Sharks, rays and skates (Chondrichthyes, Elasmobranchii) from the Upper Marine Molasse (middle Burdigalian, early Miocene) of the Simssee area (Bavaria, Germany), with comments on palaeogeographic and ecological patterns

Abstract

Elasmobranch remains are quite common in Miocene deposits and were the subject of numerous studies since the middle of the nineteenth century. Nevertheless, the taxonomic diversity of the Marine Molasse sharks, rays and skates is still largely unknown. Here, we describe 37 taxa from the lower Miocene of the Molasse Basin: 21 taxa could be identified at species level, whereas 15 taxa could only be assigned to genus and one taxon is left as order incertae sedis. The material was collected from deposits of the Auwiesholz Member of the Achen Formation (middle Burdigalian, middle Ottnangian age, ca. 17.8 Ma) exposed near Simssee, Upper Bavaria. This faunal assemblage is a mixture of shallow marine, near-coastal, pelagic and deep-water taxa. The fauna from Simssee displays different biogeographic dynamics at local and regional scales, possibly related to the intense climatic, oceanographic and tectonic events that occurred during the Eggenburgian–Ottnangian stages. The faunal relationships of the early Miocene chondrichthyan faunas from the Mediterranean Sea and Paratethys with others regions are established on the basis of qualitative (presence/absence) data. The beta diversity (Sørensen–Dice coefficient) of the Miocene Molasse elasmobranchs was used to characterize the taxonomic differentiation between localities and regions. According to our results, the fauna from Simssee shows close similarities with those from Switzerland, Austria, France and northern Germany. Faunal similarities and differences are mainly related to tectonic events and oceanographic variables (i.e. migration through seaway passages) or might represent collecting biases.

Diversity, palaeoecology and palaeoenvironmental significance of the Eocene chondrichthyan assemblages of the Bolca Lagerstätte, Italy

“…We used this index because it is one of the most commonly used indices for living and fossil communities and is regarded as one of the most effective measures of similarity based on presence/absence (Southwood & Henderson 2000 ; Magurran 2004 ; Villafaña et al . 2020 ). Analyses were carried out at the genus level.…”

The first Miocene fossils from coastal woodlands in the southern East African Rift

“…Specimens of Galeocerdo are known from the Eocene to the present, 43 while the species G. aduncus , present in the Gorongosa sample, has a temporal range from the Oligocene to the late Miocene. 43 , 60 The genus was widely distributed in the tropical and temperate seas of the Miocene, with specimens found in Madagascar, 61 North Africa, 62 , 63 Oceania, 64 Eurasia, 65 , 66 and the Americas. 67 , 68 Modern Galeocerdo ranges from pelagic waters to nearshore environments in tropical and subtropical marine ecosystems, often occurring in river estuaries.…”

First fossil record (Middle Miocene) of the viper shark Trigonognathus Mochizuki and Ohe, 1990, in the Mediterranean realm

“…This assemblage is similar to other warm-water faunas from Miocene sites documented in nearby outcrops of the Alicante province (see Martínez-Pérez et al, 2018; Ferrón et al, 2019). Examples of mixed shallow- and deep-water fish taxa are not uncommon in the fossil record (Aguilera and Rodriguez de Aguilera, 2001; Vialle et al, 2011; Carrillo-Briceño et al, 2015, 2016, 2020; Villafaña et al, 2020). Most of these examples are thought to have been the result of the migration of deep-water taxa to shallower areas during feeding and coastal upwelling processes, or elements being washed into deeper waters by turbidity currents or slumping (Vialle et al, 2011; Carrillo-Briceño et al, 2015, 2020; Martínez-Pérez et al, 2018).…”