIED A single Pa element from the Lower Antiquatonia Mem- ber of the Cambeck Formation, Lower Border Group. 11 DESCRIPTION The single Pa element specimen differs from C. unicornis only in the break up of the transverse ridges into nodes in the posterior half of the platform (a character usually seen only in C. naviculus), and in the suppression of parapet development in the posterior third of the element, to form a low flat broad posterior platform. DISCUSSION Some depression of the posterior part of the platform has been recorded in C. unicornis Pa elements (e.g., Rexroad, 1981, pi. 1, figs. 17, 22) although not to the extent to which it is developed in C. cf. unicornis. This specimen may, however, be an aberrant C. unicornis Pa y element Cavusgnathus? sp. a Plate 2, Fig. 8 MATERIAL STUDIED 2(1) Pa elements from the Cambeck Formation, Lower Border Group. DESCRIPTION Apparatus unknown. Pa elements bear a short anterior blade, free for almost all its length. The blade is composed of a large cusp with a smaller "piggy back" denticle to the anterior. Blade height is approximately twice its length. One specimen has a small denticle posterior of the cusp. The platform is higher than it is wide and is ornamented with low indistinct nodes, which become more discrete posteriorly. The medial trough is shallow and narrow, shal- lowing posteriorly and more or less closed anteriorly by convergence of the left parapet with the blade. In lateral view, the lower surface of these elements is straight or concave, and the upper surface of the platform is convex. The two most complete specimens recovered are sinis- trally curved. The lanceolate basal cavity is subsymmetri- cal and would almost certainly extend to the posterior tip of complete specimens. It is deepest and widest just ante- rior of midlength and, although constricted anteriorly, it extends under the blade. Posteriorly the cavity tapers grad- ually. DISCUSSION These specimens resemble some Pa elements of Clydag- nathus windsorensis (Globensky) but lack the discrete nodose ornament diagnostic of the genus. Genus Clydagnathus Rhodes, Austin, and Druce, 1969 Clydagnathus Rhodes, Austin, and Druce, 1969:84. DIAGNOSIS See Rhodes, Austin, and Druce (1969:84). TYPE SPECKS Clydagnathus cavusformis Rhodes, Austin, and Druce, 1969, by original designation. DISCUSSION Rhodes, Austin, and Druce (1969:85) distinguished Cly- dagnathus from Cavusgnathus "by the general anterior closure of the oral trough, by the merging of the marginal ornament with the blade and by the lateral, rather than lon- gitudinal expansion of the basal cavity." After examina- tion of large numbers of Clydagnathus from Australia, however, Nicoll and Druce (1979) concluded that the gen- era could not be differentiated using these characters. Sandberg and Ziegler (1979) considered Clydagnathus and Cavusgnathus to be distinguishable solely in terms of their respective stratigraphic positions. With the reassign- ment of Cavusgnathus windsorensis Globensky to Clydag- nathus (von Bitter and Plint, 1987) and the recognition of Cavusgnathus of Tournaisian age (see Cavusgnathus hud- soni above), this stratigraphic distinction can no longer be made. The possession of nodose rather than ridged platform- element ornament has been used to differentiate Clydagnathus from Cavusgnathus herein. This appears to be in accord with the generic concept used by other workers (e.g., Nicoll and Druce, 1979; von Bitter and Plint, 1987) but a distinction at the generic level based on this character is probably unjustified (see discussion of the family Cavusgnathidae). In addition, Clydagnathus may be polyphyletic. A phylogenetic sequence from "Spa- thognathodus" plumulus (Rhodes, Austin, and Druce) through Clydagnathus gilwernensis Rhodes, Austin, and Druce to Clydagnathus cavusformis has been proposed (Rhodes, Austin, and Druce, 1969; Austin and Hill, 1973; Sandberg and Ziegler, 1979). However, Sandberg and Ziegler (1979) suggest that Clydagnathus ormistoni (Beinert, Klapper, Sandberg, and Ziegler) evolved from Pandorinellina cf. insita (Stauffer) or Scaphignathus ziegleri Druce. Preliminary evidence suggests that Clydagnathus windsorensis (Globensky) may be a progenetic offshoot of Cavusgnathus (see discussion of CI. windsorensis). Generic revision of Clydagnathus is clearly required but must await description of the apparatus of me type species, CI. cavusformis. 12 Clydagnathus windsorensis (Globensky, 1967) Plate 2, Figs. 9-15 [v*] Cavusgnathus windsorensis Globensky, 1967:439, pi. 57, figs. 3, 4, 7, 9, 11, 19, pi. 58, fig. 1 [Pa elements] [N.B. The specimen shown in pi. 57, fig. 7 is not the holotype]. [v.] Cavusgnathus cf. windsorensis Globensky, 1967:439, pi. 57, figs. 2, 6, 10 (specimen lost); 12, pi. 58, fig. 8 [Pa elements], [vp] Cavusgnathus spp. Globensky, 1967:440, pi. 57, fig. 17 only [Pa element], [v?] Ozarkodina sp. A Globensky, 1967:446, pi. 55, figs. 1, 5, 12 only [Pb elements], [p?] Taphrognathus varians Branson and Mehl — Pierce and Langenheim, 1974:168, 169, pi. 1, figs. 3,4, 6, 7 only [Pa elements], [vp] Cavusgnathus windsorensis — von Bitter and Plint-Geberl, 1982: 194, pi. 2, figs. 1-3, 16-18 [Pa elements]; pi. 6, fig. 18 [M element] only. [vp?] Cavusgnathus windsorensis — von Bitter and Plint-Geberl, 1982:194, pi. 1, figs. 1-16; pi. 2, figs. 4-15 [Pa elements]; pi. 7, figs. 1,5-7 [Pb elements]; pi. 3, figs. 15, 16 [Sa elements]; pi. 7, fig. 12 [Sb element]; figs. 15-18 [Sc elements]. [vp] Cavusgnathus regularis type — von Bitter and Plint-Geberl, 1982:197, pi. 3, fig. 18 only [Pa element]. [vnonp]Cavusgnathus windsorensis — von Bitter and Plint-Geberl, 1982, pi. 7, fig. 2 only [= Vogelgnathus pesaquidi, Pa element]. W)\ Clydagnathus! cf. cavusformis Rhodes, Austin, and Druce — Briggs, Clarkson, and Aldridge, 1983:3-8, figs. 1,2, 3 [whole animal]. Cavusgnathus windsorensis — von Bitter and Austin, 1984, pi. 19, figs. 1-10 [Pa elements]. [v.] Clydagnathus windsorensis — von Bitter and Plint, 1987:350, 351, figs. 2.1-2.6, 2.7(specimen lost), 2.10, 2.11, 2.14-2.17 [Pa elements], fig. 2.12, [Pb element], fig. 2.13 [M element], fig. 2.8 [Sa element], fig. 2.19 [Sb element], fig. 2.18 [Sc element]. [(?)] Clydagnathus! cf. cavusformis — Aldridge, 1987, fig. 1.9 [whole animal] [cop. Briggs, Clarkson, and Aldridge, 1983, figs. 1A, 3B]. DIAGNOSIS See von Bitter and Plint (1987:351). HOLOTYPE University of New Brunswick 64-F-235 (Globensky, 1967, pi. 57, figs. 3, 4, 7). TYPE HORIZON AND LOCALITY Windsor Limestone, sample KD10 of Globensky (1967). On the Atlantic coast between the village of Skir Dhu and north shore about 330 m SW of Skir Dhu fisherman's wharf, Skir Dhu, Cape Breton Island, Nova Scotia, Can- ada. MATERIAL STUDIED Pa elements, 63(14); Pb elements, 15(8); M elements, 8(1); Sa elements, 4; Sb elements, 7(1); Sc elements, 12(6); mosUy from the lower Lynebank Formation, Lower Border Group, but also from the Cambeck Formation, Lower Border Group, the Southerness and Basal Cement- stone formations, Cementstone Group, and the Cement- stone Group of Kielder Burn, Barrow Scar, and Black Burn. DESCRIPTION Pa elements. See Globensky (1967:439) under Cavusg- nathus windsorensis, and the remarks of von Bitter and Plint (1987:351). Pb elements. The anterior process is laterally compressed. It is straight or downcurved, generally only slightly, and occasionally incurved slighUy. It becomes thicker towards the cusp and bears up to seven, commonly five, laterally compressed, elongate pointed denticles which are free for most of their length. The denticles are erect and slightly recurved, often becoming slightly reclined towards the cusp, and are highest around the middle of the process. The cusp is higher wider and thicker than the anterior den- ticles. It is reclined and recurved although usually not greatly so. The posterior process is lower than, but approx- imately equal in length to, the anterior, and may be less laterally compressed. It is straight or slightly downcurved, thins posteriorly, and bears five or six laterally compressed denticles. These denticles are subequal in size, generally smaller than those of the anterior process, and become increasingly reclined posteriorly. The basal cavity is rela- tively large. It is widest and deepest beneath the posterior edge of the cusp, and tapers posteriorly to a point at least half-way along the process. Anteriorly the cavity tapers a variable distance, but generally reaches a point approxi- mately half-way along the process. The lips of the cavity often extend downwards, creating an undulating lower profile to the element. M elements. The cusp is strongly proclined, its long axis forming an angle of approximately 130° with the axis of the posterior process. It is slightly incurved and laterally compressed, with sharp anterior and posterior edges and convex lateral surfaces. The posterior process is usually straight but may be curved at the anterior end where it joins the cusp. The thickness of the process decreases towards the posterior tip; its length may be greater than or less than that of the cusp. Depending on length, the process bears up to 10 small discrete pointed subequal denticles, that generally become more erect with respect to 13 the process posteriorly. The small asymmetrical basal cavity is widest beneath the posterior part of the cusp, and has a small, occasionally thickened lip on the inner side. The cavity tapers posteriorly to a narrow groove extending down the sharp lower edge of the process. In a few specimens, one or two small fused denticles are developed anterior of the cusp. Sa elements. See Rexroad (1958a: 18) under Hibbardella ortha. Sb elements. The anterior process is laterally compressed and straight or slightly incurved. It bears six or more later- ally compressed denticles, free for most of their length, which curve inwards and become increasingly reclined posteriorly. The sharply pointed cusp is laterally com- pressed, reclined and incurved, and is larger than the ante- rior denticles. The posterior process is laterally compressed, straight, and larger than the anterior process. It bears up to approximately 10 laterally compressed denti- cles; these increase in size and reclination towards the pos- teriormost denticles, which may be larger than the cusp. The posterobasal termination beneath these denticles may be downturned. The basal cavity is small and is located to the anterior of the cusp, aligned with its long axis. It con- tinues as a narrow groove along the sharp lower edge of the posterior process and part way along the anterior. In larger specimens, the groove is flanked by recessive basal margin. Sc elements. See Clarke (1960:8) under Hindeodella tenuis. short high blades, compared with specimens from the Lynebank Formation. von Bitter and Plint (1987) included "Ozarkodina acadiensis Globensky" in synonymy with CI. windsorensis as the Pb element. The figured specimens of Globensky (1967) have an incurved posterior process, a character not observed in other CI. windsorensis Pb elements. They are probably the Pb elements of Lochriea scotiaensis (Globensky). Five Pb elements from the Lynebank Formation are questionably assigned to CI. windsorensis herein, as they have a larger number of denticles and a smaller cusp than is usually seen in this species. The M, Sa, and Sc elements of CI. windsorensis are similar to the homologous elements of species of Cavusgnathus and Taphrognathus varians. The preference of CI. windsorensis for shallow restricted probably euryhaline environments is well documented (e.g., Plint and von Bitter, 1986; Purnell, 1989). Gould (1977:324-325) argued that progenesis represents an effective adaptive strategy in such environments. The close morphological similarity between CI. windsorensis elements, which are generally rather small, and juvenile Cavusgnathus elements suggests that CI. windsorensis evolved as a progenetic offshoot of Cavusgnathus. The species is now known from strata of Chadian (this study) and Holkerian age (von Bitter and Austin, 1984; this study) and a progenetic response to environmental stress may, therefore, have occurred more than once. DISCUSSION The apparatus of Clydagnathus windsorensis from the Northumberland trough was reconstructed from essen- tially monospecific faunas recovered from three samples of the Ellery Sike Limestone Member of the Lynebank Formation, Lower Border Group. Certain morphological similarities, especially the elongate narrow cusps of the nonplatform elements, provide additional evidence of affinity. Although similar to the type material (Globensky, 1967) and some of the material figured by von Bitter and Plint- Geberl (1982), CI. windsorensis Pa elements from the Northumberland trough are different from specimens from the Diplognathodus Zone in southwest Newfoundland (von Bitter and Plint-Geberl, 1982, pi. 1, figs. 1-16, pi. 2, figs. 4-15). The latter elements belong to an apparatus that appears to lack M elements, has abbreviated Pb elements, and has an Sa element that may have lacked a posterior process (von Bitter and Plint-Geberl, 1982). Although these differences were considered to be intraspecific ecophenotypic variation (von Bitter and Plint-Geberl, 1982), Diplognathodus Zone specimens may prove to represent a different species. In the Northumberland trough, stratigraphically younger specimens from the Cambeck Formation have blunter nodes, relatively longer, more arched platforms, and very Genus Patrognathus Rhodes, Austin, and Druce, 1969 Patrognathus Rhodes, Austin, and Druce, 1969:178. Capricornognathus Austin in Austin and Mitchell, 1975:47. DIAGNOSIS See Rhodes, Austin, and Druce (1969:178). TYPE SPECIES Patrognathus variabilis Rhodes, Austin, and Druce, 1969, by original designation. DISCUSSION The diagnosis of Capricornognathus Austin (in Austin and Mitchell, 1975) corresponds closely to the description of Taphrognathus capricornis Druce of Druce (1970). Klap- per (1971) noted the similarity between T. capricornis and Patrognathus and suggested that T. capricornis may be a younger representative of the genus. Indeed, Capricornog- nathus, according to the diagnosis of Austin (in Austin and Mitchell, 1975) differs from Patrognathus sensu Klapper (1971) only in that the former taxon may have ridged or nodose platform ornament and may possess a short poste- rior free blade and carina. In view of the overwhelming similarities between T. capricornis and Patrognathus, T. 34 capricornis, the type and only species of Capricornog- nathus, is herein placed in Patrognathus as it was by Met- calfe (1980, 1981) and Varker and Sevastopulo (1985). Although P. capricornis is partially reconstructed herein, there is little evidence for the nature of the apparatus in other species of the genus, the type species included. Consequently, expansion of the generic diagnosis to include nonplatform elements would be premature. If the apparatus of P. variabilis Rhodes, Austin, and Druce proves significantly different from P. capricornis, another generic assignment must be sought for the latter species. Patrognathus Pa elements are distinguished from those of other cavusgnathid genera by the presence of a medial anterior blade, free for all its length, with the highest den- ticle at the posterior end of the blade (Klapper, 1971). Some Pa elements of Taphrognathus! transatlanticus (von Bitter and Austin) have a similar blade profile, but the blade is a continuation of the outer parapet (von Bitter and Austin, 1984). Patrognathus capricornis (Druce, 1970) Plate 3, Figs. 1-9 [v.] Capricornognathus capricornis — Austin and Rhodes in Robison, 1981:159, text-fig. 108,5 [Pa element] [cop. Austin in Austin and Mitchell, 1975, pi. 2, figs. 10, 33]. Patrognathus variabilis Rhodes, Austin, and Druce — Austin and Davies, 1984:207, text-fig. 15, pi. 1, figs. 10, 1 1 [Pa elements], fig. 8 [Tjuvenile Pa element], [v] Patrognathus capricornis — Varker and Sevastopulo, 1985, pi. 5.6, fig. 17 [Pa element] [cop. Metcalfe, 1981, pi. 9, fig. la]. [v.p] Mestognathus beckmanni Bischoff — Armstrong and Purnell, 1987, pi. 3, fig. 5 [Pb element], fig. 7 [M element] only. [yp] Patrognathus variabilis — Armstrong and Purnell, 1987, pi. 3, figs. 8, 9 [Tjuvenile Pa elements], fig. 10 [Sc element], fig. 1 1 [M element] only. REVISED DIAGNOSIS Apparatus at least quinquemembrate. Pa elements carmin- iscaphate, straight or slightly curved, with shallow central trough; left parapet bears one or two rows of rounded nodes; right parapet bears a single row of transverse ridges or tetrahedral nodes. Pb elements angulate; M elements dolabrate; Sa element alate; Sc elements bipennate. Pa ele- ments paired with class Ilia symmetry; all others, apart from the Sa element, symmetrically paired. [(?)] Taphrognathus sp. Druce, 1969:139, pi. 41, fig. 1 [Pa element]. Taphrognathus capricornis Druce, 1970:102, pi. 15, figs. 3-5 [Pa elements]. [?] Patrognathus! cf. capricornis — Jenkins, 1974:916 [Pa element] [not figured], [v.] Taphrognathus capricornis — Austin, 1974, pi. 1, figs. 6, 19 [Pa elements]. [v(?)] Patrognathus andersoni — Austin, 1974, pi. 1, fig. 5 [Tjuvenile Pa element], [v.] Capricornognathus capricornis — Austin in Austin and Mitchell, 1975:48, pi. 2, figs. 5-12, 14-19, 21, 23, 28, 30-33 [Pa elements; N.B. magnification of specimens between x50 and x60, not x40] [figs. 9, 12 cop. Austin, 1974, pi. 1, figs. 19,6]. [v.] Patrognathus andersoni Klapper — Austin in Austin and Mitchell, 1975:52, pi. 2, figs. 3, 4, 13, 20, 22, 25 [Pa elements], figs. 1, 2, 24, 27 [Tjuvenile Pa elements; N.B. magnification of specimens between x50 and x60, not x40] [fig. 2 cop. Ausun, 1974, pi. 1, fig. 5]. [vl Neoprioniodus cf. confluens (Branson and Mehl) — Austin in Austin and Mitchell, 1975:45, table 2 [M element; not figured]. Patrognathus capricornis — Metcalfe, 1980, pi. 13, figs. 1, 2 [Pa element], fig. 3 [Tjuvenile Pa element]. [v.] Patrognathus capricornis — Metcalfe, 1981:39, pi. 9, figs. 1,2 [Pa elements]. HOLOTYPE Bureau of Mineral Resources, Canberra, CPC 7796 (Druce, 1970, pi. 15, fig. 5). TYPE HORIZON AND LOCALITY Gargoogie Oolite Member, Rockhampton Group, Queens- land, Australia (G.R. 322093, Rockhampton Sheet). MATERIAL STUDIED Pa elements, 16(1), juvenile Pa elements (Patrognathus sp. in Appendix II), 18(3); Pb elements, 5(1); M elements, 10(6); Sb elements, (1); Sc elements, 5(24). Mostly from the Bogside Limestone Member of the Bewcastle Forma- tion but also from the Lynebank and Cambeck formations, Lower Border Group, the Southerness Formation, Cementstone Group, and the Orroland Group. In addition, the material of Austin (in Austin and Mitchell, 1975) and unpublished material collected by Dr. N. J. Riley from the Craven basin has been examined. DESCRIPTION Pa elements. See Metcalfe (1981:39). Pb elements. See Rexroad (1957:36) under Ozarkodina compressa. Patrognathus capricornis Pb elements have a longer straighter anterior process than typical "O. compressa" -form Pb elements. This process bears between eight and ten subequal denticles and has a square anterobasal termination. The cusp and denticle shape 15 resemble those of the anterior blade of Pa elements of the species. M elements. See Rhodes, Austin, and Druce (1969:158, 159) under Neoprioniodus confluens. Sa elements. See Rexroad (1958a: 18) under Hibbardella ortha. Sc elements. See Hass (1953:81, 82) under Hindeodella ensis, and Clarke (1960:8) under H. tenuis. The size of denticles on the posterior process of these elements alter- nates more