Revisions of conodont biostratigraphy across the Silurian-Devonian boundary

PETER CARLS, LADISLAV SLAVÍK & JOSÉ IGNACIO VALENZUELA-RÍOS

The current conodont biozonation near the Silurian/Devonian boundary includes problematic biozones and is revised. Global applications of the zonal concepts concerning the current standard conodont zones eosteinhornensis, remscheidensis, detorta, and woschmidti are revised. New correlations are based on conodont faunas from the Požáry section (the stratotype of the Přídolí Series, Barrandian) and the Elbersreuth Orthoceratid Limestone (Frankenwald); they enable correlations with Baltic conodont faunas. The new data show that the eosteinhornensis Zone s.s. begins amid the Přídolí. The Delotaxis “detorta” plexus is not limited to the final Přídolí because it enters before the eosteinhornensis Zone. Accordingly, the use of a detorta Zone for global correlation is not recommended. The type stratum of the very particular Icriodus woschmidti is much younger than the entry of Icriodus postwoschmidti in Podolia. A succession of a woschmidti Zone and a postwoschmidti Zone in the early Lochkovian is problematic. Three new spathognathodontid species with stratigraphic potential: Zieglerodina? ivochlupaci sp. nov., Zieglerodina? klonkensis sp. nov. and Zie- glerodina? zellmeri sp. nov. are described. • Key words: Silurian/Devonian boundary, Conodont zonation, Conodont biostratigraphy, Barrandian, Frankenwald, Eastern Baltic.

CARLS, P., SLAVÍK,L.&VALENZUELA-RÍOS, J.I. 2007. Revisions of conodont biostratigraphy across the Silurian-De- vonian boundary. Bulletin of Geosciences 82(2), 145–164 (8 figures, 1 table). Czech Geological Survey, Prague. ISSN 1214-1119. Manuscript received January 10, 2007; accepted in revised form May 9, 2007; issued June 30, 2007. • DOI 10.3140/bull.geosci.2007.02.145

Peter Carls, Institut für Umweltgeologie, Technische Universität Braunschweig, Pockelsstrasse 3, D-38023 Braun- schweig, Germany • Ladislav Slavík (corresponding author), Academy of Sciences of the Czech Republic, Institute of Geology, v.v.i., Rozvojová 269, CZ-16502 Praha, Czech Republic; [email protected] • José Ignacio Valenzuela-Ríos, University of València, Department of Geology, C/. Dr. Moliner 50, E-46100 Burjassot, Spain; [email protected]

Work on the biostratigraphy of the late Silurian and earli- Discrepancies in conodont correlation are propagated est Devonian by means of conodont successions from Bo- mainly through the uncritical application of formalisms of hemia and other regions, has revealed that the literature biostratigraphic zonation. Basically, correlation does not contains several problematic aspects of identification and need a zonation, but a good zonation, of course, can pro- zonation. Conodonts are, undoubtedly, important biostra- mote communication. On the other hand, a zonation based tigraphic tools in the correlation of the Silurian/Devonian on undue taxonomy can create great confusion. This can boundary and adjacent strata. However, intense work on be recognized in the history of the conodont zonations conodont correlation during past decades brought, beside that have been proposed for the late Silurian (see Fig. 2) new and valuable data, also many problems. The Silu- and the early Devonian (Přídolí to early Lochkovian). rian/Devonian boundary is fixed in bed 20 of the limito- Problems in conodont taxonomy and formalisms in type section of Klonk (Barrandian, Czechia) where grap- zonation and stratigraphy have escalated in this interval. tolites abound. The identification and interpretation of The main purpose of this paper is to elucidate the succes- certain graptolites concerned have hardly been disputed, sion of certain guide conodonts below and across the S/D whereas Klonk conodonts have been involved in errors of system boundary and to compare conodont successions identification and correlation. Jeppsson (1988, 1989) has from different regions. described the conodont succession in the late Přídolí of the Klonk section. But in this section many beds furnish poorly informative conodont faunas. Therefore the pre- Remarks on nomenclature sent study used the Požáry section SW of Prague (Fig. 1, for description see Kříž et al. 1986), where conodonts are The generic affiliations of several multielement cono- more abundant. dont taxa treated in this text have been changed repea-

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Discrepancies within the Silurian-Devonian conodont zonation

The eosteinhornensis Zone – problems, definition and stratigraphic validity

In 1964, Walliser proposed the first conodont zonation for the Silurian System, including the eosteinhornensis Zone for the entire interval later defined as the Přídolí. This scheme has since been followed by most authors. The first concept of the index taxon Spathognathodus steinhornen- sis eosteinhornensis Walliser, 1964 was founded on the broad morphological spectrum of Pa elements present in the type stratum of this species, namely in bed 40 of the Cellon section (Carnic Alps). A rich sample from this bed has also been used by Murphy et al. (2004). After elimina- tion of the distinct representatives of Spathognathodus in- clinatus (Rhodes, 1953) (= Pa element of Wurmiella exca- vata excavata (Branson & Mehl, 1933) and its conspecific Figure 1. A location map with marked studied areas: the Elbersreuth elements, there remain abundant Pa elements of various Orthoceratid Limestone (Frankenwald) and the Požáry Quarries (Barrandian). morphologies plus various ramiform and other elements. Among these Pa elements, only some correspond to the ho- lotype of the taxon eosteinhornensis in the features that tedly. e.g., Spathognathodus crispus Walliser, 1964 was have been rightly stressed by Jeppsson (1974, p. 38) and by changed to “Ozarkodina” crispa. But its Pa element is Klapper & Murphy (1974, p. 42) and which we reiterate so different from that of the type species, that the inclu- as follows: Blade with only moderate size differences be- sion in Ozarkodina is doubtful. As the apparatus of the tween denticles; some denticles near the middle can be fu- species crispus Walliser, 1964 is not yet completely sed; basal lobes large, tending to angular and “heart-shaped” known, an erection of a new genus is not yet opportu- outlines, centered clearly behind mid-length of the blade; nous. Therefore, “O.” crispa can presently not be attri- outer lobe (more rarely also inner lobe) bearing a node or buted to an appropriate genus. Jeppsson & Merrill crest. This diagnosis is sufficient to separate the Pa element (1982) have recommended how to designate and how to of the taxon eosteinhornensis within its type stratum. Other refer to former binomina, and we follow their proposals Pa elements in the type stratum (essentially characterized where applicable. In certain cases no genus is available, by the lack of a node, greater differences in denticles, and a and the repetition of obsolete binominal combinations more anterior position of the smaller and rounded would be misleading. Then we use only a species name, (“bell-like” – sensu Jeppsson 1974, p. 39) basal lobes be- or we indicate a genus provisionally like “genus W eos- long to Zieglerodina sp. 40 (Pa elements of this taxon, teinhornensis”. which also occur in bed 40 of the Cellon section, were first In Delotaxis the intercalation of small denticles is figured by Carls 1975, pl. 2, figs 16–18 from the very basal characteristic for D. detorta (Walliser, 1964), but it also Devonian of Aragón under the identification of Oz. rem- occurs in another species: Viira (1999, pl. 4, fig. 10) scheidensis; provisionally, it is here termed Zieglerodina showed an Sb element with intercalated small denticles sp. 40 aff. remscheidensis). The generic attribution to Zieg- that differs from the elegans-detorta stock. Accordingly, lerodina Murphy et al. (2004) is supported by the associa- Viira refered to a “detorta” plexus that comprises possi- tion both in Aragón and at Cellon to elements like those bly more than one late Silurian Delotaxis with intercala- figured by Murphy et al. (2004, fig. 3 – 25(Sb), 29(Pb), tion, not only to detorta. Scarcity of material of 30(Sa), 31(Sa), 32(Sc). Sa elements that cannot be distin- Delotaxis elements with intercalation does not yet al- guished from these occur not only in the type stratum of low a decision, whether intercalation develops also in Z. remscheidensis, but are also associated with Pa elements the stock of D. silurica (Branson & Mehl, 1933), in as- of Z. repetitor Carls & Gandl, 1969 and other Přídolí and sociation with whose Sc elements similar Sb without Lochkovian species of Zieglerodina that are still unnamed intercalation occur mostly. In order to provide a collec- (cf. Murphy et al. 2004, fig. 3). Pa elements of Zieglero- tive for comparable late Silurian Delotaxis with alter- dina sp. 40 range up to the initial Lochkovian (Carls 1975, nation also beyond D. detorta,a“detorta” plexus is pl. 2, figs 16–18). The Pa elements of the taxon eosteinhor- suggested. nensis can be grouped with the shorter and higher Pb ele-

