Decapod Crustacea of the Central Paratethyan Ottnangian Stage (middle Burdigalian): implications for systematics and biogeography

Abstract

Decapod crustaceans from the Ottnangian (middle Burdigalian, Lower Miocene) of the Western and Central Paratethys remain poorly known. In this study, we review and re-describe mud shrimps (Jaxea kuemeli), ghost shrimps (Gourretia sp., Calliax michelottii) and brachyuran crabs of the families Leucosiidae, Polybiidae and Portunidae. A dorsal carapace of the genus Calliax is reported for the first time in the fossil record. Re-examination of the type material of Randallia strouhali (Leucosiidae) and Geryon ottnangensis (Geryonidae) resulted in a transfer of these species into Palaeomyra (Leucosiidae) and Liocarcinus (Polybiidae), respectively. Achelous vindobonensis, originally described as a chela of a portunid crab, probably belongs to a member of Polybiidae and is provisionally treated as Liocarcinus sp. Only two species, J. kuemeli and C. michelottii, are also known from the Karpatian, the succeeding Paratethyan stage. In most cases, the decapod assemblages of the Ottnangian consist of rather shallow-water taxa whereas the assemblages of the Karpatian consist of deep-water taxa from the middle and outer shelf. The Central Paratethyan assemblages show similarities in genus composition to the Proto-Mediterranean and recent Indo-Pacific regions. Gourretia sp. represents the earliest occurrence of the respective genus in the fossil record. The Oligocene-Early Miocene appearance of Palaeomyra and Liocarcinus in the circum-Mediterranean implies that sources of present-day diversity hotspots in the Indo-Pacific trace to the Western Tethys (as for other decapod genera), although coeval decapod assemblages in the Indo-Pacific remain poorly known.

Diversity and distribution patterns of the Oligocene and Miocene decapod crustaceans (Crustacea: Malacostraca) of the Western and Central Paratethys

“…Hyžný (2011a) reported Jaxea kuemeli Bachmayer, 1954 from the same site. All decapod taxa known from the Ottnangian strata of Austria and Germany have been revised by Hyžný et al (2015b).…”

“…From the Early Ottnangian of the North Alpine Foreland Basin decapod associations dominated by Calliax michelottii , Jaxea kuemeli (Fig. 9A) and Liocarcinus ottnangensis (Bachmayer, 1953a) have been reported (Hyžný et al 2015b). By the end of the Ottnangian a strong regression occurred in the Alpine Foredeep and this Ottnangian crisis is reflected in brackish water settings with the endemic Rzehakia fauna (Steininger 1973).…”

“…From the Ottnangian (=Helvetian), 10 species were recorded (Studer 1892, 1898; Bachmayer & Rutsch 1962; Fraaije et al 2010a; Hyžný et al 2015b). This relatively low number probably represents an underestimation influenced mainly by collection bias.…”

“…Fine, siliciclastic sedimentation typical for this stage promotes preservation of near-complete decapod bodies as exemplified by a mud shrimp J. kuemeli (Fig. 9A) and a ghost shrimp C. michelottii (Hyžný et al 2015b: fig. 5).…”

An update of phylogenetic reconstructions, classification and morphological characters of extant Portunoidea Rafinesque, 1815 (Decapoda, Brachyura, Heterotremata), with a discussion of their relevance to fossil material

“…I would agree with Ossó (2016) on their very likely affinity to the Geryonidae, particularly considering the new concept of this family. Another particular, but important, task is to revise the good fossil record of the carcinid genus Liocarcinus (Hyžný et al, 2015) in the light of its recently documented paraphyly (Plagge et al, 2016), its significant persistence in the geological time (Fig. 2) and the new concept of the Carcinidae.…”