regularly than in other cavusgnathids. DISCUSSION The apparatus of Patrognathus capricornis was recon- structed on the evidence of nonplatform elements associ- ated with Patrognathus Pa elements in the low diversity faunas of the Northumberland trough. It is also assumed that P. capricornis had a typical ozarkodinid Bauplan sim- ilar to other cavusgnathids. Unfortunately, Pa elements of Taphrognathus varians and Mestognathus often occur with Patrognathus, and reduce the level of confidence that can be placed in the assignment of some of the elements. For example, although distributional and morphological evidence suggests that the Pb elements described above belong to P. capricornis, there is a possibility that they represent juvenile Mestognathus Pb elements. Similarly, some of the M elements assigned to P. capricornis may belong to Mestognathus. One of the specimens figured as P. capricornis (PI. 3, Fig. 6) resembles some Adetognathus unicornis Pa elements (e.g., Varker and Austin, 1974, pi. 6, fig. 18) and illustrates the problems of homeomorphy in the Cavusgnathidae. M elements do not have the long anticusp of the lectotype of "Neoprioniodus confluens (Branson and Mehl)" also developed in one of the figured specimens of Rhodes, Austin, and Druce (1969, pi. 21, fig. 8). They are similar to the other figured specimen of Rhodes, Austin, and Druce (1969, pi. 21, fig. 2), and otherwise conform to their description. M elements of "Neoprioniodus confluens" form are consistently associated with P. capricornis Pa elements in the Northumberland trough, and also occur with P. capricornis in Northern Ireland (identified as N. cf. confluens by Austin in Austin and Mitchell, 1975, but not figured). M elements of this form also occur with P. variabilis Pa elements (Austin and Hill, 1973). Sa elements of "Hibbardella ortha Rexroad"-form occur with Patrognathus Pa elements in the Bogside Limestone Member and are tentatively included within the apparatus. Taphrognathus varians Branson and Mehl also bore "H. ortha" Sa elements and the specimens occurring with Patrognathus may belong to T. varians. Alternatively, this element may be vicariously shared by the two species — vicarious, as used herein, refers to the presence of morphologically indistinguishable elements in two or more species of conodont (Klapper and Philip, 1971). Because of these uncertainties the possible Sa elements of Patrognathus are included in T. varians in Appendix II. A single poorly preserved Sb element fragment, similar to a T. varians Sb element, was recovered in association with Patrognathus in this study. This element may belong to the apparatus. Sc elements assigned to P. capricornis resemble Sc elements of T. varians. Given the association of these Sc elements with Patrognathus Pa elements and the regular alternation of denticle size, similar to that of P. capricornis M elements, they probably belong to the latter species. ONTOGENY Pa elements of P. capricornis can be distinguished from other members of the genus primarily by the presence of ridges or tetrahedral nodes on the right parapet. However, the material studied and published plates clearly show that platform ornament changed through ontogeny. In very small specimens (Text-Fig. 6a; PI. 3, Fig. 4), the right par- apet is poorly developed compared to the left. As size increases, both parapets are equally developed and bear rounded nodes (Text-Fig. 6b; PI. 3, Fig. 3). At an element length of approximately 0.5 mm to 0.6 mm, the nodes of the right parapet develop a sharp angular inner surface and become tetrahedral in shape (Text-Fig. 6c; PI. 3, Fig. 7). These tetrahedral nodes then become more transversely elongate and develop into the ridges of mature elements (PI. 3, Fig. 6). Finally, in most specimens approaching 0.85 mm to 0.9 mm in length, a second row of small nodes develops in the posterior part of the left parapet (Text-Fig. 6d). Austin (in Austin and Mitchell, 1975) noted the similarity of small Pa elements of P. capricornis and P. variabilis Rhodes, Austin, and Druce to P. andersoni Klapper, and suggested that "P. andersoni could be a growth stage of both C. capricornis and P. variabilis" (Austin in Austin and Mitchell, 1975:52). However, neither P. capricornis nor P. variabilis was associated with P. andersoni in the study of Klapper (1971). Furthermore, all the specimens figured by Klapper (1971), except one, exceed 0.7 mm in length (calculated from plate) but do not appear to have tetrahedral nodes. Thus, small Pa elements of the three Carboniferous species of Patrognathus cannot be distinguished until adult characters start to develop (cf. Austin in Austin and Mitchell, 1975). Specimens of less than approximately 0.5 mm to 0.6 mm in length that lack the large flaring basal cavity of P. variabilis and the tetrahedral nodes of P. capricornis, and do not occur with specimens exhibiting adult characters of these species, 16 TEXT-FIG. 6. Ontogeny of Pa elements of Patrognathus capricornis. Figures based on actual specimens, broken parts restored: a) ROM 48814; b) ROM 48813; c) ROM 48810; d) Mil(c)565/17 (Austin and Mitchell, 1975, pi. 2, figs. 5, 19, 21). should be assigned to Patrognathus sp. (e.g., Matthews and Naylor, 1973:356, pi. 35, figs. 12, 13; Lipnjagov, 1979, pi. 2, fig. 11; Kononova in Wagner, Higgins, and Meyen, 1979, pi. 1, fig. 17; Nicoll and Druce, 1979:28, pi. 15, figs. 3, 4). The similarity between different Pa element growth stages of these three species of Patrognathus suggests peramorphic evolution of P. capricornis. Genus Taphrognathus Branson and Mehl, 1941 Taphrognathus Branson and Mehl, 1941b:181. [non] Taphrognathus Welles, 1947. Cloghergnathus Austin in Austin and Mitchell, 1975:48. REVISED DIAGNOSIS Apparatus seximembrate when fully developed. Pa ele- ments carminiscaphate to anguliscaphate with conspicu- ous central trough; anterior free blade medial or lateral; parapets nodose, transversely ridged or smooth; basal cav- ity bilaterally symmetrical to moderately asymmetrical. Pb elements angulate; M elements dolabrate; Sa element alate; Sb elements bipennate; Sc elements bipennate. Pa elements paired with Class III, rarely Class II, symmetry; all other elements, apart from the Sa, symmetrically paired. TYPE SPECffiS Taphrognathus varians Branson and Mehl, 1941b, by orig- inal designation. DISCUSSION The diagnosis of Taphrognathus is expanded to include nonplatform elements. The reconstruction is based on the nonplatform elements associated with Taphrognathus Pa elements in the low diversity faunas recovered from the Northumberland trough. Taphrognathus carinatus (Hig- gins and Varker) as reconstructed by Higgins and Varker (1982) is in broad agreement with this. It is assumed that Taphrognathus had a typical ozarkodinid Bauplan similar to previously reconstructed cavusgnathids. Taphrognathus Pa elements exhibit considerable varia- tion in many aspects of their morphology (Branson and Mehl, 1941b; Thompson and Goebel, 1969; Thompson and Fellows, 1970; Nicoll and Rexroad, 1975). In the U.S.A. this variation follows no stratigraphic or geo- graphic pattern (Thompson and Goebel, 1969; Nicoll and Rexroad, 1975). In erecting Taphrognathus as a monospe- cific genus, Branson and Mehl (1941b) considered medial anterior blade position to be diagnostic. Consequently, the variation in blade position recorded in every documented occurrence of Taphrognathus has caused some taxonomic confusion. The majority of authors have either included 17 forms showing lateral migration of the blade within Taph- rognathus or considered them to be intermediate with Cavusgnathus (see Table 3). Austin (in Austin and Mitch- ell, 1975) erected the genus Cloghergnathus to accommo- date lateral blade forms. Study of the type material and generic diagnoses of Taphrognathus and Cloghergnathus reveals that they are differentiated only by blade position. Sound taxonomic characters should be recognizable throughout the ontogeny of an organism, show a minimum of variation within populations, and not be readily modified by the environment (Blackwelder, 1967; Raup and Stanley, 1978). Blade position in Taphrognathus and Clogher- gnathus fulfils none of these criteria (see discussion of T. varians). The value of blade position as a taxonomic character is further undermined by the discordant nature of variation in the character. Taxonomic subdivisions defined on blade position, both within and between Cloghergnathus and Taphrognathus, do not correlate with the variation exhibited by other characters. Also, shifts in blade position are known to occur iteratively in the Cavusgnathidae (Druce, 1970; Austin, 1973; Mapes and Rexroad, 1986), making blade position a poor character on which to differentiate genera. Detailed palaeoecological analysis also indicates that the type species of Cloghergnathus, C. globenskii Austin, is an ecophenotype of T varians (see discussion of T. varians). Therefore, the concept of Taphrognathus is expanded to include Pa elements with lateral blades, previously assigned to Cloghergnathus. Platform -element symmetry may be of importance in both phytogeny (Lane, 1968) and functional morphology of conodonts (Aldridge et al., 1987; Nicoll, 1987). The symmetry of the Pa element pair has therefore been included in the revised diagnoses of T. varians and T. carinatus. Of the other species of Taphrognathus, T. cravenus (Metcalfe) Pa elements have medial to right blade development and a flared right parapet, probably pairing with Class Ilia symmetry. Taphrognathus rhodesi is known only from two specimens (Austin in Austin and Mitchell, 1975), and its symmetry cannot be determined. Although the close spacing of platform ribs diagnostic of T rhodesi is rarely approached in other species of the genus, the status of a species of Taphrognathus based on only two specimens is questionable. The concept of Taphrognathus discussed above con- firms the homeomorphic relationship with Adetognathus Lane noted by previous authors (Rexroad, 1958b; Austin in Austin and Mitchell, 1975; Higgins and Varker, 1982) (see discussion of the Cavusgnathidae). TABLE 3. Variation in blade position of Taphrognathus varians recorded by previous authors. Author Location Number of Number of Taphrognathids with T. varians Lateral Blades Branson and Mehl, 1941 Iowa, Missouri >74 1 T. varians ? Rexroad and Collinson, 1963 Illinois, Indiana, 16 11 Taphrognathus-Cavusgnathus Kentucky transitions Rexroad and Collinson, 1965 Illinois 297 0 ? Thompson and Goebel, 1968 Kansas > 300 9 Taphrognathus sp. Thompson and Fellows, 1970 Missouri, Arkansas, Oklahoma 12 1 New genus new species Nicoll and Rexroad, 1975 Indiana 678 < 10 T. varians transitional to Cavusgnathus Austin and Mitchell, 1975 Northern Ireland 2 15 Cloghergnathus Higgins and Varker, 1982 Ravenstonedale unknown unknown Cloghernathus carinatus Armstrong and Pumell, 1987 North Cumbria 12 194 Cloghernathus 21 Cloghergnathus-Taphrognathus intermediates This study Northumberland, North Cumbria 15 (morphotype I) 292 Taphrognathus varians (morphotypes II and DT) 18 Taphrognathus carinatus (Higgins and Varker, 1982) Plate 3, Figs. 10-15; Plate 4, Fig. 1 lv*p] Cloghergnathus carinatus Higgins and Varker, 1982:160, 161, pi. 18, figs. 1-3, 7-9, 1 1 only [Pa elements]. [vPl Cloghergnathus non-platform elements Higgins and Varker, 1982:161, pi. 18, fig. 18 [Pb element], fig. 19 [Scj element]; pi. 19, figs. 5, 6, 8 [Sa elements], fig. 20 [Sc2 element] only [all referred to as Cloghergnathus carinatus in plate caption], [vnonp] Cloghergnathus carinatus Higgins and Varker, 1982:160, 161, pi. 18, figs. 4-6, 10 only, [vnonp] Cloghergnathus non-platform elements Higgins and Varker, 1982:161, pi. 19, figs. 4, 18 only [referred to as Cloghergnathus carinatus in plate captions], [v.] Lonchodina sp. Higgins and Varker, 1982:164, pi. 18, fig. 17; pi. 19, figs. 1-3 [Sb elements], [v.] Neoprioniodus sp. Higgins and Varker, 1982:164, pi. 19, fig. 17 [M element], [v.] Cloghergnathus carinatus — Varker and Sevastopulo, 1985:200, pi. 5.5, figs. 6, 8, 10 [Pa elements] [cop. Higgins and Varker, 1982, pi. 18, figs. 1, 2, 7]. REVISED DIAGNOSIS Platform elements arched with short inner lateral or medial anterior blade one-quarter to one-fifth of element length; blade convex and crestlike, extending above height of par- apets but equal in height at its posterior end to the inner parapet; parapets nodose or transversely ridged; medial carina developed in posterior quarter of central trough; symmetry Class Illb dominant. HOLOTYPE British Museum, R30 (Higgins and Varker, 1982, pi. 18, figs. 2, 7). TYPE HORIZON AND LOCALITY Scandal Beck Limestone, sample SB2 of Higgins and Varker (1982), Ravenstonedale, Cumbria, U.K. (G.R. NY 722044). MATERIAL STUDIED Pa elements, 16(4); Pb elements, 11; M elements, 3; Sa elements, 23(1); Sb elements, 5(1); Sq elements, 5(6); Sc2 elements, 11(2); all, apart from 2 Pa elements, from the Cementstone Group of the Rothbury area. DESCRIPTION Pa elements. See Higgins and Varker (1982:160). Pb elements. The anterior process bears up to five later- ally compressed denticles which may be long and discrete or rather short. The reclined cusp is also laterally com- pressed and is taller and broader than the anterior denti- cles. The posterior process is about half the length and height of the anterior and bears three short denticles. Both processes and the base of the cusp are laterally thickened, with distinct shoulders developed alongside the denticles nearest the cusp. The processes taper distally and have a slight inward flexure. The basal cavity is deep and sur- rounded by thickened lips that pass laterally into thin zones of recessive basal margin along the narrow lower edge of the processes. The cavity tapers anteriorly and posteriorly, extending as a groove along the processes. M elements. See Higgins and Varker (1982:161) under Neoprioniodus sp. Sa elements. See Higgins and Varker (1982:161, 162) under Cloghergnathus A3 element. The elements figured by Higgins and Varker (1982) are missing the end of the posterior process. Examination of the specimens, however, suggests that the process was almost certainly short. The same is true of specimens from the Northumberland trough, with the process reduced to a small swelling at the base of the cusp in some specimens (e.g., PI. 3, Fig. 13). Sb elements. See Higgins and Varker (1982:161) under Lonchodina sp. Scj elements. These elements are indistinguishable from T. varians Sc elements. Sc2 elements. See Higgins and Varker (1982:161). The anterior process of these elements may have marked inward curvature. DISCUSSION The diagnosis given above is modified only slightly from that of Higgins and Varker (1982). With the recognition of T. varians morphotype III Pa elements (see below), inner lateral blade development and possession of a posterior carina can no longer be considered diagnostic of T. carina- tus alone. However, the crestlike blade profile, larger blade denticles, the development of more nodose or bloated par- apets, and the arching of the Pa element distinguish T. car- inatus from other members of the genus. All elements of this species also tend to be robust but this may be an ecophenotypic character as T. varians elements occurring with T. carinatus exhibit the same tendency. Pa elements are sinistral or dextral but always with an inner or, less commonly, a more medial blade. Mirror-image pairing of elements (Class II symmetry) seems unlikely; Class nib symmetry must have been dominant. Pb elements of T. carinatus differ from those of T. varians mainly in the thickening of the processes and the shortness of the posterior process. Some T. carinatus Pb elements approach the morphology of T. varians and vice versa, making specific assignment of some Pb elements difficult. Higgins and Varker (1982) suggest that the M element of T. carinatus is of "Neoprioniodus varians" form. However, the specimen they figure as the M element (pi. 19, fig. 18) has a broad, laterally compressed cusp and a short posterior process. It is of "N. scitulus" form and does not belong in Taphrognathus. "Neoprioniodus sp." of 19 Higgins and Varker (1982) has several characters in [v.] common with other elements of T. carinatus; in particular, the posterior process denticulation, the cusp, and the basal [v.] cavity are very similar to their figured Pb element. M elements identical to "Neoprioniodus sp." occur with other T. carinatus elements in the Northumberland trough. The specimen figured herein (PI. 3, Fig. 15) differs only in the shape of the anticusp and the amount of lateral thickening of the process. This specimen is only half the size of that figured by Higgins and Varker (1982) and this variation is [vnon] probably ontogenetic. M elements of "N. loxus" and "N. varians" forms, similar to those of T varians, also occur with T carinatus elements. These M elements may have been borne by some T. carinatus in place of the more robust M elements discussed above. The Sb element figured herein (PI. 3, Fig. 12) is thinner and bears less laterally compressed denticles than the elements described by Higgins and Varker (1982). It is also smaller, and these differences are probably ontogenetic. Taphrognathus carinatus and T. varians are found together in all but one sample from this study. This sample [non] (186861; Appendix He) contains no Sq elements. Although Higgins and Varker (1982) included these ele- ments in the apparatus of T. carinatus, their concept of the [(?)] species also included some Pa elements herein considered to be T. varians. Their Sci elements may therefore have [v.] been associated with T. varians, and these elements may not belong in T. carinatus. [v.] Taphrognathus varians Branson and Mehl, 1941 Plate 4, Figs. 2-15; Plate 5, Figs. 1-3 [p] [v*.] [v*] Taphrognathus varians Branson and Mehl, 194 lb: 182, pi. 6, figs. 27-33, 35^40 [Pa elements, morphotype I], fig. 34 [Pa element, morphotype II]. [non] Taphrognathus varians — Cooper, 1947:92, pi. 20, figs, [v.] 14-16. tv-] Taphrognathus varians — Rexroad and Collinson, 1963:21 , pi. 1, figs. 18-20 [Pa elements, morphotype I], fig. 22 [Pa element, morphotype III], [v.] Taphrognathus-Cavusgnathus transitions Rexroad and Collinson, 1963:20, pi. 1, figs. 21, 23, 24, 25 [Pa elements, morphotype III], [v.] Taphrognathus varians — Rexroad and Collinson, 1965:24, pi. 1 , figs. 30, 32 [Pa elements, morphotype I], fig. 3 1 [Pa element, morphotype I — III intermediate], [v.] Ozarkodina sp. Rexroad and Collinson, 1965: 13, pi. 1, fig. 6 [Pb element]. [y-] Hibbardella ortha Rexroad — Rexroad and Collinson, 1965:10, pi. 1, fig. 10 [Sa element]. Neoprioniodus loxus Rexroad — Rexroad and Collinson, 1965:12, pi. 1, figs. 11, 19 [M elements]. Neoprioniodus insolatus Hass — Rexroad and Collinson, 1965:11, 12, pi. 1, fig. 18. Taphrognathus varians — Thompson and Goebel, 1969:44, 45, pi. 5, figs. 1, 3, 5, 9, 13, 14 [Pa elements, morphotype I], figs. 2, 4, 6-8, 12, 15 [Pa elements, morphotype II]. Taphrognathus sp. Thompson and Goebel, 1969:45, pi. 5, figs. 10, 11 [Pa element, morphotype II]. Taphrognathus varians — Rhodes, Austin, and Druce, 1969:241, 242, pi. 13, figs. 4, 5. Taphrognathus varians — Thompson and Fellows, 1970:114, 115, pi. 4, figs. 10, 15 [Pa element, morphotype X\. New genus and new species Thompson and Fellows, 1970:115, pi. 4, figs. 11, 14 [Pa element, morphotype III]. Taphrognathus-Cavusgnathus transitions Austin, 1973, fig. 1.17 [Pa element, morphotype I], figs. 1.12, 1.13, 1.14, 1.15 [Pa elements, morphotype III] [cop. Rexroad and Collinson, 1963, pi. 1, figs. 18b, 24, 25, 21b, 23]. Taphrognathus varians — Austin, 1973, figs. 1.20, 1.21 [cop. Rhodes, Austin, and Druce, 1969, pi. 13, figs. 4a, 6a]. Taphrognathus varians — Jenkins, 1974, pi. 119, fig. 5 [Pa element, morphotype I?]