146 Peter Carls et al. • Conodont biostratigraphy across the Silurian-Devonian boundary

Figure 2. Development of the conodont zonation of the Přídolí (according to selected papers) in relation to the graptolite zones (right column). ments figured by Murphy et al. (2004, fig. 3 – 26–28). Ad- node and with, additionally, a more anterior position of the ditional ramiform elements in the same sample that differ basal lobes. In a time when “splitting” was considered to be from those of Zieglerodina partly belong to eosteinhornen- detrimental for conodont taxonomy and biostratigraphy, sis; the branches of Sc elements in this group do not undu- presence or lack of a node and further slight differences late and develop ledges on the outer side that are absent in were regarded as subject to intraspecific and even Zieglerodina. But there are further taxa that cannot yet be intrasubspecific variability. In the case of the Emsian separated conclusively. These remarks may promote the forms it is now evident that a subdivision is necessary: The distinction of the index taxon eosteinhornensis and its ge- earlier Emsian (mainly original late Pragian) taxon miae neric separation from Z. remscheidensis. Provisionally, we Bultynck, 1971 that lacks a node, was grouped as an earlier allude to the genus only with the term “genus W” because appearing subspecies of Cr. steinhornensis and it was as- the apparatus composition is not yet certain. The former sumed that it overlaps with Cr. steinhornensis in range. But practice of treating the taxon eosteinhornensis as a subspe- neither intraspecific nor intrageneric coherence with Cr. cies of Z. remscheidensis has proved not to apply. steinhornensis are warranted: The apparatus of miae is not When Walliser (1964) coined the taxon “eostein- yet entirely known (the Sa element is unknown) and the hornensis”, he considered it as a rather homoeomorphic overlap is inexistent. In the early to middle Zlichovian of subspecies of “Spathognathodus” steinhornensis Ziegler, the Mariposas Fm. in Celtiberia there is a succession of 1956. Later, the latter became the generotype of three different Pa elements: miae, a rather small and Criteriognathus Walliser, 1972 which was coined to house equidentate unnamed sp. nov. M, and Cr. steinhornensis. the steinhornensis plexus. A synopsis of the subsequent The middle one has short overlaps with both others. Thus, treatment and of presently available materials that had it seemed that Cr. steinhornensis included small Pa ele- originally been included in the species steinhornensis, may ments without a node on the basal lobe and had a consider- serve to illustrate how the concepts have changed. Herein, able variability. Although the generic attribution of both we erect new taxa guided by this former experience. older taxa is uncertain, this subdivision can be seen as an The type material of Spathognathodus steinhornensis example encouraging the “splitting” also of the late Silu- Ziegler, 1956 is from Emsian (mid-Zlichovian) beds in the rian and earliest Devonian populations. As these old popu- lower part of the Schönau Limestone (Kellerwald, Ger- lations were formerly included within the species many). A diplododellan Sa element is associated to it, steinhornensis but are excluded even from its genus which is a distinctive generic feature. Its typical Pa ele- Criteriognathus, they need proper species, if their genetic ments bear a node on their outer basal lobe, but the type independence is recognized. Forms that were lumped in the stratum also contains smaller Pa elements without such a subspecies “eosteinhornensis” and “remscheidensis” are

147 Bulletin of Geosciences • Vol. 82, 2, 2007 here separated on species level, if their ranges and that, indeed, have denticles of different sizes, but do not multielement apparatuses demand this. Indeed, taxa for- have them arranged as in the type material (see Murphy et merly included in the (sub)species remscheidensis are now al. 2004, pp. 13, 14). Relevant studies in Nevada (Klapper identified as Lanea Murphy & Valenzuela-Ríos, 1999 with & Murphy 1974), in Estonia (Viira 1999, Jeppsson et al. good biostratigraphic success. 1994), in the Appalachian Basin (Barnett 1971, 1972), in Evidently, the former concept that a considerable vari- the Barrandian area (Mehrtens & Barnett 1976), and in ability exists in the Emsian “Spathognathodus” st. stein- Oklahoma (Barrick & Klapper 1992) appeared that re- hornensis has influenced the rather broad concept of the ported “eosteinhornensis”. However, in these studies true taxon “eosteinhornensis”. Walliser (1964), probably in view genus W eosteinhornensis was not represented. Genus W of the Zlichovian material he had at hand (including miae, eosteinhornensis has not been figured from Baltic locali- sp. nov. M, and steinhornensis), admitted the same scope of ties. Viira & Aldridge (1998, pl. 4, figs 10, 13–17) stated assumedly intra-specific variation that he found in the type “Ozarkodina remscheidensis eosteinhornensis (Walliser, stratum (bed 40 of the Cellon section), for the vertical range 1964) sensu lato”, of which figs 13–15 are Zieglerodina? of Pa elements that he observed in the relevant Cellon sec- zellmeri, whereas the shorter and relatively higher and less tion and that he identified as “Spathognathodus st. evenly denticulated fig. 10 is a different taxon. Viira (1999, eosteinhornensis” from the base of the Přídolí onward. In pl. 3, fig. 2) refigured the specimen of the former on fig. 13 pelagic sections in Europe (outside of Baltica – where some as “Ozarkodina remscheidensis eosteinhornensis (Wal- different taxa lived) the occurrence of somewhat similar Pa liser)”. Jeppsson et al. (1994, fig. 4h, i) figured the latter elements (with small basal lobes near mid-length, without specimen and a less developed one as “ ‘O. remscheidensis ornamentation on the lobes, but mostly fairly equidentate), – O. eosteinhornensis s.l. group’ ”. Jeppsson et al. (1994, was apt to suggest an “eosteinhornensis” Zone that com- fig. 4j–m) additionally figured shorter Pa elements with prised the entire Přídolí Series. As similar Pa elements are more acute denticles of slightly less even sizes as “same found even in the late Ludlow, it has been discussed whether group as (h)”, joining them in one taxon. Associated the eosteinhornensis Zone begins that early (Cooper 1980, ramiform elements were not shown. Even Mehrtens & fig. 5). (The first co-occurrence to be discovered of genus F Barnett (1976), who had their samples from the Požáry sec- crispus and an equidentate Pa element of such aspect was tion in the Barrandian area, where characteristic that by Bultynck & Pelhate 1971, in the Armorican Massif. eosteinhornensis is found, did not figure such specimens It concerned Zieglerodina? zellmeri sp. nov.) nor did they refer in the text to the particular morphology Some authors stated that Pa elements like the holotype corresponding to the holotype. At Požáry, Pa elements with of the index are limited in the Cellon section to beds 40A well ornamented basal lobes occur from about 17 m above and 41 (Klapper & Murphy 1974, p. 42) or to beds 40 to the base of the Přídolí within about 2 m and, strikingly once 43B (Jeppsson 1974, p. 38; cf. Walliser 1964, pl. 20, again, about 5 m below the first Icriodus near the S/D figs 19–21). But even then, the downward extended range boundary (cf. Fig. 4). of the so-called eosteinhornensis Zone was not corrected For merely technical purposes, one may refer to an and restricted. “eosteinhornensis group” of taxa that have been lumped The desire to distinguish the very late Silurian from the with true eosteinhornensis in the type section at Cellon. As very early Devonian utilising the assumed phylogenetic noted above, true eosteinhornensis is known at Cellon only step from “Spathognathodus steinhornensis eosteinhor- in2mor5.5mofstrata. Actually, the occurrence of the nenis” towards “Spathognathodus steinhornensis rem- taxon eosteinhornensis s.s. corresponding to the character- scheidensis” has provoked several efforts to characterize ization by Jeppsson (1974) and by Klapper & Murphy the taxa “eosteinhornensis“ and “remscheidensis“ through (1974), has only been demonstrated in the following loca- distinctive features. Such enterprises have started from the tions: type region Carnic Alps (Walliser 1964, pl. 20, premise that the dominant feature of “eosteinhornensis”is figs 19, 21, 22); Barrandian (Jeppsson 1989, pl. 2, the rather equidentate denticulation of its blade, whereas figs 1–4); borehole Chełm (Wolska 1969, stating presence “remscheidensis” has denticles of very different sizes. The of a node, basinal facies off the Baltic Platform) and distinction was complicated through the synonymization Frankenwald (this paper). Accordingly, the current appli- of “Spathognathodus” canadensis (Walliser, 1960) with cation of the eosteinhornensis Zone beyond these records Zieglerodina remscheidensis. [This problem is eliminated is not well-founded. Its presence has been merely assumed through the attribution of canadensis to the genus Lanea on the basis of several clearly different taxa through a long Murphy & Valenzuela-Ríos, 1999, because of its broad and time-interval, across the Ludlow/Přídolí boundary (e.g., terraced basal lobes. Jeppsson (1974, p. 38) had already Bultynck & Pelhate 1971, pl. 1, figs 1–3, 21; Rexroad & stated that its white matter is distributed in a manner re- Craig 1971, pl. 82, figs 18, 10; Cooper 1980, fig. 5; minding of Ozarkodina.] Additionally, several other late Aldridge et al. 1979, p. 437, fig. 1, No. 102; Kleffner 1989, Silurian taxa have been identified as “remscheidensis” fig. 6, No. 10).

148 Peter Carls et al. • Conodont biostratigraphy across the Silurian-Devonian boundary

C G

B

D H A F

K R E J L S

N

Q I M

O P 1 mm

Figure 3. Camera lucida drawings of taxa: Delotaxis detorta, Delotaxis sp. and gen. W eosteinhornensis. •A–Delotaxis detorta, incomplete Sa, cat. No. L38675, Požáry section, sample PZ076, obliquely anterior view.•B–Delotaxis detorta, Sb element, cat. No. L38676, Požáry section, sample PZ078, inner upper view. • C, D – gen. W eosteinhornensis, Pa element, cat. No. SMF69987, EOL section, sample 5, C – outer lateral view, D – upper view.•E– Delotaxis detorta, incomplete Sc element, cat. No. L38677, Požáry section, sample PZ076, same as Fig. 8K, lateral view.•F–Delotaxis detorta, incom- plete Sb element, cat. No. L38680, Požáry section, sample PZ078, oblique inner view. • G, H – gen. W eosteinhornensis, Pa element, cat. No. SMF69988, EOL section, sample 5, G – outer lateral view, H – upper view.•I–Delotaxis sp., a strongly angular Sb element with a small denticle, cat. No. L38678, Požáry section, sample PZ076, inner lateral view, same as Fig. 8I, J. • J – Delotaxis detorta, Sb element, cat. No. L38681, Požáry section, sample PZ078, inner lateral view. • K, L – gen. W eosteinhornensis, Pa element, cat. No. L38682, Požáry section, sample PZ083, K – outer lateral view, L – upper view. • M–Delotaxis detorta, Sc element, cat. No. L38679, Požáry section, sample PZ076, same as Fig. 8L, outer lateral view.•N–Delotaxis detorta,Scele- ment, cat. No. SMF69972, erratic boulder, sample Lag Vas 4, outer lateral view.•O–Delotaxis detorta, Sc element, cat. No. SMF69973, erratic boulder, sample Lag Vas 4, inner lateral view. • P – Delotaxis detorta, Sc element, cat. No. SMF69989, EOL section, sample 6, inner lateral view. • Q – Delotaxis detorta, Sc element, cat. No. SMF69974, erratic boulder, sample Lag Vas 4, outer lateral view. • R, S – gen. W eosteinhornensis, Pa element, cat. No. L38683, Požáry section, sample PZ083, R – outer lateral view, S – upper view.

