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A short note on Middle Miocene pteropods from Northern Croatia

Holoplanktic gastropods (Pteropoda) with aragonitic shells („sea butterflies“) are in fossil record usually present as casts and molds, but they are important for paleobio- stratigraphical, paleoecological and paleogeographical research. Their findings in the Central Paratethys area are the most common in the middle Miocene deposits corresponding to the peaks of Badenian transgressive-regressive cycles. Pteropods are found in the Badenian deposits of Austria, Czech Republic, Poland, Hungary, Slovenia, Croatia, Romania, Bulgaria and Ukraine. The most diverse and numerous genera are Limacina Bosc, 1817, Vaginella Daudin, 1800 and Clio Linnaeus, 1767. In Northern Croatia they are mostly recorded in the middle Miocene (Badenian) deposits of the Medvednica Mt. in vicinity of Zagreb (Gorjanović-Kramberger, 1908 ; Kochansky, 1944 ; Bosak, 2017 ; Bošnjak et al., 2017 ; Derežić, 2018). During the middle Miocene this area paleo-geographically belonged to the southwestern margin of the Central Paratethys, and geotectonically to the Pannonian Basin System. In the Badenian outcrops of the Medvednica Mt. several pteropod species have been recorded so far: Vaginella austriaca Kittl, 1886, Clio pedemontana (Mayer, 1868), Clio fallauxi (Kittl, 1886) and Limacina valvatina (Reuss, 1867) . Recent pteropod research in Northern Croatia was mostly focused on the oldest marine Badenian deposits, exposed in Čučerje area (central part of the Medvednica Mt.) (Bosak, 2017 ; Bošnjak et al., 2017 ; Derežić, 2018). The most numerous species in „pteropod marls“ at this locality is Vaginella austriaca, which is in accordance with other findings from the Central Paratethys. Fragments of Clio pedemontana were also collected. For the first time we documented the occurrence of the representatives of the family Cavoliniidae and ?Creseidae in this area of Northern Croatia. Nannoplankton and foraminifera analyses were done in order to determine the age of the deposits and paleoenvironmental conditions. Nannoplankton analyses indicate the NN5 nannozone, as described in the available papers. The recorded foraminifera assemblages point to the deep-marine environmental conditions, based on the findings of foraminifera Bathysiphon and Rhabdamina and selective dissolution of aragonite tests (Derežić, 2018). Pteropod research in Northern Croatia contributes to the knowledge of pteropod distribution within the Central Paratethys, and their possible migration routes, including the possible short-term connection with the North Sea during the Early Badenian (Langhian) age.

Pteropods, Middle Miocene, Northern Croatia

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