New Early Bathonian Bigotitinae and Zigzagiceratinae ......New Early Bathonian Zigzagiceratinae Bigotitinae and (Ammonoidea, Middle Jurassic) 385 &Mitt a1995,1998,2000 ).Bigotites,Bajocisphinctes

Rivista Italiana di Paleontologia e Stratigrafia volume 113 no. 3 3 pls. pp. 383-399 December 2007

NEW EARLY BATHONIAN BIGOTITINAE AND ZIGZAGICERATINAE(AMMONOIDEA, MIDDLE JURASSIC)

SIXTO R. FERNANDEZ-LOPEZ1, MARIA HELENA HENRIQUES2,CHARLES MANGOLD3 & GIULIO PAVIA4

Received: May 10, 2007; accepted: September 10, 2007

Key words: ammonites, systematic palaeontology, Alpine Basin,Digne, Bas Auran, Lusitanian Basin, Cabo Mondego, Western Tethys.

Abstract. Several tens of Lower Bathonian Bigotites fromDigne-Castellane region (SE France) and Cabo Mondego area (Portu-gal) have been reviewed. Three species have been distinguished in thelowermost subzone of the Zigzag Zone (Parvum Subzone) just abovethe boundary Bajocian to Bathonian: B. diniensis Sturani [M+m], B.sturanii sp. nov. [M+m] and B. mondegoensis sp. nov. [M+m]. In theBas Auran area, a chronocline from evolute, strongly ribbed and con-stricted forms (including B. sturanii and B. diniensis) to involute formswith blunt, moderately prominent ribbing and weak constrictions (in-cluding B. mondegoensis) can be recognized. The shared taxa B. mon-degoensis sp. nov. and possibly B. diniensis Sturani permit detailedsubdivision and correlation to be established between ammonite fossilassemblages of Parvum Subzone in the Lusitanian and Alpine basins. Aseparate genus of Zigzagiceratinae, Protozigzagiceras g. nov., is pro-posed to encompass P. torrensi (Sturani) as type species. These newpalaeontological data about the youngest members of Bigotitinae andthe oldest members of Zigzagiceratinae are of biochronostratigraphicimportance for the subdivision and correlation of the basal BathonianZigzag Zone. Three successive biohorizons can be identified at theParvum Subzone in Bas Auran (French Alpine Basin) and Cabo Mon-dego (Lusitanian Basin): Diniensis, Mondegoensis and Protozigzagi-ceras biohorizons.

Riassunto. Vengono revisionate diverse decine di esemplari diammoniti appartenenti ad ammoniti del genere Bigotites del Batonianoinferiore della regione di Digne-Castellane (Francia SE) e dell'area diCabo Mondego (Portogallo). Tre specie sono distinte nella Sottozona aParvum, alia base della Zona a Zigzag, al di sopra del limite Baiociano-Batoniano: B. diniensis Sturani [M+m], B. sturanii sp. nov. [M+m] andB. mondegoensis sp. nov. [M+m]. Nell'area del Bas Auran viene rico-

nosciuto un cronoclino con transizione da forme evolute, fortementecostate e dotate di costrizioni (B. sturanii e B. diniensis) verso formeinvolute con coste tozze e moderatamente prominenti (B. mondegoen-sis). I taxa comuni alle due aree B. mondegoensis sp. nov. e possibil-mente B. diniensis Sturani permettono dettagliate suddivisioni e corre-lazioni tra le associazioni fossili ad ammoniti della Sottozona a Parvumnei bacini alpino e lusitanico. Viene istituito un nuovo genere di Zig-zagiceratinae, Protozigzagiceras g. nov., che ha P. torrensi (Sturani) co-me specie tipo e comprende esemplari dotati di ombelico aperto estadio zigzagiceratino precoce e presenti nella parte sommatale dellaSottozona a Parvum: per questi viene formulata una proposta filogeneticainnovativa di derivazione degli Zigzagiceratinae dai Leptosphinctinaedi inizio Batoniano. Questi nuovi dati riguardanti i rappresentanti piurecenti di Bigotitinae e quelli piu antichi di Zigzagiceratinae presentanogrande importanza per la suddivisione biostratigrafica e la correlazionecronostratigrafica della Zona a Zigzag alla base del Batoniano, anche aifini della proposta di selezione del G.S.S.P, del Piano Batoniano nel-l'ambito delle iniziative della International Subcommission on the Ju-rassic Stratigraphy dell'I.U.G.S. Tre successivi bio-orizzonti sono statiindividuati nella Sottozona a Parvum delle sezioni del Bas Auran (Baci-no Subalpino Francese) e di Cabo Mondego (Bacino Lusitanico):bio-orizzonti a Diniensis, Mondegoensis and Protozigzagiceras.

Introduction

Lower Bathonian ammonite fossil assemblagesfrom Europe include scarce specimens of Bigotites, res-tricted to the basal Bathonian Zigzag Zone. However,

they are relatively common (less than 5.0%) in severaloutcrops of Alpine and Lusitanian basins. More thanninety specimens coming from SE France and Portugal

1 Departamento y UEI de Paleontologia, Facultad de Ciencias Geologicas (UCM) e Instituto de Geología Economica (CSIC - UCM), 28040Madrid (Spain), [email protected].

2 Departamento Ciencias da Terra e Centro de Geociencias, Faculdade de Ciencias e Tecnologia, Universidade de Coimbra, 3000-272 Coimbra(Portugal). E-mail: [email protected].

3 Université Claude-Bernard, Lyon l,UFR des Sciences de la Terre et CNRS, UMR 5125, 27-43 bd du 11 Novembre 1918, 69622 Villeurbannecedex (France).

