Statistical analysis of British faunas

EDRIC C. DRUCE, FRANK HAROLD TREVOR RHODES, & RONALD LEYSHON AUSTIN

CONTENTS I Introduction . . . 53 2 Statistical recognition of assemblages . . . 55 3 Method ..... 56 4 Interpretation of dendrograms .... 58 5 Detailed analysis of conodont associations . 58 6 Frequency of elements in individual samples. 66 7 Conclusions 67 8 References 69

SUMMARY Three lines of evidence are reviewed that determined. This indicates common occur- suggest conodont contained multi- rences of elements and can be supplemented element conodont assemblages in life. Re- by comparisons of total stratigraphic range and construction of the original multi-element relative frequency of elements. Thirteen groups assemblages of from the Cleistopora are recognized which are compared with (K) and Zaphrentis (Z) Zones of the North assemblage models based on assemblages Crop of the South Wales Coalfield is attempted preserved in situ on shale bedding planes. using the Centclass programme on a Control Group 8 compares with a basic duboisellid Data 36oo computer. Two methods are (Class C) type of assemblage. Groups 5 and described which are of use in assemblage 6 do not appear to represent meaningful reconstruction. Polythetic cluster analysis, first groups. All other groups represent either developed for use in ecological surveys, complete or partial Lochreia type Class A provides dendrograms from which the level of assemblages. association of individual elements may be

i. Introduction THE FIRST SUGGESTION that a number of conodonts was associated in the original conodont was made by Hinde (1879 , pp. 361-364) who described what he concluded to be a natural assemblage from the Upper Genessee Shale of New York. As Lindstr6m (1964, p. 75) has pointed out, these specimens were strewn randomly over a shale surface, and it was a mere guess that they belonged together in life. Natural assemblages were first described independently by Schmidt (1934) from the lower Upper Carboniferous of the Rhineland, and by Scott (1934) from the lower Upper Carboniferous of Montana. The Lower Carboniferous/Upper Carboniferous boundary has yielded further natural assemblages 'in situ' on shale surfaces. These have been reported by Kraemer (194o), Schmidt & Mfiller

Jl geol. So¢. vol. x~8, I972 , pp. 53-70. Figs. x-8. Printed in Northern Ireland.

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(I964) , Scott (I934, i942 , i969) , Du Bois (i943) , and Rhodes (I952). The last paper, on assemblages from the of Illinois, deals in detail with the nature, interpretation, and classification of natural conodont assemblages. We also have assemblages from the Upper Carboniferous of Britain. Lange (I968) has described about seventy assemblages of late Devonian age, associated with bituminous matter. He recognized, five distinct types of association within this collection. Recently Melton & Scott (I97O) have described natural conodont assemblages of the genera Lewistownella and Scottognathus associated with impressions of soft parts that they interpret as the remains of a conodont bearing animal. Walliser (1964) recognized the repeated association of certain form species in the of Germany, and constructed model assemblage associations on the basis of common stratigraphic ranges and constant association ratios. He recognized ten natural groups and was able to show the mode of infraspecific evolution within a biological species. Recently the study of assemblages has been extended to the . Multi-element species (BergstrOm & Sweet I966 ) or statistical assemblages (Webers 1966; Schopf 1966) have been recognized from the Middle Ordovician of North America. The criteria used to recognize these assemblages are stratigraphic distribution, relative abundance (Webers I966 , p. 7), size, colour, and secondary structural features as denticulation, attachment-surface morphology, and orna- mentation (Bergstri3m & Sweet x966). The last criterion has been used to recognize an assemblage from near the Middle-Upper Devonian boundary in Germany (LindstrOm & Ziegler i965). Kohut (I969) has used a rank-correlation statistical technique to confirm the validity of the groupings suggested by Bergstr6m & Sweet (i 966) on empirical grounds. Evidence of natural conodont assemblages has been extended by the discovery of fused units from the Carboniferous of England (Austin & Rhodes I969) , the Silurian of Indiana (Rexroad & Nicoll x964), (Pollock x968), and the Middle Ordovician of Canada (Barnes 1967). We have examined the sequence of conodonts from the Lower Carboniferous of Great Britain (Rhodes, Austin & Druce i969). All our samples were recovered from chemically disintegrated samples and only disjunct units were recovered. The success of Bergstr6m & Sweet (I 966) and Webers (1966) in recognizing natural assemblages by statistical methods and the presence of natural conodont assem- blages in black shales from Carboniferous strata persuaded us to examine our faunas statistically. There are thus three general lines of evidence which suggest that conodont animals bore a multi-element conodont assemblage in life: the 'in situ' assemblages known from certain rocks representing low-energy environments, elements from insoluble residues that are fused together, and individual species that have common stratigraphic range and relative frequencies. In our attempt to reconstruct the original multi-element assemblages of lower Carboniferous age, we make three fundamental assumptions. Firstly, our com- puter analysis is based upon the assumption that relative frequency of association of elements in insoluble residues provides a guide to original association. Secondly,