. Taphrognathus varians — Austin, 1974, pi. 1, fig. 18 [Pa element, morphotype I]. Gen. nov. sp. nov. A Austin, 1974, pi. 1, figs. 11, 12 [Pa element, morphotype II]. Taphrognathus varians — Pierce and Langenheim, 1974:168, 169, pi. 1, figs. 1, 5 [Pa element, morphotype III?], fig. 2 [Pa element, morphotype II] only. Cloghergnathus globenskii Austin in Austin and Mitchell, 1975:48, 50, pi. 1, figs. 1^1, 8-15, 22, 27, 33 [Pa elements, morphotype II], figs. 7, 17, 26 [Pa element, morphotype I] [figs. 3, 8 cop. Austin, 1974, pi. 1, figs. 11,12]. Taphrognathus varians — Austin in Austin and Mitchell, 1975:53, pi. 1, figs. 5, 6, 16, 18, 19, 30 [Pa elements, morphotype I] [fig. 5 cop. Austin, 1974, pi. 1, fig. 18]. Taphrognathus varians — Nicoll and Rexroad, 1975:27, pi. 4, figs. 7-16 [Pa elements, morphotype I]. Ozarkodina sp. Nicoll and Rexroad, 1975:26, pi. 5, figs. 4- 6 [Pb elements], Hibbardella ortha — Nicoll and Rexroad, 1975, pi. 5, figs. 7, 8 [Sa elements]. Neoprioniodus loxus — Nicoll and Rexroad, 1975, pi. 5, figs. 12-14 [M elements]. Taphrognathus varians — Ruppel, 1979, pi. 2, figs. 1-3, 10 [Pa elements, morphotype I]. Taphrognathus-Cavusgnathus transition Ruppel, 1979, pi. 2, figs. 4, 5 [Pa element, morphotype III]. 20 Clydagnathusl hudsoni Metcalfe, 1980:176, pi. 13, figs. 8, 9 [Pa element, morphotype III]. [vp(?)] Cloghergnathus cravenus Metcalfe, 1981:17, pi. 11, fig. 2 only [Pa element, morphotype I]. IVJ Cloghergnathus globenskii — Metcalfe, 1981, pi. 12, figs. 1, 2 [Pa elements, morphotype II]. [v.] Taphrognathus^ sp. Metcalfe, 1981:45, pi. 10, fig. 3 [Pa element, morphotype III], [v.] Cloghergnathus rhodesi Austin — Metcalfe, 1981, pi. 10, fig. 4 [Pa element, morphotype III], [v.] Cloghergnathus globenskii — Austin and Rhodes in Robison, 1981, text-fig. 108,3 [Pa element, morphotype I] [cop. Austin and Mitchell, 1975, pi. 1, figs. 7, 17]. [vnon] Taphrognathus varians — Austin and Rhodes in Robison, 1981, text-fig. 108,1 [cop. Rhodes, Austin, and Druce, 1969, pi. 13, figs. 5a-c]. [v] Taphrognathus varians — Higgins and Varker, 1982:165, pi. 18, fig. 15 [Pa element, morphotype III], fig. 16 [Pa element, morphotype I?, specimen lost], [v.p] Cloghergnathus carinatus Higgins and Varker, 1982:160, 161, pi. 18, figs. 4-6, 10 only [Pa elements, morphotype III]. tvP(?)] Cloghergnathus non-platform elements Higgins and Varker, 1982:161, pi. 19, fig. 4 only [Pb element] [referred to as Cloghergnathus carinatus in plate caption], [v?] Neoprioniodus cf. acampylus Rexroad and Collinson — Higgins and Varker, 1982:164, pi. 19, fig. 16 [Sb element]. Cloghergnathus sp. A Austin and Davies, 1984, pi. 1, figs. 4, 19 [Pa elements, morphotype III]. [(?)] Taphrognathus sp. A Austin and Davies, 1984, pi. 1, fig. 3 [Pa element, morphotype III?], [v] Taphrognathus varians — Varker and Sevastopulo, 1985, pi. 5.5, fig. 2 [Pa element, morphotype III], fig. 4 [Pa element, morphotype I?, specimen lost] [cop. Higgins and Varker, 1982, pi. 18, figs. 15, 16]. Taphrognathus varians — Ruppel and Lemmer, 1986:34, pi. 1, figs. 1-3 [Pa elements, morphotype I], figs. 4, 5 [Pa element, morphotype III?]. Taphrognathus-Cavusgnathus transition Ruppel and Lemmer, 1986:34, pi. 1, fig. 6 [Pa element, morphotype III], [v.] Cloghergnathus cf. globenskii — Armstrong and Purnell, 1987, pi. 2, fig. 1 [Pa element, morphotype II]. [v.] Cloghergnathus-Taphrognathus intermediate Armstrong and Purnell, 1987, pi. 2, figs. 2, 3 [Pa element, morphotype II], [v.] Cloghergnathus sp. nov. Armstrong and Purnell, 1987, pi. 2, figs. 4, 5 [Pa elements, morphotype III], [v?] Cloghergnathus carinatus — Armstrong and Purnell, 1987, pi. 1, fig. 17 [Pa element, morphotype III?]. lv-l Cloghergnathus sp. indeL Armstrong and Purnell, 1987, pi. 2, fig. 6 [M element], fig. 7 [Pb element], fig. 8 [?Sa element], fig. 9 [Sc element]. [v.p] Patrognathus variabilis Rhodes, Austin, and Druce — Armstrong and Purnell, 1987, pi. 3, fig. 12 [Sa element]. [v.] Taphrognathus varians — Armstrong and Purnell, 1987, pi. 3, fig. 14 [Pa element, morphotype I], fig. 15 [Pa element, juvenile]. REVISED DIAGNOSIS Platform elements bear an anterior blade that is free for most of its length; blade denticles subequal or increasing in size anteriorly; height of posterior end of free blade and anterior end of parapets subequal; parapets transversely ridged. Class Illb symmetry dominant, Class II rarely developed. HOLOTYPE University of Missouri, C578-5 (Branson and Mehl, 1941b, pi. 6, fig. 28). TYPE HORIZON AND LOCALITY Keokuk shales and limestones (considered to be Salem by Rexroad and Collinson, 1963). The Troy locality about two miles east of Troy, on the Cuivre River in Lincoln County, State Highway 47, Missouri, U.S.A. (N.B. Not the Sylvan Beach locality.) MATERIAL STUDIED Pa elements, 372(225) [morphotype I, 13(2); morphotype n, 40(6); morphotype III, 253(32); morphotype indeL, 66(185)]; Pb elements, 46(36); M elements, 52(18); Sa elements, 11(11); Sb elements, 15(5); Sc elements, 26(116); from the Lynebank and Bewcastle formations, Lower Border Group, and from the Cementstone Group. In addition, the type and figured material of Branson and Mehl (1941a) and 60 unfigured specimens collected by them from the Sylvan Beach locality were studied. The collections of Rexroad and Collinson (1963, 1965) and Austin (in Austin and Mitchell, 1975) were also examined. DESCRIPTION Pa elements. Three intergrading Pa element morphotypes are recognized on the basis of anterior blade position: in morphotype I (PI. 4, Fig. 5) the blade is developed in a medial position terminating between the parapets of the platform; in morphotype II (PI. 4, Figs. 2, 9) it is devel- oped on the outer side of the element, with or without off- set from the parapet; in morphotype III (PI. 4, Figs. 3, 4) it is developed on the inner side with or without offset from the parapet (see Text-Fig. 7). Morphotypes II and III tend 21 Curvature Blade Morpho- Position type Straight, Medial. I less commonly sinistral or dextral. Dextral. Outer, detached, II offset from right parapet. Dextral. Outer, detached, aligned with right parapet. Dextral. Outer, continuous II with right parapet. Sinistral. Outer, detached, II offset from left parapet. Sinistral. Outer, detached, II aligned with left parapet. Sinistral. Outer, continuous with left parapet. Sinistral. Inner, detached, III offset from right parapet. Sinistral. Inner, detached, ni aligned with right parapet. Sinistral. Inner, continuous III with right parapet. Dextral. Inner, detached, III offset from left parapet. Dextral. Inner, detached, III aligned with left parapet. Dextral. Inner, continuous III with left parapet. TEXT- FIG. 7. Explanation of Pa element morphotype and blade position categories of Taphrognathus varians. to develop greater lateral curvature than morphotype I. In all other respects they are similar. At its posterior end, the anterior blade often overlaps with one or both parapets for a short distance but remains free for the greater part of its length. It bears between four and eleven denticles. These are fused apart from their tips and are generally subequal or increasing in size anteriorly apart from two or three smaller denticles often developed at the anterior end. The height of the posteriormost denticles of the free part of the blade is approximately equal to or slightf y less than that of the anterior end of the nearest parapet. The blade is usually between one-quarter and two-fifths the length of the element. The platform may be straight or sinuous but often exhibits some degree of sinistral or dextral curvature, the outer parapet being convex, the inner concave, straight, or slightly convex. The upper parts of the inner surfaces of the parapets are ornamented by weak ridges, usually becoming slightly stronger towards the posterior, often more strongly developed in larger specimens. The ridges extend part-way down the parapet surfaces, dying out towards the median trough which is generally unornamented; occasionally a weak posterior carina of a few nodes is developed. The trough may be constricted slightly at its anterior end, but is never closed, by inward curvature of one of the parapets. Irrespective of element curvature, the right parapet is often higher than the left in the anterior half of the platform. The posterior end of the platform is sharply pointed and usually terminates as a short bladelike structure, often formed as an extension of the weak carina or one of the parapets. In lateral view, the upper surface of the platform is gently convex. It has a serrated or crenulated profile, the strength of which depends on the strength of the parapet ornament The lower surface is generally slightly concave or flat, and the overall height of the element slightly decreases posteriorly. The platform width is between one-quarter and one-fifth of its length, usually widest around the midlength of the element The basal cavity is lanceolate, occupying most of the lower surface. It is widest and deepest around element midlength, tapering more rapidly anteriorly than posteriorly. It continues as a groove under part of the anterior blade, and extends to a point at, or just short of, the posteriormost tip of the element. The cavity possesses a weak medial groove for its entire length and may be subsymmetrical to moderately asymmetrical. Pb elements. See Rexroad (1957:36) under Ozarkodina compressa. T. varians Pb elements of this study differ from "O. compressa" sensu Rexroad (1957) in having slightly fewer denticles. Also, they have basal grooves that extend from the basal cavity but do not usually reach the distal ends of the processes. 22 M elements. See Branson and Mehl (194 lb: 174) under Prioniodus varians, and Rexroad (1957:34) under Neopri- oniodus loxus. M elements occur as "N. loxus" and "N. varians" morphotypes. In T varians, as may be the case in Cavusgnathus (Rexroad, 1958a; Norby, 1976), these mor- photypes differ in little other than the angle of downward deflection of the posterior process and represent extremes in the range of variation in M elements. Occasionally a small denticle is present on the lower anterior edge of the cusp. Sa elements. See Rexroad (1958a: 18) under Hibbardella ortha. These elements vary in the angle of divergence of the lateral processes. Sb elements. The anterior process is straight and bears as many as 12 denticles that alternate irregularly in size. These denticles are usually subcircular in cross-section. They are suberect at the anterior end of the process and become increasingly reclined posteriorly. The process is laterally compressed, and deflected slightly inwards and either upwards or downwards relative to the posterior pro- cess. The cusp is only slightly larger than the process den- ticles and is reclined. Although incomplete in all specimens, the posterior process is slightly longer than the anterior and is also slightly higher and less laterally compressed. It bears at least three laterally compressed major denticles with up to three minor denticles between each one. The denticles are discrete for most of their length and are inclined posteriorly. The small basal cavity is developed obliquely beneath the cusp. It has a small lip on the inner side and tapers to the anterior and posterior, continuing along the processes as a groove. Sb elements resemble Sc elements in general character but have a longer anterior process. Sc elements. See Hass (1953:81, 82) under Hindeodella ensis, and Clarke (1960:8) under H. tenuis. The posterior process of T. varians Sc elements is shorter than described by Hass (1953). The elements are variable, especially in the regularity of alternation in size of denticles on the pos- terior process and the degree of inward curvature of the anterior process. The posterobasal termination of some elements is abruptly downcurved beneath the steeply inclined posterior denticles. DISCUSSION Expansion of the generic concept of Taphrognathus to include Pa elements with a range of blade positions reduces taxonomic confusion at the genus level. Blade position, however, has also been used as a taxonomic char- acter at the species level in Taphrognathus. Taphrognathus varians sensu Branson and Mehl (1941b), T globenskii (Austin) (in Austin and Mitchell, 1975), and Taphrog- nathus sp. nov. sensu Armstrong and Purnell (1987) are differentiated primarily using blade position. In the present study, blade position was found to vary continu- ously and in discord with other characters such as curva- ture and carina development. Nicoll and Rexroad (1975) also noted the nonsystematic variation of these and other characters in their large collections of T. varians. In fact, all published work on T. varians documents variation in blade position (see Table 3). Blade position is not a sound character on which to differentiate species in Taphrognathus. In addition to its continuous variation, it varies through ontogeny (see discussion below), and is subject to environmental mod- ification. To examine its relationship with environment, the continuum of blade position was arbitrarily divided into 13 categories (Text-Fig. 7) and the environmental distribution of these categories in the Bogside Limestone Member in Ashy Cleugh (locality 10; Appendix lib) was analyzed (Text-Fig. 8). The Bogside Limestone Member was deposited below normal wave base in a restricted microtidal shallow-shelf setting subject to fluctuations in salinity and periodic agitation by storms (Purnell, 1989). The environmental gradient used in Text-Fig. 8 is the result of unconstrained seriation of sedimentological data for all samples of the Bogside Limestone Member from locality 10 (see Brower and Burroughs, 1982; Brower and Kile, 1988, for discussion of seriation). The resultant arrangement of samples, which reflects an environmental gradient of increasing restriction (Purnell, 1989), was then used in direct gradient analysis of T varians morphotypes (see Cisne and Rabe, 1978; Springer and Bambach, 1985, for discussion of gradient analysis). Morphotype I elements (approximately equivalent to T. varians sensu Branson and Mehl; A in Text-Fig. 8) and morphotype II elements (approximately equivalent to Cloghergnathus globenskii; B-G in Text-Fig. 8) are present only in the most restricted environments. Morphotype III elements have a much broader environmental range. This distri- bution of morphotypes reflects increasing variability of blade position with increasing environmental restriction and supports the hypothesis that blade position is an ecophenotypic character. This trend might be a sampling artifact, the increase in observed variation reflecting the larger number of specimens recovered from the more restricted environments. However, the variation exhibited by specimens of some samples that are not high in abundance (e.g., samples 1768632 and 1411851) suggests that the trend is real. In conclusion, blade position in T. varians is of highly dubious taxonomic significance. In the Bogside Limestone Member, specimens that would previously have been assigned to C. globenskii (the type species of Clogher- gnathus) are ecophenotypic variants of T. varians sensu Branson and Mehl. The holotype of C. globenskii also comes from a sample that includes T. varians sensu Branson and Mehl, and intermediate forms. 23 The three morphotypes of T. varians described herein differ only in blade position and serve as aids to discussion of intraspecific variation. These morphotypes are not randomly distributed. Most American T. varians faunas are dominated by morphotype I (e.g., Branson and Mehl, 1941b; Thompson and Goebel, 1969; Nicoll and Rexroad, 1975); the limited Irish fauna of Austin and Mitchell (1975) is dominated by morphotype II; Northumberland trough faunas are dominated by morphotype III (Armstrong and Purnell, 1987; this study). This geograph- ical distribution might suggest that morphotypes I, II, and III represent three subspecies (sensu Mayr, 1969:41); however, the morphotypes are not geographically mutu- ally exclusive. The separate populations show consi- derable overlap in their ranges of variation, and the distribution of morphotypes probably reflects different bias within the same range of variation in separate geographical areas. The holotype of T. varians, for example, although part of an American morphotype I- dominated fauna, is intermediate between morphotypes I and II. Taphrognathus cravenus (Metcalfe) is distinguished from T. varians primarily by the lateral flare or "winged" appearance of the anterior end of the right parapet. From the available material, it is unclear whether or not this character is consistently developed and of sufficient importance to maintain T. cravenus as a separate species. One of the specimens figured by Metcalfe (1981, pi. 11, fig. 2) lacks this character and is included in synonymy with T. varians. Metcalfe (1981) also reported a single specimen of T. rhodesi Austin (in Austin and Mitchell, 1975). This specimen is overgrown, but appears to lack the diagnostic platform ornament of T. rhodesi and is probably T. varians. The apparatus of T. varians is very similar to species of Cavusgnathus. Indeed, the nonplatform elements of T. varians, C. unicornis Youngquist and Miller, and C. altus Harris and Hollingsworth would previously have been referred to the same discrete element species. It is only because Cavusgnathus Pa elements do not occur with T. varians Pa elements in the Northumberland trough that the nonplatform elements of T. varians can be positively assigned. Although they did not reconstruct the apparatus, Nicoll (1971) and Nicoll and Rexroad (1975) suggested that "0. compressa" type elements were associated with T. varians Pa elements. This is borne out by the present study. Higgins and Varker (1982) figured two Pb elements that they considered to belong to T. carinatus. One of these is probably a T. varians Pb element, but it is possible that Pb elements of T. carinatus and T. varians intergrade. The M elements of T. varians vary in the angle of downward deflection of the posterior process between 'W. loxus" and "N. varians" type elements. American authors Restricted; fluctuating salinity and ?temperature TEXT- FIG. 8. Distribution of Taphrognathus varians Pa element morphotypes along a gradient of increasing environmental restriction in the Bogside Limestone Member. Each increment of horizontal scale equals one Pa element; sample numbers at left. 24 have in the past assigned their T. varians M elements to "N. loxus," the form with greater downward process deflection (e.g., Thompson and Goebel, 1969; Nicoll and Rexroad, 1975). The more common form of element in the Northumberland trough is of "N. varians" form. This geographic distribution corresponds to that of the Pa element morphotypes. Morphological intergradation and co-occurrence of the different forms of M element suggest that they vary intraspecifically. M elements of this type may also have been present in some T. carinatus (see discussion of T. carinatus). Sa elements of Patrognathus capricornis (Druce) are indistinguishable from those of T. varians (see discussion of P. capricornis). The specimen figured as "Clogher- gnathus? sp. indeL Sa element" by