4 Dipartimento di Scienze della Terra, via Valperga Caluso 35, 10125 Torino (Italy). E-mail: [email protected].

384 Fernández-López S., Henriques M.H., Mangold C. & Pavia G.

Fig. 1 - Geographical location of the study areas in SE France andPortugal.

have been studied (Figs. 1, 2, 3). The main purpose ofthe present paper is to provide a systematic distinctionof three species of Bathonian Bigotites recorded in the

Western Tethys. The widespread distributed species B.mondegoensis sp. nov. and possibly B. diniensis Sturani,as well as the first representatives of a new genus ofZigzagiceratinae, support the subdivision and correla-tion of Parvum Subzone in Lusitanian and Alpine ba-sins.

Systematic palaeontology

The subfamily Bigotitinae, formerly including Bi-gotites, Bigotella, Vermisphinctes, Prorsisphinctes,Spathia (?) and Stomphosphinctes (?), was establishedby Westermann (1956) as belonging to the family Par-kinsoniidae (Buckman, 1920 in 1909-30) and superfami-ly Perisphinctaceae (Steinman, 1890). However, Arkell(1957, 1958 in 1951-59) did not accept the subfamilyBigotitinae and attributed Bigotites (including Bigotella,Pseudobigotella, Haselburgites and Bajocisphinctes) tothe subfamily Leptosphinctinae (Arkell 1950) withinthe family Perisphinctidae (Steinmann, 1890; cf. Arkell1957; Pavia 1973; Galacz 1980; Besnosov & Mikhaylova1981; Callomon in Donovan et al. 1981; Besnosov 1982;Besnosov & Kutuzova 1982; Sandoval 1983; Besnosov

Fig. 2 - Stratigraphical distribution of Bigotites, Protozigzagiceras g. nov., Franchia and Zigzagiceras in Ravin d'Auran and Ravin du Bessections (France). The range line of Bigotites sp. displays the occurrence of fragmentary specimens of undeterminable species and thestratigraphic constancy of this genus through the section. Biostratigraphic logs from Fernández-López 2007.

Pc_G

Rectángulo

New Early Bathonian Bigotitinae and Zigzagiceratinae (Ammonoidea, Middle Jurassic) 385

& Mitta 1995,1998,2000). Bigotites, Bajocisphinctes andMicrobajocisphinctes show relatively simple sutures andmay be actually considered as representatives of thesubfamily Bigotitinae and family Perisphinctidae, agroup of West Tethyan Perisphinctidae branched offby proterogenesis from Leptosphinctes [M] - Cleisto-sphinctes [m] of complex sutures, which occur in theBajocian Garantiana and Parkinsoni zones (Fernán-dez-López 1985, 1987). The youngest Bathonian re-cords of Bigotites [M+m] appear to be from Portugaland Spain, at the lower part of the Macrescens Subzone(Elmi et al. 1971; Fernández-López 1988; Mangold1990; O'Dogherty et al. 2006; Fernández-López et al.2006a; level 90FD31 in Fig. 3).

The material studied in the present work is stored in two co-llections:

- Coll. SRFL&MHH: Fernández-López & Henriques Collec-tion in "Departamento de Ciencias da Terra e Centro de Geociencias"at the Coimbra University (Portugal). The inventory number of speci-mens quotes the section, the locality and the bed of the succession: e.g.02CM172 refers to a fossil sampled in Section 02 of Cabo Mondegofrom bed 142.

- Coll. PU: palaeontological collections of the "Museo di Geo-logia e Paleontologia" of the Torino University (Italy) currently storedat the Dipartimento di Scienze della Terra. Specimens are marked withthe acronym PU and a progressive registration number. Source of sam-pling is indicated with bed number within sections reported by initials:BA, sections of the Bas Auran area (lithostratigraphical column of

Sturani 1967); RB, Ravin du Bès section; RA, Ravin d'Auran section;RR, Ravin des Robines.

Genus Bigotites Nicolesco, 1918Type species: "Bigotella petri" Nicolesco (1917, p. 167, pl.1, figs. 4-5).

Synonymy: Pseudobigotella Lemoine (1918), HaselburgitesBuckman (1920 in 1909-30).

Diagnosis: Macro- and microconchs of medium to large size(Dmax.= 45-500 mm). Planulate coiling, subcircular to subrectangularwhorl section. Strongly ribbed and constricted, blunt primaries andprorsiradiate secondaries, with smooth band on venter, segmentallyenlarging after the constrictions. The ventral smooth band and thedisplacement of the secondaries on both sides of it are more con-spicuous at the beginning of each developmental segment. In con-trast, the ventral smooth band almost disappears and the secondariesbecome increasingly stronger at the end of each developmental seg-ment. Nuclei or early whorls typically with nodes in the bifurcationof the primary ribs. Suture line with suspensive lobe not stronglyretracted.

Discussion. Sexual dimorphs of Bigotites havebeen recognized by different authors (Mangold 1971a,b; Pavia 1973, p. 138; Galácz 1980, p. 105; Fernández-López 1985, p. 460; Fernández-López et al. 2006a).Macroconchs bear simple aperture, and a smooth bodychamber at the end of the ontogenic development. Mi-croconchs with lateral lappets show isocostate ribbing

Fig. 3 - Stratigraphical distribution of Bigotites, Protozigzagiceras g. nov. and Zigzagiceras in Cabo Mondego sections (Portugal). Modifiedafter Fernández-López et al. (2006a).


up to the end of the ontogenic development, and a morecompressed section as well. The maturity of the speci-mens is indicated by the uncoiling of the umbilicalseam, associated with an increasing compression of thewhorl sections in the microconchs.

Several nominal species of Bigotites have been proposed:B. petri (Nicolesco 1917, pl. 4, figs. 4-5; 1932, p. 23, pl. 2, figs.

2-4).B. haugi (Nicolesco 1917, pl. 4, fig. 1; 1932, p. 17, pl. 1, fig. 1).B. tuberculatus (Nicolesco 1917, p. 161, pl. 4, fig. 2; 1932, p. 19,

pl. 1, figs. 2-4).B. pulcher (Nicolesco 1917, p. 165; pl. 4, fig. 3; 1932, p. 21, pl. 2,

fig. 1).B. gentili (Nicolesco 1917, p. 170, pl. 4, fig. 6; 1932, p. 25, pl. 4,

figs. 1-4).B. lanquinei (Nicolesco 1917, p. 173, pl. 4, fig. 7; 1932, p. 17, pl.

