D'orbigny, 1845
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Palaeodiversity 1: 133–140; Stuttgart, 30.12.2008. 133 Juraphyllites mimatensis (D’ORBIGNY , 1845) (Ammonoidea: Phylloceratida), a Tethyan immigrant in the Upper Pliensbachian of Franconia (Jurassic, Southern Germany) HELMUT KEUPP & GÜNTER SC H WEIGERT Abstract Two well-preserved small-sized specimens of phylloceratoid ammonites are reported from the Late Pliensba- chian Spinatum Zone of Franconia. They are assigned to Juraphyllites (cf.) mimatensis (D’ORBIGNY , 1845) and re- garded as Tethyan immigrants. Due to their very similar early ontogenetic stages it seems impossible to distinguish tiny juveniles of Juraphyllites mimatensis (D’ORBIGNY , 1845) from those of contemporaneous Meneghiniceras exi- mium (V. HAUER ). Keywords: Phylloceratina, Early Jurassic, palaeobiogeography, immigration, Franconia, Germany. Zusammenfassung Zwei gut erhaltene kleinwüchsige Exemplare phylloceratoider Ammoniten werden aus der Spinatum-Zone des Ober-Pliensbachium von Franken beschrieben. Sie werden zu Juraphyllites (cf.) mimatensis (D’ORBIGNY , 1845) ge- stellt und als tethyale Einwanderer angesehen. Wegen ihrer sehr ähnlichen frühontogenetischen Stadien erscheint es praktisch unmöglich, sehr kleine Individuen von Juraphyllites mimatensis (D’ORBIGNY , 1845) von solchen des gleich zeitig vorkommenden Meneghiniceras eximium (V. HAUER ) zu unterscheiden. 1. Introduction 2. Provenance of the studied material The dark claystones of the Upper Pliensbachian The Middle Liassic Amaltheenton Formation (Upper Amaltheenton Formation of Southern Germany, particu- Pliensbachian) of Franconia crops out in the western fore- larly of Franconia, yield a relatively low diverse ammonite land of the Northern and Middle Franconian Alb and is fauna, generally dominated by the Subboreal family of the exposed in several clay-pits. Today most of them are aban- Amaltheidae. Rare immigrations of various Tethyan or doned (e. g., Kalchreuth: RIC H TER 1993; Marloffstein: Euroboreal ammonite taxa seem to be restricted to short PLÜC K EBAUM 1985; SC H MIDT KALER 2004; Reichenschwand: phases of sea level highstands, as recently pointed out by HAARLÄNDER 1961; Schnaittach: VO IGT 1968; Unterstür- SC H WEIGERT (2005) and KEUPP & SC ho BERT (2008). These mig: RIC H TER 1977, 2000; PLÜC K EBAUM 1985). The only exotic ammonites attracted special attention and were not- still active clay-pit of the Liapor Company in this area lies ed by numerous former authors (see SC H WEIGERT 2005 for in the Oberfranken district, about 1 km SSE of Butten- references; MAI S C H 2007). heim. This clay-pit substitutes the former clay-pit of Un- Soon after the publication of some findings of juvenile terstürmig which was located only 1.5 km to the south. phylloceratids from the clay-pit of Buttenheim in Franco- The latter outcrop became popular by the occurrence of nia (KEUPP & SC ho BERT 2008), two somewhat larger speci- well-preserved white-coloured amaltheids bearing their mens were found by the amateur collector Joh ANN SC ho original aragonitic shells (DULL O 1981). The stratigraphic BERT (Hirschaid). Both specimens exhibit diameters of 30 sections exposed in both clay-pits are almost identical and 43 mm, respectively, and are assigned to the unkeeled (RIC H TER 2003; HO FFMANN et al. 2007). In the former clay- juraphyllitid taxon Juraphyllites (cf.) mimatensis pit of Unterstürmig especially the upper part of the Spina- (D’ORBIGNY , 1845). This taxon, which is of Tethyan origin, tum Zone of the Upper Pliensbachian and the Lower Toar- was previously unknown from the Pliensbachian of South- cian was exposed; only from time to time expanding ern Germany. The new findings, which question earlier downwards to the Apyrenum Subzone of the Upper Pliens- determinations of juveniles, stimulated this study. bachian. In contrast, the clay-pit near Buttenheim exposes primarily beds of the Gibbosus and Apyrenum subzones, Acknowledgements expanding upwards during the progress of the last two Joh ANN SC ho BERT (Hirschaid) is thanked for his generous donation of his interesting findings for this study. The journals’ years to the upper part of the Spinatum Zone and the base referees JO AC H IM BLAU (Gießen) and CH RI S TIAN MEI S TER (Genève) of the Lower Toarcian Posidonia Shale (Fig. 1). Also in the are thanked for their advice and suggestions. clay-pit of Buttenheim well-preserved ammonites occur 134 PALAE O DIVER S ITY 1, 2008 Fig. 1. Geographical position und section of the clay pit near Buttenheim. The horizon where the Juraphyllites mimatensis (D’ORBIGNY , 1845) illustrated in Fig. 3 was found is marked by an asterisk. K EUPP & S C H WEIGERT , JURAPHYLLITES MIMATENSIS IN so UT H ERN GERMANY 135 with their primary aragonitic shells, sometimes, especially Remarks. – In several recent publications dealing within beds of the Apyrenum Subzone, showing a colour with Juraphyllitidae, the genera Meneghiniceras HYATT , pattern formed by dark, sub-concentric dotted spiral lirae 1900, Harpophylloceras SPAT H , 1927, and Juraphyllites (RIC H TER 2003; KEUPP 2005; KEUPP & SC ho BERT 2008). MÜLLER , 1939 were considered to be synonymous or of Within a collection of ca. 17.000 ammonites from the subgeneric rank (e. g., MEI S TER 1989; MACC H I O NI 2001; Upper Pliensbachian of Buttenheim there are only less than MACC H I O NI in PAVIA & CRE S TA 2002; MACC H I O NI & MEI S TER ten phylloceratids, most of them juveniles. The first phyl- 2003). Indeed, Harpophylloceras can be easily included in loceratid specimen described in this study was originally Meneghiniceras (SC H WEIGERT 2005), but the latter differs included in a small calcareous concretion. It was collected from other Juraphyllitidae by the presence of a keel in the by J. SC ho BERT (Hirschaid) in early March 2008 in the adult stage. Therefore we maintain the genus Juraphyllites higher section of the clay-pit of Buttenheim. It came from for the forms lacking a keel. undisturbed sediments 20 cm below the main fossiliferous horizon of the upper Spinatum Zone (= Hawskerense Sub- zone). The predominant ammonites of this level are the Juraphyllites mimatensis (D’ORBIGNY , 1845) different morphotypes of Pleuroceras spinatum (BRU Figs. 2–3, ? 4 GUIÈRE ) which occur mainly in the directly overlying beds. * 1845 Ammonites Mimatensis, D’ORBIGNY , 1844. – C ho The second specimen was found loose also by J. S D’ORBIGNY , p. 344, pl. 110, figs. 4–6. BERT , together with dispersedly distributed amaltheids of 1856 Ammonites Mimatensis, D’ORB ., 1845. – OPPEL , the Apyrenum Subzone in early spring 2007. p. 252. The studied ammonites are housed in the Institute of 1929 Rhacophyllites spec. ex aff. mimatensis ORB . – GUGENBERGER , p. 255, pl. 10, fig. 5, pl. 11, fig. 6, Geological Sciences, Freie Universität Berlin, collection pl.12, fig. 10. KEUPP , numbers MAn-3111 and MAn-3115. ? 