Robert Weis

Belemnites from the Upper Pliensbachian and the Toarcian (Lower Jurassic) of Tournadous (Causses, France).

Jurassic belemnites represent promising proxies especially for palaeoecological and also palaeobiogeographical reconstructions. However, basic knowledge on taxonomic composition, biostratigraphy and diversity of Early Jurassic belemnites is still dramatically low, especially for France. The present study provides new data on belemnites from the southern part of the Northwest European Province. More than 700 specimens have been collected along the Tournadous section in the Causses Basin (Southern France); they represent ten genera and 30 species belonging to Hastitidae, Megateuthididae, Passaloteuthididae, and Salpingoteuthididae. Furthermore, numerous ammonites have been collected, allowing to establish a standard chronostratigraphical scheme of the studied section and thus to assign, for the first time, a precise chronostratigraphical distribution to the Early Jurassic belemnites of Southern France. The analysis of belemnite diversity and its variations along the section compared to the well-known fauna of the northern part of the Northwest European province (Germany and England) open interesting prospective for belemnites palaeobiogeography.

Systematics and evolutionary implications of Early Jurassic belemnites from the Peri-Mediterranean Tethys

The systematic study of new belemnite assemblages from the Central Apennines and western Sicily revealed several new taxa for Italy. The specimens originate from Lower Jurassic sediments (Sinemurian–Toarcian), and their exact stratigraphic occurrence can be established by accompanying ammonite assemblages. The systematic analysis allows six genera of the suborder Belemnitina to be recognised (Subhastites, Passaloteuthis, Pseudohastites, Bairstowius, Cuspiteuthis, Megateuthis). The coeval occurrence of heterogeneous canaliculate belemnites (with alveolar grooves) was unexpected; their partially incomplete preservation does not allow assigning them safely to any existing genus, with the exception of a well-preserved specimen of Pachybelemnopsis sp. (with phragmocone, protoconch, and siphuncle). This represents the earliest known record of a belemnopseine belemnite. The Italian canaliculate belemnites are tentatively compared with canaliculate belemnites from the European Peri-Tethys, Japan, and New Zealand. A direct comparison is, however, hampered by the incomplete preservation of most of the herein reported specimens. The records of canaliculate belemnites in the Early Jurassic of Italy show remarkably heterogeneous rostrum morphologies, indicating an earlier diversification in belemnites than previously assumed.KurzfassungDie Untersuchungen zur Systematik neuer Belemnitenfunde aus dem zentralen Apennin und dem westlichen Sizilien erbrachten mehrere neue Taxa für Italien. Die untersuchten Exemplare entstammen Ablagerungen des Unteren Juras (Sinemurium–Toarcium), ihre genaue stratigraphische Position kann anhand begleitender Ammonitenfaunen festgestellt werden. Anhand der systematischen Analyse werden sechs Gattungen der Unterordnung Belemnitina nachgewiesen (Subhastites, Passaloteuthis, Pseudohastites, Bairstowius, Cuspiteuthis, Megateuthis). Das zeitgleiche Auftreten kanalikulater Belemniten mit Alveolarfurchen ist überraschend; ihre größtenteils unvollständige Erhaltung erlaubt es jedoch nicht, sie sicher einer bekannten Gattung zuzuordnen, mit Ausnahme eines gut erhaltenen Exemplars von Pachybelemnopsis sp. (mit Phragmokon, Protoconch und Sipho). Dieser Fund stellt den derzeit ältesten Nachweis der Unterordnung Belemnopseina dar. Die kanalikulaten Belemniten aus Italien werden mit Funden aus Ost-Asien, Neuseeland und einigen wenig bekannten Funden der Europäischen Peri-Tethys verglichen. Ein weiterführender Vergleich wird jedoch dadurch erschwert, dass die genaue Position der Alveolarfurche (ventral oder dorsal) bei den meisten hier beschriebenen Stücken nicht nachvollzogen werden kann. Die Funde kanalikulater Belemniten im Unteren Jura Italiens zeichnen sich insgesamt durch eine hohe Heterogenität bei der Rostrum-Morphologie und der Position der Alveolarfurchen aus, und zeugen von einer höheren Diversität der frühen Belemniten als in vorangehenden Studien angenommen.

Lower Jurassic (Pliensbachian-Toarcian) belemnites from Fresney-le-Puceux (Calvados, France): taxonomy, chronostratigraphy and diversity

ABSTRACT The present paper deals with the systematic description of the belemnite assemblages from the Lower Jurassic, collected at the Roche Blain quarry, Fresney-le-Puceux. In spite of the reduced thickness of the succession at Fresney-le-Puceux, 13 successive ammonite chronozones could be documented in this rather unique outcrop situation in mainland Europe. Twelve genera and 26 species of belemnites belonging to the Passaloteuthididae, Hastitidae, Megateuthididae, Salpingoteuthididae, and family incertae sedis are described and illustrated herein. The stratigraphical range of the belemnites is correlated with the standard ammonite zonation, using the chronozone concept: the described specimens range from the lower Pliensbachian (Davoei Chronozone) to the uppermost Toarcian (Aalensis Chronozone) while ammonites indicate the Aalenian (Murchisonae Chronozone) to be present too, but these beds delivered no identifiable belemnites so far. The belemnite diversity from Normandy is compared to data from coeval outcrops in Western and Central Europe.