Medusae are widespread and form blooms in many contemporary marine environments. Despite their presumed abundance in ancient oceans, their fossil record is comparatively rare. A review paper (Young & Hagadorn, 2020) listed only 13 confirmed deposits of fossil medusae associated with specific paleoenvironmental settings. Although most medusa fossils have been preserved in paleoenvironments such as shallow sandy shores, estuaries, and lagoons, they may also be fossilised in deeper muddy environments. The material we studied consists of specimens preserved in the Eocene flysch of the Adriatic foreland near the Dinaric trust front. The fossil medusae in question were discovered in a quarry on the Slovenian coast. The putative medusa moulds occur on the lower bedding plane of the medium-grained sandstone, that was formed by an hyperpicnal flow. They exhibit positive relief, are circular to ellipsoidal, and vary in size from 6.5 to 24.5 cm. Most specimens stand in isolation, but some partially overlap. The morphology of these fossils is consistent with that of cnidarian medusae and appear to be analogues of extant scyphozoan Discomedusae. Fossilisation may have occurred after the sinking of the decaying medusa bloom, followed by possible further benthic downward transport leading to the accumulation of medusa carcasses in deep water. Indeed, recent observations indicate that several extant Discomedusae sink rapidly after the collapse of a bloom and accumulate on the seafloor (jelly-biomass deposits), where they are exposed to further processes.
Primary Presenter: Alenka Malej, NIB PIRAN (alenka.malej@nib.si)
Authors:
Boštjan Rožič, University of Ljubljana, Faculty of Natural Sciences and Engineering, Ljubljana, Slovenia (Bostjan.Rozic@ntf.uni-lj.si)
Alfred Uchman, Jagiellonian University, Institute of Geological Science, Krakow, Poland ()
Luka Gale, University of Ljubljana, Faculty of Natural Sciences and Engineering, Slovenia ()
Branko Čermelj, National Institute of Biology, Marine Biology Station, Piran, Slovenia ()
Timotej Verbovšek, University of Ljubljana, Faculty of Natural Sciences and Engineering, Slovenia ()
Alenka Malej, National Institute of Biology, Marine Biology Station, Piran, Slovenia (alenka.malej@nib.si)
CANDIDATE FOSSIL MEDUSAE FROM EOCENE FLYSH (ADRIA FORELAND, SLOVENIA)
Category
Scientific Sessions > SS056 Jellyfish in the Changing Ocean
Description
Time: 06:30 PM
Date: 7/6/2023
Room: Mezzanine