Armstrong and Purnell (1987, pi. 2, fig. 18) does not have the characteristic triangular cusp cross-section but is tentatively retained within T. varians. The single specimen of Neoprioniodus cf. acampylus recovered by Higgins and Varker (1982) has a small indistinct basal cavity halfway along its length, and closely resembles T. varians Sb elements. The state of preservation of the specimen precludes a definite assignment. ONTOGENY During ontogeny the relative proportions of different parts of T. varians Pa elements change markedly (see Text-Fig. 9). The smallest specimen recovered (0.2 mm in length; Text-Fig. 9a) is essentially bladelike with discrete pointed denticles and a short low platform developed as a slight expansion of the upper part of the posterior third of the element. The basal cavity is developed beneath the blade rather than the incipient platform. With increasing matu- rity (Text-Fig. 9b, c), the platform becomes better devel- oped but is only weakly ornamented. At this stage, the blade is medial in position, about half the length of the ele- ment, and still bears more discrete denticles than at adult stage. The element is straight and the basal cavity extends under both the platform and the blade. Variation in blade position develops only after this stage, enabling differenti- ation of morphotypes I, II, and III (Text-Fig. 9d, e, f)- Some immature Pa elements of T. varians resemble T.I transatlanticus in their small size and weak platform orna- ment. One figured specimen (PI. 4, Fig. 7) illustrates this resemblance. Only close examination of the platform under SEM reveals that the right parapet bears incipient ornament consisting of slight pinching and swelling rather than the unornamented surface characteristic of T.I trans- atlanticus (see discussion of TP. transatlanticus). In addi- tion to variation in blade position, increase in size and maturity is accompanied by relative shortening of the free blade to one-quarter to one-fifth of element length, devel- opment of stronger and more numerous transverse ribs on the parapets, and constriction of the anterior end of the basal cavity restricting it to the lower surface of the plat- form. Published plates and the collection of Branson and Mehl (1941b) suggest that most T. varians Pa elements from the U.S.A. have an upper surface that is flat or slightly concave in its posterior half, whereas T. varians Pa elements of this study generally have convex upper platform surfaces. These differences are probably ontogenetic. Most figured T. varians from the U.S.A. and the specimens of Branson and Mehl (1941b) are over 1 mm in length; comparatively few specimens of this size have been found in the Northumberland trough. The few smaller specimens of T. varians that have been figured by American authors generally have convex upper platform surfaces (e.g., Rexroad and Collinson, 1963, pi. 1, figs. 18, 21). A few large specimens encountered in this study do, however, retain a convex platform surface as a consequence of being arched. Text-Fig. 9 also illustrates the ontogeny of Pb elements. The smallest specimens (j) are short and straight; the processes have only two or three sharply pointed denticles; the basal cavity is relatively large and elongate, tapering to the ends of the processes. With increasing maturity the number of process denticles increases and the basal cavity becomes relatively smaller and more constricted. The ontogeny of the ramiform elements is not known. Pa ELEMENT SYMMETRY The symmetry classification of Lane (1968) (Text-Fig. 10) provides a convenient means of discussing the pairing of Pa elements in conodont apparatuses. Lane (1967, 1968) discussed the phylogenetic significance of Pa element symmetry in some early Pennsylvanian taxa, and the dif- ferentiation of Adetognathus and Cavusgnathus on the basis of Pa element symmetry illustrates its potential taxo- nomic significance. Pa element symmetry varies both within and between genera of the Cavusgnathidae (Table 1) and may prove to be a useful character in any system- atic revision of the family. Pa element symmetry also has considerable functional significance and may provide evi- dence in determining whether conodont apparatuses per- formed a grasping or filter-feeding function (Aldridge, 1987; Nicoll, 1987). Pa elements that are herein considered to be T. varians have previously been assigned to symmetry Class I (Lane, 1968; Druce, 1973; Austin in Austin and Mitchell, 1975) and Class II (Austin in Austin and Mitchell, 1975). The present collection of more than 400 T. varians Pa elements has enabled a detailed reassessment of their symmetry. On the basis of curvature and blade position, Pa elements were assigned to one of thirteen categories (Text-Fig. 7). Morphotype III elements (Text-Fig. 11; categories H-M) 25 1mm TEXT-FIG. 9. Ontogeny of Pa and Pb elements of Taphrognathus varians. Figures based on actual specimens with broken parts restored: a) ROM 48831; b) ROM 48828; c) ROM 48830; d) NG2/267; e) TGI/569; 0 ROM 48829; g) ROM 48824; h) ROM 48825; i) ROM 48822; j) ROM 48834; k) TG 1/439; 1) ROM 48832. far outnumber morphotype I and II elements (Text-Fig. 11; categories A-G). This disproportionate representation and the absence of morphotype III elements in the collection of Austin and Mitchell (1975) suggests that morphotype II elements did not pair with morphotype III elements (Class Ilia symmetry). Too few morphotype II specimens were available to test this hypothesis statistically. Not enough morphotype I specimens have been recovered in this study to assess their symmetry in the Northumberland trough. Pa element pairing in T. varians morphotype III can, however, be statistically analyzed. Because it cannot be assumed that the data for each of the categories H to M are normally distributed and do not have significantly different variances, nonparametric procedures were used. Of the 288 morphotype III Pa elements that have been categorized, 133 are sinistral (H, I, J) and 155 are dextral (K, L, M). Spearman's rank correlation indicates a positive relationship between the distributions of sinistral and dextral elements (P < 0.01) (see Purnell, 1989, for all Spearman's rank correlation data and results). This may be interpreted in two ways: either T. varians that bore morphotype III Pa elements existed in two forms, one with dextral and the other with sinistral Pa elements, which were numerically balanced and had a consistent pattern of co-occurrence; or Pa elements were paired sinistral with dextral and in the same animal. Although some cavus- gnathids may have had Pa elements that were asymmet- rically paired in terms of curvature (Rexroad, 1981), the possibility of a consistent 1:1 relationship between animals with dextral pairing and those with sinistral seems remote. Thus elements assigned to categories H, I, and J were paired with K, L, and M (Text-Fig. 12). H, J, and M are the most common and abundant element forms (Text-Fig. 11). H and J must have paired with M (Text-Fig. 12), and the hypothesis that the combined distribution of H and J is unrelated to that of M is rejected (P < 0.01). A relationship between J and M is supported statistically (P < 0.001), but the distributions of H and M are not significantly correlated (P > 0.05). Given that sinistral and dextral 26 Symmetry Class and Description la Bilaterally symmetrical unpaired elements. lb Bilaterally symmetrical conodont elements, symmetrically paired. Ilia Illb IV "Two mirror imaged and oppositely curved specimens form a bilaterally symmetrical conodont element pair." (Lane, 1968:1259). "Morphologically identical asymmetrical elements that are paired with respect to curvature but not with respect either to development of the platform or to attachment of the blade to the platform." (Lane, 1968:1260). "...asymmetric conodont element pair consisting of two morphologically distinct elements., [with].. opposite directions of curvature [and] imperfect mirror-image pairing..." (Lane, 1968:1260). "...asymmetric, curvature absent or indistinct and no mirror-imaged or opposable asymmetric element [known]..." (Lane, 1968:1261). TEXT- FIG. 10. Symmetry classification of Lane (1968) illus- trated by hypothetical Taphrognathus varians Pa element pairing. elements were paired, however, this lack of correlation is puzzling as there is little other than M type elements with which H forms could have paired (Text-Fig. 11). The relationship between H and L is supported statistically (P < 0.05) but because of the small numbers of L type elements, H:L pairing was probably less common. None of the six remaining pairing permutations is supported by significant Spearman's rank correlations but, unless elements could be unpaired, at least some of them must have occurred. Only two are considered unlikely because of the rarity of both elements of the pair (Text-Fig. 12). In the majority of cases, therefore, T. varians morphotype III paired with Class Illb symmetry. Class II symmetry (see Text-Fig. 10) is also possible but, given the variability of Pa elements of the species and their tendency to develop a higher right anterior parapet, was probably rare. The 16 specimens in the Austin and Mitchell (1975) col- lection considered herein to be T. varians morphotypes I and II are inadequate for a detailed analysis of symmetry. The range of blade positions and curvature exhibited by these specimens and the morphotype II material of this study is, however, consistent with Class Illb symmetry (Text-Fig. 13). European collections of T. varians contain few morphotype I Pa elements. They may have paired together or with morphotype II or III elements (Class Illb symmetry dominant), but the small number of known specimens precludes more rigorous analysis. Most American T. varians faunas are, however, dominated by morphotype I elements. The original collection of Branson and Mehl (1941b) includes 70 specimens from the Sylvan Beach locality. Of these, 61 elements have determinable curvature of which 30 are sinistral, 16 are dextral, and 15 are straight. These numbers suggest that sinistral-dextral and sinistral-straight pairing (Class Illb symmetry) were most common; dextral-dextral pairing and straight-straight pairing (Class lb symmetry) were rare (Text-Fig. 14). Again, the morphological variability of these specimens and the tendency to develop a higher right anterior parapet suggests that Class II was rarely if ever developed. Taphrognathus cf. varians MATERIAL STUDIED Two Pa elements from the Cementstone Group in the Rothbury and Kielder areas. DISCUSSION These specimens differ from T. varians only in exhibiting a marked lateral bulging of the anterior end of the right parapet. Whether such specimens represent a distinct taxon or variant T. varians Pa elements is unclear. 27 TEXT- FIG. 11. Distribution of Taphrognalhus varians blade position/curvature categories in the Lower Border and Cementstone groups. Scale bar equals 10 Pa elements; sample numbers at left. N.B. Diagram includes only T. varians-yieldmg samples. Taphrognalhus sp. a Plate 5, Figs. 5a, b MATERIAL STUDIED One Pa element from the Harden Member, Middle Border Group, superjacent to the Black Burn Formation. DESCRIPTION The apparatus of this species is unknown. The anterior blade of the Pa element is located on the left side. The blade is continuous with the outer parapet and bears four blunt denticles, the middle two of which are largest. The denticles are fixed apart from their tips and are not later- ally compressed. The blade is free for its entire length and makes up one-quarter of the length of the element. The platform is sinistral, the outer parapet convex, the inner more or less straight. The parapets have rounded crests and bear weak transverse ridges which increase slightly in strength posteriorly. The right parapet is slightly higher than the left in the anterior half. The medial trough is shal- low and unornamented. It is open anteriorly and shallows towards the bluntly pointed posterior end of the element. In lateral view the element is gently arched, the platform height slightly decreasing posteriorly. Platform width is just over one-quarter of its length, widest in the anterior half. The basal cavity is lanceolate and subsymmetrical, 28 Uncommon I L Very rare Uncommon Less common HM 1 M Very rare Uncommon Common Uncommon Common TEXT-FIG. 12. The nine possible pairings of Pa elements of Taphrognathus varians morphotype HI in the present study. Relative fre- quency categories based on the results of Spearman's rank correlation of blade position/curvature categories. TEXT-FIG. 13. Likely Pa element pairing in Taphrognathus vari- ans morphotype II (based on the collection of Austin and Mitchell, 1975; and this study). Letters indicate blade position/ curvature categories. and occupies most of the lower surface of the element. It is widest and deepest at element midlength and bears a medial groove. Posteriorly the cavity tapers gently to the end of the element. DISCUSSION The single Pa element of Taphrognathus sp. a differs from other species of Taphrognathus chiefly in the form of the anterior blade, the roundedness of the parapet crests, and the shallowness of the medial trough. It is very similar to specimens identified as Cloghergnathus sp. A and Taph- rognathus sp. B, in Marchant (1978) and Rees (1987) respectively. 29 Common Rare Symmetry class Ilia Symmetry class lb TEXT-FIG. 14. Likely Pa element pairing in Taphrognathus varians morphotype I (based on the collection of Branson and Mehl, 1941b). Symmetry classes after Lane (1968; see Text-Fig. 10). Taphrognathus? transatlantic us (von Bitter and Austin, 1984)? Plate 5, Figs. 4a, b MATERIAL STUDIED One Pa element from the Bogside Limestone Member of the BewcasUe Formation, Lower Border Group. DESCRIPTION See von Bitter and Austin (1984:101-106). The Pa ele- ment recovered from the Bogside Limestone differs from TP transatlanticus in bearing an anterior blade that does not increase in height posteriorly. DISCUSSION Because of the differences from typical TP. transatlanticus noted above, and its poor state of preservation, the single specimen recovered has been assigned to TP. transatlanti- cus!. In erecting T. transatlanticus, von Bitter and Austin (1984:100) noted that neither Taphrognathus nor Cavusgnathus were ". . . sufficiently broad to comfortably and unequivocally include the new species." The same is true of the revised concept of Taphrognathus. Both T. varians and T carinatus bore M elements, whereas TP transatlanticus did not. No other species of Taphrognathus has the posteriorly enlarging Pa element blade denticles or the unornamented parapets of TP transatlanticus. A single specimen of Taphrognathus sp. A was recovered by Davies (1980), figured by Austin and Davies (1984, pi. 1, fig. 3), and considered by von Bitter and Austin (1984) to be T transatlanticus. This element appears to have incipient ornament on the right parapet and is probably a juvenile T. varians element. Similar specimens have been recovered in this study (e.g., PI. 4, Fig. 7). Given the resemblance between juvenile T. varians Pa and Pb elements (PI. 4, Figs. 7, 8, 10, 14) and their mature counterparts in TP transatlanticus, the latter species may have evolved progenetically from T. varians. Family Gnathodontidae Sweet, 1988 Genus Gnathodus Pander, 1856 Gnathodus Pander, 1856:33. [non] Gnathodus Fieber, 1866. Dryphenotus Cooper, 1939:386. Westfalicus Moore and Sylvester-Bradley, 1957:21. DIAGNOSIS (After Lane, Sandberg, and Ziegler, 1980; Austin and Rhodes in Robison, 1981.) Apparatus probably seximem- brate: Pa element carminiscaphate; basal cavity asymmet- ric, inner side bears parapet and is narrower and extends further anteriorly than the more expanded outer side. Pb elements angulate; M elements dolabrate; Sa element alate; Sb elements bipennate; Sc elements bipennate. Pa elements paired with Class II symmetry; other elements, except the Sa, paired symmetrically. TYPE SPECIES Polygnathus bilineatus Roundy (1926) by subsequent des- ignation (I.C.Z.N. opinion 1415, Tubbs, 1986). Gnathodus cuneiformis Mehl and Thomas, 1947 Plate 5, Fig. 7 Gnathodus cuneiformis Mehl and Thomas, 1947:10, pi. 1, fig. 2. 30 Gnathodus cuneiformis — Ziegler in Zicglcr, 1981:123-6, Gnathodus — pi. 1, figs. 1-5 [with full synonymy]. DIAGNOSIS See Lane, Sandberg, and Ziegler (1980:130). HOLOTYPE University of Missouri, C654-4 (Mehl and Thomas, 1947, pi. 1, fig. 2). TYPE HORIZON AND LOCALITY Greenish-grey and red argillaceous limestone, Fern Glen Formation, units 9-11 of Mehl and Thomas (1947); bluff of the Meramec River at CasUewood, Missouri, U.S.A. MATERIAL STUDIED A single Pa element from a loose sample of the Glebe Limestone Member, Cementstone Group. DESCRIPTION Apparatus unknown. See Mehl and Thomas (1947:10) for Pa element description. DISCUSSION Only the Pa elements of this species are known. The spec- imen recovered closely resembles the holotype, consid- ered by Lane, Sandberg, and Ziegler (1980) to represent a younger morphotype of the species. Gnathodus0. simplicatus (Rhodes, Austin, and Druce, 1969) Plate 5, Fig. 6 Gnathodus simplicatus Rhodes, Austin, and Druce, 1969:107, pi. 8, fig. 5; pi. 18, figs. 2-5. DIAGNOSIS See Rhodes, Austin, and Druce (1969:107). HOLOTYPE British Museum, X89 (Rhodes, Austin, and Druce, 1969, pi. 18, fig. 4). TYPE HORIZON AND LOCALITY Sample ZLA 33 of Rhodes, Austin, and Druce (1969), North Crop, South Wales Coalfield, U.K. (precise locality details are confused in Rhodes, Austin, and Druce, 1969). MATERIAL STUDIED A single Pa element from the Harden Member, Middle Border Group, superjacent to the Black Burn Formation. DESCRIPTION Apparatus unknown. See Rhodes, Austin, and Druce (1969: 107) for description of Pa elements. DISCUSSION See Davies (1980) for the only recent synonymy for this species. Only the Pa elements are known. The specimen recovered in this study is very similar to the holotype, but does not have the regularly sloping upper surface consid- ered to be diagnostic by Rhodes, Austin, and Druce (1969). It is also similar to G. simplicatus from Ireland fig- ured by Johnston and Higgins (1981). According to Lane, Sandberg, and Ziegler (1980), an expanded asymmetric basal cavity and the development of an inner parapet are diagnostic of Gnathodus. The simple carminiscaphate Pa elements of this species should probably be referred to another genus, but without knowledge of the apparatus this new generic assignment cannot be determined. Family Mestognathidae Austin and Rhodes in Robison, 1981 Genus Mestognathus Bischoff, 1957 Mestognathus Bischoff, 1957:36. DIAGNOSIS See von Bitter, Sandberg, and Orchard (1986:32). TYPE SPECIES Mestognathus beckmanni Bischoff, 1957, by original des- ignation. Mestognathus beckmanni Bischoff, 1957 Plate 5, Figs. 8, 9 Mestognathus beckmanni Bischoff, 1957:37, pi. 2, figs. 4- 6, 8, 9 [Pa elements]. [(?)] Ozarkodina macra Branson and Mehl — Metcalfe, 1980:173, fig. 3 (table) [Pb elements] [not figured]. [v] Ozarkodina macra— Metcalfe, 1981, pi. 19, fig. 6 [Pb element]. 