4, figs. 5-6, pl. 5, figs. 1-2).B. thevenini (Nicolesco 1917, p. 176, pl. 4, figs. 8-9; 1932, p. 30,

pl. 6, figs. 1-4).B. admirandus (Buckman 1921 in 1909-30, pl. 203A-B).B. trifurcatus Buckman (1926 in 1909-30, pl. 622).B. acurvatus Wetzel (1937, p. 96, pl. 10, fig. 12).B. pusillus Wetzel (1937, p. 96, pl. 10, fig. 13).B. diniensis Sturani (1967, p. 40, pl. 18, fig. 1; pl. 16, fig. 4).

As to comparable Lower Bathonian dimorphiccouples, differences are as follows:

Bajocisphinctes [M] - Microbajocisphinctes [m]differ by being of lower adult size, more compressed,fine-ribbed, with primaries less prominent but moreacute, typically with relatively simple sutures. "Bigo-tites'' lenki, proposed by Schmidtill & Krumbeck(1931, p. 884, pl. 9, fig. 2) shows morphological featuresof Bajocisphinctes (Fernández-López 1985, p. 487;1987).

Planisphinctes [m] - Lobosphinctes [M] lack thesmooth band on venter enlarging segmentally after theconstrictions, as well as the relatively simple sutures and

the nodes in the bifurcation of the primary ribs charac-teristic of Bigotites [M+m]. The sutures of Plani-sphinctes [m] - Lobosphictes [M] show a slender firstlateral and a strongly retracted suspensive lobe.

A further microconch of the Bajocian/Bathonianboundary, Phaulozigzag [m], results to be combinedwith the macroconch provisionally cited as Lobosphinc-tes? [M] by Fernández-López et al. (2006a, p. 261, fig. 9).These dimorphs (both lacking parabolic nodes) showmore involute shells and rather finer ribbing than thePlanisphinctes [m] - Lobosphinctes [M] dimorphic pair,although they share similar complex suture pattern.

Procerites [M] - Siemiradzkia [m] show parabolicnodes in the earliest whorls.

Zigzagiceras [m] - Procerozigzag [M] and Fran-chia [M+m] show a zigzag stage of ribbing character-istic of the earliest whorls of Zigzagiceratinae. Suturelines in specimens of the dimorphic couple Zigzagi-ceras [m] - Procerozigzag [M] are relatively complexalso. However, representatives of Franchia [M+m] dis-play simple sutures and suspensive lobe not stronglyretracted.

Distribution: Bigotites is a characteristic genusof West Tethyan Perisphinctidae scarcely mentioned,apart of certain Bajocian species from southern areasof Europe, in Britain (Arkell 1959 in 1951-59, Callo-mon & Cope 1995, Chandler et al. 2001), Germany(Dietze et al. 2004, Dietze & Dietl 2006), France(Mangold 1971a,b, Mangold & Rioult 1997, Rioult etal. 1997), Portugal (Fernández-López et al. 2006a,b),Iberian Basin (Fernández-López 1985, 1987), SubbeticBasin (Sandoval 1983, Sandoval et al. 2001), SubalpineBasin (Sturani 1967, Pavia 1973, Torrens 1987, Inno-centi et al. 1990), Western Carpathians (Schlögl et al.2005), Hungary (Galácz 1980), Caucasus and GreatBalkhan (Besnosov & Mitta 1998, 2000). First repre-

Fig. 4 - Bivariate scatter for Bigotitesdiniensis Sturani. Plot of um-bilical width (U) and whorlwidth (W) against shell dia-meter (D). H = holotype.


sentatives of the genus occur in the Bajocian Garantia-na Biochron of Mediterranean and Submediterranean

provinces. Bathonian specimens of Bigotites studied inthe present work correspond to three species: B. di-niensis Sturani, B. sturanii sp. nov., B. mondegoensis sp.nov.

Bigotites diniensis Sturani [M + m]Pl. 1, figs 1-6

1967 Bigotites diniensis n. sp. Sturani, p. 40, pl. 16, figs. 4a-b(paratype), pl. 18 figs, la-b (holotype).

Material: 32 specimens from the Parvum Subzone of Digne-Castellane region have been studied. 6 from Chaudon section (Sturani1967): PU31606[M], PU31607[M], PU31609[M], PU31610[M],PU31611[M], PU31612[M]. 18 from Bas Auran area: bed BA14(PU31614[M], PU111311[m]), bed BA16 (PU111281[m]), bed BA17(PU111267[m], PU111268[M?]), bed BA18 (PU111259[M?]), bedBA19 (PU111249[m], PU111251[m], PU111254[M]), bed BA20(PU111147[m], PU111152[M], PU111165[m], PU111166[m],PU111243[m], PU111244[m]), interval BA20-17 (PU111545[m]), bedRA75 (PU111543[m]), bed RA079 (PU111541[M]). 1 from La Blachesection: PU111448[M] (Puma 1975). 6 from La Palud section (Innocen-ti et al. 1990): PU111449[m], PU111450[m], PU111451[M],PU111452[M], PU111453[m?], PU111454[m?].

Origin of the name: From Dinium, the Latin name of Digne,region which yielded the syntypes of the species.

Type specimens: There are four syntypes from the ParvumSubzone of Chaudon (Pl. 1, figs. 1-4). The holotype PU31606 figuredby Sturani (1967, pl. 18, fig.l) is refigured here in Plate 1, figs. la-b. Theparatype PU31607 figured by Sturani (1967, pl. 16, fig. 4) is refigured inPlate 1, figs. 4a-c.

