Bollettino della Società Paleontologica Italiana Modena, Novembre 1999
Origin of Gnathodus bilineatus (Roundy, 1926) related to goniatite zonation in Rheinisches Schiefergebirge, Germany
Dieter MEISCHNER Tamara NEMYROVSKA Institut fiir Geologie und Palaontologie Institut geologichnykh nauk Universi tar Gi:ittingen Natsionalnoi Akademii Nauk Ukrainy
KEYWORDS- Conodonts, Zonation, Correlation, Carboniferous, Visean, Rheinisches Schiefergebirge, Germany.
ABSTRACT-A gap in our knowledge ofconodont zonation is closed by faunas ftom a limestone turbidite seri es in Rheinisches Schiefergebirge, Germany. Gnathodus bilineatus (Roundy, 1926) sensu lato originates with two morphotypes high in the Pericyclus-Stufe, eu II, Lower Carboniferous. Gn. bilineatus romulus n.ssp. enters stili in the uppermost Entogonites nasutus Zone. Gn. bilineatus remus n.ssp. follows suite in the E. grimmeri Zone. Gn. bilineatus bilineatus appears in the Goniatites crenistria Zone. Gn. girtyi Hass, 1952 precedes Gn. bilineatus romulus n.ssp. by just a few beds and therefore starts within the Entogonites nasutus Zone. The ancestry ofGn. praebilineatus Belka, 1985, most likely the ancestor o(Gn. bilineatus, remains uncertain. !t is recommended to set the base of the Gnathodus bilineatus Zone with the first appearance ofGnathodus bilineatus romulus n.ssp.
RIASSUNTO- [C origine di Gnathodus bilineatus (Roundy, 1926) in relazione alla zonazione a goniatiti nel Rheinisches Schiefergebirge, Germania] -Le fauna a conodonti ritrovate in torbiditi calcaree nella regione del Rheinisches Schiefergebirge, Germania, consente di risolvere i problemi relativi alla biozonatura del Carbonifero inferiore. Gnathodus bilineatus (Roundy, 1926) sensu lato si origina, con due moifotipi, nella parte alta del Pericyclus-Stufe, eu IL Carbonifero inferiore. Gnathodus bilineatus romulus n.ssp. compare nella parte alta della Emogonires nasutus Zone. Gn. bilineatus remus n.ssp. appare poco dopo, nella E. grimmeri Zone. Gn. bilineatus bilineatus compare nella Goniatites crenistria Zone. Gn. girtyi Hass, 1952 precede Gn. bilineatus romulus n.ssp. di alcuni strati e quindi inizia durante la Entogonires nasutus Zone. Il progenitore di Gn. praebilineatus Belka, 1985, da cui probabilmente si è originato Gn. bilineatus, rimane indefinito. La base della Gnathodus bilineatus Zone viene indicata dalla comparsa di Gnathodus bilineatus romulus n.ssp.
INTRODUCTION ORIGIN OF GN BILINEATUSINTERMS OF AMMONOID STRATIGRAPHY Gnathodus bilineatus embraces a large group of morphotypes with bilineate ornamentation on their Bischoff (1957) gave a first account of Lower platforms. They span the interval from the latest early Carboniferous conodonts from the Rheinisches Visean through the Serpukhovian. The group displays Schiefergebirge, followed by Voges (1959, 1960). high specific and intraspecific diversity and a number Neither of them established a formai Gnathodus of variations as described and figured by many bilineatus-Zone. Voges (1959, tab. l, pp. 270, 283; co nodo n t workers (Lane & Straka, 1974; Higgins, 1960, p. 26) defined an 'anchoralis- bilineatus lnter- 1975; Metcalfe, 1981; Higgins & Wagner-Gentis, regnum' as the time-interval between the termination 1982; Park, 1983; Belka, 1985; Schonlaub & Kreutzer, of Scaliognathus anchoralis and the appearance of 1993; Perret, 1993; Nemirovskaya & Nigmadganov, Gnathodus bilineatus which he (Voges, 1960, tab. 5, p. 1993; Belka & Korn, 1994; Krumhardt et al., 1996; 29) dated as within the Pericyclus-Stufe, Entogonites Spalletta & Perri, 1998). nasutus Zone (eu II 8). This datum was confirmed by The Gnathodus bilineatus group is significant in the Meischner (1970, fig. 2, p. 1171) who also, on the stratigraphy of the Carboniferous. Three conodont basis of more conodont faunas, emended a Gnathodus zones are named after its members. These are the