Acta Geologica Polonica, Vol. 66 (2016), No. 2, pp. 175–204 DOI: 10.1515/agp-2016-0008 Systematic palaeontology of the Perisphinctoidea in the Jurassic/Cretaceous boundary interval at Le Chouet (Drôme, France), and its implications for biostratigraphy CAMILLE FRAU1, LUC G. BULOT2, WILLIAM A.P. WIMBLEDON3 and CHRISTINA IFRIM4 1Groupement d’Intérêt Paléontologique, Science et Exposition, 60 bd Georges Richard, 83000 Toulon, France. E-mail: [email protected] 2UM 34 Aix-Marseille Université ; CNRS (UMR 7330) ; IRD (UMR 161), Centre Saint-Charles, Case 67, 3 Place Victor Hugo, 13331 Marseille Cedex 03, France. E-mail: [email protected] 3School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, United Kingdom. E-mail: [email protected] 4Institut für Geowissenschaften, Ruprecht-Karls-Universität, Im Neuenheimer Feld 234, 69120 Heidelberg, Germany. E-mail: [email protected] ABSTRACT: Frau, C., Bulot, L.G., Wimbledon, W.A.P. and Ifrim, C. 2016. Systematic palaeontology of the Perisphinctoidea in the Jurassic/Cretaceous boundary interval at Le Chouet (Drôme, France), and its implications for biostratigraphy Acta Geologica Polonica, 66 (2), 175–204. Warszawa. This study describes ammonite taxa of the Perisphinctoidea in the Jurassic/Cretaceous boundary interval at Le Chouet (Drôme, France). Emphasis is placed on new and poorly known Himalayitidae, Neocomitidae and Olcostephanidae from the lower part of the Jacobi Zone auctorum. Significant results relate the introduction of Lopeziceras gen. nov., grouping himalayitid-like forms with two rows of tubercles, and Praedalmasiceras gen. nov., grouping the early Berri- asian Dalmasiceras taxa. Study of the ontogenetic sequences of both genera show that they were derived from late Tithonian Himalayitidae. This supports the distinction between the subfamilies Himalayitinae and Dalmasiceratidae subfam. nov. Content, variation, dimorphism and vertical range of the Neocomitidae Berriasella, Pseudoneocomites, Elenaella and Delphinella are discussed. A conservative use of the Olcostephanidae Proniceras is followed herein. Keywords: Ammonites; Berriasian; Cretaceous; Biostratigraphy; Le Chouet; France. INTRODUCTION ian. Herein we focus on the Perisphinctoidea taxa that were originally reported by Wimbledon et al. (2013) This contribution completes the systematic descrip- from the Jacobi Zone auctorum. tion of the ammonite faunas collected across the Juras- sic/Cretaceous boundary at Le Chouet (Les Près, Drôme, GEOLOGICAL SETTING southeast France) as part of the work of the Berriasian Working Group of the International Subcommission on The reader is referred to the work of Wimbledon et Cretaceous Stratigraphy (I.S.C.S, I.U.G.S.). Previous ar- al. (2013) for further details about the lithology, bios- ticles (Bulot et al. 2014; Frau et al. 2015) concentrated tratigraphy (ammonites, calpionellids and calcareous on the families Ataxioceratidae Buckman, 1921, Hi- nannofossils) and magnetostratigraphy documented malayitidae Spath, 1925 and the first representatives of at Le Chouet. To avoid redundancy, we chose to syn- the Neocomitidae Salfeld, 1921 from the upper Tithon- thesize the data discussed herein on Text-fig. 1. The 176 CAMILLE FRAU ET AL. bed numbers used herein follow those in Wimbledon REPOSITORIES OF SPECIMENS et al. (2013). By comparison with the original ammonite distri- All specimens studied are deposited in the Frau/Bu- bution published by Wimbledon et al. (2013, fig. 12), lot collection at the Musée Paléontologique de several changes have been made by Bulot et al. (2014) Provence (MPP) of Aix-Marseille Université. The fol- and Frau et al. (2015), to which the reader is referred. lowing abbreviations indicate the repository of speci- It should be noted that the previous report of Dalma- mens mentioned in the text: siceras cf. crassicostatum Djanélidzé, 1922a in bed 97 FSL: University of Claude Bernard; Lyon-I. was based on a poorly preserved specimen, that is herein UJF-ID: University of Grenoble. referred to Praedalmasiceras gen. nov. progenitor (Op- MNHN.F: Muséum National d’Histoire Naturelles de pel in Zittel, 1868). A re-investigation in the upper part Paris. of the section allowed the first representatives of the BSPM: Bayerische Staatssammlung für Paläontologie genus Delphinella Le Hégarat, 1971 to be found, in und Geologie, Münich. beds 113 to 120, and of Berriasella of the oppeli (Kil- CNIGR: F.N. Chernyshev Central Research Geologi- ian, 1889) – moreti Mazenot, 1939 group in bed 120. cal Museum, St. Petersburg. Text-fig. 1. Locality map of Le Chouet (Les Près, Drôme, SE France) and integrated stratigraphy and vertical range of the Perisphinctoidea taxa studied in this work. Grey line indicates the E. cularense biohorizon sensu