Type horizon: The penultimate limestone bed of the "Marno-calcaires a Cancellophycus auctt.", below the "Terres Noires" Forma-tion. The highest bed of the marly-limestone alternation in Chaudonwas correlated with bed 12 of the Bas Auran Section by Sturani (1967 p.14), and the type horizon of B. diniensis was attributed to the Conver-gens Subzone (equivalent to the Parvum Subzone).

Type locality: Chaudon, Alpes de Haute Provence, South-EastFrance. In the upper course of the Ravin de la Coueste (= Ravin desOzoards of ancient authors), at the place called "le Touert", midwaybetween the village of Chaudon and the Col de Corobin (Col de laClappe of ancient authors), some five hundred metres West of thiscol.

Repository: Museo di Geologia e Paleontologia of the TorinoUniversity (Italy).

Diagnosis: Evolute Bigotites (U/D= 43-54 % in post-juvenilestages up to 115 mm in size) with isodiametric to slightly compressedsection, respectively in macro- and microconchs, and with acute andprominent ribbing.

Measurements:

Abbreviations: M= macroconch, m= microconch, D= shell diameter, H= whorl height, W= whorl width, U= umbilicus, Ni/2= primaries per half whorl,Ne/2= secondaries per half whorl.


Fig. 5 - Cross sections through the phragmocones and body cham-ber (stippled) of Bigotites diniensis Sturani: a) specimenPU31611[M], paratype, Pl. 1, fig. 2; b) specimenPU31606[M], holotype, Pl. 1, fig. 1; c) specimenPU31610[M], topotype, Pl. 1, fig. 3; d) specimenPU31607[M], paratype, Pl. 1, fig. 4; e) specimenPU111243[m], Pl. 1, fig. 5; f) specimen PU111449[m], Pl.1, fig. 6. Scale bar 1 cm.

Description. Adult shells of medium or large size,from microconchs reaching 94 mm of maximal diameter(Pl. 1, fig. 6) to macroconchs surpassing 100 mm andexpected to reach several decimetres in diameter. Nomacroconchs are known possessing the complete bodychamber. Evolute coiling, with values of umbilical ratioranging from 43 to 54%, decreasing in the successivestages of the ontogenic development (Fig. 4; Pl. 1, fig.2), except by egression of the umbilical seam in the adult

body chamber (Fig. 4; Pl. 1, figs. 5-6). Whorls vary insection from low-oval, to subquadrate or subcircularcontour and high-oval, with convex flanks (Fig. 5).The ribbing is sharp and strong. Ribs are rod-like, witha low proportion of simple ribs up to the beginning ofthe body chamber. There are about 15-22 primaries perhalf whorl, most of which biplicate, a few simple. Thesecondaries are less sharp; up to at least 50 mm diameterthey are interrupted and displaced on both sides of amedian smooth line (Pl. 1, fig. 4). The whorls increaseby segments between more or less well marked con-strictions, one or two every half a whorl. Suture linerelatively simple, with suspensive lobe not strongly re-tracted (Fig. 6a).

Discussion and comparisons with related species.Bigotites petri (Nicolesco), the type species of the genus,is the nearest looking Bajocian representative. B. dinien-sis Sturani, however, has a more quadrangular whorlsection and is more evolute.

Distribution. B. diniensis Sturani occurs in theBathonian Parvum Subzone of different localities ofDigne-Castellane region: Chaudon, Bas Auran. LaBlache, La Palud (Puma 1975, Innocenti et al. 1990).Specimens of this species have been found at the stra-tigraphic interval RA079 - RA049 (Fig. 2; levels 21 -14 of Sturani 1967) in Ravin d'Auran Section. Twofragmentary specimens, comparable to this species,have been identified in Cabo Mondego in levels02CM134 and 02CM172 from the Parvum Subzone(Fig. 3).

Fig. 6 - Septal suture of Bigotites: a) B. diniensis Sturani, specimenPU31607[M], paratype, Pl. 1, fig. 4; b) B. mondegoensis sp.nov., specimen 07BV174/3[m], paratype, Pl. 3, fig. 9. Scalebar 2 mm.

PLATE 1

Bathonian specimens of Bigotites diniensis Sturani from the SubalpineBasin (Parvum Subzone, Zigzag Zone). All specimens reproduced atnatural size, except fig. 2 (x0,9). Scale bar 1 cm. Black spot marks thelast septum of the phragmocone. The specimens figured here and insubsequent plates are whitened with magnesium oxide prior tophotography.Fig. 1 - Incomplete phragmocone of macroconch; oral (a) and late-ral (b) views; specimen PU31606[M], holotype, Chaudon (Les

Reichasses). Fig. 2 - Incomplete phragmocone of macroconch; spe-cimen PU31611[M], topotype, Chaudon (Les Reichasses). Fig. 3 -Incomplete phragmocone of macroconch; ventral (a) lateral (b) andoral (c) views; specimen PU31610[M], topotype, Chaudon (LesReichasses). Fig. 4 - Incomplete phragmocone of macroconch; oral(a) lateral (b) and ventral (c) views; specimen PU31607[M], para-type, Chaudon (Les Reichasses). Fig. 5 - Incomplete phragmoconeof microconch; specimen PU111243[m], Bas Auran. Fig. 6 - Micro-conch with complete body chamber; black spot mark the last sep-tum of the phragmocone; specimen PU111449[m], La Palud section(Innocenti et al. 1990).

1�� # ��%�� /��"�� 2�� #� 3��4 �FG

1a 1b2

3a 3b 3c

4a 4b 4c

5 6


Bigotites sturanii sp. nov. [M + m]Pl. 2, figs 1-4

Material: 13 specimens from the Parvum Subzone of Bas Auranregion have been studied: bed BA19 (PU111242[m], PU111253[M]),bed RA75 (PU111544[m]); interval BA19-20 (PU111252[M]); bedBA20 (PU111230[M?]; PU111231[m?], PU111232[M], PU111233[M],PU111234[m], PU111235[M?], PU111236[M?], PU111237[M],PU111238[M]).

