Taxonomic and stratigraphic remarks on Placites urlichsi Bizzarini, Pompeckjites layeri (Hauer), Carnites floridus (Wulfen) and Sageceras haidingeri (Hauer)

Abstract

Investigations of an Lower Carnian Wettersteinkalk ammonoid fauna found in the Hochobir massif (Carinthia/Austria) gave rise to problems in the taxonomic relationship within the Triassic ammonoid Family Pinacoceratidae. The morphological parameters of the ammonoid genus Pompeckjites are rather unclear. Morphological variation of at least two ammonoid species as Pompeckjites layeri Hauer on one end, Placites urlichsi Bizzarini on the other end have to be take into account. Numerous field surveys, studies and excavations on upper Wettersteinkalk sites within the Karavank Mountains and Hallstatt-facies sites in the Northern Calcareous Alps were implemented and compared with the reference sites in the Dolomites. As a consequence of our investigations, the Hochobir Wettersteinkalk ammonite assemblage is thought to be equivalent in time to the ammonoid fauna of the Upper San Cassian Formation. The frequent occurrence of the Julian (Lower Carnian) ammonoid Placites urlichsi Bizzarini may be a powerful tool in field investigations for a refined correlation of the upper Wettersteinkalk reef limestone to the coeval basinal facies of the Upper San Cassian Formation (Lower Carnian/upper Trachyceras aonoides Zone). As a result of this study Placites urlichsi was included in the genus Pompeckjites. This paper could be an attempt to recognize the differences in juvenile forms of Pompeckjites layeri and Placites urlichsi and other similar disciform ammonoid genera like Carnites floridus and Sageceras sp. based on suture lines, polished transversal-sections and morphological features.