1930 Rhacophyllites cf. mimatensis (D’ORBIGNY ). – MO NE S TIER , p. 8, pl. 11, fig. 1. 1934 Rhacophyllites mimatensis (D’ORBIGNY ). – MO NE S 3. Systematic palaeontology TIER , p. 16, pl. 5, figs. 17, 19, 24–30, 34–35. 1934 Rhacophyllites libertus (GEMMELLAR O ). – MO NE S TIER , p. 17, pl. 6, figs. 1, 6. Suborder Phylloceratina AR K ELL , 1950 ? 1934 Rhacophyllites mimatensis (D’ORBIGNY ) var. vin- Superfamily Phylloceratoidea ZITTEL , 1884 ensis. – MO NE S TIER , p. 17, pl. 5, figs. 36–37. Family Juraphyllitidae AR K ELL , 1950 pars 1963 Rhacophyllites mimatensis (D’ORBIGNY ). – SGUA Z zo NI , p. 46, pl. 21, fig. 10, non fig. 4. ? 1970 Juraphyllites libertus (GEMMELLAR O ). – BRAMBIL Genus Juraphyllites MÜLLER , 1939 LA , p. 262, pl. 55, fig. 2. 1977 Juraphyllites mimatensis (D’ORBIGNY ). – WIEDEN Type species: Phylloceras diopsis GEMMELLAR O , 1884. MAYER , p. 36, pl. 1, figs. 3, 8b. Fig. 2. Juraphyllites mimatensis (D’ORBIGNY , 1845), holotype, lost; reproduction of D’ORBIGNY ’s illustration; Upper Pliensbachian; Mt. Mimat, Dept. Lozère, France. Diameter 42 mm. 136 PALAE O DIVER S ITY 1, 2008 Fig. 3. Juraphyllites mimatensis (D’ORBIGNY , 1845); Pliensbachian, upper part of the Spinatum Zone, Hawskerense Subzone; But- tenheim, northern Bavaria, Germany; MAn-3111. 29.2 mm in diameter. – A. Lateral view. B. Ventral view. C. Oblique view showing the large missing shell fragment due to a presumed crustacean attack. D. Close-up of Fig. 3A showing the suture line. 1989 Juraphyllites mimatensis (D’ORBIGNY ). – MEI S TER , France and named after the type locality, the Mont Mimat south p. 30, pl. 2, fig. 10, pl. 3, figs. 4, 17a, b. of Mende (Dept. Lozère). Because of the apparent lost of the 1994 Juraphyllites mimatensis (D’ORBIGNY ). – JO LY in type specimen originally housed in the RENAUX collection in FI S C H ER , p. 98, fig. 31, pl. 27, figs. 3a–c, 4. Montpellier, JO LY (in FI S C H ER 1994) designated a neotype, a 2000 Juraphyllites mimatensis (D’ORBIGNY , 1845). – mould coming from the middle Upper Pliensbachian (Margari- JO LY , p. 29–30, figs. 41–43, pl. 3, fig. 6a, b. tatus Zone) of Mt. Guilhaumard near Tournadous. This neotype, however, is much less complete than the lost holotype, following Types: Juraphyllites mimatensis was first described by the illustration by D’ORBIGNY (1845) (Fig. 2). D‘ORBIGNY (1865) from the Upper Pliensbachian of Southern Occur rence: From different localities of the Grands Caus- K EUPP & S C H WEIGERT , JURAPHYLLITES MIMATENSIS IN so UT H ERN GERMANY 137 Tab. 1. Measurements of specimens related to Juraphyllites mimatensis (d = diameter; u = umbilicus; wh = whorl height; ww = whorl width). d u u/d wh wh/d ww ww/d ww/wh specimen (mm) (mm) (%) (mm) (%) (mm) (%) (%) MAn-3111 29.2 (Fig. 3) 24.2 6.6 27 11.6 48 7.9 32.5 68 MAn-3115 43 6.8 15.8 24.0 56 12.1 28 50 (Fig. 4) Neotype 34.5 10 29 16 46 9.8 28 61 (JO LY in FI S C H ER 1994) Coll. JO LY no. 99-1 Cornus 27.3 8.8 32 12.3 45 7.3 27 59 (JO LY 2000) Coll.