late bilineatus bilineatus Zone from the one originally Visean Gn. bilineatus-Zone and two Serpukhovian termed 'bilineatus Zone' by Bèiger (1962, p. 152). zones: Gn. bilineatus bollandensis an d Gn. postbilineatus, Meischner (1970, fig. 2) speculated that Gn. bilineatus respectively. The world-wide distribution of the taxa may derive from either Gn. semiglaber or Gn. delicatus, of the bilineatus group and their apparent diagnostic - the latter h e figured as overlapping with Gn. bilineatus features make them reliable tools for long-ranging in the ammonoid Zone eu II 8. Weyer (1972) reported correlation. Gn. bilineatus from the Pericyclus-Stufe of the Harz 428 D. MEISCHNER, T NEMYROVSKA
Mountains. materia! entered the basin. During the Tournaisian This early origin of Gn. bilineatus was generally and lower Visean this is expressed in reduced thickness accepted that time by authors dealing with conodont/ of shales, alum-shaies and cherts in basinai positions, ammonoid-correlation in Europe (Ben der et al., 1971; condensed sequences on top of drowned Devonian Paproth et al., 1983; Conii et al., 1990; Riley, 1990a, reefs, an d tholeiitic basalti c volcanism in the southeast. 1993). Later in Belgium the first appearance of Gn. In the Scaliognathus anchoralis Zone some of the bilineatus was dated as V2b or Warnantian (Groessens, former reefs were revived an d started to shed limestone 1974; Belka & Groessens, 1986), and in England as turbidites into the adjacent depressions (Meischner the base of late Asbian (Varker & Sevastopulo, 1985; 1971, p. 18, fig. 6). These beds are intercaiated with Riley, 1993). the younger part of the chert series to form what is When Belka (1985) described Gn. praebilineatus as regionaily called 'Kulm-Kieselkaik' (cherty limestones). a Visean homeomorph of the Tournaisian species Gn. Simultaneously the volcanic activity changed to delicatus, the exact position of the origin of Gn. ex.Plosive keratophyre type the frequent, cm-thin ashes bilineatus in terms of the ammonoid zonation became of which are intercalated with the cherty limestones uncertain as it was not clear where in the supposed and cherts. lineage Gn. praebilineatus -bilineatus the specimens of The former shelf was subsequendy drowned and Voges (1959), Weyer (1972) and those ascribed to Gn. delivered limestone turbidites of the "Kulm- delicatus (and pardy Gn. cf. cuneiformis) by Meischner Plattenkalk" during the upper Visean ( Goniatites- (1970) had to be placed. The materia! on which Stufe), before the whole area was covered by the Meischner (1970, fig. 2) had based his schematic prograding flysch and molasse deposits of the newly phylogeny of the Gnathodus species was therefore forming Variscan mountains in the younger part of revised during a sabbatical ofTamara Nemyrovska in the upper Visean and in the Namurian. Gottingen, 1996. Despite the marked contrasts between the facies of Some of the uncertainty about the origin of Gn. the alum shales, cherts and cherty limestones, the bilineatus may be due to unsatisfactory correlation of reduced sequences, and the limestone turbidites within goniatite zones between Germany and other regions the Rheinisches Schiefergebirge, the basinal sequence (Riley, 1990a, 1990b, 1993; Korn, 1996). The German is remarkably persistent, lateraily. Individuai beds with zonation around the criticai boundary as established specific fauna and cm-thin tuffs can be traced over by Nicolaus (1963) was recently revised by Korn major parts of the basin (Nicolaus, 1963; Meischner, ( 1996). The lower boundary of the Goniatites-Stufe (eu 1962, 1971). The generai sequence ofblack shaies an d III) was shifted from the base of the Entogonites cherts followed by lighter-coloured, variegated, grimmeri Zone to the beginning of Goniatites hudsoni caicareous cherts, then dark shaies and siltstones, can ( =Goniatites