31 Mestognathus beckmanni — von Bitter, Sandberg, and Orchard, 1986:35-37, pi. 1, figs. 1-8, 23; pi. 2, figs. 1- 5, 9; pi. 3, figs. 1-5, 9; pi. 4, figs. 1-5, 9; pi. 12, figs. 1- 6; pi. 13, figs. 1-9; pi. 14, figs. 1-12; pi. 15, figs. 1-12; pi. 16, figs. 1-12; pi. 17, figs. 1-13; pi. 19, figs. 1-5; pi. 20, figs. 3, 6, 10, 12; pi. 23, figs. 1-3; pi. 25, figs. 7-9; pi. 26, fig. 4; pi. 27, figs. 3, 4, 7 [Pa elements] [with full synonymy for Pa element]. [yp] Cavusgnathus unicornis Youngquist and Miller — Armstrong and Purnell, 1987, pi. 1, fig. 13 only [Pb element]. [vnon] Mestognathus beckmanni — Armstrong and Purnell, 1987, pi. 3, figs. 4, 5, 6, 7. DIAGNOSIS See von Bitter, Sandberg, and Orchard (1986:37). HOLOTYPE Phillips University (Marburg), Bi 1957/35 (Bischoff, 1957, pi. 2, fig. 4). TYPE HORIZON AND LOCALITY Lower Goniatites Stufe, cu III a, small quarry 1 km north of Lethmathe, immediately north of the Waldcafe, on the road between Lethmathe and Schwerte, Topographic Sheet Hohenlimburg, Germany. MATERIAL STUDIED Pa elements, 86(3); Pb elements, 1; from the Bogside Limestone Member of the Bewcastle Formation, Lower Border Group, and the Cementstone Group, Akenshaw Burn. Unpublished material, including 5 Pb elements, col- lected by Dr. N. J. Riley from the Craven basin was also examined. DESCRIPTION Pa elements. See von Bitter, Sandberg, and Orchard (1986:3-7, 36-37). Pb elements. The anterior process is straight and bears eight to ten laterally compressed, slightly reclined denti- cles with sharp triangular tips. The denticles are all fused for more than half their length but become more fused towards the cusp; they are largest and least fused immedi- ately anterior of the process midlength. The process is lat- erally thickened with a distinct rib or ridge developed below the base of the denticles, especially on the outer side. This rib thins towards the anterior end and the sharp lower edge, and extends along the long axis of the cusp. The cusp is as much as two or three times the length and width of the largest process denticles. It is strongly reclined at an angle of 150° from the long axis of the ante- rior process and, in mature specimens, has an irregularly stepped or weakly serrated anterior edge. The serration appears to be caused by the incorporation of two or three anterior denticles into the cusp during ontogeny. The pos- terior process is straight and is deflected downwards at an angle of approximately 40° from the anterior process. It is similar to the anterior process in terms of length, denticle size and shape, and the thin lower margin, but is less thick- ened and slightly lower. The posterior end is commonly missing, but the process bears as many as nine or more denticles which are increasingly reclined posteriorly. The basal cavity is narrow and elongate; it is situated beneath the cusp and does not extend along the thin lower edges of the processes, both of which bear a zone of recessive basal margin (eversion strips). White matter is developed along the growth axes of the cusp and posterior denticles espe- cially. DISCUSSION von Bitter, Sandberg, and Orchard (1986) were uncertain if Mestognathus bore nonplatform elements, but did not rule out the possibility that they may have been present under optimum conditions. The present study suggests that in certain environments M. beckmanni bore a pair of Pb elements similar in form to "Ozarkodina macra." In the Northumberland trough this distinctive Pb element has been recovered with M. beckmanni Pa elements from the Bogside Limestone Member (Appendix lib) and from the 3 m thick Tombstone Limestone, which has also yielded M. beckmanni (Armstrong and Purnell, 1987). Metcalfe (1980) recorded seven specimens of "O. macra" associ- ated with M. beckmanni in five samples through the Emb- say Limestone Member in the Craven basin. A further three specimens were reported by Metcalfe (1981), two occurring with M. beckmanni, one within 2 m of a M. beckmanni-yiclding sample. Five specimens of "O. macra" collected by Dr. N. J. Riley from the Craven basin were all associated with M. beckmanni Pa elements. The rest of the fauna recovered by Metcalfe (1980, 1981) and Riley is made up of species of Gnathodus and Klado- gnathus Rexroad with Patrognathus capricornis (Druce) and rare Polygnathus bischoffi Rhodes, Austin, and Druce. None of these conodonts bore Pb elements of "O. macra" form. In addition to this evidence of association, certain aspects of the morphology of these Pb elements, notably the anterior process denticles and cusp, are similar to M. beckmanni Pa elements (compare PI. 5, Fig. 9 with von Bitter, Sandberg, and Orchard, 1986, pi. 16, fig. 7, for example). The small basal cavity, the well-developed ever- sion strips, and the overall robust structure of the element are also reminiscent of M. beckmanni Pa elements. Mestognathus bipluti Higgins probably also bore Pb elements similar to those described above. Five such Pb elements were assigned to Clydagnathus windsorensis (Globensky) by Plint and von Bitter (1986, table 1) and by von Bitter and Plint (1987, table 1), but were recovered from a sample which contains no Pa elements of CI. 32 windsorensis (sample IDM-3-21). This sample does, however, contain nine Pa elements of M. bipluti and Mestognathus spp. Mestognathus praebeckmanni Sandberg, Johnston, Orchard, and von Bitter, 1986 Plate 5, Fig. 10 Mestognathus praebeckmanni Sandberg, Johnston, Orchard, and von Bitter in von Bitter, Sandberg, and Orchard, 1986:34, 35, pi. 1, figs. 32-34; pi. 7, figs. 1-5; pi. 8, figs. 1-1 1; pi. 9, figs. 1-1 1; pi. 10, figs. 1-7, 10, 1 1; pi. 11, figs. 1-10 [with full synonymy], [vp] Mestognathus beckmanni — Armstrong and Purnell, 1987, pi. 3, fig. 4 only. DIAGNOSIS See von Bitter, Sandberg, and Orchard (1986:35). HOLOTYPE United States National Museum 257757 (von Bitter, Sand- berg, and Orchard, 1986, pi. 8, figs. 1^, 8, 10). TYPE HORIZON AND LOCALITY Facies de Leffe, Banc 60 of Groesscns (1971, log 6, sec- tion 8), route between Salet and Bioul, 8 km NW of Dinant, Belgium. MATERIAL STUDIED Pa elements, 9(2) from the lower Lynebank Formation, Lower Border Group. DESCRIPTION Pa elements. See von Bitter, Sandberg, and Orchard (1986:3-7, 34, 35). DISCUSSION Many of the specimens of M. praebeckmanni from the Northumberland trough are transitional to M. beckmanni, with similar overall proportions and a vertical anterior left parapet termination. All other taxonomic characters are, however, typical of M . praebeckmanni and similar speci- mens were included in this species by von Bitter, Sand- berg, and Orchard (1986, pi. 10, figs. 1-7, pi. 11, figs. 1-3, 5, 6). In general, M. praebeckmanni Pa elements from this study resemble morphotype 2 of von Bitter, Sandberg, and Orchard (1986) more closely than they do morphotype 1 or 3. Mestognathus praebeckmanni-M. beckmanni intermediates Plate 5, Figs. 11, 12 Mestognathus cf. beckmanni — von Bitter, Sandberg, and Orchard, 1986:27, pi. 23, figs. 1, 2. [vp] Mestognathus beckmanni — Armstrong and Purnell, 1987, pi. 3, fig. 6 only. MATERIAL STUDIED Pa elements, 8(1); from the Bogside Limestone Member of the Bewcastle Formation and the Lynebank Formation, Lower Border Group, and from the Cementstone Group, Akenshaw Bum. DISCUSSION The Northumberland trough represents an area where M. beckmanni and M. praebeckmanni co-existed. In such areas, von Bitter, Sandberg, and Orchard (1986) expected considerable morphologic intergradation between the two species, and this has proved to be the case in this study. One group of intermediate forms are close to M . praebeck- manni in morphology but have an anterior left parapet area, the most important criterion in differentiating species of Mestognathus, which approaches that of M . beckmanni (PI. 5, Figs. 11a, b). In most of these specimens, the ante- rior left parapet termination is vertical with a small ante- rior denticle developed. Occasionally the parapet area is more raised than that developed by M. praebeckmanni. Other intermediate specimens are close to M. beckmanni in morphology but possess a low parapet area and/or a rel- atively large, only slightly everted basal cavity similar to M. praebeckmanni (PI. 5, Figs. 12a-c). These characteris- tics are also exhibited by juveniles of M. beckmanni; con- sequently, only specimens longer than 0.7 mm are considered intermediate. Specimens below this size are assigned to Mestognathus sp. 33 Family Polygnathidae Bassler, 1925 Genus Polygnathus Hinde, 1879 Polygnathus Hinde, 1879:361. Hindeodella Bassler, 1925:219. Ctenopolygnathus Miiller and Miiller, 1957: 1084. DIAGNOSIS (After Klapper and Philip, 1971; Klapper et al. in Robison, 1981.) Apparatus seximembrate; Pa elements carminiplan- ate (carminiscaphate in earliest species); Pb elements angulate; M elements dolabrate; Sa element alate; Sb ele- ments digyrate; Sc element bipennate. TYPE SPECIES Polygnathus dubius Hinde, 1879, by subsequent designa- tion of Miller (1889:520). Polygnathus bischoffi Rhodes, Austin, and Druce, 1969 Plate 6, Figs. 1,3 [v*] Polygnathus bischoffi Rhodes, Austin, and Druce, 1969:184-5, pi. 13, figs. 8-11. Polygnathus bischoffi — Klapper in Ziegler, 1975:275-6, Polygnathus — pi. 4, fig. 5 [with synonymy]. DIAGNOSIS See Rhodes, Austin, and Druce (1969:184). HOLOTYPE British Museum, X349 (Rhodes, Austin, and Druce, 1969, pi. 13, fig. 11). TYPE HORIZON AND LOCALITY Sample SCC of Rhodes, Austin, and Druce (1969), South Wales Coalfield, Fall Bay, Gower, South Wales. MATERIAL STUDIED Pa elements, 28(6); M elements, 1(1); from the lower Lynebank Formation, Lower Border Group. In addition, the type specimens of Rhodes, Austin, and Druce (1969) and the collection of Austin and Mitchell (1975) were examined. DISCUSSION The Pa elements from the Northumberland trough have deeper anterior adcarinal troughs and larger basal cavi- ties with more pronounced lips than the holotype and paratypes of P. bischoffi. These differences are almost certainly ontogenetic; no specimens that would have exceeded 0.8 mm in total length were found in this study, whereas the holotype is 1.32 mm long and both paratypes are over 1 mm. The other figured specimen (hypotype) of Rhodes, Austin, and Druce (1969) is, however, 0.725 mm long and has a larger basal cavity. Austin and Mitchell (1975) recorded, but did not figure, P. bischoffi Pa elements from the Lower Carboniferous Shale, Northern Ireland. These elements range in length between 0.4 mm and 1.6 mm; only specimens of over 0.75 mm develop small basal cavities. Although the adcarinal troughs of the Pa elements from the Lower Border Group are deeper than those of larger specimens, they can still be distinguished from Pa elements of P. inornatus E. R. Branson in lacking the conspicuously high right anterolateral margin charac- teristic of the latter species. Small Pa elements of P. bischoffi with their larger basal cavities resemble Pa elements of Pseudopolygnathus minutus Metcalfe, the holotype of which is only 0.56 mm long. Metcalfe (1981) suggested that P. bischoffi evolved from Ps. minutus, presumably peramorphically; alternat- ively, although the ranges of the two species are not completely concurrent (Higgins and Austin, 1985:250-1, table 6), Ps. minutus Pa elements may be immature P. bischoffi elements. The single complete M element recovered that probably belongs to P. bischoffi is of "Neoprioniodus confluens" form. The posterior process is less downwardly deflected than it is in the M elements of P. mehli Thompson (see below) but, from the available material, P. bischoffi M elements cannot be distinguished from Patrognathus capricornis (Druce) M elements. Polygnathus mehli Thompson, 1967 Plate 6, Figs. 2, 4-7, 9-11 DESCRIPTION [?] Bryantodus planus Huddle, 1934:75-6, pi. 10, fig. 8 [Pb Pa elements. See Rhodes, Austin, and Druce (1969: element]. 184-5). Polygnathus mehli Thompson, 1967:47, 48, pi. 2, figs. 1-6 M elements. See Rhodes, Austin, and Druce (1969: 158- [Pa elements]. 9) under Neoprioniodus confluens. [?p] Neoprioniodus confluens (Branson and Mehl) — Rhodes, 34 Austin, and Druce, 1969:158, pi. 21, fig. 2 only [M element]. Polygnathus lacinatus Huddle — Higgins, 1971, pi. 1, figs. 6, 8 [Pa elements]. Polygnathus mehli — Klapper in Ziegler, 1975:307-8, Polygnathus — pi. 6, fig. 4 [Pa element] [with Pa element synonymy]. Polygnathus lacinatus — Austin in Austin and Mitchell, 1975:52, pi. 1, figs. 28, 29, 31, 32 [Pa elements]. Polygnathus aff. P. lacinatus sensu Rhodes, Austin, and Druce— Nicoll and Druce, 1979:29, pi. 16, fig. 10 [Pa element]. [(?)] Polygnathus lacinatus asymmetricus Rhodes, Austin, and Druce— Metcalfe, 1981, pi. 9, fig. 5 [Pa element]. Polygnathus mehli latus Johnston and Higgins, 1981:92, 94, figs. 5.11-5.15 [Pa elements] [with partial synonymy]. "Polygnathus" mehli— Chauff, 1981, pi. 2, figs. 9, 10, 22- 25, 35, 36 [Pa elements]. Polygnathus mehli — Austin and Davies, 1984, pi. 1, fig. 2; pi. 2, fig. 33(?); pi. 3, figs. 10, 12 [Pa elements]. Polygnathus lacinatus — Austin and Davies, 1984:196, text-fig. 1, pi. 2, figs. 1, 32 [Pa elements]. Polygnathus mehli latus — Varker and Sevastopulo, 1985:192, pi. 5.2, figs. 9, 10 [Pa elements]. Polygnathus mehli mehli — Varker and Sevastopulo, 1985:192, pi. 5.2, figs. 11, 12, 15, 18 [Pa element]. Polygnathus mehli— Belka, 1985, pi. 14, fig. 13 [Pa element]. DIAGNOSIS Pa element diagnostic, see Thompson (1967:48). HOLOTYPE University of Missouri, C-994-17 (Thompson, 1967, pi. 2, figs. 1,2). TYPE HORIZON AND LOCALITY Pierson Formation, Unit 19; Roaring River State Park south entrance, road cut on west side of State Highway 112, locality F of Thompson (1967), Barry County, Mis- souri, U.S.A. MATERIAL STUDIED Pa elements, 165(14); Pb elements, 13(5); M elements, 9; Sa elements, 2(4); Sc elements, 6(2); from the Liddel For- mation, Lower Border Group, and the Harden Member, Middle Border Group. DESCRIPTION Pa elements. See Thompson (1967:48) under P. mehli, and Rhodes, Austin, and Druce (1969:188-91) under P. lacinatus. Pb elements. The anterior and posterior processes are subequal in length and are downcurved and slightly incurved. The anterior process bears four or five large lat- erally compressed, triangular denticles, free for most of their length. They are largest towards the middle of the process and increasingly reclined towards the cusp. The length of the denticles commonly exceeds the depth of the process beneath them, which exceeds them only slightly in thickness. The reclined cusp is similar in shape to the ante- rior denticles but is higher and wider, although sometimes only slightly so. The posterior process bears six to eight smaller less compressed and less discrete denticles. They are subequal in size and become increasingly reclined pos- teriorly. The elongate basal cavity is widest and deepest beneath the cusp, tapering to a point at or near the anterior tip of the element and to halfway along the posterior pro- cess. M elements. See Rhodes, Austin, and Druce (1969:158) under Neoprioniodus confluens. Sa element. The lateral processes diverge anteriorly at an angle of slightly less than 180° in a horizontal plane, and at 90° to 100° in a vertical plane. They are relatively short and have a thick wedgeshaped cross-section. Process height and width are subequal towards the cusp, but width gradually decreases laterally. The processes are slightly curved downwards, with an inflection point at midlength, and each bears four discrete isolated denticles that are rounded in cross-section. The upper part of the recurved and slightly reclined cusp is also round in cross-section, but becomes more laterally compressed towards the base. The posterior process joins the cusp at a higher level than the lateral processes. It is wedgeshaped in cross-section and tapers posteriorly in height and slightly in width. The figured specimen (PI. 6, Figs. 10a, b) bears only a single small broken denticle, but the posterior process may be more denticulate. The basal cavity is shallow and everted, and tapers along the lateral processes to narrow grooves flanked by recessive basal margins. It continues along the posterior process as a slightly broader groove. Sb elements. The Sb elements of P. mehli are unknown. Sc elements. Two morphotypes occur, differing in the form of the anterior process. The more common form of process (PI. 6, Fig. 11) extends anteriorly from the cusp and is flexed outwards slightly, then gently inwards 35 through about 45°. It is laterally compressed and bears six discrete slighUy laterally compressed denticles that increase in size anteriorly. The process also thins and curves slightly downwards towards the anterior end. The other form (PI. 6, Fig. 9) is sharply deflected downwards and inwards through 90°. It is also laterally compressed, thinning anteriorly, and bears at least five discrete slightly incurved denticles. Apart from one or two minor denticles adjacent to the cusp, these denudes decrease in size along the process. In all other respects, these two morphotypes are similar. The recurved and slighUy reclined cusp is lat- erally compressed towards the base but becomes more rounded in cross-section upwards. It is wider and longer than the largest process denudes. The laterally com- pressed posterior process is over twice the length of the anterior. It is straight and bears slightly laterally com- pressed reclined denticles, which alternate in size with one to three minor denticles between each major denticle. There is an overall increase in the size of the major denti- cles toward the posterior, the posteriormost two being con- siderably larger than the others. The posterobasal termination of the process is deflected downwards. The shallow elongate basal cavity is widest and deepest beneath the cusp, where a slight lip is developed on the outer side. The cavity tapers posteriorly to a groove that extends along the process to the posterobasal deflection. Anteriorly it tapers to a point halfway along the process. DISCUSSION The reconstruction of the apparatus of this species is based chiefly on the abundant but monospecific fauna from sam- ple 108763. The apparatus is very similar to that of other Polygnathus species (e.g., Nicoll, 1985; Klapper and Philip, 1971). Pa elements of P. mehli from the Northumberland trough vary in the width and posterior extension of the basal cavity, the degree of cavity eversion, the prominence of the recessive basal margin, the strength of the pseudokeel, the strength of the platform ornament, the degree of expansion of the posterior half of the platform, and the pointedness of the posterior tip. Polygnathus mehli mehli is distinguished from P. mehli latus Johnston and Higgins, in having fainter ribs, a narrower basal cavity, and a narrower platform (Johnston and Higgins, 1981). These characters were found to vary discordantly and the elements have not been assigned to subspecies. Marchant (1978) noted the variability of P. mehli Pa elements in his Irish material, but was also unable to recognize P. mehli mehli and P. mehli n. subsp. of Johnston (1976)(= P. mehli latus). M elements of P. mehli are similar to those of Patrognathus capricornis (Druce) but have a more strongly downwardly deflected posterior process with a broader groove along its lower surface. Sa elements resemble "Hibbardella macrodentata Thomas"; Sc elements with a downflexed incurved anterior process resemble "Hindeodella corpulenta Branson and Mehl." Family Spathognathodontidae Hass, 1959 Genus Lochriea Scott, 1942 Lochriea Scott, 1942:298. Paragnathodus Meischner, 1970:1 173 (nom. nud.). Paragnathodus Higgins, 1975:70. DIAGNOSIS (After Norby, 1976.) Apparatus at least quinquemembrate; Pa elements carminiscaphate with free anterior blade and large posterior basal cavity, the upper surface of which is either unornamented or bears one or two nodes. Pb ele- ments angulate; M elements dolabrate; Sa element alate; Sc elements bipennate. The Pb, M, Sc, and probably the Pa elements, were symmetrically paired. [v*] [v *?1 TYPE SPECIES [v] Lochriea montanaensis Scott, 1942, by original designa- tion (a subjective junior synonym of Spathognathodus tv-l commutatus Branson and Mehl, 1941c). DISCUSSION The generic concept followed herein is the same as that of Norby (1976) and Rexroad and Horowitz (1990). The multielement composition of the genus was reconstructed on the evidence of bedding plane assemblages (Scott, 1942; Norby, 1976). Lochriea scotiaensis (Globensky, 1967) Plate 6, Figs. 12a, b Gnathodus scotiaensis Globensky, 1967:441, pi. 58, figs. 2-7, 10, 12 [Pa elements]. Ozarkodina acadiensis Globensky, 1967:445, pi. 55, figs. 6,9-11, 14 [Pb elements]. Neoprioniodus singularis (Branson and Mehl) — Glob- ensky, 1967:444-5, pi. 55, figs. 23, 24 [M elements]. Gnathodus scotiaensis — von Bitter and Plint-Geberl, 1982:202, pi. 6, figs. 13-15 [Pa elements], fig. 20 [M element]. 