The Silurian “remscheidensis interval Zone” fusing and is unacceptable. The main distinguishing crite- rion considered was the uniformity versus variation of Close to the Ludlow/Přídolí boundary, the steinhornensis denticle sizes in the Pa elements. Apparatus reconstructi- plexus produced early members with increasingly uneven ons were not taken into account. Under the concept of denticulation that were attributed to “Ozarkodina” rem- intra-specific evolution with interbreeding, no species scheidensis. When a “remscheidensis interval Zone” was were separated. But differences in non-Pa elements sug- therefore proposed for most of the Přídolí, the name of a gest even generic difference from Zieglerodina remschei- taxon that is actually a Devonian species, was introduced densis. Moreover, Zieglerodina remscheidensis s.s. is into Silurian biozonation (see Fig. 1). That would be con- the successor of Zieglerodina sp. 40 (Carls 1975, pl. 2,

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figs 16–18) and enters as late as after the entries of the De- vonian index fossils Acastella heberti, Platyorthis monni- eri and Icriodus sp. ex gr. woschmidti that range in the uniformis Zone – i.e. well in Lochkovian time (Carls 1975). [The attribution of the type stratum of remschei- densis to the late Silurian by Jeppsson (1988), was an er- ror – see below.]

Discussion of the detorta Zone

The intercalation of small denticles between large ones is, according to Jeppsson (1974, pp. 21, 22), diagnostic for the identification of the taxon Delotaxis elegans detorta (Walliser, 1964). In the conodont samples studied through the middle and late Přídolí up to the Lochkovian beds of the Požáry Quarries, there are elements of Delota- xis, virtually up to the end of the Silurian, with small den- ticles intercalated between the “normal” big ones. This feature has been observed previously in actually latest Silurian successions at other localities (Jeppsson 1974, p. 22; 1988; 1989). In the standard sections at Cellon and Klonk, De- lotaxis elegans detorta has only been reported above the range of gen. W eosteinhornensis and below the base of the Devonian. The multielement taxon D. detorta was designated by Jeppsson (1988, p. 25) as the index of the detorta Zone, the range of which was assumed to be only the latest Přídolí. This was based mainly on the Cellon section, which has, however, a remarkably low diversity in the early Přídolí. It is possible that intercalation of small denticles in Delotaxis is not a phylogenetically distinctive but a general feature, but we have not investigated this. [It should be taken into account that there exist very frequent specimens, mainly Sc and Sa elements, of Delotaxis that have one to three thin and short denticles only immediately behind or anterior of the cusp but lack small denticles in more distal interspaces. The presence of small denticles only in these proximal positions is not considered relevant for a (sub)specific identification.] When elements resembling Delotaxis elegans but with intercalated small denticles were found in samples from the East Baltic Beyrichien-Kalk (Jeppsson 1972, p. 56; 1974, p. 22), they were identified as Delotaxis elegans detorta and they were assumed to indicate the final Silurian cono- dont zone. However, in the Baltic successions (excepting the Chełm bore), there is no gen. W eosteinhornensis s.s., reference to which might enable to control the lower limit of the range of D. detorta. Moreover, the interval immedi- ately below the Silurian-Devonian boundary cannot be Figure 4. Požáry section. Stratigraphical distribution of relevant cono- demonstrated in the Baltic area by means of overlying rele- dont taxa from the interval below the Silurian/Devonian boundary of the Požáry section. Lithology: 1 – calcareous shale, 2 – limestone beds, mostly vant faunas, as such are lacking there. Thus, the Baltic grainstones and packstones. Bed numbering after Kříž et al. (1986). ranges of D. detorta cannot be calibrated according to the

150 Peter Carls et al. • Conodont biostratigraphy across the Silurian-Devonian boundary same conodont criteria that have been applied in the Cellon and Klonk sections. The development of alternating denticle sizes is not limited to the lineage elegans – detorta. Viira (1999, pl. 4, fig. 10) has figured an Sb? element as “Oulodus elegans detorta (Walliser)”; this specimen has single small denticles in at least four interspaces of its anterior branch, but it is probably not conspecific with D. elegans nor D. detorta, because similar specimens are absent from most samples that contain abundant and well balanced elements of Delotaxis elegans. However, similar ele- ments, although generally without intercalated small denticles, are not too scarce in Nordic erratics of late Silu- rian age. One was figured by Walliser (1964, pl. 30, fig. 5, without stratigraphic information). In Nordic erratics they often occur with Delotaxis ex gr. salopia-silurica. Viira’s specimen demonstrates that the appearance of small denticles represents a more widespread trend in Delotaxis and is not, per se, a reliable basis for the recognition of a conodont zone. In material from the type section of the Přídolí, there are elements of Delotaxis with a few alternating denticles (Figs 3, 8) appearing 10 m below the entry of gen. W eosteinhornensis, and they range beyond the latter up to the end of the Silurian (Fig. 4). This means that a detorta Zone as a successive appearance zone with the index chosen by Jeppsson (1988) would not represent the uppermost Pří- dolí, but a relevant interval preceding the eosteinhornensis Zone s.s., whereas the interval between the appearances of genus W eosteinhornensis and Icriodus hesperius would be the eosteinhornensis Zone proper in the sense of succes- sive appearance zonation. As evidence of the wider occurrence of this succes- sion, there is D. detorta in the Elbersreuth Orthoceratid Figure 5. Elbersreuth section. Stratigraphical distribution of relevant Limestone in the Frankenwald below genus W eostein- conodont taxa from the interval below the Silurian/Devonian boundary of hornensis (Fig. 5), whereby the observation from the the Elbersreuth Orthoceratid Limestone (Frankenwald). Lithology: 1 – thin-bedded to well-bedded cephalopod grainstones, 2 – massive Loch- Požáry section is corroborated. These results provoke kovian cephalopod grainstones with dacryoconarids, 3 – laminated karst doubts about the assumedly final Přídolí ages of upper- fillings of Lochkovian age. most Silurian horizons in the East Baltic and of the Beyrichien-Kalk, as far as they are dated by means of D. detorta. Devonian conodont record is the locality of the famous Transgression Horizon, from which Bischoff & Sanne- mann (1958) obtained their condensed Lochkovian fauna Additional evidence with Pedavis pesavis. This condensed level is underlain unconformably by the EOL. Together with J. Gandl and D. Conodont data from the Elbersreuth Al-Rawi, P. Carls sampled the EOL in 1968. The measured Orthoceratid Limestone section is shown in Fig. 5. The present section base is 3.30 m below the Transgression-Horizon. There are two A succession of conodont samples from the Elbersreuth different horizontal Lochkovian karst fillings parallel to Orthoceratid Limestone (= EOL) on the Schübelebene of the bedding that are 6 cm and 7 cm thick; their conodonts the Frankenwald (NE Bavaria) has been studied in order to are not considered herein. The lowermost beds of the EOL test the above results. This section also furnishes some evi- are reported to bear Kockelella variabilis (Walliser, 1957). dence for correlation with Baltica. The EOL conodonts contribute to the correlation with Bal- This small abandoned quarry with late Silurian to Late tic successions.

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Comments on conodont faunas from some Silurian-Devonian boundary. But in the EOL A. cf. prae- samples shown on Table 1 cox is of mid-Přídolí age.

Sample EOL 1 (13 cm to 30 cm above the section base) – Sample EOL 6 (2.28 to 2.45 m above section base) –In This fauna is as old as or, possibly, younger than the level Nevada, Klapper & Murphy (1974) have found the delta at which alternating denticle sizes in the ramiform ele- morphotype of Oz. typica within the upper range of Pele- ments of Spathognathodontidae (?Zieglerodina sp.) appear kysgnathus index, i.e. between the crispa Zone and the end and Delotaxis of the elegans stock enters. In the upper Lud- of the Přídolí; the specimens figured by Walliser (1964, fordian of Gotland these features are observed in the mid- pl. 22, figs 16, 18 – only) are from near the bed 39A of the dle of member b of the Hamra Fm. (Jeppsson et al. 1994, Cellon section, i.e. virtually at the entry of gen. W eostein- fig. 3). hornensis. From the evidence in Nevada, at the Cellon, and at Elbersreuth a range of the delta morphotype from near Sample EOL 3 (80 cm to 100 cm above the section base) – the middle of the Přídolí into its last quarter can be establis- The presence of one specimen of Icriodus results from ad- hed. The presence of one Sc element of D. detorta with one mixture of Devonian conodonts in a palaeokarst fissure; small denticle in each interspace on the bar confirms that the single Pa element of gen. W eosteinhornensis may have the full degree of alternation is reached within the eostein- the same provenance. In any case, it would occur before the hornensis acme. One Pa element of Coryssognathus du- acme of this index. bius provides evidence for the presence of the species.