schmidtianus syn.). l t coincides now with be followed over greater parts of the external pre- the base of a prominent marker-horizon in the Variscan basins ofEurope, Asia Minor and Centrai Asia, Rheinisches Schiefergebirge, the "grimmeri-Bank" the major facies changes being synchronous at least in (Text-fig. 3). the Harz Mountains, southern England, Montagne Noire and South Portugal (Engel eta!., 1983). Nicolaus (1963) Korn (1996) In the area south of Arnsberg in Westphalia, limestone turbidite activity persisted from the Se. Goniatites-Stufe, eu III Goniatites-Stufe, eu III anchoralis- into the Gn. bilineatus Zone (Text-fig. 2). Goniatites cren. crenistria Goniatites crenistria A continuous section from the Kulm-Kieselkaik into Goniatites globostriatus the shales and limestones of the Kulm-Plattenkaik was Goniatites cren. schmidtianus Goniatites hudsoni sampled at Ober-Rohre by Meischner in 1967. The _ Entogonites grimmeri Entogonites grimmeri conodonts were used for the construction of the Entogonites nasutus Entogonites nasutus stratigraphic chart in Meischner (1970, fig. 2), but were Pericyclus-Stufe, eu II Pericyclus-Stufe, eu II never published in detail. The section in the former limestone quarry of Ober- Rohre, which is now part of the waterworks of the town GEOLOGICAL SETTING, NATURE OF THE RECORD of Sundern, consists of thinly bedded shaies, cherts an d acidic tuffs intercaiated with limestone turbidites (Text- The Lower Carboniferous sediments in the fig. 3). The criticai interval extends over 20 m from Rheinisches Schiefergebirge originated in the foreland the upper Entogonites nasutus to the Goniatites crenistria of the Variscan (= Hercynian) Orogen (Text-fig. 1). crenistria Zone, i.e. by definition: across the Pericyclus/ Deep-water Kulm facies was bordered in the norrhwest Goniatites (eu II/eu III) boundary. lt contains the typical by a calcareous shelf on which Carboniferous goniatites at reasonable frequencies (Nicolaus, 1963). Limestone and detritailimestones were deposited (Text- The boundary between the Pericyclus- and fig. 2). The earlier part of the sequence was controlled Goniatites-Stufen in the sense ofKorn (1996) is drawn by extensional tectonics during which litde clastic at the base of the "grimmeri-Bank" just above the ORIGIN OF GNATHODUS BILINEATUS 429
Upper Carboniferoui(SJLESIAN) with cool nom'
Upper CorboniferoudSILESIAN) withoul cool seoms
lower Carbonifero'a
Upper Oevo,ion (FRASN.IAN, fAMENN IAN)
Mi dd le Oevonion ( EIFELIAN. CIVETIAN)
lowet Oevonian (GEOINN IAN, • SlECENIAN, EMSIAN)and al der
Metomorphic roclu ?De..,onian ond older o Synudimentory volcanic rocks. o • ma · bo,oltic lovos
Text-fig. l -Geologica! sketchmap of Rheinisches Schiefergebirge east of the river Rhein, localiry Ober-Rohre indicated by arrow. (From Meischner, 1971, fig. 3, modified).
limestone bed of conodont sample No.8. E. grimmeri "grimmeri-Bank", i.e.: 3 m below the base of the E. occurs frequendy together with Goniatites hudsoni in grimmeri Zone or between conodont samples 12 and this bed. Single specimens of E. grimmeri are found 13. lower down in the sequence, the lowest ones ca. 4 m As an old quarry wall in a now protected water lower or halfway between conodont sample Nos. 11 supply area, the section is stili accessible, and may even and 12, where they mark the base of the E. grimmeri be resampled, with the permission of the owners, Zone. The uppermost E. nasutus was found in this Stadtwerke Sundern, Schwemker Ring l, 59846 outcrop by Helmkampf (1969, Taf l) 7 m below the Sundern, Sauerland. 430 D. MEISCHNER, T NEMYROVSKA
LOWER IO 20 30km CARBONIFEROUS SEDIMENTATI ON
Latest Pericydus-Stufe
Text-fìg. 2- Sedimentation in the upper Pericyclus-Stufe (upper eu II) in Rheinisches Schiefergebirge east of the river Rhein, locality Ober- Réihre indicated by arrow. (From Meischner, 1971, fig. 6, modified).