36 HOLOTYPE University of New Brunswick, 64-F-266 (Globcnsky, 1967, pi. 58, figs. 2, 10). TYPE HORIZON AND LOCALITY Windsor Limestone, sample KD12 of Globcnsky (1967). On the Atlantic coast between the village of Skir Dhu and North Shore, about 330 m SW of Skir Dhu fisherman's wharf, Skir Dhu, Cape Breton Island, Nova Scotia, Can- ada. MATERIAL STUDIED A single Pa element from the lower Lyncbank Formation, Lower Border Group, and the specimens from the Codroy Group of Newfoundland, Canada, in the collection of von Bitter and Plint-Geberl (1982). DESCRIPTION Pa element. See Globensky (1967:441) under Gnathodus scotiaensis. M element. This element, although identified and figured by von Bitter and Plint-Geberl (1982), has not been described. DISCUSSION No diagnosis exists for this species. Only the Pa and M elements are known; "Ozarkodina acadiensis" may be the Pb element. These elements resemble the homologous ele- ments of L. commutata much more closely than they do Gnathodus; Norby (1976:149) suggested that G. scotiaen- sis was probably a "variety or subspecies" of L. commu- tata. ConsequenUy, these elements are assigned to Lochriea herein. The single Pa element recovered from the Northumberland trough differs from the description and the comparatively large figured specimens of Globensky (1967:441, pi. 58, figs. 2-7, 10, 12; holotype is 0.74 mm long) chiefly in the straightness of the upper posterior part of the blade, and in bearing fewer denticles. It is, however, very similar to some specimens from the Codroy Group of SW Newfoundland (von Bitter and Plint-Geberl, 1982). Superficially, some Pa elements of L. scotiaensis resemble those of G.? simplicatus (Rhodes, Austin, and Druce) but the two species can be easily distinguished by the size of the basal cavity. Lochriea sp. indet. Plate 6, Fig. 13 MATERIAL STUDIED Pb elements, (3); M elements, 10(1); mostly from the Cementstone Group, Akenshaw Burn, but also from the Cambeck Formation, Lower Border Group. DESCRIPTION Pb elements. See Higgins (1961:218, 219) and Rhodes, Austin, and Druce (1969:198, 199) under Subbryantodus subequalis. M elements. See Hass (1953:88) and Rhodes, Austin, and Druce (1969:160) under Prioniodus singularis and Neop- rioniodus montanaensis respectively. DISCUSSION Rexroad and Horowitz (1990) include a full synonymy for multielement L. commutata. Other species of Lochriea probably bore nonplatform elements indistinguishable from those of L. commutata (Norby, 1976). In the absence of associated Pa elements, the M and incomplete Pb ele- ments from this study can only be assigned to Lochriea sp. indet. Family Unknown Genus Vogelgnathus Norby and Rexroad, 1985 Vogelgnathus Norby and Rexroad, 1985:2. DIAGNOSIS See Purnell and von Bitter (1992:316). TYPE SPECIES Spat ho gnathodus campbelli Rexroad, 1957, by original designation. Vogelgnathus gladiolus Purnell and von Bitter, 1992 Plate 7, Figs. 1-8 [v*] Vogelgnathus gladiolus Purnell and von Bitter, 1992:320- 23, figs. 8.1-8.5 [Pa elements], figs. 8.6, 8.10 [Pb elements], figs. 8.7, 8.9 [M elements], fig. 8.8 [Sb element], fig. 8.11 [Sc element] [with full synonymy]. DIAGNOSIS See Purnell and von Bitter (1992:320). 37 HOLOTYPE Royal Ontario Museum, ROM 48667 (Purnell and von Bitter, 1992, figs. 8.2, 8.4). TYPE HORIZON AND LOCALITY Bed 1 .8-2. 1 m above base of 40 cm shale unit exposed in quarry and waterfall section through Bogside Limestone Member, BewcasUe Formation, Lower Border Group, Ashy Cleugh, Bewcastle, Cumbria, U.K. (G.R. NY 56497700 to NY 56547695). Bed collected as sample 258624. MATERIAL STUDIED Pa elements, 127(3); Pb elements, 4; M elements, 7; Sb elements, 10(3); Sc elements, 14(17); almost all from the Bogside Limestone Member of the Bewcastle Formation, but also from the Cambeck Formation, Lower Border Group, and the Cementstone Group in Akenshaw Burn. DESCRIPTION See Purnell and von Bitter (1992:320-23). DISCUSSION Purnell and von Bitter (1992) include full description and discussion of V. gladiolus from the Northumberland trough. Vogelgnathus kyphus Purnell and von Bitter, 1992 Plate 7, Figs. 9, 10, 12 [v*] Vogelgnathus kyphus Purnell and von Bitter, 1992:323-25, figs. 10.1-10.6 [Pa elements], fig. 10.7 [Sb element] [with full synonymy], DIAGNOSIS See Purnell and von Bitter (1992:323). HOLOTYPE Royal Ontario Museum, ROM 48677 (Purnell and von Bitter, 1992, figs. 10.3-10.5). TYPE HORIZON AND LOCALITY Bed 2.6-3.0 m above base of Birky Cleugh Limestone Member, Main Algal Formation, Lower Border Group, Birky Cleugh, Bewcastle, Cumbria, U.K. (G.R. NY 58997540 to NY 59017540. Bed collected as sample 88725. MATERIAL STUDIED Pa elements, 129(2); Sb elements, 2 (both broken during photography); 1 Sa element and 2 Sc element fragments which may belong to V. kyphus were also recovered. DESCRIPTION See Purnell and von Bitter (1992:323-25). DISCUSSION Purnell and von Bitter (1992) include full description and discussion of V. kyphus from the Northumberland trough. Vogelgnathus pesaquidi Purnell and von Bitter, 1992 Plate 7, Fig. 11 tv*] Vogelgnathus pesaquidi Purnell and von Bitter, 1992:325- 27, figs. 11.1-11.12 [Pa elements], figs. 11.13-11.15 [Pb elements], figs. 12.1-12.3 [M elements], figs. 12.4-12.7 [Sa elements], figs. 12.8, 12.9 [Sb elements], figs. 12.10, 12.11 [Sc elements] [with full synonymy]. DIAGNOSIS See Purnell and von Bitter (1992:325). HOLOTYPE Royal Ontario Museum, ROM 48680 (Purnell and von Bitter, 1992, fig. 11.2). TYPE HORIZON AND LOCALITY Beds 2.1-3.7 m above apparent base of Sanford Lime- stone, Miller Creek Formation, lower Windsor Group, near Windsor, Nova Scotia, Canada. MATERIAL STUDIED Pa elements, 23(3); Sc elements, (4); from the Bewcastle, Main Algal, and Cambeck formations, Lower Border Group; the Orroland Lodge and Barlacco Heugh forma- tions, Orroland Group; the Southemess Formation, Cementstone Group; and the Cementstone Group of Aken- shaw Burn. DESCRIPTION See Purnell and von Bitter (1992:325-27). DISCUSSION With the exception of one poorly preserved specimen from the Bewcastle Formation, Pa elements from the Northum- berland trough are V. pesaquidi morphotype II of Purnell and von Bitter (1992). Vogelgnathus cf. pesaquidi Plate 8, Fig. 1 MATERIAL STUDIED Pa elements, 4(1); from the BewcasUe Formation, Lower Border Group. 38 DESCRIPTION Apparatus unknown. Pa elements are more elongate and have less laterally compressed denticles and processes than those of V. pesaquidi. The basal cavity is shallower and less expanded laterally than morphotype n Pa ele- ments of V. pesaquidi. The cavity is lanceolate in outline and in some specimens is not pointed posteriorly. Order Prioniodinida Sweet, 1988 Family Prioniodinidae Bassler, 1925 Genus Kladognathus Rexroad, 1958 [non] Cladognathus Burmeister, 1847:364. Cladognathus Rexroad, 1957:28. Kladognathus Rexroad, 1958a: 19. Lambdagnathus Rexroad, 1958a: 19, 20. Cladognathodus Rexroad and Collinson, 1961:6. Magnilaterella Rexroad and Collinson, 1963: 1 1—14. DIAGNOSIS (Modified from Rexroad, 1981:11.) Platform elements not developed; M elements dolabrate with prominent anticusp; Sa elements alate; Sb elements bipennate; Sc elements bipennate; Sd elements tertiopedate. The S elements have discrete pointed denticles. TYPE SPECIES Cladognathus prima Rexroad, 1957, by original designa- tion. DISCUSSION The concept of Kladognathus employed herein is based on that of Rexroad (1981), Horowitz and Rexroad (1982), and Rexroad and Horowitz (1990). Apparatus reconstruction is based on the statistical studies of Horowitz and Rexroad (1982), confirming the tentative suggestion of Norby (1976). Kladognathus tenuis (Branson and Mehl, 1941a) Plate 8, Figs. 2, 3 [p] Prioniodus peracutus Hinde, 1900:343, pi. 10, fig. 22 only [M P element]. Ligonodina tenuis Branson and Mehl, 1941a: 170, pi. 5, figs. 13, 14 [Sc a elements]. Prioniodus scitulus Branson and Mehl, 1941a: 173-4, pi. 5, figs. 5, 6 [M a elements]. Ligonodina levis Branson and Mehl, 1941b: 185, pi. 6, fig. 10 [Sc p element]. Lambdagnathus fragilidens Rexroad, 1958a: 19, pi. 6, figs. 10-16 [Sd elements]. Kladognathus tenuis — Rexroad, 1981:13, pi. 2, figs. 19, 21, 24-26 [Sc a elements], fig. 20 [Sc P element]. Kladognathus tenuis — Rexroad and Horowitz, 1990:505- 6, pi. 3, figs. 28-30 [M elements], 21-24 [Sa elements], 25-27, 33 [Sb elements], 16-20 [Sc elements], 12-15 [Sd elements] [with full synonymy]. DIAGNOSIS See Rexroad (1981:13). HOLOTYPE University of Missouri, C543-3 {Ligonodina tenuis Bran- son and Mehl, 1941a, pi. 5, fig. 13). TYPE HORIZON AND LOCALITY The Caney Shale immediately below the higher of the two conspicuous bands of concretions; steep bank of black fis- sile shales at the side of State Highway 48, about 6 miles south of Ada, Pontotoc County, Oklahoma, U.S.A. MATERIAL STUDIED Sa elements, 1; Sb elements, 1; Sc a elements, 3; indeter- minate Sc elements, (4); from the Lower Lynebank and Cambeck formations, Lower Border Group, and the Cementstone Group of Akenshaw Burn. DESCRIPTION M elements. See Rhodes, Austin, and Druce (1969:161— 3) under Neoprioniodus peracutus and Neoprioniodus scitulus. Sa element. See Rexroad (1958a: 18) and Rhodes, Austin, and Druce (1969:113) under Hibbardella milleri and Hib- bardella (Hibbardella) milleri respectively. Sb elements. See Rexroad and Collinson (1963:14-17) under Magnilaterella robusta. Sc a elements. See Branson and Mehl (1941a: 170) and Rhodes, Austin, and Druce (1969:138) under Ligonodina tenuis, and Rexroad (1957:32) under L. hamata. Sc P elements. See Rhodes, Austin, and Druce (1969:134) under Ligonodina levis. Sd elements. See Rexroad (1958a: 19) under Lambdag- na thus fragilidens. DISCUSSION Nicoll and Rexroad (1975) recovered "Neoprioniodus tulensis (Pander)," "Hibbardella abnormis Branson and Mehl," "Magnilaterella sp.," "Ligonodina magnilaterina 39 Rhodes, Austin, and Druce," and "L. levis Branson and Mehl" from the Sanders Group of Indiana and Kentucky. Table 1 of Nicoll and Rexroad (1975) shows that these ele- ments co-occur in approximately the same proportions rel- ative to each other, independently of the abundance of other species, in four formations. The elements closely resemble those of Chesterian K. tenuis and were probably borne by Meramecian K. tenuis or a closely related spe- cies. This reconstruction is partly supported by the statisti- cal analysis of Nicoll and Rexroad (1975:15). Order Unknown Family Unknown Genus "Apatognathus" [non] Apatognathus Branson and Mehl, 1934a:201. DISCUSSION Branson and Mehl (1934a) erected Apatognathus as a monotypic genus for sharply arched conodont elements with an apical cusp and two denticulate parallel or slightly divergent processes. Elements with this morphology occur in the Devonian and Lower Carboniferous but are absent from the lowest part of the Carboniferous (Scott and Col- linson, 1961; Varker, 1967). The majority of conodont workers have regarded the Carboniferous forms as proba- ble homeomorphs (e.g., Rexroad and Collinson, 1963) or morphic equivalents (Varker, 1967) which should be assigned to a different genus (e.g., Rexroad and Collinson, 1963; Klapper, 1966; Varker, 1967). The Devonian and Carboniferous apatognathid elements almost certainly belonged to markedly different apparatuses (Nicoll, 1980). Despite the strength of the argument on both stratigraphic and morphological grounds, no genus has been formally erected to receive the Carboniferous species. Sweet (1988:115) "loosely referred" one Carboniferous apatognathid species to Hindeodus, but the reasoning behind this decision was not adequately explained. The Carboniferous apatognathid apparatus (see below) does not fit Sweet and Clark's diagnosis of the genus (in Robison, 1981) and lacks "the curious extensiform digyrate [Sb] element" that Sweet (1988:116) considered the most diagnostic feature of the apparatus of Hindeodus. Sweet (1988) conceded that his interpretation of Hindeodus was probably too broad; Carboniferous apatognathids are herein assigned to "Apatognathus" with order and family unknown. Evidence for the apparatus of "Apatognathus" comes from a fused cluster (Austin and Rhodes, 1969) and the recurrent association of elements (summarized by von Bitter, Sandberg, and Orchard, 1986:12, table 1). Rexroad and Thompson (1979) suggested that "Apatognathus" scitulus bore an apparatus composed of elements previously described as "Spathognathodus scitulus (Hinde)," "Ozarkodina laevipostica Rexroad and Collinson," "Apatognathus porcatus (Hinde)," and "A. scalenus Varker." Nicoll (1980) and Dean (1987) believed that the apatognathid elements of this apparatus were represented by elements of "Apatognathus porcatus" form and "Apatognathus geminus (Hinde)" form. These apparatus reconstructions, and that proposed for "A." cuspidatus Varker herein, are different from Apatognathus varians Branson and Mehl sensu Nicoll (1980), and the element notational scheme of Nicoll (1980) cannot be applied to "Apatognathus." The apatognathid elements of "Apatognathus" may have formed a symmetry transition series (Rexroad and Thompson, 1979; Sweet, 1988) and the element notation Sa, Sb, and Sc is used to indicate their increasing asymmetry, chiefly in terms of process incurvature (contra Nicoll, 1980; Austin et al. in Robison, 1981). This notation implies analogy rather than homology with the elements of other genera. Unlike those of the majority of conodonts, the Pa and Pb elements of "Apatognathus" represent the vicariously shared, conservative parts of the apparatus, and it is the S elements that evolved more rapidly. The distributional data, however, suggest that Pb elements were not always developed in the apparatus (see von Bitter, Sandberg, and Orchard, 1986:12). Rexroad and Thompson (1979) suggested that "Apatognathus varians," "Hibbardella separata (Branson and Mehl)," and "Lonchodina sp. a" sensu Rhodes, Austin, and Druce (1969) may have formed part of the "Apatognathus" apparatus. These elements were found by Druce, Rhodes, and Austin (1972) to be statistically associated in the Lower Carboniferous of the North Crop of the South Wales coalfield. However, considering the relative rarity of the "species" in this study (Druce, Rhodes, and Austin, 1972), and the lack of supporting distributional data, it is unlikely that all of these elements were borne by "Apatognathus." N.B. Shortly after final submission of this manuscript, a new genus, Synclydognathus Rexroad and Varker, 1992, was erected to accommodate Carboniferous apatognathids. 40 "Apatognathus" cuspidatus Varker, 1967 Plate 8, Figs. 4-9 [p] Apatognathus) porcata (Hindc) — Rexroad and Collinson, 1963:8, pi. 1, fig. 8 [?Sc element], figs. 10, 11 [Sb elements] only. [p?l Ozarkodina laevipostica Rexroad and Collinson, 1963: 19, pi. 1, figs. 1, 2, 4 only [Pb elements]. [p?] Spathognathodus scitulus (Hinde) — Rexroad and Collinson, 1963:20, pi. 2, figs. 14, 31 only [Pa elements]. [p] Apatognathus) porcata — Globensky, 1967:438, pi. 56, fig. 24 only [Sa element]. Apatognathus") cuspidata Varker, 1967:131, pi. 17, figs. 4, 6-8, 10 [Sb elements]. Apatognathus! librata Varker, 1967:134, pi. 18, figs. 3, 6, 8,9,12, 13 [Sa elements]. Apatognathus") petila Varker, 1967:135, pi. 17, fig. 1 1; pi. 18, figs. 7, 10, 11 [Sc elements]. [(?)] Apatognathus porcata — Thompson and Goebel, 1969:21, pi. 2, fig. 1 [Sb element]; pi. 4, fig. 23 [Sc element]. Apatognathus petilus — Rhodes, Austin, and Druce, 1969:72, pi. 20, figs. 12-14, 17 [Sc elements]. Apatognathus cf. libratus — Rhodes, Austin, and Druce, 1969:75, pi. 20, fig. 8 [Sa element], [p?] Spathognathodus scitulus — Rhodes, Austin, and Druce, 1969:232, pi. 8, fig. 10 only [Pa element]. [(?)] Apatognathus") cuspidatus — Reynolds, 1970:7, pi. 3, fig. 4 [Sb element]. [(?)] Apatognathus") libratus— Reynolds, 1970:7, pi. 3, fig. 9 [Sa element]. Apatognathus") petilus — Reynolds, 1970:7, pi. 3, fig. 5 [Sc element]. Apatognathus scalenus Varker — Austin and Aldridge, 1973, pi. 2, fig. 6 [Sc element]. Apatognathus petilus — Austin and Aldridge, 1973, pi. 2, fig. 9 [Sa element]. Apatognathus cuspidatus — Austin and Husri, 1974, pi. 10, figs. 8(?), 15 only [Sb elements]. [(?)] Apatognathus libratus — Austin and Husri, 1974, pi. 10, fig. 6 [?Sc element]. [(?)] Apatognathus minutus Austin and Husri, 1974:51, pi. 10, figs. 1, 2, 5, 9 [Pb elements?]. Apatognathus petilus — Austin and Husri, 1974, pi. 10, fig. 7 [Sc element]. Spathognathodus scitulus — Austin and Husri, 1974, pi. 7, fig. 10; pi. 8, fig. 6? [Pa elements]. [(?)] Apatognathus cuspidatus — Metcalfe, 1980:299, pi. 37, fig. 1 [Sb element?]. Apatognathus libratus — Metcalfe, 1980:300, pi. 37, fig. 4 [Sa element]. Spathognathodus scitulus — Metcalfe, 1980, pi. 38, fig. 7 [Pa element]. [p(?)] Apatognathus libratus — Metcalfe, 1981, pi. 13, fig. 1 only [Sa element]. [p] Apatognathus petilus — Metcalfe, 1981, pi. 13,figs.4,5 [Sc elements], 7 [Sc element?] only. Apatognathus cuspidatus — Metcalfe, 1981, pi. 13, figs. 8 [Sb element], 9 [Sb element?]. Apatognathus sp. Metcalfe, 1981, pi. 13, fig. 10 [Sc element]. Prioniodina laevipostica — Metcalfe, 1981, pi. 19, fig. 1 [Pb element], [v.] Apatognathus cuspidatus — Higgins and Varker, 1982, pi. 19, figs. 11, 13, 19 [Sb elements], [v?] Apatognathus libratus — Higgins and Varker, 1982: 157, pi. 19, fig. 12 [Sa element]. [v?] Spathognathodus scitulus — Higgins and Varker, 1982: 164, 165, pi. 19, fig. 14 [Pa element]. Apatognathus libratus — Austin and Davies, 1984, pi. 3, fig. 19 [Sb element]. [(?)] Apatognathus petilus — Austin and Davies, 1984, pi. 3, fig. 20 [Sc element?]. IpJ Spathognathodus scitulus — Austin and Davies, 1984, pi. 3, fig. 18 only [Pa element]. 'Apatognathus' cuspidatus — Varker and Sevastopulo, 1985:196, pi. 5.4, figs. 1, 2 [Sb elements] [fig. 2 cop. Varker, 1967, pi. 17, fig. 8]. 'Apatognathus' petilus — Varker and Sevastopulo, 1985:198, pi. 5.4, figs. 3-5 [Sc elements] [figs. 4, 5 cop. Varker, 1967, pi. 18, fig. 10; pi. 17, fig. 11]. 'Apatognathus' libratus — Varker and Sevastopulo, 1985:198, pi. 5.4, figs. 8-11 [Sa elements] [cop. Varker, 1967, pi. 18, figs. 6, 8, 12, 13]. [v.] 'Apatognathus' cuspidatus — Armstrong and Purnell, 1987, pi. l,fig. 1 [Sb element], [v.] 'Apatognathus' aff. libratus — Armstrong and Purnell, 1987, pi. 1, fig. 4 [Sa element], [v.] 