Origin of the name: dedicated to Carlo Sturani, palaeontolo-gist in "Dipartimento di Scienze della Terra", Torino University.

Type specimens: specimen PU111233 figured in Plate 2, figs,lab is the holotype. Three paratypes have been figured in Plate 2, figs.2-4, respectively PU111312, PU11242, PU111253.

Type horizon: Bed 075 of Ravin d'Auran Section, Parvum Sub-zone, in Fig. 2. Bed BA20 of the "Marno-calcaires à Cancellophycus", inBas Auran region (after Sturani 1967).

Type locality: Bas Auran, Alpes de Haute Provence, South-EastFrance.

Repository: Museo di Geologia e Paleontologia of the TorinoUniversity (Italy).

Diagnosis: Largely evolute Bigotites (U/D= 45-58 % in post-juvenile stages up to 115 mm in size) macro- and microconchs, withmoderately acute ribbing and well marked constrictions.

Measurements:

Description. Adult shells of medium or large size.No adult conchs are known possessing the completebody chamber. Evolute coiling, with values of umbilicalratio ranging from 45 to 56%, decreasing in the succe-ssive stages of the ontogenic development (Fig. 7; Pl. 2,fig. 1). Whorls vary in section from low-oval to subcir-cular contour, with convex flanks (Figs. 8a-b). The rib-bing is moderately acute and moderately prominent,with a low proportion of simple ribs in the phragmo-cone. There are about 17-21 primaries per half whorl,most of which biplicate, a very few simple. The second-aries are less sharp; up to at least 30 mm diameter theyare interrupted and displaced on both sides of a mediansmooth line. The whorls increase by segments betweenwell marked constrictions, one every half a whorl. Su-ture line relatively simple, with suspensive lobe notstrongly retracted.

Discussion and comparisons with related spe-cies. Bigotites petri (Nicolesco) shows a more acuteand prominent ribbing. B. diniensis Sturani has a morequadrangular whorl section and is less evolute.

Distribution. All syntypes of B. sturanii sp. nov.

Fig. 7 - Bivariate scatter for Bigotitessturanii sp. nov. Plot of um-bilical width (U) and whorlwidth (W) against shell dia-meter (D). H = holotype.


Fig. 8 - Cross sections through the phragmocones of Bigotitessturanii sp. nov. (a-b) and B. mondegoensis sp. nov. (c -f): a) specimen PU111233[M], holotype, Pl. 2, fig. 1; b)specimen PU111253[M], paratype, Pl. 2, fig. 4; c) speci-men 02CM172/115[m], paratype, Pl. 3, fig. 7; d) specimen02CM172/6[m], paratype, Pl. 3, fig. 5; d) specimen02CM172/9[M], paratype, Pl. 3, fig. 2; f) specimen02CM146/2[M], holotype, Pl. 3, fig.l. Scale bar 1 cm.

have been found at the stratigraphic interval RA075 -RA071 (Fig. 2; levels 20 - 19 of Sturani 1967), pertai-ning to the lower part of the Parvum Subzone, in Ravind'Auran Section. So far, at Cabo Mondego no speci-

mens have been found of B. sturanii sp. nov., whichcharacterize lowermost Bathonian strata in Bas Auran.

Bigotites mondegoensis sp. nov. [M + m]Pl. 3, figs 1-10

1987 Planisphinctes acurvatus (Wetzel). Torrens, pl. 4, figs. 1,5,6.2006 Bigotites gr. diniensis Sturani [M]. Fernández-López et al.

2006a, figs. 7a-b.2006 "Bigotites" acurvatus (Wetzel) in Torrens [m]. Fernández-

López et al. 2006a, figs. 8a-c.Material: 18 specimens from the Parvum Subzone of Cabo

Mondego area have been studied. 8 specimens from Cabo MondegoSection 02: 02CM146/2[M], 02CM156/9[m], 02CM168/2[m],02CM172/6[m], 02CM172/9[M], 02CM172/115[m], 02CM176/10[m],02CM176/10[m], 02CM180/5[m]. 10 specimens from Serra de Boa Via-gem Section, around 4 km east of Cabo Mondego: 07BV174/l[m],07BV174/2[m], 07BV174/3[m], 07BV174/4[m], 07BV174/5[m],07BV174/6[m], 07BV174/7[m], 07BV174/8[m], 07BV174/9[m],07BV174/10[M].

Origin of the name: after the Cabo Mondego region, betweenFigueira da Foz and Murtinheira (Portugal) which has yielded thesyntypes of the taxon described.

Type specimens: The holotype is the specimen 02CM146/2figured in Plate 3, fig. 1. Several paratypes have been figured in Plate3, figs. 2-10.

Type horizon: Bed 146 of Section 02, Parvum Subzone, indi-cated in Fig. 3.

Type locality: Section 02 of Cabo Mondego, Portugal (Fernán-dez-López et al. 2006a).

Repository: Fernandez-Lopez & Henriques Collection in "De-partamento de Ciências da Terra e Centro de Geociências", CoimbraUniversity (Portugal).

Diagnosis: Moderately evolute Bigotites (U/D= 40-45% inpost-juvenile stages up to 110 mm in size) macro- and microconchs,with moderately prominent ribbing and weak constrictions.

Measurements:


PLATE 2

Bathonian specimens of Bigotites sturanii nov. sp. (figs. 1-4) and Bigotites mondegoensis sp. nov. (figs. 5-10) from Bas Auran sections (AlpineBasin, Parvum Subzone, Zigzag Zone). Natural size. Scale bar 1 cm.Fig. 1 - Incomplete phragmocone of macroconch; lateral (a) and ventral (b) views; specimen PU111233[M], holotype. Fig. 2 - Incompletephragmocone of macroconch; specimen PU111252[M], paratype. Fig. 3 - Incomplete microconch; specimen PU111242[m], paratype. Fig. 4 -Incomplete phragmocone of microconch; specimen PU111253[m], paratype. Fig. 5 - Incomplete phragmocone of macroconch; specimenPU111312[M]. Fig. 6 - Incomplete phragmocone of microconch; specimen PU111271[m]. Fig. 7 - Incomplete phragmocone of macroconch;specimen PU111317[M]. Fig. 8 - Microconch with complete body chamber; specimen PU111314[m]. Fig. 9 - Incomplete phragmocone ofmicroconch; oral (a) and lateral (b) views; specimen PU111311[m]. Fig. 10 - Incomplete phragmocone of microconch; ventral (a) and lateral (b)views; specimen PU111308[m].