Sample EOL 4 (106 cm to 120 cm above section base – Sample EOL 7 (2.40 m to 2.45 m above section base) – above the lower karst filling) – No conodont present might Most gen. W eosteinhornensis have a node on the outer ba- be attributed to the “eosteinhornensis group”. Wurmiella sal lobe, but welding of denticles does not occur. Two Sc reclinata is known from the Grebenski “Horizon” of the elements of D. detorta have one small denticle in each in- Vaigatch Peninsula that has been correlated with the Kau- terspace. gatuma “Stage” of Estonia. The Sb element figured by Viira (1999, pl. 4, fig. 10) as “Oulodus elegans detorta Sample EOL 8 (2.65 m to 2.75 m above section base) – The (Walliser)” from the upper part of the Ohesaare “Stage”, acme of gen. W eosteinhornensis has ended, 2 of its Pa ele- with small denticles in several interspaces of its anterior ments have nodes, but no fusion of denticles; the Pa ele- branch, is matched here by one similar Sb element of D. si- ments of Wurmiella reach over 20 denticles. lurica–salopia that has one small denticle just in front of the cusp and one between the first and second big posterior Sample EOL 9 (3.02 m to 3.20 m above section base) – The denticles. Sc elements of D. detorta have a few intercalated Pa specimens of Wurmiella excavata are small, short, but small denticles on the posterior branch. This sample be- high. There is only one small Pa element of gen. W eostein- longs in the range Kaugatuma–Ohesaare and below the hornensis with a small node. Oz. nasuta is in upper Kauga- acme of gen. W eosteinhornensis s.s. At low accumulation tuma and Ohesaare Fm. of Estonia (Viira 1983). rate, more than 80 cm below the acme of gen. W eostein- hornensis, the sample proves the entry of alternating denti- Sample EOL 10 (3.20 to 3.32 m above section base) – Gen. culation in two Delotaxis stocks. W eosteinhornensis has not been found and is either very scarce or extinct. Thus, this sample corresponds to some- Sample EOL 5 (2.11 to 2.27 m above the section base) – where in the late Přídolí part of the Klonk section, from bed This is the first sample with hundreds of Pa elements of 12 onward, because gen. W eosteinhornensis ends below gen. W eosteinhornensis s.s. They have the large basal ca- bed 12 (Jeppsson 1988, tab. 1). At Klonk, gen. W eostein- vity in a rather posterior position, mostly with a node on the hornensis overlaps with “Ozarkodina s. remscheidensis outer lobe, and many have the median denticles of the sensu nov.” of Jeppsson (1989, pl. 2, figs 6–11) (= Ziegle- blade fused; within the underlying 65 cm (not sampled rodina? klonkensis sp. nov.). This taxon is missing in the beds) the acme of this taxon might still be extensible. EOL. The Wurmiella Pa elements have about 10 anterior The deposition of the EOL was interrupted close to the denticles, the cusp, and 4–5 posterior ones, which may pro- Silurian-Devonian boundary and karstification occurred. vide an additional mark. Within the Early Lochkovian, further conodont faunas The specimens of the Pa element of Amydrotaxis? cf. were deposited; they begin with Icriodus woschmidti in the praecox are smaller than the one figured by Viira (1999, lower karst filling shown in Fig. 5. pl. 4, fig. 11; 2000, pl. 4, fig. 1). The taxon was reported If the scarce occurrences of Amydrotaxis? praecox and from the eastern Baltic, above local finds of the Delotaxis of Oz. nasuta in Baltica and in the EOL are considered to- detorta plexus, and it was considered to be just below the gether, it appears that the eosteinhornensis s.s. acme was

152 Peter Carls et al. • Conodont biostratigraphy across the Silurian-Devonian boundary

Table 1. Distribution of conodont taxa in samples from the Elbersreuth Orthoceratid Limestone (Frankenwald). Abreviations: X – present, XX – very frequent, a – some Sb with sharp angle, ? – presence uncertain, O – present, but probably karst reworked

Sample / Taxon 12345678910 Sample weight (kg) 6.0 4.2 3.8 2.2 3.0 2.3 1.0 3.6 2.0 1.4 Coryssognathus dubius X Coryssognathus sp. X X X X Delotaxis elegans Xa Xa X Xa Xa X Delotaxis detorta XXXX Delotaxis sp. ex gr. salopia-silurica XXXXXX XX Wurmiella excavata XXX XXXXXX Wurmiella? reclinata X Ozarkodina typica delta morph X X X Ozarkodina nasuta X W eosteinhornensis s.s. O XXXXXXX ?Zieglerodina sp. sp. X X ? XXXX Amydrotaxis? cf. praecox X near the Ohesaare Stage. Accordingly, D. detorta in the nasuta, which is unknown in the Devonian, reaches the end Ohesaare corresponds only to the early part of its range in of gen. W eosteinhornensis. the Požáry section. Collating Jeppsson’s observations of D. detorta from the latest Silurian of the Cellon and from the Klonk sec- tions (Jeppsson 1988, p. 25) and the youngest findings The range of Delotaxis detorta from the Požáry versus the East Baltic ones, it appears that in the Eastern Baltic in the East Baltic only the lower part of the range of D. detorta has been observed, and that begins before gen. Jeppsson (1988, p. 25) reported Delotaxis detorta from the W eosteinhornensis. It is not warranted that the Baltic Beyrichien-Kalk with the ostracods Nodibeyrichia geda- conodont faunas survived the eosteinhornensis acme, but nensis and Kloedenia wilkensiana, i.e. from the top of the their earlier end cannot be excluded. stratigraphic succession of Gotland. Viira (2000) found it in the East Baltic region in the Ohesaare Stage; occasio- nally, it is associated with Ozarkodina nasuta (Viira, 1983) Some Spathognathodontidae and it may be followed by Amydrotaxis? praecox Viira of the late Silurian 2000, which is quite scarce and is also still within the range of O. nasuta. Viira (2000, p. 53) stated rightfully that the Within the Spathognathodontidae of the late Silurian, the detorta range does not reach the base of the Devonian in technical steinhornensis plexus comprises the apparatuses the Baltic. with alternating denticulation of ramiform elements. Three In the EOL, we have found comparable data: Delotaxis groups of them can easily be distinguished within this ple- detorta enters before Amydrotaxis? cf. praecox (see Ta- xus: ble 1), and O. nasuta is still found above both. The Baltic A) Pa elements with a large, broad and asymmetrical setting cannot be calibrated directly with the range of gen. basal cavity in a rather posterior position and with rather W eosteinhornensis, because on the entire Baltic Platform equidentate denticulation of the blade. This kind corre- this taxon has only been erroneously identified (no speci- sponds to gen. W eosteinhornensis; it can be subdivided men with a node on the basal lobe has been found); how- according to two criteria that vary independently: a) A ever Wolska (1969, p. 586) mentioned it from the Chełm node at least on the outer lobe or without a node. b) Some borehole in the basinal deposits, which means that it could denticles near the cusp are fused or all have free tips. The reach the margin of Baltica. It did not occur on the platform holotype of the taxon eosteinhornensis has a node and its either because the biofacies was inappropriate or because denticles are not fused. The most characteristic specimens at its time the late Silurian regression had begun. The asso- are those with both node and fusion. The fusion increases ciations in the Požáry section and in the EOL prove that: with maturity. Murphy et al. (2004, p. 15, 16) defined cor- 1. the index of the detorta Zone appears before the index of responding morphotypes. the eosteinhornensis Zone (see Figs 4, 5), 2. the ranges of B) Pa elements with the centre of their smooth basal the latter and of Amydrotaxis? praecox overlap, and 3. O. cavity close to mid-length, with a fairly symmetrical

153 Bulletin of Geosciences • Vol. 82, 2, 2007

“bell-like” (sensu Jeppsson 1974, p. 39) outline of the basal tionally reported up to the top of the Kuressaare Regional cavity, and with rather equal heights of their denticles. Stage (the Kudjape Beds) from the Kolka borehole by Viira Their equidentate condition was the reason for their origi- & Aldridge (1998), which is considered as late Ludlow nal inclusion in the taxon eosteinhornensis, but their basal (latest Ludfordian). lobes distinguish them. Nevertheless, they were techni- Combining the age criteria of the full development of cally joined in the informal eosteinhornensis group for D. elegans, of the good development of alternating provisional classification. This group consists of a num- denticulation in Z.? zellmeri, the reports of the Pa element ber of independent taxa that still await evaluation. of the latter from Estonia, and the upper range of the “Oz.” C) Pa elements with their basal lobes as in group B, but crispa alpha 2 morph, our erratic sample L1 should be as- with markedly unequal sizes of their denticles. Some of signed to immediately below the Ludlow/Přídolí boundary. these Pa elements are joined to ramiforms that are close to The apparatus of Z.? zellmeri is also found at the Požáry those of the multi-element genus Zieglerodina Murphy et section in the basal bed of the Přídolí, and we reject the ref- al. 2004. Corresponding elements figured from the type erences that have been made repeatedly by means of it to stratum of Zieglerodina remscheidensis (Ziegler, 1960) are gen. W eosteinhornensis. Reports of gen. W eosteinhor- helpful guides for the separation. Where apparatus recon- nensis from strata of Ludfordian and early Přídolí age must struction was not yet possible, the Pa elements with uneven generally be doubted. denticulation were joined in the collective remscheidensis group. Additionally, there are late Silurian taxa with incipient Framework of late Silurian conodont or developed alternation in their ramiform elements that do succession in the Požáry section not fit in the groups A–C; e.g., Zieglerodina? klonkensis and some correlations sp. nov. and Parazieglerodina plodowski Carls, Slavík & Valenzuela-Ríos, 2005 both with transversely extended The conodont succession of the late Ludlow and Přídolí at basal cavities. Požáry is under study. At present, the following levels im- In Cellon bed 40 the groups A, B and C are present and portant for conodont biostratigraphy can be reported: were originally attributed to the taxon eosteinhornensis. 9.2 m below the Ludlow/Přídolí GSSP boundary there Therefore the identification of quite various Pa elements is Parazieglerodina plodowskii Carls et al., 2005 with ini- from other beds of the Cellon section and other sources un- tial development of alternating denticulation in its der this name is easy to understand. Due to local conditions ramiforms, co-occurring with Pedavis latialatus (Walliser, of partly low conodont diversities in the Cellon collections 1964). from the latialatus Zone onwards, the local entries of Pa el- 8.2 m below the series boundary “Oz.” snajdri enters. ements of group B are, in this historically important sec- The transition from the latter to “Oz.” crispa occurs 7.0 m tion, as late as in the initial Přídolí. This is rather delayed, if below the boundary. compared to samples with Zieglerodina? zellmeri sp. nov. The last Ped. latialatus occurs 3.2 m below the bound- and additional “Oz.” crispa in the present erratic boulder ary and is accompanied by Ozarkodina cornidentata L1 from Baltica and in western Armorica (Bultynck & (Viira, 1983), and 3.0 m below the boundary Ozarkodina Pelhate 1971) that can be correlated from the late Lud- ambiqua (Viira, 1983) occurs. In the East Baltic Ohesaare fordian onwards. Authors who would include such fairly borehole, the former is released by the latter near the pas- equidentate Pa elements in the taxon eosteinhornensis, sage between the regional stages K2 and K3. would have to begin the eosteinhornensis Zone amid the “Ozarkodina” crispa is very abundant 1.80 m below the Ludfordian. This was, indeed, practised by Kleffner (1989, Ludlow/Přídolí boundary. fig. 6). In the basal bed of the Přídolí there is Zieglerodina? In erratic sample L1 with Zieglerodina? zellmeri sp. zellmeri. Ozarkodina typica (= Spathognathodus primus = nov. there were also 7 Pa elements of the alpha 2 morph of Ozarkodina confluens auctorum) occurs 20 cm above the “Ozarkodina” crispa (Walliser, 1964) sensu Viira & base of the Přídolí; these specimens are comparable to Aldridge, 1998 (see Fig. 6H, I); additionally, there are Viira’s (2000, pl. 2, fig. 8) find from the stage K4. abundant Delotaxis elegans of large and robust growth; 7.0 m above the boundary the first Delotaxis elegans this taxon is reported by Jeppsson et al. (1994, fig. 3) to be has single small denticles only next to the cusp (this incipi- frequent in the East Baltic from the beginning of the Přídolí ent stage of alternation does not prove D. detorta: there onward. must be additional small denticles intercalated along a The specimens of “Ozarkodina” crispa alpha 2 morph branch. sensu Viira & Aldridge (1998, pl. 2, figs 1, 2; pl. 3, fig. 11) 14.5 m above the boundary the first Delotaxis detorta are identical to those from the Estonian Sauvere Beds with several intercalated small denticles and Ziegle- where this taxon enters; but the “alpha 2 morph” is addi- rodina? ivochlupaci sp. nov. occur (see Figs 3, 4). Both