'Apatognathus' scandalensis Higgins and Varker — Armstrong and Purnell, 1987, pi. 1, fig. 3 [Sa element]. REVISED DIAGNOSIS Apparatus at least quinquemembrate: Pa elements carmin- iscaphate with large triangular anterior denticle; Pb ele- ments angulate; Sa elements alate (lacking posterior process), symmetrical, apatognathid with recurved apical cusp; Sb elements bipennate, apatognathid with large incurved reclined cusp and incurved reclined anterior pro- cess denticles; Sc elements bipennate, apatognathid with incurved reclined cusp and strongly incurved anterior pro- cess. HOLOTYPE University of Sheffield, Department of Geology, 28(6) BB205 (Varker, 1967, pi. 17, fig. 7). TYPE HORIZON AND LOCALITY Great Limestone, Borrowdale Beck, Stainmore, Cumbria, U.K. (G.R. NY 834160). 41 MATERIAL STUDIED Pa elements, 7(3); Pb elements, 1(1); Sa elements, 8(1); Sb elements, 7(3); Sc elements, 4(4); from the Bogside Lime- stone Member, Bewcastle Formation, and the Lynebank Formation, Lower Border Group. DESCRIPTION Pa elements. See Clarke (1960:21) and Rhodes, Austin, and Druce (1969:232) under Spathognathodus scitulus. Pb elements. See Rexroad and Collinson (1963: 19) under Ozarkodina laevipostica, and Rhodes, Austin, and Druce (1969:195) under Prioniodina laevipostica. Sa elements. See Varker (1967:134) under Apatognathus! librata. Note differences in orientation terminology if ele- ments are considered to be alate. Sb elements. See Varker (1967:131) under Apatognathusl cuspidata. Sc elements. See Varker (1967:135) under Apatognathusl petila. DISCUSSION The apparatus of "A." cuspidatus was reconstructed on the evidence of association of elements in samples 108768 and 108769 from the Lynebank Formation, Lower Border Group, and on the association of elements in previous studies. Because of the vicarious sharing of Pa and Pb ele- ments between "Apatognathus" species, "A." cuspidatus is the oldest available name for this species. The range charts and element abundances of Varker (1967), Davies (1980), and Dean (1987) suggest that elements of "A. scalenus Varker" form may sometimes have been present in the apparatus of "A." cuspidatus, possibly representing the M elements. No elements of this form were found in this study. ''Apatognathus" sp. a MATERIAL STUDD2D Sb elements, 1(1); Sc elements, 2; from the Cambeck For- mation, the Bogside Limestone Member, Bewcastle For- mation, and the Lynebank Formation, Lower Border Group. DESCRIPTION Sb elements. See Higgins and Varker (1982:158) under Apatognathus scandalensis. Sc elements. See Higgins and Varker (1982:157) under Apatognathus asymmetricus. DISCUSSION The partial reconstruction of this species is based on the limited evidence of association in this study and the con- current ranges of the elements in Ravenstonedale, Cum- bria (Higgins and Varker, 1982). This reconstruction is tentative and the species is placed in open nomenclature. "Apatognathus" sp. indet. Plate 8, Fig. 10 MATERIAL STUDIED Pa elements, 3(3); from the Cambeck, Main Algal, and Lynebank Formations, Lower Border Group, and the Bar- lacco Heugh Formation, Orroland Group. DESCRIPTION Pa elements. See Clarke (1960:21) and Rhodes, Austin, and Druce (1969:232) under Spathognathodus scitulus. DISCUSSION Because of the vicarious sharing of Pa elements in "Apatognathus," Pa elements that are not associated with identifiable S elements cannot be specifically assigned. Some of these elements (e.g., PI. 8, Fig. 10) have greater posterior extension of the basal cavity than typical "Apatognathus" Pa elements. Genus Indeterminate Gen. a sp. a Plate 8, Figs. 11,12 MATERIAL STUDIED Pa elements, 4(2); M elements, 1; from the Bewcastle and Cambeck formations, Lower Border Group. DESCRIPTION Pa elements. Pa elements are carminate, laterally com- pressed, and bladelike with slight arching and lateral cur- vature. The only complete specimen bears 14 denticles including a minor anterior "piggy-back denticle," but the broken specimens suggest that more may be developed. The denticles are laterally compressed and elongate, fused apart from their tips. They are rather bluntly pointed in the two larger specimens recovered (including PI. 8, Fig. 11), more sharply so in smaller specimens. Apart from the minor denticle, the denticles are highest at the anterior end, decreasing in height towards the inconspicuous cusp, increasing slightly over the basal cavity then declining to the posterior end. The anterior termination of the element is straight and almost vertical with an anterobasal angle of approximately 70° to 80°. The basal cavity is elongate and subsymmetrical, the outer lip slightly more flared than the inner. It is widest and deepest just posterior of midlength, tapering gradually to the anterior and posterior, and bears a 42 medial groove. The cavity extends to the posterior end of the element as a groove, but does not reach the posterior tip. White matter is present through the length of the four or five denticles over the basal cavity but is absent from the others. M elements. The single M element recovered is dolabrate with a long recurved cusp, the tip of which is missing. The anterobasal corner is also broken and the element may have possessed a short anticusp. The large symmetrical basal cavity occupies the whole of the lower surface of the element. It is sharply elliptical in outline, deepest and wid- est under the posterior margin of the cusp, and bears a medial groove. The upper posterior surface of the cavity is continuous with the posterior margin of the cusp and bears three broken reclined denticles forming the posterior pro- cess. DISCUSSION The generic assignment of Lower Carboniferous species that bore a simple carminate Pa element is problematic (see Rexroad and Thompson, 1979; Norby and Rexroad, 1985, for discussion). Pa elements similar to those described above but stratigraphically older were tenta- tively given the generic name Synprioniodina Bassler by Rexroad and Thompson (1979) on the basis of probable M element morphology. The probable M element of this spe- cies, however, is not of "Synprioniodina" form. When the apparatuses containing Pa elements of this type have been reconstructed, new generic names will be required, as was the case with Vogelgnathus Norby and Rexroad. Conse- quently open nomenclature has been used in preference to an obsolete or inappropriate name. Pa elements of Gen. a sp. a were found in association with Cavusgnathus unicornis, Vogelgnathus gladiolus, and V. pesaquidi, none of which have M elements like that described above. The M element probably belongs to Gen. asp. a. ACKNOWLEDGMENTS This research was undertaken as part of a NERC funded Ph.D. project at the University of Newcastle upon Tyne. I am indebted to Dr. Howard Armstrong (now at the University of Durham) for his supervision of all conodont-related areas of this project, and particularly for lengthy discussions regarding problems of conodont taxonomy. Dr. R. J. Aldridge (University of Leicester), Dr. R. L. Ethington (University of Missouri -Columbia), Dr. N. J. Riley (BGS Keyworth), Dr. J. E. Whittaker (British Museum (Natural History)), and Dr. P. H. von Bitter (Royal Ontario Museum) are thanked for access to and/or loan of material in their care. The assistance provided by Peter von Bitter and Joan Burke (Royal Ontario Museum) is also gratefully acknowledged. Dr. G. K. Merrill and Dr. C. A. Sandberg are thanked for their reviews of the manuscript. The manuscript was completed during tenure of a Leverhulme Trust Study Abroad Studentship at the Royal Ontario Museum. 43 Appendices APPENDIX I: LOCALITY DETAILS 1. Whitton Glebe Farm. Five metres of Glebe Limestone Member exposed in disused quarry. Grid reference: NU 051005. References: Garwood, 1931; Fowler, 1936. 2. Birky Hill. Birky Hill Limestone Member. No in situ exposure, loose blocks on site of old workings. Grid ref- erence: NZ 048991. References: Garwood, 1931. 3. Allerdene. Old workings south of Allerdene Farm. No in situ exposure, loose blocks of Glebe Limestone Member. Grid reference: NU 025009. References: Fowler, 1936. 4. Snitter Mill. Patchy exposure of Cementstone Group in stream. Grid reference: NU 03130296. References: Fowler, 1936. 5. Snitter. Patchy exposure of Cementstone Group in Back Burn. Grid reference: NU 03050358. References: Fowler, 1936. 6. Alwinton. Barrow Scar, Alwinton Gorge on the River Coquet. Approximately 50 m of Cementstone Group exposed. Samples taken from south side of gorge. Grid reference: NT 904062. References: Westoll, Robson, and Green, 1955. 7. Chatdehope Burn. Patchy exposure through upper Cementstone Group. Grid reference: NT 720020. Refer- ences: Cater, Briggs, and Clarkson, 1989. 8. Kielder Burn. Very poor exposure of Cementstone Group in banks of burn. Grid reference: NY 636938. Refer- ences: Fowler, 1936. 9. Akenshaw Burn. Faulted and folded exposure through approximately 80 m of upper Cementstone Group. Grid reference: NY 605895-611897. References: Fowler, 1936. 10. Ashy Cleugh. Section through almost all of the Bewcas- de Formation, Lower Border Group (locality 25 of Leeder, 1974b). Grid reference: NY 56497700- 58087665. References: Day, 1970; Leeder, 1974b. 1 1 . Antonstown Burn. Section through 7 m of Bogside Lime- stone Member, Bewcastle Formation, Lower Border Group. Grid reference: NY 56577739. References: Day, 1970. 12. Birky Cleugh. Section through uppermost Bewcastle For- mation, whole of Main Algal Formation, and Lower Antiquatonia Member of Cambeck Formation, Lower Border Group (locality 33 of Leeder, 1974b). Grid refer- ence: NY 58857540-59437542. References: Day, 1970; Leeder, 1974b. 13. Whitberry Burn. Section through all but the lower part of Cambeck Formation, Lower Border Group. Grid refer- ence: NY 52207403-52027407. References: Day, 1970. 14. Ellery Sike. Section through lower Lynebank Formation, Lower Border Group (locality 21 of Leeder, 1974b). Grid reference: NY 54337584-54507575. References: Day, 1970; Leeder, 1974b. 15. Bothrigg Burn. Section through lower Lynebank Forma- tion, Lower Border Group (locality 22 of Leeder, 1974b). Grid reference: NY 54587591-54807598. References: Day, 1970; Leeder, 1974b. 16. River Black Lyne SE of Holmhead Farm, a) Common Flat Limestone Member, Lynebank Formation, b) Section through upper Lynebank Formation and Bogside Lime- stone Member, Bewcastle Formation, Lower Border Group. Grid references: a) NY 54377851; b) NY 54167822-54117821. References: Day, 1970. 17. Harden Bum. Patchy exposure through Liddel Forma- tion, Lower Border Group, and Harden Member, Middle Border Group (locality 15 of Leeder, 1974b). Grid refer- ence: NY 51709070-52149015. References: Leeder, 1974b. 18. Black Bum. Patchy exposure through possible Arnton Fell Formation?, Lower Border Group (locality 11 of Leeder, 1972, 1974b). Grid reference: NY 47878880- 48768869. References: Leeder, 1972, 1974b. 19. Black Bum. Folded and faulted section through Black Burn Formation, Lower BordeT Group, and Harden Member, Middle Border Group (localities 7, 8, and 9 of Leeder, 1974b). References: Leeder, 1974b. 20. Black Pool, Tweeden Burn. Uppermost exposed lime- stone of the Liddel Formation, Lower Border Group (part of locality 18 of Leeder, 1974b). Grid reference: NY 48968643. References: Leeder, 1974b. 44 21. Ettleton Sike. Section through lower Arnton Fell Forma- tion, Lower Border Group (locality 12 of Leeder, 1974b). Grid reference: NY 47108640. References: Leeder, 1974b. 22. West of Drum, near Kirkbean. Basal Cementstone For- mation, Cementstone Group; patchy exposure in stream. Grid reference: NX 976612. References: Craig, 1956. 23. South of Brickhouse near Kirkbean. Basal Cementstone Formation, Cementstone Group; patchy exposure in stream. Grid reference: NX 979601. References: Craig, 1956. 25. Southerness Foreshore. Folded section through whole of Southerness Formation, Cementstone Group. Grid refer- ence: NX 971521. References: Craig, 1956. 26. Portling outlier. Conglomerates, sandstone, and shales of Cementstone Group. Grid reference: NX 882535. Refer- ences: Deegan, 1973. 27. Rerrick outlier, below Orroland. Section through Orro- land Lodge and Barlacco Heugh formations, Orroland Group. Grid reference: NX 778463. References: Deegan, 1973. 24. Southerness Lighthouse. Basal beds of Gillfoot Forma- tion, Cementstone Group. Grid reference: NX 978542. References: Craig, 1956. 45 APPENDIX II: CONODONT ELEMENTS RECOVERED o o c 3 CO 5 2 3 9 c 3 9 Id c 3 cr £ g *» i» ■o 13 &) 0) o o r c (/> 8 g &? CO Lower Borde Lower Borde Lower Bordei Lower Borde Lower Borde Lower Bordei Lower Bordei Lower Bordei Lower Bordei Lower Bordei Lower Bordei Lower Bordei Lower Borde Lower Bordei Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Bordei Lower Bordei Lower Bordei Lower Borde. Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Lower Borde Bewcaslle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcastle Bewcaslle Bewcastle Bewcastle U Lynebank U Lynebank U Lynebank U Lynebank U Lynebank U Lynebank M Lynebank L Lynebank L Lynebank L Lynebank L Lynebank L Lynebank L Lynebank L Lynebank L Lynebank L Lynebank L Lynebank L Lynebank L Lynebank L Lynebank L Lynebank L Lynebank L Lynebank L Lynebank L Lynebank L Lynebank Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls jside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Common Flat Ls Rawney Ls 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 16b 16b 16b 16b 16b 16b 16b 16b 16b 16b 16b 16b 16b 16b 16b 16b 16b 16b 16b 16b 16b 16b 16b 16a 5 5 5 5 5 Ellery Sike Ls Ellery Sike Ls Ellery Sike Ls Ellery Sike Ls Ellery Sike Ls Ellery Sike Ls Ellery Sike Ls 887t2 88711 88710 88709 88708 88707 88706 88705 108791 108790 108789 108788 108787 108786 108785 108784 108783 108782 108781 108780 108779 108778 108777 108776 108775 108774 108773 108770 108769 108768 108767 108794 108729 108724 108722 108719 108714 108712 88768 88763 8876 88760 88759 88758 88757 88756 88755 88754 88751 88750 88748 1.37 1 37 1 33 1 35 1 29 1 36 1 36 1 32 1 20 1 32 1 36 1 12 1 31 1 26 1 21 0 82 1 38 1 38 1 39 1 1 1 42 1 42 1 40 1 45 1 43 1 36 1 33 1 12 1 34 1 33 1 22 1 32 1 39 1 42 0 67 1 49 1 38 1 06 1 27 1 45 1 1 1 1 04 1 39 1 38 1 42 1 32 1 44 1 35 1 23 1 34 1 20 1417 1416 1415 1414 1413 1412 1408 1407 1449 1448 1447 1446 1445 1444 1443 1442 1441 1440 1439 1438 1437 1436 1435 1434 1433 1432 1431 1519(UF) 1518 1517 1516 1460 1496 1495 1494 1493 1492 1491 1484 1483 1426 1425 1424 1423 1422 1421 1482(UF) 1481 1420 1419 141 1(') ID (1) 2—6 6(1) 2(3) 1 1 8 4(1) 1 1 — 2 — — 1 (1) 10(2) (5) - - 1 8 (7) 10 2 2 2 (1) (2) (8) 6(1) 13(1) 6 1 6 4(4) (16) (2) 7 (1) 1 17 (1) 1(D - (D (1)1 - ' (D ~ in CO & o (1) - 3 — 10) 1 (2) 1 - - 112) (1) — 8 6 (4) 3 2(1) 26 10(9) (4) _ _ 4 _ _ - - 1 (1) - 3 (1) 1(1) - 1 — — 1 (1) 50 (6) (5) 44 9 4 5 10 6 1 2 1 4 18 4 1 2 5 2 (5) 1 — 3 1 1 1(1) 1(1) 1(1) 2 1(4) 1 3(6) (D (4) (1) - - (i)e 1 1 2(1) 2 (11) (1) (1) (1) (3) - (3) - (6) - (1) - - - (1) - (1) 1 4(1) 2(3) (1) - 1(1) - 3(8) 1 1 (3) (1) - — 1 (9) — 1(1) 1 2(2) (4) 2 4 7 — 5 (1) (15) (1)» - 12(1) (4) - - - - (1) - — 4(1) 6(9) 1 — 2 — 1 — 4 3 1"(1) 3 (2) — 2 2 (5) — 17 1 1 25 — 12 1(1) 1 2 2(2) 2A(2) (2) — 3 - - - - - (1) - 15 10 2 — 1 1 - (1) d) — 12— — - 1(1) (1) - - 2(1) - - (1) 19-(4) (1) 1(1) - (1) 1 2 - (1) (1) 1t(1) (5) - 2 — 3 1 — 1 5 (1) 1 (3) 1 - (1) 1 2(1) 3(1) - 2(1) - 1(1) 14(6) (1) (1) 14 1 — (8) (1) (5) (1) 47 o o c "O Tl o —I 3 DJ O =5 2 9 3 CD CU 3 © c 3 cr CD 0) c/> CD co co CD Q. O o CD CO w CO C 3 CX CD Si o CQ c CO a o c C/> & C co T! Cu o CQ 0) »■•► 3" C CO s o c Co T3 & C co g &J CD Cr CD <-> 6- CD O ?*■ 5' CD 3 CD Q. 5' CD ■g 0J T3 5 5 CD CD CO Co o O ■n o tl Cu O CQ 3 Cu 3- C CO 8 C/> "0 Cu ~? o CQ 3 cu c CO en ■o QJ Cu ~7 o CQ 3 Cu 3- C CO CO T3 0) Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Lowe Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Border Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bewcast Bogside Ls. Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls Bogside Ls 1768640 1768639 1768638 1768637 1768636 1768635 1768634 1768633 1768632 1768631 1768630 258629 258628 258627 258626 258625 258624 258623 258622 258621 258620 141 18519 141 18518 14118517 141 18516 14118515 14118514 14118513 141 18512 1411851 1 141 18510 1411859 1411858 1411857 1411856 1411855 1411854 1411853 1411852 1411851 1.30 1 29 1 25 1.19 1 23 1.40 1 29 1 35 1 40 1.37 1.37 1 00 1 28 1.21 1.15 1.15 1 20 1 30 1 36 1.37 1 34 1 90 1 25 1 20 1 23 1 22 1.25 1.12 1 24 1.17 16 16 33 19 19 1147 1146 1145 1144 1143 1142 1141 1140 1139 1138 1137 1344 1057 1343 1056 1055 1054 1053 1052 1051 1050 1271-5 1049 1048 947 945 944 1266-70 943 942 946 941 940 939 938 937 936 935 934 933 932 931 930 929 — — 1 1 - - - (1) 1 — - - 1 - (3) - - (1) - - - 1(1) - (1) — — - 1 — (1) - 1(1) - 3(1) (D - (1) - 2 — 1 1(1) 5 — (4) - 2 — — — (1) (1) — — - - - (1) 2 1(1) 2 2 - 1(1) 1 1 — (3) (1) 6(1) 2(1) (2) (2) 1(1) - (2) - - - 2 1(1) 1 (1) (2) 1 — 3 1 2 — APPENDIX lib. Conodont elements recovered from the Bogside Limestone Member, Bewcastle Formation, locality 10. 48 3 ■o 3- r< ^ .?< ^ Hi Cu cu 0) (Q 3 Cu 3- C (ft •O ~f Cu r> T) Ti T> £■ 3- 3- 3" 3- CD 3- O O O (Q 3 Cu c (n 3" O O O (Q 3 CU 3 C 3- -^ O 3 ai Cu Cu 0) Cu V) co co CQ (Q CQ CD CD CD CD CO CD 3 Cft 3 (ft 3 cn 3 (ft s 2 -* 2 cu s 2 2 3 5r ft. 5" ft 5T ft ST ft ST ft. ST ft 3 3 3 3 "^ CU (O 3 CD 3 Cft Tl 9 CD 0) 0) -a CU 0) -a CD 5' p. 3 (ft "O Cu' 3 (ft 3 (ft cu' 3 (ft CU 3 (ft to O cu 3 (ft CO C (0 •o -o 0) o c" (ft TJ CU o 3 o o o to o o c* Cft CO DJ CD 3 CU CD 2 DJ CD 3 DJ CD CO O CO 3 CD 3 Cft Cft 3- CD CD 3 cu o o Q. co 3' CO 3 C 3 -i TT90 1427 1489 1488 1487 1486 1485 1522 1521 1383 1480 1479 1478 1477 1476 1475 1474 1473 1472 1471 1470 1469 1468 1467 1466 1465 1464 1463 1462 1406 1405 1404(UF) 1251 1250 1381 1249 1380 1379 1248 1342 1247 1378 1377 1376 1375 1246 1373(UF) 1372 1459 1245 1371 1370 1369 1368 1» CU o cq 3 Cu 3 C co ■ co T3 ff ■o Cu o 3 co' T> CU O cu c CO <0 3 CU c Co C 3 O' o CU O cu •>; c co ' o CO' TI 3 O CU r: c Co CQ 3 cu 3 c CO 3 &> O CD 3 CO CO' 2? - (1) 4 2(2) (1) (1) (12) - 1 (1) - (1) — 4 — 6 — — 2 — 1 3 1(7) (2) - (1) (2) (3) 5 - - - - 2(1) (4) (1) - (1) 1 - (2) - - (1) - ■ (1) 1 - - 2(1) (1) - (1) 1 1 - - 1 (2) 1 - 2 — (5) 1 2 3 — — — (1) — — (1) & CQ 3 CU 3 c CO (/> T3 Tl CU (1) (1) — 5 (5) - (6) - (8) - - - - - (7) - - - - — — (8) — - - - - - (5) - - - (4) (5) - - (4) — - APPENDIX He. Conodont elements recovered from the Bewcastle, Main Algal, and Cambeck formations, localities 10, 12, and 13. UF residue not completely picked; 0 cavusgnathid; t Hindeodus fragments?; r rare. 50 H t* ri * T3 Tl « 0J « SF 3 Q) 0) 3- 3" 3- «-> o Co O CO to 1' 5 0) 8- co 0) r— o o 3- o CQ 0) c CO 2 o 0) 3 c CO £ O CQ 3 0) 3 c CO 0) 3 0) c CO *: 0) O co. 3 0) 3 c CO *: 0) 3- 1 3 01 3 c CO 0? ■o 3- -> O CQ 3 0) 3 c CO 3" 1 3 &> 3 c (0 2* 3- •^ O CO 3 0) 3 c CO 3" a o CQ 3 0) 3 c CO 3- a o CQ 3 0) 3 c CO CQ CD c5~ 3 5 c CO CQ 1 CD CQ~ 3 &) 3 c CO 1 CD CQ- 3 CU 3 c CO 1 CD <5" 3 0) 3 c CO 1 CD <6~ 3 &> 3 c CO 1 cd 3 01 3 c CO CQ CD 3 c CO o CD 0 CD 3 0 CD 3 O CD 3 C CO 3 Q. CD CD 0 CD C CO 3 Q. CD CD* 0 CD 3 C CO 3 a CD CD O CD 3 C CO 3 Q. CD CD (f) 3 a CD CD 3 5' 0) CD 3 5? 