CONODONTS Devonian or Tournaisian species, but may go unnoticed with younger, Visean taxa. A certain contro! The nature of the host-rocks suggests that all the is available by the occurrence of characteristic species conodonts are reworked and incorporated in turbidity of the underlying Siphonodella- and Scaliognathus currents that travelled from intra-basinal carbonate anchoralis zones. Such reworked elements are rare shoals to deep bottoms. Older conodont species that throughout the sequence. were already extinct at the time of the fìnal deposition Species of different contemporaneous, neritic and of their elements may therefore be admixed with the pelagic facies may still occur mixed in the turbidites. coeval faunas. This is obvious in the case of Upper However, shallow water species are rare in the samples ;;-1 :><
q -·o- ...... () UJ -.::ro c.n P.:. -·-:J o :J p.) s :J l r;-g_ .... o (3'<: 3 o·o·o o i; ;'i o;:;; ...,., " o o ::::-:3 ?; :o P- v;· ;:! :J o j::: :J ::n o n o <..., (L'l M () M (b ('!) p_. 0 s Q :J -· cn cn :=r-::r-n,..., :::::P'""",.., O'"" g_ (b ,.., ;:::: o VJ §. n ('!)<"'UO· ,_.tnU'""t;O c:ìE:=i'ld .... gso..: 7 o(") O<,"'"'"'...,(; r;-" :::;-::r-0\· (b :;o3 ::r <.;;tç).-."'P-"'Z""o :::;-...,.-. 9 2 Rheinisches Schiefergebirge, Germany § Disused quarry at Ober-Rohre Waterworks Goniatite zonation Goniatites -Stufe < . grimmeri Goniatites hudsoni -Zone I -Zone CJ z () ::r: l l Il l l tg l ·-- (il" o N ...... ,.,. :;, o Samples co EXPLANATION OF PLATE l All illustrateci specimens are houseci in Institut unci Museum fiir Geologie unci Palaontologie, Gottingen, Germany. Only Pa elements are illustrateci. Magnifìcation: x80. Fig. l - Gnathodus aff. pseudosemiglaberThompson & Fellows. Sample No. 13. Figs. 2-3, 5, 7, 9-1 O, 14, 17 Gnathodus praebilineatus Belka. 2, 5) Samp1e No. 15; 3, 10, 14, 17) Sample No. 13; 7, 9) Sample No. 14. Figs. 4, 8 - Gnathodus pseudosemiglaberThompson & Fellows. Sample No. 13. Figs. 6, 11-12, 15 Gnathodus delicatus Branson & Mehl transitional to Gnathodus praebilineatus Belka. 6) Sample No. 15; 11) Sam\ìle No. 13; 12, 15) Sample No. 14. Figs. 13, 16, 18 Gnathodus praebilineatus Be ka transitional to Gnathodus bilineatus (Rounciy). 13, 18) Sample No. 13; 16) Sample No. 11. D. MEISCHNER, T NEMYROVSKA, ORIGIN OF GNATHODUS BILINEATUS P!. l 434 D. MEISCHNER, T NEMYROVSKA ti p of the element. The specimens of Gn. praebilineatus and the carina which is expanded posteriorly to some from Ober Rohre correspond to those described by degree, and a row of small denticles on the ourer side Belka (1985). They have a long, rather narrow, not of the posterior part of the carina, parallel to the latter. well developed parapet, a shallow groove between the The shape of the parapet of the earliest asymmetrical and a long, simple, posteriorly positioned Gn. bilineatus forms resembles to some extent the canna. parapet shape of the latest Gn. bilineatus from the Meischner (1970, fìg. 2) listed these forms partly Serpukhovian of South Tien Shan (Nigmadganov & as Gn. delicatus which, according to Belka (1985), is Nemirovskaya, 1992) and the Pyrenees (Buchroitner, an older, Tournaisian, of Gn. praebi- 1979; Perret, 1993). Descriptions of Gn. praebilineatus lineatus, partly as Gn. cf. cuneijormis. The newly and two new subspecies of Gn. bilineatus are given described subspecies of Gn. bilineatus he regarded as belo w. transitional between these species and Gn. bilineatus. The new forms are imroduced as formai subspecies. There are also specimens which resemble forms from There is not much sense in Open Nomenclature in a the Cima di Plotta Formation of the Carnic Alps case like this when two clearly idemifìable, equally (Schoenlaub & Kreurzer, 1993) and from the Visean forms are represented among about l 00 sections ofSlovenia and Serbia (Stojanovich-Kuzenko, specrmens. 