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we assume that, in the absence of any known Lower Carboniferous assemblages, we may use those of the Upper Devonian and especially those of the Upper Carboniferous to provide models for our present reconstructions. These have been used to interpret our computer-based groupings. Thirdly, we have assumed that the hypothetical assemblages we have reconstructed by these two methods may be tested by a comparison of the relative frequencies and stratigraphic ranges of their component elements.

2. Statistical recognition of assemblages Any method of classifying objects into sets involves two independent choices. Firstly, it may be divisive, dividing the original population into successively smaller groups, or it may be agglomerative, combining individuals into successively larger groups. Secondly, the classification may be monothetic, every group at every stage being defined by the presence or absence of particular attributes, or it may be polythetic, the groups being defined by general similarity of attribute structure. Lambert & Williams (r 966) have examined each of these four possible hierarchi- cal analyses in turn and conclude, in the case of the ecological analysis which most resembles our present situation, the most meaningful is the agglomerative, poly- thetic method. The strategy of fusion employed in our present programme is based on centroid sorting, where the most similar pairs of individuals are added together to produce new synthetic individuals, who are in turn compared with all others. Lambert and Williams have shown that, although this strategy requires more computer storage than a 'nearest neighbour' sorting, it does produce groups which grow in information content and become less sensitive to errors as the analysis proceeds. The programme developed by Dr Williams provides a direct print-out of the final dendrogram, with the component species numbers represented along the horizontal baseline, and the relative level of each subpopulation above the baseline reflecting its position in the overall hierarchy. The requirements of a 'good' dendrogram are that the groups should be well marked and differentiated at roughly comparable levels, and that they should be meaningful in the light of their independent data. Our results satisfy both these requirements. We wish to record, however, that similar analyses made upon samples from the D Zone of Scotland and the North Crop of the South Wales Coalfield gave ambiguous results. We interpret these as due to the smaller size of the Scottish and Welsh samples, ade- quate sample size being a fundamental requirement of this particular programme. This same programme has also been employed for the recognition of lithological facies (Veevers I969). The relative rarity of Devonian conodont assemblages has led us to base our model for these faunas on typical Pennsylvanian Class A assem- blages (Rhodes I962 , p. W73 ). These generally consist of one or more pairs of platform type conodonts, arbitrarily designated as anterior, one or more pairs of arched blades, with or without a third denticulate process (such forms as Ozarko- dina and Hibbardella) and several pairs of 'posterior' elements, including such

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pick-shaped forms as Neoprioniodus, and such elongate blade-like forms as hindeo- dellids and ligonodinids. There are limitations to the statistical recognition of assemblages. In attempting to reconstruct the original associations of individual conodont specimens isolated by chemical disintegration, several problems are evident. Many biological and sedimentary factors act to disperse the disjunct elements. The various types of elements may vary greatly in morphology and size. This affects their hydrodynamic characters and winnowing, and sorting may often take place. Further, the variation in morphology will produce varying degrees of breakage, which are important during predation, burial, compaction, and recovery. Finally, there is the question of identification. For instance, at the generic level broken polygnathids are more readily identified than broken hindeodellids, which can be confused with broken ligonodinids or lonchodinids. Similarly, broken neoprion- iodids and ozarkodinids can also be misidentified. At the specific level, broken platforms may still be identifiable but badly broken bars and blades are virtually unidentifiable. Thus, the complete history of a conodont apparatus, from death to recovery, places a continual bias on the preferential recognition of the platforms, and this may tend to obscure any original basic numerical relationship between individual elements. One result of the whole selection of data for cluster analysis is sometimes to segregate and differentiate as separate groups the new (and generally rapidly evolving) components of assemblages from the long ranging, stable, 'parent stock' with which they are associated in the living animal. Thus, we should expect some of our later 'groups' to be incomplete assemblages, which would require for their completion, the addition of hindeodellid, ozarkodinid, and neoprioniodid elements from a long-ranging stock. The recognition of these supplementary components may not be easy, for form species of such genera as , Neoprioniodus, or Hindeodella may belong to more than one biologic species (Tatge ~956).