3" c cd F5' O' 3 CO 3 CO 3 10 s 2 2 5 2 2 o £ £ $ £ $ s CO 8! CO 0) 0> 0) 3 3 3 3 _ Tl O CO 0) o O ■> a -* a t) o O T3 O X) -n .o ■Q CO CO 3 w CD 3 0) CD 3 u 3 CD a> 0) co' 3" CD c CO CO ■p CO T3 a 3 Co' 3 55' tj 0) 0) TJ 0) 0) 3 CO cu 3 CO 0) 3 CO Q> 3 CO 0) 3 CO 0) 3 CO 3- 3- 3" C CO 3" 3- c si c c Q. C ■p 0) p 0) CO 3 CD CO 3 CD 0) 0 0 Q. CD CO 01 CO o 2 2 S3 3 Q. 3 z 8? ? CO o CO ff TJ 0) 8? S CO o CO y CO o CO o? ff 2 o? 5 2 c/> 0 3 CO 3 CO CD 3- - 1 1(1) 11 (3) ------ - 3 3 28 — 6 — 1 (1) 1(2) (2) (1) — — 14 — — 62 7 _ _ _ 4 (1)« 23 (2) 5 — — r (1) 1 86 (1) (1) 1 1 (7) 1 26 (1) (1) 14(1) (1) 1 — (1) 2 — (1)« (3)« r 1(2) - - 1(1) - - 7 8 2t - 1 — (1) (2) (1) (1) (1) - (2) (1) (1) (2) 6 (4) (1) 1 - - (1) - 3 (1) 2 3 1 1 3(1) — 5(1) 3(8) 1(1) (2) (2) - (1) (9) 4(2) 1(10)5(2) 1(1) (1) 3 6(3) (2) 30 13 13 (1) 23 28 67 "(1) 51 o O o o o cu OJ CU Q) 0) ■<: ■<: <; •«: ^ c c "C c c 3 01 O) o> 3 O) CQ 3 o cu o 0) s> s> £> s> CU 3 cu 3 CD 3- CD 3 0> O) 5 O) O) Ol 5 O) o O T) c c £ C c «Q O) o» O) 0) 3 3 3 3 3 ^ ^ <: CO CD 3 ■o CD 31 O O =3- 3- c c c c CU 3 CU 5 ft) 3 CD 3 CD 3 cu 3 c O) tfl o 5 o 2 o 2 o 2 o 2 C P. c Q 3- C Q ra- ce Q C Q s CD 3 i O O) o> O) O) 01 0» 3 CD O 3 o Tj 73 o o O o o o o> 0) "1 o CD C 3 CD C/> 3 TJ TJ T3 (D CD 2 2 2 2 2 2 p p o c 5' 3 CD c? CD Q. CD -1 CD R CD "DO CD 3 3 Q. TJ 2 ff CO cr co o CO CD s Lower Border Liddel — 20 108792 1 44 1450 — 20 3 33 11(25) 5 3(1) (1) Middle Border — Harden 17 108766 1.31 1430 Lower Border Liddel — 17 108764 1.23 1515 1 13 4 5 4(16) — 2 — — 1 (1) (5) (1) Lower Border Liddel — 17 108763 1 30 1514 Lower Border Liddel — 17 108760 1 40 1512 1 2 (5) — Lower Border Liddel — 17 108758 1 40 1511 5 16 4 16 8 10 2 3 — — (7) 1(3) — Lower Border Liddel — 17 108756 1.43 1509 Lower Border Liddel — 17 108754 1.42 1508 1 — — 2 (3) (1) 3 — — — (7) (2) — Lower Border Liddel — 17 108752 1 49 1507 Lower Border Liddel — 17 108751 1.43 1506» 25 1 1 — 49 5(18) 24(14) 6 3 2 2(1) (10) — — Lower Border Liddel — 17 108747 1.34 1505 Middle Border — Harden 19 108745 1.20 1429 Lower Border U Black Burn — 19 108742 0 86 1504 Lower Border U Black Burn — 19 108739 0 93 1503 Lower Border L Black Burn — 19 108737 0 96 1502 Lower Border L Black Burn — 19 108735 1 09 1501 Lower Border Arnton Fell — 21 108734 1 02 1428 APPENDIX lid. Conodont elements recovered from the Liddel, Black Burn, and Arnton Fell formations and the Harden Member, locali- ties 17, 19-21. f juvenile; 0 cavusgnathid; * includes 2 juveniles; " 18 anterior platform and blade fragments included inC. hud- soni Pa elements. 52 o 3 Cu O o O 3 3- o t) "0 TJ TJ T) T) 8* CD 3 CD 3 CD 3 Q. CD & O o O O o o Q C C C CD ^" ^5" ^" ^" *5* S" t> 0 TJ 3- co CO CO en CQ O 3 i o Bl •<; c to 3 (n in' 3 & 3 c en 3' 8- o CD 3 to O & 3 c to 3 8- o 3 3 01 o o 01 o 3 Si' ■D 0) tu ■> o (Q 3 01 3 c en 2 cV O O CO 3 01 3 c (n 0) tJ S' o 3 5>' co o "0 O cf 3 Cu 3 c on Co 3- oj o? 5 2 fc? » ff -H -H U) 0) T3 T> 3- 3" ■* O O ' OJ CD C/> CX CD CD 3- 9 o o Q. CD on 3(1) 4 — 2 2 4(3) 3(9) 3 - (9) 67 2(2) 1 - - d) - 3(1) - 4(6) 3 1 — — 1 1 (1) - - 1 (D 3 — 1 1 — 16 — 7 1/1 cl — (D 1 — 1 7 4 — 2 - — 2 1 — 2 - 1 3 1 1 1(1) 2(3) (D (1) 1(1) (2) - 4(2) (1) 23 (1) - 79 (51) 3—3 1 - 4 (1) (4) (1) 1 (1) 30 34 51 38 35 7 1 1 3 3 4 4 (D (D 19 7 1 2 1 — 2 (1) (D 1 (1) (1) d) 1 (2) (1) 7 — 1 4 1 3 55 Literature Cited r- ALBERCH, P., S. J. GOULD, G. F. OSTER, and D. S. WAKE 1979 Size and shape in ontogeny and phylogeny. Paleobiology 5:296-317. ALDRIDGE, R. J. 1987 Conodont paleobiology: a historical review. In Aldridge, R. J., ed., Palaeobiology of con- odonts. Chichester, Ellis Horwood, pp. 11-34. ALDRIDGE, R. J., D. E. G. BRIGGS, E. N. K. CLARKSON, and M. P. SMITH 1986 The affinities of conodonts — new evidence from the Carboniferous of Edinburgh, Scot- land. Lethaia 19:279-291. ALDRIDGE, R. J., M. P. SMITH, R. D. NORBY, and D. E. G. BRIGGS 1987 The architecture and function of Carboniferous polygnathacean conodont apparatuses. In Ald- ridge, R. J., ed., Palaeobiology of conodonts. Chichester, Ellis Horwood, pp. 63-76. ARMSTRONG, H. A. and M. A. PURNELL 1987 Dinantian conodont biostratigraphy of the Northumberland trough. Journal of Micro- palaeontology 6:97-112. AUSTIN, R. L 1973 Phylogeny and homeomorphy of conodonts in the Lower Carboniferous. Geological Society of America, Special Paper 141:105-116. 1974 The biostratigraphic distribution of con- odonts in Great Britain and the Republic of Ireland. International Symposium on Belgian Micropaleontological Limits, Namur, Publi- cation 3:1-17. AUSTIN, R. L, ed. 1987 Conodonts: investigative techniques and appli- cations. Chichester, Ellis Horwood. 422 pp. AUSTIN, R. L. and R. J. ALDRIDGE 1973 Conodonts from horizons with Goniatites crenistria Phillips in North Wales and the Isle of Man. Geological Magazine 110:37-42. AUSTIN, R. L. and R. B. DAVIES 1984 Problems of recognition and implications of Dinantian conodont biofacies in the Britis Isles. Geological Society of America, Special Paper 196:195-228. AUSTIN, R. L and P. J. HILL 1973 A Lower Avonian (K zone) conodont fauna from near Tintern, Monmouthshire, Wales. Geologica et Palaeontologica 7:123-134. AUSTIN, R. L and S. HUSRI 1974 Dinantian conodont faunas of County Clare, County Limerick and County Leitrim, an appendix. International Symposium on Bel- gian Micropaleontological Limits, Namur, Pub- lication 3:18-69. AUSTIN, R. L and M. MITCHELL 1975 Middle Dinantian platform conodonts from County Fermanagh and County Tyrone, North- ern Ireland. Geological Survey of Great Britain, Bulletin 55:43-54. AUSTIN, R. L and F. H. T. RHODES 1969 A conodont assemblage from the Carbonifer- ous of the Avon Gorge, Bristol. Palaeontology 12:400-405. BASSLER.R.S. 1925 Classification and stratigraphic use of con- odonts. Geological Society of America, Bulle- tin 36:218-220. [Abstract] BATESON, W. 1886 The ancestry of the Chordata. Quarterly Journal of Microscopical Sciences 26:535-571. 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Transactions of the Leeds Geological Association 8:399-408. VARKER, W. J. and G. D. SEVASTOPULO 1985 von BITTER, P. H. 1976 The Carboniferous System: part 1 — conodonts of the Dinantian Subsystem from Great Britain and Ireland. In Higgins, A. C. and R. L. Austin, eds., A stratigraphical index of conodonts. Chichester, Ellis Horwood, pp. 167-210. Paleoecology and distribution of Windsor Group (Visean-?Early Namurian) conodonts, Port Hood Island, Nova Scotia, Canada. Geo- logical Association of Canada, Special Paper 15:225-241. YOUNGQUIST, W L and A. K. MILLER 1949 Conodonts from the late Mississippian Pella Beds of south-central Iowa. Journal of Paleon- tology 23:617-622. ZIEGLER,W.,ed. 1975 1977 1981 Catalogue of conodonts, volume U. Stuttgart, E. Schweizerbart'sche Verlagsbuchhandlung. 404 pp. Catalogue of conodonts, volume HI. Stuttgart, E. Schweizerbart'sche Verlagsbuchhandlung. 574 pp. Catalogue of conodonts, volume IV. Stuttgart, E. Schweizerbart'sche Verlagsbuchhandlung. 445 pp. 62 Plates 63 PLATE 1, FIGS. 1-14 Figs, la, b. Hindeodus crassidentatus (Branson and Mehl)?. Lateral and upper views of Pa element ROM 48777, sample 78864, xlOO. Figs. 2-14. Cavusgnathus hudsoni (Metcalfe) x60. 2a-c. Lateral, lower, and upper views of sinistral Pa P element ROM 48778, sample 108751. 3a, b. Lateral and upper views of immature sinistral Pa a element ROM 48779, sample 108751. 4a, b. Lateral and upper views of immature sinistral Pa element ROM 48780, sample 108751. 5a-c. Lateral, upper, and lower views of sinistral Pa a/P element ROM 48781, sample 108751. 6. Upper view of aberrant dextral Pa element ROM 48782, sample 108758. 7a, b. Lateral and upper views of variant dextral Pa P/y element ROM 48783, sample 108764. 8. Lateral view of dextral Pa y element ROM 48784, sample 108764. 9. Lateral view of Pb element ROM 48786, sample 108751. 10. Lateral view of Sc element ROM 48785, sample 88754. 11. Posterior view of Sa element ROM 48787, sample 108751. 12. Lateral view of Sc element ROM 48788, sample 108751. 13. Lateral view of Sb element ROM 48789, sample 108751. 14. Lateral view of M element ROM 48790, sample 108754. 64 M * S •/*•*- t *£ *£ PLATE 2, FIGS. 1-15 Figs. 1-5, 7. Cavusgnathus unicornis Youngquist and Miller x60. la, b. Upper and lateral views of dextral Pa p/y element ROM 48791, sample 88717. 2. Upper view of sinistral Pa P element ROM 48792, sample 88776. 3. Lateral view of straight Pa a element ROM 48793, sample 88776. 4. Lateral view of aberrant sinistral Pa element ROM 48794, sample 209862. 5. Lateral view of sinistral Pa y element ROM 48795, sample 209862. 7. Lateral view of M element ROM 48796, sample 209863. Figs. 6a, b. Cavusgnathus cf. unicornis Youngquist and Miller. Upper and lateral views of dextral Pa element ROM 48797, sample LA5, x60. Fig. 8. Cavusgnathus? sp. a. Upper view of sinistral Pa element ROM 48798, sample 108701, x60. Figs. 9-15. Clydagnathus windsorensis (Globensky) xlOO. 9. Lateral view of dextral Pa element ROM 48799, sample 88758. 10a, b. Lateral and upper views of sinistral Pa element ROM 48800, sample 88757. 1 1 . Lateral view of Pb element ROM 48801, sample 88756. 12. Lateral view of M element ROM 48802, sample 88756. 13. Posterior view of Sa element ROM 48803, sample 88756. 14. Lateral view of Sb element ROM 48804, sample 88756. 15. Lateral view of incomplete Sc element ROM 48805, sample 88756. 66 $+* 10b PLATE 3, FIGS. 1-15 Figs. 1-9. Palrognathus capricornis (Druce) xlOO. 1. Lateral view of M element ROM 48806, sample 108778. 2. Upper view of Pa element ROM 48807, sample 1968710. 3a, b. Lateral and upper views of immature Pa element ROM 48813, sample 14118513. 4. Upper view of immature Pa element ROM 48814, sample 14118513. 5. Lateral view of M element ROM 48808, sample 1768701. 6a, b. Lateral and upper views of Pa element ROM 48809, sample 108701. 7a, b. Lateral and upper views of Pa element ROM 48810, sample 14118513. 8. Lateral view of Pb element ROM 4881 1, sample 14118517. 9. Lateral view of incomplete Sc element ROM 48812, sample 14118517. Figs. 10-15. Taphrognathus carinatus (Higgins and Varker) x80. 10. Posterior view of Sa element ROM 48815, sample 156876. 11. Lateral view of Sc2 element ROM 48816, sample 156871. 12. Posterior/lateral view of Sb element ROM 48817, sample 196861. 13. Posterior view of Sa element ROM 48818, sample 196861. 14. Lateral view of Pb element ROM 48819, sample 196861. 15. Lateral view of M element ROM 48820, sample 196861. 68 ? «1^ J..4 * c . i- -^l PLATE 4, FIGS. 1-15 Fig. la, b. Taphrognathus carinatus (Higgins and Varker). Lateral and upper views of Pa element ROM 48821, sample 196861, x80. Figs. 2-15. Taphrognathus varians Branson and Mehl x80. 2. Upper view of dextral morphotype II Pa element ROM 48822, sample 1768631. 3a, b. Lateral and upper views of sinistral morphotype DI Pa element ROM 48823, sample 88710. 4a-c. Lateral, upper, and lower views of dextral morphotype III Pa element ROM 48824, sample 1768633. 5. Upper view of slightly sinuous morphotype I Pa element ROM 48825, sample 108773. 6. Upper view of dextral morphotype D/I Pa element ROM 48826, sample 258621. 7. Upper view of immature Pa element ROM 48827, sample 1411852. 8. Lateral view of immature Pa element ROM 48828, sample 258622. 9. Upper view of dextral morphotype II Pa element ROM 48829, sample 108767. 10. Upper view of immature Pa element ROM 48830, sample 256866. 1 la, b. Lateral and upper views of immature Pa element ROM 48831, sample 258620. 12. Lateral view of Pb element ROM 48832, sample 1768634. 13. Lateral view of Pb element ROM 48833, sample 258620. 14. Lateral view of immature Pb element ROM 48834, sample 258625. 15. Lateral view of M element ROM 48835, sample 14118511. 70 Mfci^tit*,. M PLATE 5, FIGS. 1-12 Figs. 1-3. Taphrognathus varians Branson and Mehl x80. 1. Posterior view of Sa element ROM 48836, sample 108790. 2. Lateral view of Sb element ROM 48837, sample 108790. 3. Lateral view of Sc element ROM 48838, sample 108790. Figs. 4a, b. Taphrognathus? transatlantic us (von Bitter and Austin)?. Oblique lateral view of Pa element ROM 48839, sample 258622, a x80, b x340. Figs. 5a, b. Taphrognathus sp. a. Lateral and upper views of sinistral Pa element ROM 48840, sample 108745, x80. Fig. 6. Gnathodusl simplicatus (Rhodes, Austin, and Druce). Lateral view of Pa element ROM 48841, sample 108745, xlOO. Fig. 7. Gnathodus cuneiformis Mehl and Thomas. Upper view of Pa element ROM 48842, sample 196863, xlOO. Figs. 8, 9. Mestognathus beckmanni Bischoff x60. 8a, b. Lower and upper views of sinistral Pa element ROM 48843, sample 209862. 9. Lateral view of Pb element ROM 48844, sample 258629. Fig. 10. Mestognathus praebeckmanni Sandberg, Johnston, Orchard, and von Bitter. Oblique upper view of dextral Pa element ROM 48845, sample 439 of Armstrong and Pumell (1987), x60. Figs. 11, 12. Mestognathus praebeckmanni-M . beckmanni intermediates x60. 11a, b. Lower and lateral views of dextral Pa element ROM 48846, sample 88750. 12a-c. Lateral, upper, and oblique lower views of dextral Pa element ROM 48847, sample 1768630. 72 0±. *%Xw • . ^>rr *»*' \^*--. J0 Wfpk DPoPW V&x*-' >-' ■v-««e*^»- PLATE 6, FIGS. 1-13 Figs. 1,3. Polygnathus bischojfi Rhodes, Austin, and Druce x80. 1. Upper view of Pa element ROM 48848, sample 88751. 3. Lower view of Pa element ROM 48849, sample 88750. 10a, b. Posterior and oblique lateral views of Sa element ROM 48856, sample 108763. 11. Lateral view of Sc element ROM 48857, sample 108763. Figs. 2, 4-7, 9-1 1 . Polygnathus mehli Thompson x80. 2. Oblique upper view of Pa element ROM 48850, sample 108760. 4. Lower view of Pa element ROM 48851, sample 108745. 5. Lateral view of M element ROM 48852, sample 108763. 6. Lateral view of Pb element ROM 48853, sample 108763. 7. Lateral view of Pb element ROM 48854, sample 108763. 9. Lateral view of Sc element ROM 48855, sample 108763. Fig. 8. Polygnathus sp. Lateral view of immature Pa element ROM 48858, sample 108745, x80. Figs. 12a, b. Lochriea scotiaensis (Globensky). Lower and lateral views of Pa element ROM 48859, sample 88760, xlOO. Fig. 13. Lochriea sp. Lateral view of M element ROM 48860, sample 209863, x60. 74 - I - *. 10a PLATE 7, FIGS. 1-12 Figs. 1-8. Vogelgnathus gladiolus Purnell and von Bitter xl80. la, b. Lateral and upper views of Pa element ROM 48667, sample 258624. 2. Lateral view of Pa element ROM 48668, sample 258622. 3. Lateral view of variant Pa element ROM 48861, sample 1768636. 4. Oblique lower view of Pa element ROM 48669, sample 14118517. 5. Lateral view of Sb element ROM 48672, sample 1768634. 6. Lateral view of Sc element ROM 48675, sample 141 18517. 7. Lateral view of Pb element ROM 48674, sample 1768635. 8. Lateral view of M element ROM 48673, sample 258622. Figs. 9, 10, 12. Vogelgnathus kyphus Purnell and von Bitter xl80. 9. Upper view of Pa element ROM 48676, sample 88727. lOa-c. Lateral, lower, and upper views of Pa element ROM 48677, sample 88725. 12. Lateral view of Sb element ROM 48679, sample 88726. Figs. 11a, b. Vogelgnathus pesaquidi Purnell and von Bitter. Lateral and lower views of morphotype II Pa element ROM 48683, sample 1768701, xl80. 76 K*>* V-' w.» V. « 10b PLATE 8, FIGS. 1-12 Fig. 1. Vogelgnathus cf. pesaquidi Pumell and von Bitter. Lateral view of Pa element ROM 48862, sample 256862, xl80. Figs. 2, 3. Kladognathus tenuis (Branson and Mehl) x80. 2a, b. Lower posterior and oblique lateral views of Sa element ROM 48863, sample 88754. 3. Lateral view of Sea element ROM 48864, sample 88754. 6. Lateral view of Sb element ROM 48866, sample 141 18513. 7. Lateral view of Sc element ROM 48867, sample 108768. 8. Lateral view of Pa element ROM 48869, sample 108767. 9. Lateral view of Pb element ROM 48870, sample 108767. Fig. 10. "Apatognathus" sp. Lateral view of Pa element ROM 48871, sample 1768702, xlOO. Figs. 4—9. "Apatognathus" cuspidatus Varker xlOO. 4. Posterior? view of Sa element ROM 48865, sample 108790. 5. Posterior? view of Sa element ROM 48868, sample 108768. Figs. 11, 12. Gen. a sp. a xlOO. 11. Lateral view of Pa element ROM 48872, sample 88776. 12. Lateral view of M element ROM 48873, sample 88776. 78 N tSfc ROYAL ONTARIO MUSEUM LIFE SCIENCES PUBLICATIONS INSTRUCTIONS TO AUTHORS Authors should 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 they are not currendy offered for publication elsewhere. 1. General Papers for publication are accepted from ROM staff members and research associates, and from researchers reporting on work done with ROM collections. Monographs on the flora and/or fauna of Ontario by authors not affiliated with the ROM may be considered for publication. Financial contributions towards publication may be required. Authors are expected to write clearly and concisely and to omit any material not essential for an understanding of the main theme of the paper. 2. Format Manuscripts (including captions, synonymies, literature cited, and tables) should be typed double-spaced on standard letter-size paper with a 4-cm (1*) margin on all sides. Three photocopy copies should be submitted to the Head of Publications and Print Services; the original should be retained by the author. The submission should include a separate sheet giving the author(s) names and affiliations, the title of the publication, the series if applicable, the number of typed pages, the number of tables, and the number of plates and figures. 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If captions are lengthy, they may be placed on the facing page. A scale or magnification factor should be included. Authors are reminded that when illustrations are reduced, magnification factors will change, and that they are responsible for the conversion. For details, see the Guide to Authors and Editors. • ROYAL ONTARIO MUSEUM LIFE SCIENCES PUBLICATIONS Life Sciences Contributions are a numbered series of scientific publications of varied subject matter. Most recent contributions include the following: 148 Shallow-Water Hydroids of Bermuda: The Athecatae Dale R. Calder 1988, 112 pp., ill., $24.50, ISBN 0-88854-339-5 155 Revision of the World Species of Spalangiopelta (Hymenoptera: Chalcidoidea: Pteromalidae: Ceinae) D. Christopher Darling 1991, 48 pp., ill., $11.00, ISBN 0-88854-395-6 154 Shallow-Water Hydroids of Bermuda: The Thecatae, Exclusive of Plumularioidea Dale R. Calder 1991, 144 pp., ill., $24.50, ISBN 0-88854-354-9 153 Silurian Trilobites from the Northern Yukon Territory Rolf Ludvigsen and Ronald P. Tripp 1990, 64 pp., ill., $12.95, ISBN 0-88854-349-2 Related titles published by the Royal Ontario Museum: The Reconstruction of Fossil Organisms Using Cluster Analysis: A Case Study from Late Paleozoic Conodonts Peter H. von Bitter and Glen K. Merrill 1990, 32 pp., ill., $8.00, ISBN 0-88854-352-2 LSC 143 Phylogeny, Speciation, and Palaeoecology of the Early Carboniferous (Mississippian) Conodont Genus Mestognathus Peter H. von Bitter, Charles A. Sandberg, and Michael J. Orchard 1986, 120 pp., ill., $25.00, ISBN 0-88854-319-0 152 The Type Species of the Ordovician Trilobite Genus Isotelus: I. gigas Dekay, 1824 David M. Rudkin and Ronald P. Tripp 1989, 24 pp., ill., $10.25, ISBN0-88854-345-X 151 The Structure of the Call Note System of the Warbling Vireo Daryl Hoioes-Jones and Jon C. Barlow 1988, 40 pp., ill, $11.00, ISBN 0-88854-343-3 150 Late Cretaceous-Early Tertiary Dinoflagellates and Acritarchs from the Kashi Area, Tarim Basin, Xinjiang Province, China Mao Shaozhi and Geoffrey Norris 1988, 100 pp., ill., $25.00, ISBN 0-88854-334-4 149 Occurrence of the Cladid Inadunate Crinoid Thalamocrinus in the Silurian (Wenlockian) of New York and Ontario George C. Mcintosh and Carlton E. Brett 1988, 20 pp., ill., $7.75, ISBN 0-88854-342-5 LSC 136 Late Palaeozoic Species of Ellisonia (Conodontophorida): Evolutionary and Palaeoecological Significance Peter H. von Bitter and Glen K. Merrill 1983, 64 pp., ill., $7.50, ISBN 0-88854-294-1 LSC 106 Conodont infrastructure: The Subfamily Acanthodontinae C. R. Barnes and D. /. Slack 1975, 24 pp., ill., $3.95, ISBN 0-88854-179-1 A catalogue of ROM publications in print is available from University of Toronto Press 10 St. Mary Street, Suite 700 Toronto, Ontario M4Y 2W8 Canada Tel. (416) 978-2229 Fax (416) 978-4738 ISBN 0-88854-405-7 ISSN 0384-8159