1996), and the specimen illustrateci by Weyer (1972, Abb. 13) from the E. nasutus Zone ofGermany. The relation of Gn. delicatus an d Gn. praebilineatus remains uncertain. In the E. nasutus Zone there occur PALAEONTOLOGY a few specimens transitional between the two species together with the characteristic forms of Gn. Genus GNATHODUS Pander, 1856 praebilineatus. However, there remains a gap of 20 m in section between the last true Gn. delicatus and the Type species- Porygnathus bilineatus Roundy, 1926 (Tubbs, 1986). fìrst true Gn. praebilineatus. A relatively rich fauna (No. 18) in this gap has neither of the species. Gnathodus bilineatus includes a number of GNATHODUS BILINEATUS BILINEATUS (Roundy, 1926) variations. Some of them are characterised by a very Pl. 3, fìg. 18 broad triangular platform with a highly asymmetrical anterior margin, a high and wide, well developed The type subspecies is well known and easily parapet, coarse ornamentation of the outer platform, identifìed (see Krumhardt et al., 1996, for synonymy). and very long and strong, expanded parapet which extends posteriorly beyond the posteri or margin of eup. Others are more symmetrical with a well developed, GNATHODUS BILINEATUS REMUS n.ssp. wide parapet, gently rounded outer platform and poor Pl. 3, fìgs. 13-14, 17, 19 ornamentation on the outer platform. Stili other forms correspond to a more common conception of the Holotype- Pl. 3, fìg. 14. subspecies Gn. bilineatus bilineatus, with an almost rectangular outer platform with subconcentrically Locus typicus - Abandoned quarry at Ober-Rohre arranged rows of nodes, a well developed, moderately waterworks, town of Sundern, district of Arnsberg, wide parapet, a shallow groove between the parapet Westphalia, Sample No. 8, Pericyclus-Stufe (eu Il), EXPLANATION OF PLATE 2 Ali illustrated specimens are housed in Institut und Museum fur Geologie und Palaomologie, Gottingen, Germany. Only Pa elements are illustrated. Magnifìcation: x80. Figs. 1-3 - Gnathodus praebilineatus Belka transitional to Gnathodus bilineatus (Roundy). Sample No. 11. Fig. 4 - Gnathodus austini Belka. Sample No. 13. Figs. 5, 7, 10-13, 16 - Gnathodus praebilineatus Belka. 5, 11) Sample No. 11; 10) Sample No. 8; 7, 12, 13, 16) Sample No. 13. Fig. 6 - Gnathodus pseudosemig!dberThompson & Fellows. Sample No. 13. Fig. 8 Gnathodus aff. subbilineatus Lane, Sandberg & Ziegler. Sample No. 3. Fig. 9 Gnathodus delicatus Branson & Mehl transitional to Gnathodus praebilineatus Belka. Sample No. 20. Fig. 14 - Gnathodus praebilineatus Belka transitional to Gnathodus bilineatus romulus n.ssp. Sample No. 11. Fig. 15 Gnathodus praebilineatus Belka transitional to Gnathodus bilineatus remus n.ssp. Sample No. 11. Figs. 17-18 - Mestognathus beckmanni Bischoff. 17) Sample No. 12; 18) Sample No. 13. D. MEISCHNER, T NEMYROVSKA, ORIGIN OF GNATHODUS BIL!NEATUS P!. 2 436 D. MEISCHNER, T NEMYROVSKA uppermost Entogonites grimmeri-Zone, 0.5 m below GNATHODUS BILINEATUS ROMULUS n.ssp. E. grimmeri-Bed. Pl. 3, figs. 1-12, 15-16 Derivatio nominis - After Remus, legendary co- Holotype- Pl. 3, fig. 15. founder of Rome, twin brother of Romulus. Locus typicus- Abandoned quarry at Ober-Rohre Material- 45 specimens. waterworks, town of Sundern, district of Arnsberg, Westphalia, Sample No. 8. Pericyclus-Stufe (eu Il), Description- Pa element with very wide, triangular, Entogonites grimmeri-Zone, 0.5 m below E. grimmeri- asymmetrical platform. The well developed parapet