154 Peter Carls et al. • Conodont biostratigraphy across the Silurian-Devonian boundary

C A

D E B

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F H

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M K

L N

Figure 6. Camera lucida drawings – Zieglerodina? zellmeri sp. nov. (A–G, J–N). • A,B–Paelement (holotype), cat. No. L38684, Požáry section, sam- ple PZ030, A – inner lateral view, B – upper view.•C–Scelement, cat. No. SMF69980, erratic boulder, sample L1, inner lateral view. • D – incomplete Sa element, cat. No. SMF69981, erratic boulder, sample L1, posterior view.•E–Sbelement, cat. No. SMF69982, erratic boulder, sample L1, inner lat- eral view.•F–Paelement (paratype), cat. No. L38685, Požáry section, sample PZ030, inner lateral view.•G–Pbelement, cat. No. L38686, Požáry sec- tion, sample PZ030, same as Fig. 8P, inner lateral view.•J–Melement, cat. No. SMF69983, erratic boulder, sample L1, inner lateral view. • K,L–Pa element, cat. No. SMF69984, erratic boulder, sample L1, K – inner lateral view, L – upper view. • M – Pb element, cat. No. SMF69985, erratic boulder, sample L1, inner lateral view.•N–Paelement, cat. No. SMF69986, erratic boulder, sample L1, inner lateral view. “Ozarkodina” crispa.•H,I–Paele- ment (lost), erratic boulder, sample L1, H – lower lateral view, I – upper view. taxa also co-occur about half a meter higher (sample follow almost 17 m without record of it. A last sample with PZ078, see Fig. 4). This association also exists in Baltic gen. W eosteinhornensis s.s. (without welding of denticles) erratic Lag Vas 4 proving an early range of the D. detorta is 5.3 m below the first specimen of Icriodus. in Baltica. 27 m above the GSSP, Zieglerodina? klonkensis sp. At Požáry, 17.7 m above the boundary gen. W nov. enters; it is known through about 13 m up to 3 m be- eosteinhornensis s.s. enters; it abounds in about 1.5 m; then low the Silurian/Devonian boundary.

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The youngest record of D. detorta is 20 cm below the succession of entries in the course of time and irrespective of first Icriodus sp. the regions: 1. Zieglerodina? zellmeri sp. nov. during fading 20 cm above the Icriodus sp., Icriodus hesperius of the crispa plexus; 2. the D. detorta and Zieglerodina? Klapper & Murphy, 1974 enters. 1 m above the latter mark ivochlupaci sp. nov.; 3. Amydrotaxis? praecox; 4. gen. W I. aff. transiens Carls & Gandl, 1969 corresponds to the eosteinhornensis;5.Zieglerodina? klonkensis sp. nov.; earliest Lochkovian radiation of its genus. Previously, the 6. Icriodus sp. sp. The presence of Ozarkodina nasuta and entry of Warburgella of the rugosa group has been used as other Ozarkodina s.s. seem to be more sporadic in pelagic an approximation to the Silurian/Devonian boundary, facies than in the shallow Baltic waters and contribute only about 2.5 m above the entry of Icriodus hesperius. occasionally to the correlation. The Baltic spathognatho- dontan Pa element that has been most frequently figured under the name of “eosteinhornensis”isZieglerodina? ze- Collation of late Silurian conodont llmeri sp. nov., that overlaps with “Oz.” crispa. According distribution in the sections of Požáry to experience with the taxa crispa and eosteinhornensis and Elbersreuth and in the eastern Baltic s.s., in pelagic facies, there is a long interval between both that comprises the early third or half of the Přídolí. The late The correlation of the conodont successions at Elbersreuth part of this separating interval has the D. detorta still wit- and in the Požáry section is most reliably based on the rich hout the index eosteinhornensis. Only this interval could samples (acme) of gen. W eosteinhornensis observed at be called the “detorta Zone”, within the early Přídolí, but both localities. Additionally, the entry of Delotaxis detorta we do not recommend the use of this fact for formal zona- occurs, at both localities, shortly before the appearance of tion purposes, although the early entries of D. detorta are gen. W eosteinhornensis (cf. Figs 4, 5). Accordingly, relevant for correlations. Formalizing the zonation does D. detorta in the Baltic localities, may be supposed to ap- not really enhance the correlation, and the move of the zo- pear as early. As the Nordic erratic Lag Vas 4 contains the nal name from the end of the Přídolí to below its middle same association of the D. detorta and Zieglerodina? would be confusing. ivochlupaci sp. nov. as appears in the Požáry section, the regional entry of D. detorta in the Baltic in the early Přídolí is corroborated. That the youngest Baltic conodont faunas Conodonts above the Silurian-Devonian are in the early half of the Přídolí, it accords with the ab- boundary (the “woschmidti Zone”) sence of true gen. W eosteinhornensis from that region. However, one can alternatively argue that this index is eit- The woschmidti Zone is considered and widely used as the her too young to be present in that region before the late earliest Devonian conodont Zone. It was already installed Silurian regression, or that it is withhold through the shal- when all earliest Lochkovian Icriodus s.l. were still attribu- low facies. The latter version can be suggested through the ted to I. wo. woschmidti. However, by and by, it turns out preference this taxon has for deeper waters and it would that there was an early radiation of the woschmidti group, forbid to draw conclusions on the age from the absence in after which typical I. woschmidti Ziegler, 1960 have a rat- shallow facies. Additional criteria are available: In the Bal- her late appearance and a marginal taxonomic position tic successions, Amydrotaxis? praecox follows the entry of (compare irrespective of original identifications: Carls D. detorta (Viira 2000, p. 4); at Elbersreuth, there is one re- 1975, pl. 2, fig. 21; Uyeno 1981, pl. 5, figs 32, 33, also pre- cord (cf.) together with rather early D. detorta and at the en- sent in bed 159 of the Požáry section; none strictly identical try of gen. W eosteinhornensis. This points to the following with I. woschmidti s.s.). The named taxon with wide distri-

Figure 7. Camera lucida drawings of Zieglerodina? ivochlupaci sp. nov. • A,B–Paelement (holotype), cat. No. L38687, Požáry section, sample PZ076, A – upper view, B – lateral view. • C,D–Paelement (paratype), cat. No. L38689, Požáry section, sample PZ076, C – lateral view, D – upper view. •E–Pbelement, cat. No. L38692, Požáry section, sample PZ076, inner lateral view.•F–Melement, cat. No. L38693, Požáry section, sample PZ076, in- ner lateral view. • G,H–Paelement (paratype), cat. No. L38688, Požáry section, sample PZ076, G – upper view, H – outer lateral view.•I–Scelement, cat. No. L38690, Požáry section, sample PZ076, inner lateral view. • J – Sa element, cat. No. L38694, Požáry section, sample PZ076, posterior view. • K – Sb element, cat. No. L38691, Požáry section, sample PZ076, inner lateral view.•L–Paelement, cat. No. SMF69975, erratic boulder, sample Lag Vas 4, lateral view. • M – Pa element (paratype), cat. No. L38695, Požáry section, sample PZ076, lateral view. • N – Pa element, cat. No. L38698, Požáry section, sample PZ078, lateral view. • O – Pa element, cat. No. SMF69976, erratic boulder, sample Lag Vas 4, lateral view. • P,T–Paelement (paratype), cat. No. L38696, Požáry section, sample PZ076, P – upper view, T – lateral view. • Q,R–Paelement, cat. No. L38699, Požáry section, sample PZ078, Q – lateral view, R – upper view. •S–Paelement, cat. No. SMF69977, erratic boulder, sample Lag Vas 4, lateral view. •U–Paelement (paratype), cat. No. L38697, Požáry section, sample PZ076, lateral view. • V,X–Paelement, cat. No. L38700, Požáry section, sample PZ078, V – upper view, X – lateral view. • W – Pa element, cat. No. SMF69978, erratic boulder, sample Lag Vas 4, lateral view. • Y – Pa element, cat. No. SMF69979, erratic boulder, sample Lag Vas 4, lateral view.

