An earlyMiocene deep‐water decapod crustacean faunule from theSlovenian part of theStyrianBasin, and its palaeoenvironmental and palaeobiogeographical significance

Abstract

A new decapod crustacean faunule is described from the early Miocene of the Slovenian part of the Styrian Basin. The Ivnik Beds exposed at the Cinzat locality contain seven species: Calliax michelottii (Axiidea: Callianassidae), Lepidophthalmus paratethyensis sp. nov. (Axiidea: Callianassidae), Jaxea kuemeli (Gebiidea: Laomediidae), Styrioplax exiguus (Brachyura: Chasmocarcinidae), Goneplax gulderi (Brachyura: Goneplacidae), Neopilumnoplax pohorjensis sp. nov. (Brachyura: Mathildellidae) and Retropluma slovenica sp. nov. (Brachyura: Retroplumidae). Numerous specimens of well-preserved Styrioplax exiguus permitted its redescription and re-assignment of its familial placement to Chasmocarcinidae. Neopilumnoplax pohorjensis sp. nov. constitutes the first fossil occurrence of the genus known to date. The decapod association, as well as other faunal elements, suggests low-energy deep-water depositional environment with epibathyal water depth of more than 125 m. The studied locality is situated in the Ribnica-Selnica graben filled with sediments once deposited in the Central Paratethys sea. Based on the affinities of decapod genera of the Central Paratethys and the Proto-Mediterranean, we conclude that the exchange of decapod faunas between these regions was probably regulated by an anti-estuarine circulation permitting an easier incursion of species from the Proto-Mediterranean into the Paratethys and simultaneous hindering the Paratethyan endemics (Styrioplax) from entering the Mediterranean.Key words: Decapoda, early Miocene, Central Paratethys, Slovenia, deep-water environment, palaeobiogeography. DECAPOD crustaceans from Neogene strata of northeastern Slovenia are poorly known. Records are limited to isolated specimens from occasional construction or earth works, and no decapod association has been previously recorded.Previous records of Miocene decapods from the Slovenian part of the Styrian Basin (Table 1) are those by Glaessner (1928) and Mikuz (2003). Glaessner (1928) described Microplax exiguus on the basis of three specimens from the Langhian ('Badenian') mudstones of two different localities, the towns of St Egydi ( Sentilj) and St Leonhard (Lenart) within the Kungota Formation. Almost a century later, Mikuz (2003) reported on remains of Portunus monspeliensis Milne Edwards, 1860, from the grey sandstone of the same formation cropping out near the town of Sentilj.This study describes the first decapod crustacean faunule from Slovenia. The assemblage was collected from the Ivnik Beds at the locality Cinzat on the northern slopes of Mt Pohorje. Decapod remains are a dominant group in the grey to brownish siltstones of the early Miocene ('Karpatian') age. GEOLOGICAL AND STRATIGRAPHICAL SETTINGThe studied locality Cinzat is situated in the RibnicaSelnica graben, within the westernmost parts of the Styrian Basin, Slovenia. It is situated approximately 15 km west of Maribor (GPS coordinates: 46°32 0 35.05″N, 15°26 0 35.15″E), a city near the northern Slovenian border

Early Miocene decapod Retropluma slovenica Gašparič & Hyžný, 2014 from Govce beds of Tunjice Hills (Central Slovenia)

“…The genus is represented today by seven species of Indo-Pacific and North-Western Pacific distribution (McLay, 2006). Gašparič & Hyžný, 2014 from Early Miocene siliciclastic sequence of Rovček creek in Tunjice Hills represents an important report, which further enhances our knowledge of Early Miocene decapod communities in Paratethys of Slovenia. The species was previously known from a single Early Miocene locality on northern slopes of Pohorje mountain range, so the new locality expands the geographical distribution of the species to the western part of Slovenian Basin of Paratethys which was in Early Miocene very close to the Mediterranean and most likely connected to it through the Slovenian corridor.…”

New reports of crab Styrioplax exiguusGlaessner, 1928 (Decapoda, Brachyura) from Miocene beds near Maribor, Slovenia

“…Največ tovrstnih fosilnih ostankov v Sloveniji najdemo v eocenskih plasteh Istre (Pavlovec & Pavšič, 1985;Mikuž, 2010a) in miocenskih plasteh okolice Kamnika in Zasavja (križnar, 2006;križnar & Preisinger, 2008;Mikuž, 2010b;Mikuž & Pavšič, 2003). Iz miocenskih plasti slovenskega dela Štajerskega bazena Paratetide imamo do sedaj podatke o redkih posameznih najdbah fosilnih rakovic (glaessner, 1928;Mikuž, 2003), o bogati združbi fosilnih rakov deseteronožcev iz spodnjemiocenskih plasti nahajališča Činžat na severnem pobočju Pohorja pa sta poročala gašParič in Hyžný. (2015).…”

“…Posamezne primerke te vrste poznamo tudi iz globjemorskih spodnjemiocenskih (karpatijskih) plasti nahajališča Cerova -Lieskove na Slovaškem (Hyžný & scHlögl, 2011), preko 70 primerkov pa je bilo pred kratkim opisanih tudi iz miocenskih plasti karpatijske starosti na nahajališču Činžat na severnem pobočju Pohorja (gašParič & Hyžný, 2015), ki so se prav tako usedale v globjemorskem okolju.…”

“…Pred kratkim opisan nov material (gašParič & Hyžný, 2015) je razkril podrobnosti na prsnici moških primerkov, ki rakovico Styrioplax exiguus zanesljivo uvrščajo v družino Pilumnidae in podružino Chasmocarcininae, na kar sta sicer opozorila že karasawa in kato (2003).…”

“…Najdbe primerkov rodu Styrioplax so evidentirane iz spodnjemiocenskih (karpatskih) in srednjemiocenskih (badenijskih) plasti centralne Paratetide (glaessner, 1928;Hyžný & scHlögl, 2011;gašParič & Hyžný, 2015). Ostanki rakovic Styrioplax exiguus so pogosti v miocenskih plasteh severovzhodne Slovenije (glaessner, 1928;gašParič & Hyžný, 2015), kjer jih sedaj poznamo s šestih nahajališč (sl.…”