Bed. extends anteriorly far beyond the amerior margin of the platform, which is therefore extremely Derivatio nominis -After Romulus, legendary asymmetrical. Parapet high and wide, arched in latera! founder of Rome, twin brother of Remus. view, consisting of up to 12-14 transverse ridges, steeply dropping imo the wide, deep trough berween carina Material- 52 specimens. and parapet. Outer margin convex ameriorly and here higher than the carina. The parapet ends posteriorly Description - Pa element with moderately wide, by merging with the carina. asymmetrical platform, inner parapet well developed, Ourer platform wing-shaped, triangular, very wide long, rather wide and high, consisting of transverse in its most amerior part, amerior margin oblique, ridges, ending before the posterior tip of the element posteri or o ne rounded, moderately convex an d covered by merging with the carina dose to its posterior end. by discrete, medium-sized nodes arranged parallel to Long, posteriorly slightly expanded carina, extending the lateral-posterior margin of the platform, i.e. at an little beyond the posterior margin of the platform. angle of 45-80° to the carina. Gerontic specimens show Groove berween parapet and carina moderately wide almost subconcemrical rows of nodes. and deep. The third amerior transverse ridge of the Carina well developed, long, extending posteriorly parapet usually crosses the groove and reaches the beyond the platform and consisting of fused denticles carina. This feature is presem on all morphotypes of or nodes which are coarser fosteriorly. Gn. bilineatus, Gn. praebilineatus and Gn. girtyi from Juveniles show almost al the features characteristic the type section. Outer platform wide and rounded, of this subspecies: strong asymmetry, triangular shape mostly flat or slightly convex, rarely subquadrate to of the platform, long expanded carina and nodose semirounded, ornamented with one or rwo rows of ornamemation on che outer platform. nodes parallelling the outer margin. In juvenile specimens the nodes are scattered randomly an d occupy Remarks- Gn. bilineatus remus differs from the other preferemially the margina! part of the outer platform. known taxa of Gn. bilineatus by its triangular shape, There are also juveniles with a smooth and flat outer the highly asymmetrical amerior margin, an d the long, platform, bur che parapet is always well developed. expanded carina, which extends far beyond the posterior end of the platform. The platform is Remarks-This subspecies differs from Gn. bilineatus considerably more strongly ornamented than in Gn. bilineatus by its semirounded, poorly ornamented outer bilineatus romulus. platform, the narrow carina, the wide and high parapet, and the deep, wide trough berween parapet and carina. Occurrence- Samples 3, 4, 6, 7, 8, 9, Entogonites lt differs from Gn. bilineatus remus n.ssp. by the less grimmeri- imo Goniatites crenistria-Zones. asymmetrical shape, a more slender carina, which does EXPLANATION OF PLATE 3 Ali illustrateci specimens are houseci in Institut unci Museum fi.ir Geologie unci Palaontologie, Gottingen, Germany. Only Pa elements are illustrateci. Magnifìcation: x80 (except Fig. 18). Figs. 1-2, 9-1 O - Gnathodus girtyi Hass. l, 2) Sample No. 8; 9) Sample No. 13; l O) Sample No. l l. Fig. 3 - Gnathodus cf. meischneri Austin & Husri. Sample No. 13. Figs. 4-8 - Gnathodus meischneri Austin & Husri. Sample No. 13. Figs. 11-12, 15-16 - Gnathodus bilineatus romulus n.ssp. 11 , 12, 16) Sample No. 11; 15) Holotype, sample No.8. Figs. 13-14, 17, 19 - Gnathodus bilineatus remus n.ssp. Sample No.8; Fig. 14 = Holorype. Fig. 18 - Gnathodus bilineatus