156 Peter Carls et al. • Conodont biostratigraphy across the Silurian-Devonian boundary

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157 Bulletin of Geosciences • Vol. 82, 2, 2007 bution that appears closest to the lower Devonian system 1972). The transition from the elsana to the tiro Zone is boundary is I. hesperius Klapper & Murphy, 1974. A for- found in Celtiberia just above the common type stratum of mal woschmidti Zone would begin somewhere within the Icriodus transiens, Icriodus bidentatus, Icriodus rectan- early half of the Early Lochkovian. Additionally, the age of gularis, Pelekysgnathus elongatus, and Zieglerodina repe- the type strata of the zonal index Icriodus woschmidti Zieg- titor, which also furnished Ancyrodelloides carlsi ler, 1960 and of Zieglerodina remscheidensis (Ziegler, (Boersma, 1973) and a somewhat paucidentate Zie- 1960), have been implied in complex errors and must be glerodina aff. remscheidensis (see Carls & Gandl 1969, assessed. pl. 19, fig. 2). The type stratum of Icriodus wo. woschmidti When Jeppsson (1988, pp. 26, 27) expressed his opin- and probably also that of Zieglerodina remscheidensis are ion that the type strata of Zieglerodina remscheidensis therefore slightly younger than the basal bed of submember and of Icriodus woschmidti at Untenrüden are of late Silu- d1c gamma of the Luesma Formation in Celtiberia, which rian age, he assumed that the taxon that he would publish bears the conodonts just mentioned. None of these cono- (in 1989) as “Ozarkodina s. remscheidensis (Ziegler, donts has ever been found in Silurian beds. Of course, the 1960) sensu nov.” warranted the correlation between the age of a taxon is not delimited downwards through the age Silurian beds 11–12 of the Klonk section and the type of its type stratum. Nevertheless, it must be taken into ac- stratum in the Untenrüden section. Jeppsson (1989, p. 21, count that the index of the traditional first Devonian cono- pl. 2, figs 6–11) figured Pa elements of this taxon consid- dont zone ranges rather high, as compared to the other ering them as “an off-shore ecotype of O. s. remschei- Devonian taxa just mentioned. densis” with “neotenic characters”. Irrespective of all Comparatively old specimens of “Icriodus wo. wo- biostratigraphical implications, the distinct morphology schmidti” have been figured by Carls (1975, pl. 2, of the figured Pa elements cannot warrant a taxonomic figs 19–21, from 1 m below the first Devonian shelly fauna identification with Z. remscheidensis, nor does the Sa ele- of Celtiberia with Acastella heberti). The old Celtiberian ment (Jeppsson 1989, pl. 3, fig. 15) with a rather open angle specimens do not exhibit the extreme shapes of transverse between both branches suggest an inclusion in the species ridges that characterize the holotype and the bigger remscheidensis. This taxon, as characterized by the Pa el- paratypes of Icr. woschmidti. Instead, they have lateral ements, is a separate species that we erect as Zie- denticles that are better offset and trend morphologically glerodina? klonkensis sp. nov. towards other species. Herein, these specimens are re- Jeppsson (1988, pp. 26, 27) compiled several localities, garded to represent results of an early radiation from which at which Icriodus woschmidti Ziegler, 1960 seems to ap- several species, including those mentioned above, have de- pear in Silurian horizons. One of these horizons is its type veloped. In view of this development, the type material of stratum in the section of Untenrüden, measured and sam- Icr. woschmidti appears as a rather specialized side branch, pled by Ziegler (1960). Ziegler stated this section to belong which corresponds to its younger age. to the “Ockrige Kalke” (= Ochreous Limestones) Member In the Podolian succession, the entry of Icriodus at the base of the Hüinghausen Formation. The name of postwoschmidti Mashkova, 1968, formally the second Ockrige Kalke does not imply any relation with the pelagic zonal index of the Lochkovian, is reported from about 15 m Thuringian Ockerkalk horizon (= Ochre Limestone). It is a above Monograptus uniformis angustidens that marks the local unit in the Rhenish Facies of shallow waters. In the start of the Devonian (Nikiforova 1977, fig. 4). Thus, the section, beds a to i were distinguished. range of I. postwoschmidti begins within the range of Bed a (= 1) furnished the first Warburgella rugosa Acastella heberti and almost 100 m below Acastella tiro. rhenana G. Alberti, 1962, which indicates a Devonian age This means that a zonal scheme with a woschmidti and a of the entire section. Alberti (1962) reported, from the postwoschmidti Zone according to the restricted indexes same bed, “incomplete cephala of an A. (Acastella), that would imply uncertainty as to their succession. are close to A. (Acastella) heberti elsana” R. & E. Richter, The index of the postwoschmidti Zone and I. transiens 1954. This trilobite marks the second trilobite zone after Carls & Gandl, 1969 were synonymized (Ziegler 1971, the Monograptus uniformis boundary at the beginning of pp. 233–235) and the taxa found together with I. transiens the Devonian. In bed g (= 8), G. Alberti found pygidia of were considered to characterize the postwoschmidti Zone; “A. (Acastella) tiro?” with initial marginal spines. This fea- but the synonymization is refutable and the age relations ture indicates attribution to an early part of the tiro Zone or are not certain, as the origins are unknown. Icriodus to the transition toward this zone. Bed g is the type stratum hesperius is the named species in Nevada and Bohemia of Icriodus wo. woschmidti, and bed e, about 1 m below that appears most closely to the beginning of the Devo- bed g, is the type stratum of Zieglerodina remscheidensis. nian. A succession of hesperius Zone and revised post- Neither is Silurian. The succession of early Lochkovian woschmidti Zone for the interval before Ancyrodelloides Acastella taxa is one of the best controlled phylogenetic carlsi would be more appropriate than the traditional lineages in the Lochkovian (compare comments by Gandl formalisms.

158 Peter Carls et al. • Conodont biostratigraphy across the Silurian-Devonian boundary

Systematic descriptions sample Lag Vas 4 found by Peter Laging near Vastorf (Lüneburg), a limestone with Protochonetes furnishing Family Spathognathodontidae Hass, 1959 also Delotaxis elegans of the detorta plexus, Pa elements (SMF69975-SMF69979). Genus Zieglerodina Murphy et al., 2004 Etymology. – Dedicated to the memory of the late Prof. Dr. Type species. – Spathognathodus remscheidensis Ziegler, Ivo Chlupáč, Univerzita Karlova, Prague, the successful 1960. biostratigrapher and inspiring researcher of the Barrandian Palaeozoic. Remarks. – The type species of Zieglerodina has a charac- teristic Sa element (see Murphy et al. 2004, p. 14). Virtu- Depositories. – National Museum Prague (Czech Repub- ally the same shape is present in Zieglerodina repetitor and lic), catalogue Nos.: L38687–L38700, Forschungsinstitut in its unnamed successor (= “Ozarkodina” sp. N of Carls und Naturmuseum Senckenberg, Frankfurt a. M., Ger- 1987 in the lower part of the Nogueras Fm. in Celtiberia). many), catalogue Nos: SMF69975–SMF69979. This suggests that the Sa elements can characterize linea- ges and, thus, may be useful for the subdivision of the ge- Diagnosis. – Pa element: Small, paucidentate (about 10–11 nus Zieglerodina s.l. The Sa elements associated to the new denticles), unequidentate, mostly with the following arran- species erected herein (whose holotypes are Pa elements) gement of denticles: a) 1 anterior “germ” denticle; b) a differ from the Sa element found with Zieglerodina rem- group of usually 3 higher and stronger denticles, c) com- scheidensis. Therefore it might become necessary to attri- monly 2 smaller ones, d) the cusp, often not high, e) a group bute the new species to other generic units, when the re- of mostly 3 denticles with triangular tips in a sloping line, cords have been completed. Therefore the new species are f) 1–2 small final denticles. Basal lobes small, not orna- treated as Zieglerodina? At present, Zieglerodina is the mented, forming a nearly symmetrical “bell-shaped” vault genus that would be indicated by Pb, M, Sb, and Sc ele- centered slightly behind midlength and often wider than ments. The range of Zieglerodina s.l. begins in the late long (oval outline). Ludfordian, but the new taxa range mainly in the Přídolí. Probably, early Zieglerodina s.l. were derived from Para- Description. – Pa element: (see diagnosis). There is a dif- zieglerodina Carls et al., 2005 through increase in the inter- ference in the Pa elements from smaller overall size and calation of small denticles between the bigger ones on the lower numbers of denticles in the erratic material to hig- branches of ramiform elements. her numbers in sample PZ078: The outer lobe is often more anterior than the inner one, but their shapes are simi- lar. Zieglerodina? ivochlupaci sp. nov. Pb element: Pattern of the form taxon Ozarkodina Figures 7A–Y, 8Q–S denckmanni Ziegler, 1956. The blade is rather straight in oral view. Commonly it has 6 anterior denticles that are Holotype. – The Pa element cat. No. L38687 (National Mu- stronger than the posterior ones; the cusp is high and slen- seum, Prague) figured on Fig. 7A, B and Fig. 8Q–S. der; the posterior blade has commonly about 10 denticles with only a few small ones intercalated. The aboral mar- Type locality. – The Požáry Quarries – the type section of gins form an angle of 135°–150°. the Přídolí Series. M element: Pattern of the form taxon Neoprioniodus bicurvatus Walliser, 1964; anteriorly 2 feeble denticles Type stratum. – Limestone sample No. PZ076 – correspon- may occur. ding to bed No. 133 of the Požáry section according to Kříž Sc element: The Sc elements correspond to the tradi- et al. (1986, fig. 6), Požáry Formation, 14.5 m above the tional parataxon “Hindeodella priscilla” of former con- Přídolí GSSP. cepts. The alternation of denticle sizes is more developed than in the Sb elements. Possibly, there are two pairs; the Paratypes. – Pa elements (L38688 to L38689, L38695 to anterior branch is very short and nearly horizontal in one L38697). pair and slightly longer and moderately bent downwards in another pair present in the sample. Additional figured material. – a) Stratotypical: Pb element Sb element: The Sb elements are much stouter and L38692, M element L38693, Sc element L38690, Sb ele- shorter than in the remscheidensis apparatus (= parataxon ment L38691, Sa element L38694. b) From the approxima- Plectospathodus alternatus Walliser, 1964). The anterior tely 5 cm thick limestone bed PZ078, about 45 cm above branch is commonly broken; it seems to be slightly the type stratum (L38698–L38700). c) From Nordic erratic shorter than the posterior one. The element describes a

