Kimmeridgian and early Tithonian cephalopods from the Kisújbánya Limestone Formation, Zengővárkony (Mecsek Mountains, southern Hungary), their faunal composition, palaeobiogeographic affinities, and taphonomic character

Abstract

A new collection at Zengővárkony (Mecsek Mountains, Hungary) provided a rich and diverse but poorly preserved cephalopod-dominated fossil assemblage representing the Kimmeridgian and the lower Tithonian. The material came from mixed scree, soil, and amongst roots affected by weathering processes having been exposed to the elements for a long time. The nautiloid Pseudaganides strambergensis is the first record from the Mecsek Mountains. Due to the weathering, the ammonite fauna consists of mainly fragmentary and dissolved individuals that comprises 528 specimens belonging to 34 species and 30 genera out of which 20 species and 15 genera are reported for the first time from the Mecsek Mountains. The fauna includes specimens of known taxa. No new taxa are introduced. Based on the comparison with other faunas, this assemblage most closely resembles the fauna of the Venetian Alps (Italy). Additional faunal elements include aptychi (Laevaptychus latus, Lamellaptychus murocostatus), belemnites (Hibolithes semisulcatus), and an indetermined brachiopod. The first record of Spiraserpula spirolinites, an encrusting fossil polychaete preserved on the internal mould of a Taramelliceras shell fragment indicates favourable bottom conditions for the epifauna. The presence of Aspidoceras caletanum, Gravesia aff. gigas, and Pseudowaagenia inerme indicates faunal connections with the Submediterranean Province of the Tethys, which is in line with the tectonic and palaeogeographical position of the Mecsek Zone during the Late Jurassic. The ammonite assemblage represents elements of five Tethysian ammonite zones of the Kimmeridgian and Tithonian. The lower Kimmeridgian Herbichi Zone is indicated by Streblites tenuilobatus and Praesimoceras herbichi. The upper Kimmeridgian Acanthicum Zone is indicated by Aspidoceras acanthicum, and the Cavouri Zone by Mesosimoceras cavouri and Aspidoceras caletanum. The upper Kimmeridgian Beckeri Zone is suggested by Hybonoticeras pressulum and Pseudowaagenia inerme. Whereas Gravesia aff. gigas, Lithacoceras aff. siliceum, and Malagasites? denseplicatus are faunal elements characterising the Early Tithonian Hybonotum Zone. Phylloceratid and lytoceratid specimens account only for 12% of the fauna, while the majority of the specimens belong to the Oppeliidae and Ataxioceratidae (60%).