bilineatus (Rounciy). Sample No. 3, x 70. Figs. 20-21 - Gnathodus praebilineatus Belka. Sample No. 12. Fig. 22 - Gnathodus bilineatus romulus n.ssp. transitional to Gnathodus bilineatus bilineatus (Rounciy). Sample No. 4. D. MEISCHNER, T NEMYROVSKA, ORIGIN OF GNATHODUS BILINEATUS P!. 3 438 D. MEISCHNER, T NEMYROVSKA not extend posteriorly much beyond the platform, long. The platform is ornamented by randomly and by the poorly ornamented outer platform. spaced, irregularly scattered nodes. In some specimens they can be arranged in rows, the innermost ones Occurrence- Samples 3, 4, 6, 7, 8, 9, 10, 11, 12, parallel to the carina, the others longitudinal or uppermost E. nasutus- into Go. crenistria-Zones. following the shape of the cup. The main differences between Gn. praebilineatus and the first Gn. bilineatus in O ber Rohre are as follows: GNATHODUS PRAEBILINEATUS Belka 1985 (l) in Gn. praebilineatus the inner parapet is not Pl. l, figs 2-3, 5, 7, 9-10, 14, 17; Pl. 2, figs 5, 7, 11, completely developed, it is longer and narrower than 16; Pl. 3, figs. 20-21 in Gn. bilineatus, its transverse ridges are irregular, and the posterior ones can be replaced by nodes; (2) the 1985 Gnathodus praebilineatus- BELI EXPLANATION OF PLATE 4 Al! illustrateci specimens are houseci in Institut unci Museum fur Geologie unci Palaontologie, Gorringen, Germany. Only Pa elemenrs are illustrateci. Magnifìcation: x80. Figs. 1-3 - Pseudognathodus mermaidus Austin & Husri. l, 3)Sample No.8; 2) Sample No. 13. Fig. 4 - Bispathodus stabilis (Branson & Mehl) transitional to Lochriea commutata (Branson & Mehl). Sample No. 11. Figs. 5, 7, 11, 23 - Pseudognathodus homopunctatus Ziegler. 5) Sample No. 11; 7) Sample No.9; 11) Sample No. 15; 23) latera! view, Sample No.9. Fig. 6 - Pseudopolygnathus symmutatus (Rhocies, Austin & Druce), latera! view. Sample No. 8. Figs. 8-9, 12 - Lochriea cracoviensis Belka transitional to L. commutata (Branson & Mehl). 8, 9) Sample No. 13; 12) Sample No. 12. Figs. 10, 18 - Bispathodus stabilis (Branson & Mehl). 10)SampleNo.l3; 18)SampleNo.ll. Figs. 14, 16, 19 - Bispathodus stabilis transitional to Lochriea cracoviemis Belka. Sample No. 18. Fig. 15 - Vogelgnathus campbelli (Rexroaci). Sample No. 18. Figs. 17, 20-22 - Lochriea commutata (Branson & Mehl). 17, 21) Sample No. 11; 20) Sample No. 13; 22) Sample No. 14. D. MEISCHNER, T. NEMYROVSKA, ORlGIN OF GNATHODUS BILINEATUS P!. 4 15 ' '· 21 23 440 D. MEISCHNER, T NEMYROVSKA round semiglaber-type parapets and a thick and found in the lowermost sample of the section thus still posteriorly much expanded carina. We include, allowing for a time gap between the two species. No however, in praebilineatus their early representatives of forms transitional between Gn. semiglaber and Gn. Gn. bilineatus. The specimens of von Bitter & Plint- praebilineatus (like in the Carnic Alps and Cantabrian Geberl (1982, pl. 6, figs. 9-11) from Canada look very Mountains) or between Gn. pseudosemiglaber and Gn. similar to Gn. praebilineatus, whereas forms illustrateci praebilineatus were found in the O ber Rohre section. by Austin & Husri (1974, pl. 3, figs. 4-5 ), which Belka We recommend that the lower boundary of the regarded as Gn. praebilineatus, in our opinion look more Gnathodus bilineatus-Zone should be set at the first similar to true Gn. bilineatus. This demonstrates the appearance of Gnathodus bilineatus romulus in the wide range in the understanding of Gn. praebilineatus uppermost E. nasutus-Zone, dose to the beginning of which is partly due to the reasons mentioned above. the E. grimmeri-Zone. Belka himself in his last papers (Belka & Korn, 1994; Belka & Lehmann, 