159 Bulletin of Geosciences • Vol. 82, 2, 2007 continuous bow of only feeble curvatures (lateral and ver- Holotype. – The Pa element figured by Jeppsson, 1989, tical) and does not form a marked angle at the basal cav- pl. 2, fig. 9a–c, LO5897 of the type collection at the Depar- ity. The inner lip of the basal cavity forms a small, slightly tment of Historical Geology and Palaeontology, University vaulted pyramid often recalling the lip of the Sa element. of Lund, Sweden. Behind the cusp there are commonly 3 big denticles and in each interspace 1 or 2 (3) small ones; in the posterior end a Type locality. – The GSSP section at Klonk. few denticles are crowded, one of which almost reaches the size of the cusp (this feature is reminiscent of Type stratum. – Bed 12, about 2.5 m below the S/D boun- Ozarkodina s.s.). dary, late Přídolí. Sa element: The basal cavity has a round posterior lip forming a rounded and rather short vault. The aboral mar- Paratypes. – Pa element figured by Jeppsson (1989), pl. 2, gins of the branches form angles between 110° and 135°. figs 6 (LO 5895, Klonk bed 11), 8 (LO5896, Klonk bed Each branch has, in its distal half, about 3 big denticles and 12), 10, 11 (LO5898-LO5899, Klonk bed 12). more small ones. The groove on the anterior face of the cusp is less pronounced than in the remscheidensis group. Additional material. – M and S elements figured by Jep- The alternation of denticle sizes fades distally, but the out- psson (1989), pl. 3, figs 13–18 from Klonk, bed 12 ermost denticles decrease in size, diverge increasingly, and (LO5913–LO5918). describe a sloping arc. Etymology. – Material of this taxon was first described Remarks.–IfZieglerodina? ivochlupaci sp. nov. was a from the Silurian/Devonian GSSP section of Klonk, Cze- descendant of Parazieglerodina plodowskii, it was pro- chia. bably separated from it by several intermediate taxa; Pb and Sb elements are the most similar ones. The similarities Depository. – Department of Historical Geology and Pala- with the type species of Zieglerodina in the Pa element eontology, University of Lund, Sweden. consist in the presence of an anterior group of bigger den- ticles and in the simple basal lobes. Diagnosis. – Pa element: Zieglerodina? with Pa elements The Pb element is shorter than those of the remschei- of moderate size, straight and thin blade; about 9 to 10 an- densis group, but otherwise it differs little. The M element terior and 5 to 6 posterior denticles plus low cusp; 4 to does not distinguish both groups. Differences in the Sb 6 denticles in anterior comb with evenly rounded profile, and Sc are obvious and can contribute to a future generic followed by mostly 4 smaller ones sloping toward cusp; separation from the remscheidensis group as well as posterior denticles slope with curved profile, amid them the Sa. one or two as strong as cusp; tongue-shaped basal lobes en- The conodont material obtained from 4.4 kg of lime- tirely behind mid-length, forming a short but broad vault stone of the type stratum comprised: 66 Pa, 21 Pb, over that is slightly asymmetrical, has narrow but high necks 9 M, 16 Sc, 21 Sb, 6 Sa. Although the extraction was not and low flange-like rims, no nodes. exhaustive and many fragments as well as subordinate numbers of other spathognathodontid elements are present, Remarks. – Jeppsson (1989, p. 27) argued that the “O. stein- the material suggests the presence in the apparatus of: 1 Sa, hornensis group (Jeppsson 1975)” had a “marked tendency 2 pairs of Sb, 2 pairs of Sc, and 1 pair of M elements. Pb to form local populations” and “that a large number of con- and Pa elements exist in a surplus suggesting both higher temporaneous populations existed in the Silurian” with production and recovery rates. This trend is quite common “little evidence for these representing distinct lineages... in in Zieglerodina and contrasts with the balances in the gigantic web of a single lineage”. This opinion resulted Wurmiella. in the present taxon being synonymized in “Ozarkodina It seems that Z.? ivochlupaci is biostratigraphically sig- steinhornensis remscheidensis” with “adaptation to an of- nificant shortly before the eosteinhornensis Zone s.s. and fshore environment” and “neotenic aspects”. Additionally, that it can mark the early part of the range of the Delotaxis its Přídolí occurrence was mistakenly regarded as coeval detorta plexus in the late part of the early Přídolí. with the intra-Lochkovian type stratum of Zieglerodina remscheidensis. The Sa element figured by Jeppsson (1989, pl. 3, Zieglerodina? klonkensis sp. nov. fig. 15) differs moderately but clearly from the figured ones in the type material of the taxon remscheidensis 1989 Ozarkodina steinhornensis remscheidensis (Ziegler, (Ziegler 1960, pl. 15, figs 1, 2); it is broader and has a wider 1960) sensu nov. – Jeppsson, p. 28, pl. 2, figs 6–11; angle between the branches, which contributes to the spe- pl. 3, figs 11–18. cific differences.

160 Peter Carls et al. • Conodont biostratigraphy across the Silurian-Devonian boundary

C

A B E F D

K

I

G H J L

1 mm

N

P

O M

Q R S

Figure 8. Digital camera pictures; specimens uncoated – gen. W eosteinhornensis (A–F), Delotaxis detorta (G–H, K–L), Delotaxis sp. (I–J), Zieglerodina? zellmeri sp. nov. (M–P), Zieglerodina? ivochlupaci sp. nov. (Q–S). • A–C – gen. W eosteinhornensis, Pa element, cat. No. L38682, Požáry section, sample PZ083, A – upper view, B – lower view, C – outer lateral lower view. • D–F – gen. W eosteinhornensis, Pa element, cat. No. L38683, Požáry section, sample PZ083, D – outer lateral view, E – upper view, F – lower view. • G, H – Delotaxis detorta, incomplete Sa, cat. No. L38675, Požáry section, sample PZ076, G – anterior view, H – posterior view. • I, J – Delotaxis sp., a strongly angular Sb element, cat. No. L38678, Požáry section, sample PZ076, same as Fig. 3I, I – outer lateral view, J – inner lateral view. • K – Delotaxis detorta, incomplete Sc element, cat. No. L38677, Požáry section, sam- ple PZ076, same as Fig. 3E, lateral view.•L–Delotaxis detorta, Sc element, cat. No. L38679, Požáry section, sample PZ076, same as Fig. 3M, outer lat- eral view. • M–P – Zieglerodina? zellmeri sp. nov., Pa element (holotype), cat. No. L38684, Požáry section, sample PZ030, M – upper view, N – outer lateral view,O–Paelement (paratype), cat. No. L38685, Požáry section, sample PZ030, outer lateral view,P–Pbelement, cat. No. L38686, Požáry sec- tion, sample PZ030, same as Fig. 6G, outer lateral view. • Q–S – Zieglerodina? ivochlupaci sp. nov., Pa element (holotype), cat. No. L38687, Požáry sec- tion, sample PZ076, Q – outer lateral view, R – inner lateral view, S – upper view.

161 Bulletin of Geosciences • Vol. 82, 2, 2007

Jeppsson has described and figured the Klonk material cal University of Braunschweig, who furnished the cono- so that no additional morphological details have to be donts of sample L1, a Nordic erratic boulder. added. Diagnosis. – (Mature Pa element): Pa big, long, low, multi- Stratigraphic position. – In the Požáry section, Z.? klon- dentate (close to 15 denticles), rather equidentate, with ne- kensis is currently known from 13 m to about 3 m below the arly straight aboral margins (lateral view) and little lateral Silurian/Devonian boundary; in the Klonk section it ranges curvature, rather horizontal oral margin with moderate within the late Přídolí (Jeppsson 1988, tab. 1). Its absence slope near posterior end; unornamented basal lobes with from the EOL suggests a gap in the late Přídolí. bell-shaped vault centered slightly behind midlength; white matter scarce, not reaching deeply into blade.