3" Method The data were analyzed by Dr W. T. Williams of the C.S.I.R.O. Division of Computing Research, Canberra, using an agglomerative and polythetic programme. The method of recognizing repetitive association (based on the presence or absence of form species in a particular sample) was used because studies of Cambro-Ordovician faunas had shown that there was little difference between the results obtained from this qualitative data and from a separate analysis of quantitative data based on the relative frequency of form species in each sample (Druce in press). The analysis employed the information statistic approach using the CENTCLASS program on a Control Data 36oo computer (Williams et al. 1966; Lambert and Williams I966 ). The analysis was undertaken on conodonts from the Cleistopora (K) and Zaphrentis (Z) Zones of the North Crop of the South Wales Coalfield, and was conducted on 58 observations (samples) and 66 attributes

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•Io. I. Chart of presence (-F) of conodont species in samples from K & Z Zones of the North Crop, South Wales Coalfield. Species are arranged in groups defined by dendrogram.

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(species). The total number of specimens was 7,000, and these were fairly evenly distributed amongst the samples.

4. Interpretation of dendrograms The typical dendrogram (Fig. 2) shows two primary branches, and when the linear distribution of component species is analyzed, we recognize three principal types of association. The right-hand branch includes seven groups, each showing a high level of heterogeneity between and within the groups. They form the 'tall skyscraper blocks' on the right of the dendrogram. These seven groups include forms composed of medial and posterior element associations, two semi- complete assemblages of anterior, medial, and posterior elements, and one of the anterior elements only. It seems to us that there are at least two reasons for this degree of heterogeneity. Firstly, four of the groups are members of stable evolu- tionary lines of medial and posterior elements from which individual components were incorporated into short-ranging 'whole' assemblages. Secondly, these assemblages were themselves very plastic in an evolutionary sense, and their 'specific' components show rapid diversification and replacement. The only instance in which we can recognize an association of anterior and posterior elements is in Group I I, where all the elements share a relatively rapid evolutionary develop- ment, and almost identical stratigraphic range. The left-hand primary branch is made up of two types of association. The right- hand sub group of this branch, the median third of the total plot, includes form with a very high level of association (Groups 5 and 6). They represent rare species. Group 6, which is associated at a lower level with Group 5, is made up of five relatively rare species, four of which are platforms. The remaining major category includes Groups I-4, these represent more or less meaningful associations of conodonts in terms of the present Carboniferous assem- blage models. Group 3 is one in which there is chaining, only two similar spathog- nathodids being linked at a high level.

5. Detailed analysis of conodont associations Group I Clydagnathus cavusformis Rhodes, Austin and Druce Clydagnathus gilwernensis Rhodes, Austin and Druce Patrognathus variabilis Rhodes, Austin and Druce vogesi Rhodes, Austin and Druce plumulus plumulus Rhodes, Austin and Druce Spathognathodus plumulus nodosus Rhodes, Austin and Druce This is a group of forms with limited stratigraphic range in the lower part of the K Zone. The dendrogram suggests there are two similar but distinct associations within the group. Subgroup A consists of species 4, 3, 6, and 5, including Clydagnathus gilwernensis, Spathognathodus plumulus nodosus, Pseudopolygnathus vogesi, and Clydagnathus cavusformis.