1998) demonstrated that his conception of Gn. praebilineatus is wider now than it has been in his origina! description of the species (Belka, 1985). Dr. Zdzislaw Belka commented on some questionable specimens ofhis species Gn. praebilineatus and contributed useful Range- From the base of the Gn. austini-Zone into discussions. Dr. Dieter Korn, Dr. Nick Riley and Dr. Dieter Weyer the lower part of the Gn. bilineatus-Zone (Belka, 1985). supplied important detail concerning the ammonoid zonation. Dieter Korn was especially helpful with information o n the section Lower part of upper Visean of Spain, lower p art of the at Ober-Rohre. Dr. George Sevastopulo vetted the MS lingustically. Alba Formation (Belka & Korn, 1994, Belka & Our sincere thanks are due to ali of them. The Sradrwerke Sundern, Lehmann, 1998). Early Upper Visean of England Herr Wortmann, are thanked for their kind co-operation. (Asbian; i t enters before E. grimmeri and extends into This study was made possible by a visiting scienrisrs' grant from Deutsche Forschungsgemeinschaft DFG to the second author the Goniatites globostriatus-Zone, Riley, personal (Grant No. 436 UKR 17/18/96). communication, March, 1997). Lower Visean of the Carnic Alps (Italy, section Dolina, Spalletta & Perri, 1998. Austria, Cima di Plotta fm, Schoenlaub & Kreutzer, 1993). Lower Visean ofMiddleAsia, Middle APPENDIX Tien Shan (Nigmadganov, personal communication, LIST OF CONODONT NAMES March, 1997). Genus Bispathodus Mi.iller, 1962 Occurrences in the studied section- Sample Nos. 6, Bispathodus stabilis (Branson & Mehl, 1934) Il), Bispathodus stabilis Morphotypes l, 2 Lane, Sandberg & 11, 12, 13, 14, 15, Pericyclus-Stufe (eu Entogonites Ausrin, 1974 nasutus- to E. grimmeri Zone, an d a single specimen in sample No. 6, Goniatites crenistria-Zone (reworked?). Genus Gnathodus Pander, 1856 Gnathodus austini Belka, 1985 Gnathodus bilineatus bilineatus (Roundy, 1226) Gnathodus bilineatus bollandensis Higgins & Bouckaert, 1968 CONCLUSIONS Gnathodus bilineatus remus n.ssp. Gnathodus bilineatus romulus n.ssp. The first appearance of Gnathodus bilineatus romulus Gnathodus cuneiformis Mehl & Thomas, 1947 n.ssp. is recorded in conodont sample No. 12 a little Gnathodus delicatus Branson & Mehl, 1938 below the first occurrence of Entogonites grimmeri in Gnathodus girtyi Hass, 1959 Gnathodus meischneri Austin & Husri, 1974 the section, which, by definition, means: within the Gnathodus mermaidus Austin & Husri, 1974 uppermost Entogonites nasutus-Zone, Pericyclus-Stufe, Gnathodus postbilineatus Nigmagdanov & N emirovskaya, 1992 of the German goniatite zonation. Gnathodus praebilineatus Belka, 1985 The present study explains the statements ofVoges Gnathodus pseudosemiglaber Thompson & Fellows, 1970 Gnathodus semiglaber Bischoff, 1957 (1959, 1960) and Weyer (1972) about the first Gnathodus subbilineatus Lane, Sandberg & Ziegler, 1980 appearance of Gn. bilineatus in the E. nasutus-Zone Gnathodus texanus auer. Germanorum Meischner, 1970 since their illustrateci specimens are evolutionary older Gnathodus typicus Cooper, 1939 than Gn. bilineatus bilineatus. Gnathodus sp. A Ebner, 1977 Gn. praebilineatus may be considered the immediate Genus Lochriea Scott, 1942 ancestor of Gn. bilineatus. Forms transitional between Lochriea commutata (Branson & Mehl, 1941) the two species occur in the uppermost Pericyclus-Stufe, Lochriea cracoviensis Belka, 19 8 5 but not higher in the section. The relation of Gn. delicatus and Gn. praebilineatus remains unsolved in Genus Mestognathus Bischoff, 1957 Mestognathus beckmanni Bischoff, 1957 the studied section. 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