Zieglerodina? zellmeri sp. nov. Description. – The apparatus of Zieglerodina? zellmeri is Figures 6A–G, J–N, 8M–P close to that of Zieglerodina, but distant from gen. W eos- teinhornensis. The Pa element reaches over 1.1 mm length; 1971 Spathognathodus steinhornensis eosteinhornensis it is rather straight and low, equidentate, often with 14 or Walliser 1964. – Bultynck & Pelhate, pl. 1, fig. 2a, b over 15 denticles that have scarce white matter mainly near (non figs 1, 3); Fig. 2, B1. the tips; it has a bell-shaped basal cavity centered closely 1983 Spathognathodus steinhornensis eosteinhornensis behind mid-length and lateral thickenings of only moderate Walliser, 1964. – Viira, text.-fig. 4, samples 67.40 m strength. Denticles adjacent to the cusp are often small, but and 64.65 m (basal Äigu beds). commonly the cusp does not protrude strongly. Associated 1998 Ozarkodina remscheidensis eosteinhornensis (Walli- spathognathodontan Pb elements resemble the parataxon ser, 1964) sensu lato. – Viira & Aldridge, pl. 4, “Ozarkodina denckmanni” with a low and long posterior figs 13–15 (14 and 15 from basal Äigu beds with late branch (contrasting with the short Pb element of gen. W “Ozarkodina” parasnajdri). eosteinhornensis) and have a protruding cusp that can in- corporate neighbouring denticles. The M elements corres- Holotype. – The Pa element cat. No. L38684 figured on pond to the parataxon “Neoprioniodus bicurvatus”, are Figs 6A, B, 8M, N. long, equidentate, and hardly have germs of anterior den- ticles. The prevailing Sa element, which probably belongs Paratype. – The Pa element cat. No. L38685 figured on to this taxon, is broadly winged with an angle of 120° to Figs 6F, 8O. 130° between both branches; it has 6 to 9 stronger denticles on each branch and some intercalated small ones; it is Additional material. – a) stratotypical Pb element cat. No. much wider than its homologues in Zieglerodina s.s. and L38686 figured on Figs 6G, 8P, b) from the erratic boulder gen. W eosteinhornensis. The Sb element resembles that L1 from Vastorf near Lüneburg: 2 Pa (SMF69984 figured of Zieglerodina in its inconspicuous basal cavity and in on Fig. 6K, L; SMF69986 figured on Fig. 6N), 1 Pb the gentle and even curvature of the blade without a mar- (SMF69985 figured on Fig. 6M), 1 Sa (SMF69981 figured ked angle. The denticles of Sb and Sc elements alternate on Fig. 6D), 1 Sb (SMF69982 figured on Fig. 6E), 1 Sc intensely in size. The anterior branch of the Sc element is (SMF69980 figured on Fig. 6C), 1 M (SMF69983 figured horizontal and moderately incurved and bears about 8 big on Fig. 6J). denticles and a few intercalated small ones; the long po- sterior bar is feebly undulated, and slight lateral thicke- Depositories. – National Museum Prague (Czech Repub- nings cause rounded ledges below the denticles on both lic), catalogue Nos.: L38684–L38686. Forschungsinstitut sides. und Naturmuseum Senckenberg, Frankfurt a. M., Ger- many), catalogue Nos: SMF69980–SMF69986. Remarks. – The equidentate aspect of the Pa element has induced former workers to consider this taxon as belonging Type locality. – The Požáry Quarries – the type section of to the index eosteinhornensis. With the exception of a sin- the Přídolí Series. gle Pa element from the type bed that has a steep ridge along the outer side of its cusp and is rather a malformation, Type stratum. – Limestone sample No. PZ030 – correspon- we have not seen the ornamentation of the basal lobe(s) nor ding to old bed No. 96 (basal bed of the Přídolí) of the Po- their more posterior position and larger outlines that cha- žáry section according to Kříž et al. (1986, fig. 6), Požáry racterize gen. W eosteinhornensis as well as welded den- Formation, Přídolí. ticles. Reference of these specimens to eosteinhornensis is considered unwarranted. Etymology. – After Dr. Henning Zellmer, formerly Techni- The widely expanded branches of the Sa element may

162 Peter Carls et al. • Conodont biostratigraphy across the Silurian-Devonian boundary constitute a means to separate the taxon zellmeri from Braunschweig. The study was partly developed with the support of Zieglerodina, when more insight is available. the Institute of Geology ASCR, v.v.i. (Institutional project: The stratigraphic positions of the Baltic material are AV0Z30130516). The final stage of the study was supported by the close to the base of the Äigu Member (k3bÄ) of the Grant agency of the ASCR (project No. B300130613). Peter Kaugatuma Fm. in Estonia just before the end of “Ozar- Laging, Scharnebeck/Lüneburg has provided several erratic lime- stone boulders of Baltic provenance – we thank him kindly. A for- kodina” parasnajdri. The position at the beginning of the mer draft of this article was read critically by Richard Aldridge and Přídolí in the Požáry section, just above the end of “O”. Svend Stouge; Ruth Mawson provided constructive criticism for crispa, corroborates the common correlation of the Esto- the present article. We have profited greatly from their comments nian sections with the Barrandian standard. and thank them kindly. Responsibility for remaining inadequacies is, of course, ours. Conclusions References 1. The late Silurian and Early Lochkovian development of spathognathodontan and icriodontid conodont taxa requi- ALBERTI, G. 1962. Unterdevonische Trilobiten aus dem Fran- res a more detailed taxonomic subdivision than has been kenwald und Rheinischen Schiefergebirge (Ebbe- und Rem- practised hitherto. Biostratigraphical conclusions must not scheider Sattel). Geologisches Jahrbuch 81, 135–156. only rely on conodonts against other evidence. ALDRIDGE,R.J.&SCHÖNLAUB, H.P. 1989. Conodonts. In HOL- 2. The eosteinhornensis Zone s.s. begins amid the LAND, C.H. & BASSETT, M.G. (eds) A Global Standard for the Přídolí; it is not demonstrable in the Baltic outcrops regions Silurian System. National Museum of Wales, Geological Se- (Scania-Gotland-Estonia). ries 9, 274–279. 3. The Delotaxis detorta plexus begins before the ALDRIDGE, R.J., DORNING, K.J., HILL, P.J., RICHARDSON, J.B. & eosteinhornensis Zone and it is not limited to the final SIVETER, D.J. 1979. Microfossil distribution in the Silurian Přídolí. In the Baltic and in the Požáry section its entry is of Britain and Ireland. In HARRIS, A.L., HOLLAND, C.H. & closely associated to Zieglerodina? ivochlupaci sp. nov. A LEAKE, B.E. (eds) The Caledonides of the British Isles, Geo- corresponding formal zone is not recommended. The as- logical Society of London, Special Publication 8, 433–438. sumed limitation of a “detorta Zone” to the final Přídolí is BARNETT, S.G. 1971. Biometric determination of the evolution of refuted. Spathognathodus remscheidensis: A method for precise intra- 4. Zieglerodina? zellmeri sp. nov. begins in the range basinal time correlations in the northern Appalachians. Jour- of “Oz.” crispa close to the Ludlow-Přídolí boundary in nal of Paleontology 45, 274–300. the East Baltic, in the Armorican Massif and at Požáry. BARNETT, S.G. 1972. The evolution of Spathognathodus rem- Several early reports of the eosteinhornensis Zone corre- scheidensis in New York, New Jersey, Nevada, and Czecho- spond to it. slovakia. Journal of Paleontology 46, 900–917. 5. Zieglerodina? klonkensis sp. nov. is erected for a BARRICK, J.E. & KLAPPER, G. 1992. Late Silurian-Early Devo- taxon found by Jeppsson (1988; 1989) but originally in- nian Conodonts from the Hunton Group (Upper Henryhouse, cluded in Zieglerodina remscheidensis. Z. remscheidensis Haragan, and Bois d’Arc Formations), South-Central ranges only within the Early Lochkovian. Oklahoma. Oklahoma Geological Survey Bulletin 145, 19–65. 6. The radiative development of the genus Icriodus s.l. BISCHOFF, G.C.O. & SANNEMANN, D. 1958. Unterdevonische Conodonten aus dem Frankenwald. Notizblatt des Hessischen near the beginning of the Devonian is intense but is still in- Landesamtes für Bodenforschung 86, 87–110. completely known. The type stratum of the very particular BOERSMA, K.T. 1973. Description of certain Lower Devonian Icriodus woschmidti is much younger than the entry of platform conodonts of the Spanish central Pyrenees. Leidse Icriodus postwoschmidti in Podolia. A succession of a Geologische Mededeelingen 49, 285–301. woschmidti Zone and a postwoschmidti Zone in the Early BRANSON,E.B.&MEHL, M.G. 1933. Conodonts from the Bain- Lochkovian is not appropriate. The widespread Icriodus bridge (Silurian) of Missouri. University of Missouri Studies 8, hesperius marks the beginning of the Devonian very closely; 39–53. a zone near the beginning of the Devonian should bear its BULTYNCK, P. 1971. Le Silurien Supérieur et le Dévonien name instead of the name woschmidti Zone. A post- Inférieur de la Sierra de Guadarrama (Espagne Centrale); woschmidti Zone would require a revised characterization. Deuxième partie: Assemblages de Conodontes a Spathognat- hodus (1). Bulletin de l’Institut Royal des Sciences Naturelles de Belgique 47, 1–43. Acknowledgements BULTYNCK,P.&PELHATE, A. 1971. Découverte de la Zone a eosteinhornensis (Conodontes) dans le Synclinorium Médian The Alexander von Humboldt Foundation awarded a fellowship to du Massif Armoricain. Mémoire du B.R.G.M. 73: Colloque Ladislav Slavík and supported his stay at Technische Universität ordovicien-silurien, 189–197.

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CARLS, P. 1975. Zusätzliche Conodonten-Funde aus dem tieferen Spathognathodontidae (Conodonts). University of California, Unterdevon Keltiberiens (Spanien). Senckenbergiana Lethaea Riverside Campus Museum Contribution 6, 1–25. 56, 399–428. NIKIFOROVA, O. 1977. Podolia. In MARTINSSON, A. (ed.) The Si- CARLS, P. 1987. Ein Vorschlag zur biostratigraphischen Redefini- lurian-Devonian Boundary, I.U.G.S. Series A 5, 52–64. tion der Grenze Gedinnium/Siegenium und benachbarter Unter- REXROAD,C.B.&CRAIG, W.W. 1971. Restudy of conodonts Stufen. Courier Forschungs-Institut Senckenberg 92, 77–121. from the Bainbridge Formation (Silurian) at Lithium, Mis- CARLS,P.&GANDL, J. 1969. Stratigraphie und Conodonten des souri. Journal of Paleontology 45, 684–703. Unter-Devons der östlichen Iberischen Ketten (NE Spanien). RHODES, F.H.T. 1953. Some British Lower Palaeozoic conodont Neues Jahrbuch für Geologie und Paläontologie Abhand- faunas. 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