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The level of association of these forms is high and their ranges are similar. It seems very probable that C. gilwernensis and C. cavusformis were functionally similar in the original conodont assemblage. It is even possible that they performed the same function as S. plurnulus nodosus within the same species of animal, and that their morphological differences represent the normal range of infraspecific variation of the conodontifer in that they are closely similar in size and such variation is known in other cases (Rhodes 1952). Ps. vogesi, although it at first appears func- tionally distinct from both of these previous form-species, and could possibly represent a typical assemblage of the Class A type (Rhodes 1962, p. W73), nevertheless has sufficient gross structural similarities to them to suggest that it may have had a similar function. Subgroup B consists of S. plurnulus plumulus and Patrognathus variabilis (Species 2 and I). The wide apron and general form of the latter species make it seem improbable that it was functionally interchangeable with the former. It seems more likely that it may have been a functional homeomorph of the clydagnathid ele- ment of Group IA. One problem that arises is that of whether or not each of these subgroups had additional elements within their original assemblages. If they are examples of Class A type assemblages, they would lack a typical hindeodellid group, a neo- prioniodid-type group and possibly an ozarkodinid-spathognathodid-type group, unless the spathognathodids of the S. plumulus group functioned in this way. This lack was probably supplied by the members of Group 12, which suggest a conservative 'battery component" to which the more rapidly changing associated platform types were successively added.

Group 2 sp. A Rhodes, Austin and Druce antetexanus Rexroad and Scott Gnathodus simplicatus Rhodes, Austin and Druce Lonchodina sp. B Rhodes, Austin and Druce Plectospathodus? sp. A Rhodes, Austin and Druce Ozarkodina cf. 0. delicatula Stauffer and Plummer bischojfi Rhodes, Austin and Druce Polygnathus lacinatus lacinatus Huddle Polygnathus lacinatus circaperipherus Rhodes, Austin and Druce Polygnathus lacinatus prelobatus Rhodes, Austin and Druce Pseudopolygnathus nodornarginatus E. R. Branson This is a group of short-ranging forms, many of which are known only from a single sample. The significance of the level of association may not be great. If the forms do represent original associations, there are probably two broad subgroups. Subgroup 2A includes a very rare cavusgnathid, and an equally rare gnathodid, each known from only a single common locality, and a more common but atypical gnathodid, G. simplicatus, which may have served either as a platform or as a spathognathodid-type blade. The lonchodinid and the plectospathodid are very rare (three specimens of each) and the association may not be significant. This

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assemblage does not resemble any known natural grouping, and we interpret it as the result of the occurrence of a number of rare forms in two successive samples. Group 2B consists of two polygnathid species, a pseudopolygnathid and an ozarkodinid. Of the polygnathids, there are three subspecies of P. lacinatus repre- sented, and these are almost certainly functionally similar. In spite of the fact that Pseudopolygnathus nodomarginatus is assigned to a different genus, it seems probable that it was functionally similar to the Polygnathus lacinatus group: its oral morphol- ogy is closely similar, and its basal cavity is fundamentally similar in structure. P. bischofi is close to both of these species and was also possibly functionally similar. If it was not present in the same species of conodontifer, it seems probable that it existed in a very similar form. These platforms and Ozarkodina delicatus would lack other components if they constituted a Class A type assemblage. Groups 12 and 13 could clearly provide these elements, and such an association would seem necessary to balance the conodont 'budget' of components in the higher Z Zone.

Group 3 Angulodus walrathi Hibbard Prioniodina latericrescens Branson and Mehl Spathognathodus plumulus shirleyae Rhodes, Austin and Druce Spathognathodus sp. nov. A. Rhodes, Austin and Druce

This group consists of a prioniodid, an angulodid, and two rare, short ranging spathognathodids. It may represent an original association, but P. latericrescens and Angulodus sp., have longer ranges than the spathognathodid components.