Description. Adult shells of medium to large size,from microconchs reaching 50 mm of maximal diameter(Pl. 3, fig. 4) to macroconchs exceeding 500 mm in dia-meter (Pl. 3, fig. 1). No macroconchs are known dis-playing the complete body chamber. Moderately evo-lute coiling, with values of umbilical ratio ranging from40 to 45%, decreasing in the successive stages of theontogenic development (Fig. 9), except by egression ofthe umbilical seam in the adult body chamber. Whorlsvary in section from low-oval to high oval contour, withconvex flanks (Figs. 8c-f). The ribbing is moderatelyacute and moderately prominent. There are about 16-21 primaries per half whorl, most of which biplicate, avery few simple. The secondaries are less sharp; up to atleast 40 mm diameter they are interrupted and displacedon both sides of a median smooth line. The whorls in-

crease by segments between weak constrictions. Sutureline relatively simple, with suspensive lobe not stronglyretracted (Fig. 6b).

Discussion and comparisons with related spe-cies. Nineteen specimens of this species have beenfound at the stratigraphic interval RA061 - RA039(Fig. 2; levels 17 -13 pars of Sturani 1967) of Ravind'Auran section (Pl. 2, figs. 5-10): bed BA14(PU111308[m], PU111309[m], PU111310[m],PU111311[m], PU111312[M], PU111313[m],PU111314[m], PU111315[m?], PU111316[m?],PU111317[M], PU111318[M], PU111319[m]), bedRA39 (PU111567[m]), bed BA17 (PU111269[m],PU111270[m?], PU111271[m]), bed RA47(PU111550[m], PU111560[m], PU111561[m]). Theyshow the following mensurational values:

Fig. 9 - Bivariate scatter for Bigotitesmondegoensis sp. nov. Plot ofumbilical width (U) andwhorl width (W) againstshell diameter (D). H = ho-lotype.


As showed in Plate 2, figs. 6, 9, 10, the umbilicusvariability of Bas Auran specimens spans 35 to 50 (vs.40-45) and surpasses the relative umbilical values ofsyntypes of B. mondegoensis sp. nov. However, wecould refer these French specimens to the new speciesas, associated with such a more evolute morphotype,some shells (Pl. 2, figs. 7, 8) show geometric shape, weakribbing and constrictions characteristic of B. monde-goensis sp. nov.

Bigotites petri (Nicolesco), B. diniensis Sturani, B.sturanii sp. nov. and Bigotites acurvatus (Wetzel 1937, p.96, pl. 10, fig. 12) show more evolute coiling, moreprominent and rod-like ribs and stronger constrictions.In contrast, microconchs of B. mondegoensis sp. nov. aremore strongly ribbed than Planisphinctes planilobusBuckman (1922 in 1909-30, pl. 327); they may shownodes in the bifurcation of the primary ribs and displaya suspensive lobe not strongly retracted.

Distribution. Syntypes of B. mondegoensis sp.nov. have been found at the stratigraphic interval02CM146 - 02CM180, at the middle part of the ParvumSubzone, in Cabo Mondego region (Fig. 3). Specimensof this moderately evolute species are relatively com-mon in Bas Auran and have been identified at the strati-graphic interval RA061 - RA044, at the middle part ofthe Parvum Subzone. A microconch specimen, possiblyreferable to this new species, has been figured by Dietze& Dietl (2006, pl. 7, fig. 4) as Planisphinctes acurvatusfrom the Convergens Subzone of the Swabian Alb re-gion.

Evolution and biochronostratigraphy

Bigotites seems to be an endemic genus of WestTethyan perisphinctids during early Bathonian. First re-presentatives of the genus occur in the Bajocian Ga-rantiana Biochron of Mediterranean and Submediterra-nean provinces, displaying a high diversity. In contrast,Bathonian ammonite fossil assemblages from WesternTethys include scarce specimens of Bigotites. At theDigne-Castellane region, a chronocline from evolute,with acute and prominent ribbing, and well constrictedforms (including B. sturanii sp. nov. and B. diniensisSturani) to involute forms with blunt, moderately pro-minent ribbing and weak constrictions (including B.mondegoensis sp. nov.) can be recognized. This chrono-cline can be interpreted as a peramorphic result of apalingenetic evolutionary process. Consequently, thespecies B. sturanii sp. nov., B. diniensis Sturani and B.mondegoensis sp. nov. make up a Bathonian peramor-phocline (cf. Dommergues et al. 1986, 1989, Guex et al.2003, Guex 2007). This specialized lineage includes thelast known representatives of the genus and subfamily,

which became extinct during the latest Bathonian Zig-zag Biochron (Macrescens Subzone).

Several authors have suggested that near the Ba-jocian-Bathonian boundary, and shortly before its ownextinction, Bigotites seems to have been at the origin ofat least two main lineages of Bathonian perisphinctids,evolving in different directions: Procerites [M] - Siemi-radzkia [m] through Planisphinctes [m] - Lobosphictes[M] and Zigzagiceras [m] - Procerozigzag [M] throughFranchia [M+m] (cf. Arkell et al. 1957, Arkell 1958 in1951-59, Sturani 1967, Hahn 1969, Mangold 1971a,b,Callomon in Donovan et al. 1981, Sandoval 1983).However, in accordance with the sutural complexity,ornamentation and biochronostratigraphic distribution,it seems more probably that the dimorphic group Plani-sphinctes [m] - Lobosphictes [M] represents a direct de-rivative of some Late Bajocian species of the group ofVermisphinctes [m] - Prorsisphinctes [M], as suggestedby Stephanov (1972), and this dimorphic group may beincluded among the youngest Leptosphinctinae (To-rrens 1987, Innocenti et al. 1990, Fernández-López etal. 2006a).