Tavera et al. (1994) 177 PERISPHINCTOIDEA ACROSS THE JURASSIC/CRETACEOUS BOUNDARY IN FRANCE SYSTEMATIC PALAEONTOLOGY velopment of prominent tubercles. Umbilical tubercles radially elongated. Microconchs smaller than macro- All dimensions of specimens are given in mil- conchs and never developing a macroconch stage. Su- limetres: Dmax = larger measurable diameter, D = ture line markedly dissected with dissymmetric lateral adult diameter, U = umbilical diameter; Wh = whorl lobe. height, Wb = Whorl breath. Ratios such as U/D, Wh/D and Wb/D are dimensions as a percentage of the adult DISCUSSION: Mazenot (1939, p. 33) referred Am- diameter. In synonymy, we distinguished the macro- monites chaperi Pictet, 1868 to the genus Berriasella conch and microconch specimens. Uhlig, 1905, and more specifically to his group of All specimens are coated with ammonium chloride. “Berriaselles à deux rangs de tubercules”. Recent lit- erature is highly confusing regarding the generic treat- ment of A. chaperi. Following Le Hégarat (1973), Order Ammonoidea Zittel, 1884 most authors included A. chaperi in Malbosiceras Suborder Ammonitina Hyatt, 1889 Grigorieva, 1928 (type species: A. malbosi Pictet, Family Himalayitidae Spath, 1925 1867); a view that is consistent with Mazenot’s origi- Family Himalayitinae Spath, 1925 nal opinion. Besides, it should be noted that some au- Genus Lopeziceras gen. nov. thors regarded A. chaperi as a Protacanthodiscus (= Chapericeras Hoedemaeker, 1981 nomen nudum) Spath, 1925 (Patrulius 1969; Lefeld 1974; Boughdiri 1994). DERIVATION OF THE NAME: Named in honour of Hoedemaeker (1981, p. 245) introduced a new Jean-Pierre, Martine and Emmanuel Lopez, the owner genus Chapericeras for early Berriasian berriasellids of the Le Chouet hameau, for their hospitality and with two rows of tubercles (A. chaperi, Hoplites tarini friendship during our fieldwork seasons. Kilian, 1889, Berriasella aizyensis Mazenot, 1939 and Berriasella aspera Mazenot, 1939) that were placed in TYPES SPECIES: Ammonites chaperi Pictet, 1868. It Malbosiceras and Mazenoticeras Nikolov, 1966, by Le should be noted that Chapericeras was introduced by Hégarat (1973, table 5). Ammonites chaperi was des- Hoedemaeker (1981) with A. chaperi as the type ignated as the type species, but the genus lacks a for- species. As pointed out by Klein (2005), Chapericeras mal description and therefore is a nomen nudum is a nomen nudum since it does not fulfil article 13.1.1 (I.C.Z.N. Code article 13.1.1). Nevertheless, it is ob- of the I.C.Z.N. Code. vious that the ontogenetic sequence of the early Berri- asian forms with lateral and umbilical tubercles, gen- DIAGNOSIS: Small to medium size, dimorphic Hi- erally included in Malbosiceras and Mazenoticeras, do malayitidae with compressed planulate shell. Whorl not match that of the type species of these genera, e.g. section subrectangular with flat or flattened venter at Malbosiceras malbosi (Pictet, 1867) and Mazeno- all stages of ontogeny. Deep ventral groove on phrag- ticeras broussei (Mazenot, 1939). The same is true for mocone evolving towards a ventral band in adult. Or- Protacanthodiscus and its type species Protacan- namentation composed of up to four stages: (i) hi- thodiscus andreaei (Kilian, 1889), recently revised by malayitid stage (with prorsiradiate, simple, rigid ribs Frau et al. (2015). which sometimes bear minute lateral tubercles on the The re-examination of the type material supple- innermost whorls) (D < 20 mm); (ii) intermediate mented by the detailed analysis of the material col- stage (with rigid to dense, straight to prorsiradiate, bi- lected at Le Chouet (see discussion below) showed us furcate ribs at diameters between 20 mm and 50 mm. that Hoplites tarini, Hoplites macphersoni Kilian, Branches of ribs projected forward on upper flank and 1889, Hoplites vasseuri Kilian, 1889, Hoplites castroi ending as pinched tubercles on ventral shoulder, some- Kilian, 1889, Berriasella aspera and Berriasella times denser with sporadic single and fasciculate ribs); aizyensis are junior subjective synonyms of Ammonites (iii) subadult stage (with alternating bi- and trifurcate chaperi. and this motivates us to introduce Lopez- primary ribs connected, more or less, to variable num- iceras gen. nov. ber of intercalatories. Primary ribs thicken on umbili- Dalmasiceras aristidis Mazenot, 1939 should also cal shoulder and at the furcation point, forming pro- be included in Lopeziceras gen. nov., since it shares gressively lateral tubercles) (D < 70 mm); (iv) great affinities with L. chaperi, from which it can only macroconch stage (with ribbing stronger on body be distinguished by the occurrence of minute lateral tu- chamber, ribs spaced with attenuation at mid flank. bercles on