Group 4 Ozarkodina macra Branson and Mehl Polygnathus inornatus inornatus Branson and Mehl Polygnathus inornatus rostratus Rhodes, Austin and Druce Polygnathus lobatus lobatus Branson and Mehl Polygnathus lobatus inflexus Rhodes, Austin and Druce isosticha Cooper SiphonodeUa sp. nov. A Spathognathodus cf. S. cyrius Cooper

This is a meaningful association of relatively short'ranging polygnathids, siphonodellids, ozarkodinids and spathognathodids in the higher part of the K Zone. The two polygnathid species, P. lobatus and P. inornatus, each of which is represented by two subspecies, are very similar to one another, and are interpreted as functionally identical within an assemblage. Possibly the siphonodellids rep- resented a distinct assemblage, or an extreme variation of the more general polygnathid type. The presence orS. cf. S. cyrius and O. macra provided some, but not all, of the additional Class A elements, the remainder probably being derived from the continuing stable stock of Groups 12 and 13.

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Group 5 Angulodus sp. B Gnathodus delicatus Branson and Mehl HibbardeUa (HibbardeUa) cf. H. macrodentata Thomas Neoprioniodus el. N. armatus Hinde Prioniodina oweni Rhodes, Austin and Druce Prioniodina prelaevipostica Rexroad and Collinson Pseudopolygnathus cf. P. longiposticus Branson and Mehl Pseudopolygnathus multistriatus Mehl and Thomas Scaphignathus ? sp. A Rhodes, Austin and Druce Spathognathodus pulcher Branson and Mehl Spathognathodus sp. B Rhodes, Austin and Druce

This is a high level grouping of species that show no obvious relationship to one another. This is the residual association of many rare and short ranging forms, and does not seem to represent a meaningful natural group.

Group 6 Apatognathus sp. nov. A Rhodes, Austin and Druce Clydagnathus sp. A Rhodes, Austin and Druce Clydagnathus el. C. darensis Rhodes, Austin and Druce Gnathodus? sp. nov. Rhodes, Austin and Druce Scaphignathus ? sp. B Rhodes, Austin and Druce This is an association of platforms, some of them represented by only one or two specimens from the middle part of the K and Z succession. It is difficult to infer much from their association. Group 7 Clydagnathus darensis Rhodes, Austin and Druce Clydagnathus unicornis Rhodes, Austin and Druce

These two forms show a very high level of association. They were both pre- sumably associated in the same natural assemblage. The presence of additional components in this long ranging group is problematical, but it shows some resemblance in range to Group I I and rather less to Group 12. Either of these could supply additional Class A components, although Group I I may be complete in itself. Group 8 Apatognathus varians Branson and Mehl Hibbardella separata Branson and Mehl Lonchodina sp. A Rhodes, Austin and Druce This is an important group in the lower Z Zone, consisting of a hibbardellid, a lonchodinld and an apatognathid. This association is very suggestive of a Duboisella type assemblage with the apatognathid perhaps serving functionally in place of the ligonodinid, or the neoprioniodid elements. The association involves

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relatively rare species, but it suggests that the basic duboisellid (Class C) type assemblages were already established by early Mississippian times.

Group 9 Angulodus sp. C. Rhodes, Austin and Druce Spathognathodus anteposicornis Scott Spathognathodus costatus s.s. (E. R. Branson) Spathognathodus elongatus (Branson and Mehl) Spathognathodus cf. robustus (Branson and Mehl) This group is an association of broadly similar spathognathodids and an angu- lodid. It is difficult to interpret, but may be part of a Lochriea-type Class A assem- blage. It is possible, but probably less likely, that the spathognathodids may have functioned in a hindeodellid capacity (Fig. 4). Group xo Neoprionidus barbatus (Branson and Mehl) Ozarkodina parva Huddle This is apparently a stable association of the typical neoprioniodid-ozarko- dinid elements of a Class A type assemblage, which supplemented shorter lived platform components with a changing succession of Class A conodontifers through- out K and Z times. It may also have combined with hindeodellids, and perhaps other components from Groups 12 and I3.

Group x I Ligonodina beata Rhodes, Austin and Druce Polygnathus communis s.s. Branson and Mehl Spathognathodus costatus sulciferus (Branson & Mehl) Spathognathodus tridentatus (E. R. Branson) This probably represents an almost complete Class A type assemblage, in which the ligonodinid served either a hindeodellid or a neoprioniodid element function. The frequencies of the components are broadly similar (Fig. 6). The spathog- nathodids are closely similar to one another and were probably functionally interchangeable within similar assemblages.