Further, the phylogenetic derivation of Zigzagi-ceratinae (Buckman, 1920), in particular Zigzagiceras[m] - Procerozigzag [M] and Franchia [M+m], fromBigotites [M+m], as supported by Sturani (1967) andTorrens (1987), or from Phaulozigzag [m] - Lobo-sphinctes? [M], as suggested by Fernández-López et al.(2006a), need to be assessed according to very accuratebiochronological data. Rather than a Bathonian speciesof Bigotites, the immediate predecessor of Franchia[M+m], bearing simple suture line, and Zigzagiceras[m] - Procerozigzag [M], displaying complex suture,may be a more primitive species of Zigzagiceratinae

PLATE 3

Bathonian syntypes of Bigotites mondegoensis sp. nov. from the CaboMondego area (Lusitanian Basin, Parvum Subzone, Zigzag Zone).Natural size. Scale bar 1 cm. Black spot marks the last septum ofthe phragmocone.Fig. 1 - Incomplete phragmocone of macroconch; specimen02CM146/2[M], holotype. Fig. 2 - Incomplete phragmocone ofmacroconch; specimen 02CM172/9[M], paratype. Fig. 3 -Incompletephragmocone of microconch; specimen 02CM180/5[m], paratype.Fig. 4 - Microconch with complete body chamber; specimen07BV174/l[m], paratype. Fig. 5 - Incomplete phragmocone of micro-conch; specimen 02CM172/6[m], paratype. Fig. 6 - Incomplete mi-croconch; specimen 07BV174/8[m], paratype. Fig. 7 - Incompletephragmocone of microconch; specimen 02CM172/115[m], paratype.Fig. 8 - Incomplete phragmocone of microconch; specimen 07BV174/2[m], paratype. Fig. 9 - Incomplete phragmocone of microconch;ventral (a) lateral (b) and oral views; specimen 07BV174/3[m], para-type. Fig. 10 - Microconch with complete body chamber; ventral (a)and lateral (b) views; specimen 07BV174/l[m], paratype.

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showing complex suture line and only a short zigzagstage, without smooth band on external region, deve-loped during the earliest Bathonian (as proposed by Fer-nández-López et al. 2006a, fig. 9). Bearing such primi-tive morphological traits, however, only two incompletespecimens have been so far discovered in the upper partof the Parvum Subzone (Figs. 10-11) in Cabo Mondegoand Bas Auran areas; these primitive morphological fea-tures are present also in "Zigzagiceras torrensi" Sturani(1967, p. 47, pl. 2, fig. 4, pl. 21, fig. 3) and "Zigzagicerastorrensi variecostatum" Sturani (1967, p. 48, pl. 2, fig. 5,pl. 13, fig. 4, pl. 19, fig. 5, pl. 20, fig. 2) from the Ma-crescens Subzone, as well as in two specimens taxono-mically determined as "Zigzagiceras aff. torrensi Sturani[m]" by Dietze and Chandler (1997, pl. 1, figs. 3-4).

Fig. 10 - Protozigzagiceras g. nov. sp. aff. P. torrensi (Sturani).Oral (a) and lateral (b) views. Incomplete phragmoconeof macroconch; specimen PU31694[M]. D = 35.0. H =11.0 (0.31). W = 12.5 (0.36). U = 12.6 (0.36). W/H = 1.14.Ni/2 = 24. Ne/2 = 42. Ne/Ni = 1.8. Scale bar 1 cm.Parvum Subzone (Zigzag Zone, Bathonian). Bas Auran(France).

In order to encompass these species of Zigzagice-ratinae, recorded at least in the Bathonian Parvum, Con-vergens and Macrescens subzones and bearing primitivemorphological traits such as nuclei or early whorls withan incipient and short zigzag stage, and primaries rela-tively dense, we propose a separate genus, the new nameProtozigzagiceras g. nov. (type species, "Zigzagicerastorrensi" Sturani, 1967; Fig. 12) and the following diag-nosis: Macro- and microconchs of small or mediumsize, with planulate and evolute coiling, subcircular tosubrectangular whorl section, nuclei with primaries re-latively dense and a short zigzag stage restricted to theearly whorls, without parabolae, parabolic nodes orsmooth band on external region, and showing relativelycomplex suture line with a slender first lateral lobe.Franchia [M+m], showing a simple suture line, consti-

Fig. 11 - Protozigzagiceras g. nov. sp. aff. P. torrensi (Sturani).).Oral (a) and lateral (b) views x2. Oral (c) and lateral(d) views xl. Incomplete phragmocone of microconch;specimen 04CM183/l[m]. D = 24.0. H = 7.4 (0.31). W =8.9 (0.37). U = 10.9 (0.45). W/H = 1.20. Ni/2 = 19. Scalebar 1 cm. Parvum Subzone (Zigzag Zone, Bathonian).Cabo Mondego (Portugal).

tutes an apomorphic group derived from Protozigzagi-ceras [M+m]. In this phyletic scheme, also the coupleZigzagiceras [m] - Procerozigzag [M] represents a groupderived from Protozigzagiceras g. nov. [M+m] (Fig. 13).This new genus, consequently, should be considered theimmediate predecessor of both mentioned taxa and theoldest Zigzagiceratinae so far known in the Bas Auranarea.

These new palaeontological data about theyoungest members of Bigotitinae and oldest membersof Zigzagiceratinae are of biochronostratigraphic signifi-cance for the subdivision and correlation of the basalBathonian Zigzag Zone. The lowest occurrences of Bi-gotites mondegoensis sp. nov. and Protozigzagiceras g.nov. correspond to two successive biostratigraphicevents allowing to distinguish three successive biohori-zons at the Parvum Subzone in Bas Auran (AlpineBasin) and Cabo Mondego (Lusitanian Basin). Conse-quently, three biostratigraphic units may be named: Di-niensis, Mondegoensis and Protozigzagiceras biohori-zons.