Group 12 Hindeodella subtilis Ulrich and Bassler Spathognathodus cf. S. cristulus Youngquist and Miller This is another stable stock group, which presumably supplied the stable ele- ments in evolving Class A assemblages, perhaps including the Polygnathus inornatus group (Group 4), the spathognathodids (Group 9) or the clydagnathids (Group 7) in mid-section and the P. lacinatus group (Group 2) in the upper part of the suc- cession. S. cristulus may have functioned in either an ozarkodinid or, less probably, a neoprioniodid capacity in the assemblage. The biggest objection in accepting the association of the two components of this group is the longer range of H. subtilis.

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This may suggest, however, either that S. cf. S. cristulus had an earlier structural homeomorph in a similar type of assemblage or that H. subtilis was also present in one or more earlier and distinct assemblages (perhaps with Groups I and 4 in that order). The frequency fit between the two forms is reasonably good (Fig. 7)- S. cf. S. cristulus is known from strata of Cleistopora Zone age in Australia (Druce 1969) and its absence in this fauna may be due to a paucity of cristulus bearers, which is suggested by the rare occurrence of H. subtilis in the K Zone.

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F I o. 4. Frequency analysis of Group 9 conodont elements. Total thickness of succes- sion is 2 x o feet.

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Group x3 Hindeodella corpulenta Branson and Mehl Neoprionfi~dus confluens (Branson and Mehl) Spathognathodus crassidentatus (Branson and Mehl)

This also appears to be the conservative root stock of Class A conodontifers to which other short-lived platform components were successively added in K-Z times. The possible associated groups are discussed above. The function of S. crassidentatus is obscure: it may have functioned either as an ozarkodinid type or a platform type element. It may also have occupied an ozarkodinid position, as does a

Ozo~oelinoporvo > Neoprk~tdodus l)or~lleus

I 1 l L I • ! I l • 5 I0 15 2O Z,S 30 Fr e (luen ¢ y %

vxo. 5. Frequency analysis of Group Io conodont elements. Total thickness of suc- cession is 2xo feet.

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congeneric species in Lochriea, and have survived changes in successive component platforms of other form genera.

6. Frequency of elements in individual samples A parallel source of data concerning original numerical and associational relationships is provided by the relative frequency of supposedly associated ele- ments. If certain form species were associated together in fixed ratios, this should be reflected in their present frequency distribution. We have plotted a series of graphs which show these relationships for several of the more meaningful groups. Group 9 shows a close correspondence in frequency between the spathognatho- did components, but little correspondence with the much older angulodids. Group IO also shows a close correlation in frequency of the ozarkodinid and neoprioniodid elements, as does Group i I for all the major components. Figure 6 which represents Group I I, indicates that this frequency is not a direct reflection of total conodont frequency for the section, but has a valid comparative basis. Group 12 shows a major difference in stratigraphic ranges, but a similar fre- quency over the common range of the two elements. Presumably S. cf. S. cristulus was either preceded by a functionally similar spathognathodid in the lower part of the section or alternatively was present in K Zone times, its non-appearance in our collections being a function of the rarity of the host conodontifer.

200'

ZLI6

: ZLA3O_/%==-%--~ --ZL&27 "-¢ =" ~= " ='~ .,. =.-~.q,~.Z ~, ~,~,= ,

ZLtl 150' ZLm "~"--" ? "~ = ZL*Z3..'-&l'k'7"-T ~I

-- ZLA,S --t~6 r~.r Or~-~ --ZL&I ~' "~z z I I = _-z.,o ;':_':: ::,i

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ZLI T "~"'~ k'.--',--: --~ 7,-:'-Z~ \ 50' KLI9 I z = i t I 1

|

I- KL 16 ) ~---.--~-'-" S. costatu sulciteru'. o ,o 20 so go ~o do zb 6 lg ~o is 6 ,b 2'o 3'o6 ,b io 6 Jb F~o. 6. Frequency analysis of Group I I conodont elements showing tom] conodont abundance per kilogram of sample from the K and Z Zones of the North Crop of the South Wales Coalfield. Frequency for dements is expressed as % of tom] conodont fauna.

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Group 13 (Fig. 8) shows an excellent corresponding frequency over a common stratigraphic range.