Fig. 12 - Protozigzagiceras g. nov. torrensi (Sturani). Holotype.Lateral (a) and oral (b) views. Incomplete phragmoconeof macroconch; specimen PU31676[M]. At D = 43.0: H= 15.1 (0.35), W = 17.7 (0.41), U = 19.4 (0.45), W/H =1.17, Ne/Ni = 1.7. Scale bar 1 cm. Macrescens Subzone(Zigzag Zone, Bathonian). Bas Auran (France).

The Diniensis Biohorizon is characterized by theoccurrence of Bigotites diniensis representatives and itcorresponds to the lowest part of the Bathonian ZigzagZone. It encompasses the stratigraphic intervals RA085- RA062 (Fig. 2, levels 23 - 18 of Sturani 1967) in Ravind'Auran Section and RB071 - RB054 (Fig. 2, levels 23 -18 of Sturani 1967) in Ravin du Bès Section. It is repre-sented in Cabo Mondego by the stratigraphic intervals02CM123 - 02CM145 in the Section 02 and FC1- FC17in the Section 90 as illustrated in Fig. 3.

The Mondegoensis Biohorizon is defined by thelowest occurrence of Bigotites mondegoensis sp. nov.representatives. It encompass the stratigraphic intervalsRA061 - RA044 (Fig. 2, levels 17 -14 of Sturani 1967) inRavin d'Auran Section and RB053 - RB034 (Fig. 2, le-vels 17 - 14 of Sturani 1967) in Ravin du Bès Section,taking into account the occurrence of B. mondegoensissp. nov. at the level RA061. It is represented in CaboMondego by the stratigraphic intervals 02CM146 -02CM182 in the Section 02 and FC18 - FC43 in theSection 90, as illustrated in Fig. 3, taking into accountthe occurrence of B. mondegoensis sp. nov. at the level02CM146.

The Protozigzagiceras Biohorizon is defined bythe lowest occurrence of Zigzagiceratinae representa-tives, in particular Franchia [M+m] and Protozigzagi-ceras [M+m]. It encompasses the stratigraphic inter-vals RA043 - RA034 (Fig. 2, level 13 of Sturani1967) in Ravin d'Auran Section and RB033 - RB026(level 13 of Sturani 1967) in Ravin du Bès Section,taking into account the occurrence of Franchia fromRA035 and Protozigzagiceras g. nov. from level 13.The Protozigzagiceras Biohorizon is represented inCabo Mondego by the stratigraphic intervals02CM183 - 02CM198 in the Section 02 and FC44 -

Fig. 13 - Phylogenetic scheme of the first genera of Zigzagicerati-nae, originated and diversified from Leptosphinctinaeduring latest Parvum Subzone (Zigzag Zone, Early Batho-nian), before the extinction of Bigotites.

FD11 in the Section 90 as illustrated in Fig. 3, takinginto account the occurrence of Protozigzagiceras g.nov. at the level 04CM183.

Conclusions

Two new species of Bigotites are described andassigned to the subfamily Bigotitinae (Westermann1956) and family Perisphinctidae (Steinmann 1890): B.sturanii sp. nov. and B. mondegoensis sp. nov. The spe-cies B. sturanii sp. nov., B. diniensis Sturani and B.mondegoensis sp. nov. make up a Bathonian peramor-phocline. Bigotites, the last West Tethyan genus of thesubfamily Bigotitinae, became extinct during the ZigzagBiochron (Macrescens Subzone) lacking of known des-cendent taxa. A separate genus of the subfamily Zigza-giceratinae (Buckman 1920), Protozigzagiceras g.nov., is proposed to encompass P. torrensi (Sturani)and similar species, bearing a short zigzag stage andprimaries relatively dense in the early whorls, asso-ciated with relatively complex suture lines, recordedat least in the Parvum, Convergens and Macrescenssubzones. The first genera of Zigzagiceratinae origi-


nated and diversified from Leptosphinctinae, during theZigzag Biochron (Parvum Subzone) and before the ex-tinction of Bigotites.

These new palaeontological data about theyoungest members of Bigotitinae and oldest membersof Zigzagiceratinae are relevant in understanding theevolution of the West Tethyan Perisphinctidae duringearliest Bathonian. These new taxa of Perisphinctidaeare of particular relevance for the biochronostrati-graphic subdivision and correlation of the basal Batho-nian Zigzag Zone. Three successive biohorizons can

be recognized in the Parvum Subzone at Bas Auran(Alpine Basin) and Cabo Mondego (Lusitanian Basin):Diniensis, Mondegoensis and Protozigzagiceras bio-horizons.

Such biochronostratigraphic results are of bio-chronostratigraphic importance for the subdivisionand correlation of the base of the Zigzag Zone and willassume a basilar role in the construction of the proposalof the basal boundary stratotype of the Bathonian Stage.The G.S.S.P, formal proposal is in progress under theaccordance of the International Subcommission of theJurassic Stratigraphy.

Acknowledgements. The authors wish to express their acknowl-edgement to B. Cavallo, A. Defaveri, M. Guiomar, D. Olivero, M.Pavia, P. Rosso for help in the sampling of the Bas Auran sections,and V. Dietze and A. Galácz for the critical reading of the manuscriptand suggestions made. This work has been funded by the CGL2004 -0694/BTE (MEC - CSIC) Project (S.R. Fernández-López) and theTorino University Grants 2006, 2007 (G. Pavia).

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Documents

New Early Bathonian Bigotitinae and Zigzagiceratinae ......New Early Bathonian Zigzagiceratinae Bigotitinae and (Ammonoidea, Middle Jurassic) 385 &Mitt a1995,1998,2000 ).Bigotites,Bajocisphinctes