7. Conclusions One of the continuing problems in conodont studies is the recognition of natural assemblages of conodonts, which were originally associated in a single animal. The present paper describes two methods which are of value in assemblage reconstruction. Polythetic cluster analysis, first developed for use in ecological surveys, provides dendrograms from which the level of association of individual elements may be determined. This provides an indi- cation of common occurrences of elements in particular samples. These data may be supplemented by comparison of total stratigraphic range, and relative frequency of the elements. H~nde~del/o $ubH//$ Spolhognothodu$ The 'clusters' of elements thus obtained c~ S. crispu/us may then be compared with assemblage models based on assemblages preserved in situ on shale bedding planes. A number of hypothetical assemblages may thus be established. The present methods, though having considerable potential value, also have limitations, the most serious of which is the ambiguity concerning the com- pleteness of cluster associations in relation to original assemblages. It is shown that in large samples, agglomerative polythetic cluster analysis provides a valuable method of reconstruct- ing original multi-element conodont as- semblages, which are consistent with models derived from other sources, and with data from stratigraphic ranges and relative frequencies of the component

\ 0 5 7Io. 7. Frequency analysis of Group i ; | 5 J0 x2 conodont elements. Total thickness Frequency =/= of succession is 2 I O feet.

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i i t

. .

V rxr-Lr

1- 1 |

jail [ ,.-,_;':

N~

-._--_--

~_

to livens t~gnotl~lu$ crOd~tad~tO~

o / ~ ~o 20 l,,, [ L I 1 ~ I l _ J 0 5 0 5 O0 15 2o F r e q u e n ¢ X %

FIG. 8. Frequency analysis of Group x 3 conodont dements. Total thic]mess of suc- cession is 21 o feet.

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elements. We recognize that such reconstruction implies the need for drastic revision of current taxonomic practice, by which a single multi-element unit could at present be designated by any one of several different names of its component elements. We submit that the recognition of multi-element assemblages will give added precision to the use of conodonts in stratigraphy, and throw new light on their geographical and ecological distribution. It may even contribute to solving the continuing enigma of their zoological affinities.

ACKNOWLEDGEMENTS. We wish to thank Dr W. T. Williams of the C.S.I.R.O. Computer Labora- tory, Canberra (now of the James Cook University, Townsville, Australia) and Dr J. M. Lambert, Botany Department, University of Southampton, England for their considerable help and con- structive comments. Permission to publish this paper has been received by one author (E. C. Druce) from the Director of the Bureau of Mineral Resources, Geology and Geophysics, Commonwealth of Australia.

8. References AUSTIN, R. L. & RHODES, F. H. T. x969. A conodont assemblage from the Carboniferous of the Avon Gorge, Bristol. Palaeontolog~, z2, 4o0-405. BARNES, C. R. z967. A questionable natural conodont assemblage from Middle Ordovician limestone, Ottawa, Canada. J. Paleont., 4x, I557-156o. BERGSTR6M, S. M. & SWEET, W. C. x966. Conodonts from the Lexington Limestone (Middle Ordovician) of Kentucky and its lateral equivalents in Ohio and Indiana. Bull. Amer. Paleont., 5 o, 27z-~I. DRUCE, E. C. I969. Upper Paleozoic conodonts from the Bonaparte Gulf Basin, north western Australia. Bull. Bur. Miner. Resour. Geol. Geophys. Aust., 98, 1-242. (in press). Statistical analysis ofconodonts from the Upper and Lower Ordovician (Tremadoeian) of Western Queensland. Du Boxs, E. P. 1943. Evidence on the nature of conodonts. J. Paleont., I7, 155-I59. Hlm~E, G. J. 1879. On annelid jaws from the Cambro-Silurian, Silurian and Devonian formations in Canada and from the Lower Carboniferous in Scotland. Q. Jl geol. Soc. Lond., 35, 351-369. KOHUT, J. z969. Determination, statistical analysis and interpretation of current conodont groups in Middle and Upper Ordovician strata of the Cincinnati Region (Ohio, Kentucky, and Indiana) J. Paleont., 43, 392-4 I2. KRn.mJER, A. I94o. Neue Fischspuren im Palaozoicum des Sauerlandes. Abh. Landesmus. Naturk. Mtinster, x, 49-53- LAMBERT, J. M. & WILLIAMS, W. T. 1966. Multivariate methods in plant ecology VI : Comparison of information-analysis and association-analysis. J. Ecol., 54, 635-664 • LANOE, F. I968. Conodonten-Gruppenfunde aus Kalken des tieferen Oberdevon, Geol. paldont., Abh., 2, 37-57. LINDSTR6M, M. z964. Conodonts, Amsterdam (Elsevier). LXNDSTR6M, M. & ZIEOLER, W. x965. Ein Conodontentaxon aus vier morphologisch verschiedenen Typen. Fortschr. Geol. Rheinld Westf., 9, 2o9-218. MELTON, W. & SCOTT, H. W. I97o. Progress report on the study of the conodont-bearing animal. Proc. N. Central Sect., Geol. Soc. Am., Abs., 2, 395. POLLOCK, C. A. I968. Questionable Silurian natural conodont assemblages from Indiana. Abstr. Program N. Central Sect. Geol. Soc. Am., 49- REXROAD, C. B. & NICOLL, R. I964. A Silurian conodont with tetanus. J. Paleont., 38, 771-773 • RHODES, F. H. T. z952. A classification of Pennsylvanian conodont assemblages..I. Paleont., ,,6, 886--9ox.

Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/128/1/53/4884414/gsjgs.128.1.0053.pdf by guest on 29 September 2021 7 ° E.C. Druce, F. H. T. Rhodes & R. L. Austin

RHODES, F. H. T. x962. Recognition, interpretation and Taxonomic position of conodont assemblages Treatise on Invertebrate Paleontology, W, W7o-W83. Geol. Soc. Amer. and Univ. Kansas Press (New York). RHODES, F. H. T., AUSTIN, R. L. & DRUCE, E. C. x969. British Avonian (Carboniferous) conodont faunas, and their value in local and intercontinental correlation. Bull. Br. Mus. nat. Hist. (Geol.), Supp. 5, I-313. SeHoPV, T. J. M. I966. Conodonts of the Trenton Group (Ordovician) in New York, Southern Ontario and Quebec. Bull. N.Y. St. Mus. Sci. Serv., 405, x-93. SeH~DT, H. x934. Conodonten-Funde in ursprunglichen Zuzammenhang. Paldont. Z., x6, 76-85 . Sen~DT, H. & MOt LER, K.J. I964. Weitere Funde von Conodonten-Gruppen aus dem oberen Karbon des Sauerlandes. Paldont. Z., 38, Io5-I35. SCOTT, H. W. x934. The zoological relationships of the conodonts. J. Paleont., 8, 448--455 . x942. Conodont assemblages from the Heath Formation, Montana. J. Paleont., x6, 293-3oi. x969, Discoveries bearing on the nature of the conodont animal. Micropaleontology, x5, 42o- 426. TATOE, U. x956. Conodonten aus dem germainischen Muschelkalk. Paldont. Z., 3 o, to8--I27. VEEVZRS, J. J. i969. Associations of fossils, grain-types, and chemical constituents in the Upper Devonian and Lower Carboniferous limestones of the Bonaparte Gulf Basin, northwest Australia. J. sedim. Petrol., 39, x x I8-113x. WAt.LISER, O. H. x964. Conodonten des Silurs, Abh. hess. Landesamt. Bodenforsch., 4 x, 1-Io6. WEBEm, G. F. 1966. The Middle and Upper Ordovician conodont faunas of Minnesota. Bull. Minn. geol. Surv., SP-4, I-I23. WXLLtAMS, W. T., LASmERT, J. M. & LANCE, G. N. I966. Multivariate methods in plant ecology. V: Similarity analyses and information-analysis. J. EcoL, 54, 427-446.

Submitted 3 ° June x97o; revised manuscript received i8 November I97o; read 24 June I97o.

E. C. Druce, Bureau of Mineral Resources, Canberra, Australia. F. H. T. Rhodes, Geology Department, The University of Michigan, Ann Arbor, Michigan. R. L. Austin, Geology Department, University, Southampton, England.

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