Granulatocincta, Harzhauser & Landau & Janssen, 2022

Harzhauser, Mathias, Landau, Bernard & Janssen, Ronald, 2022, The Clavatulidae (Gastropoda, Conoidea) of the Miocene Paratethys Sea with considerations on fossil and extant Clavatulidae genera, Zootaxa 5123 (1), pp. 1-172 : 153-154

Clavatulidae diversity in the Central Paratethys Sea and adjacent regions

Clavatulid diversity was low during most of the early Miocene with only four species recorded from the Eggenburgian stage and one from the Ottnangian stage [note that occurrences from the Egerian stage are not considered herein]. This number increased to 15 species during the Karpatian, coinciding with the onset of the Miocene Climatic Optimum ( Zachos et al. 2001). About 62.5% of the early Miocene (Karpatian) species persist into the middle Miocene, suggesting that the turnover at the early/middle Miocene boundary was not severe. The climatic warming caused a range expansion of many marine organisms into the Central Paratethys Sea ( Harzhauser et al. 2003), which might have raised clavatulid diversity. The next major diversity increase occurred during the Badenian (Langhian), when 61 Clavatulid species are recorded from the Central Paratethys Sea. Already during the late Badenian, however, a distinct decline down to 12 species occurred. This decline might have been triggered by the Miocene Climatic Transition during the Serravallian ( Shevenell et al. 2004), which resulted in a major loss of thermophilic species in the Paratethys Sea ( Harzhauser & Piller 2007; Harzhauser et al. 2018). Most of the clavatulid genera became extinct in the Paratethys during the Badenian/Sarmatian Extinction Event ( Harzhauser & Piller 2007). Consequently, the Sarmatian was characterized by a strongly reduced clavatulid diversity with only six species representing only two genera Granulatocincta nov. gen. and Olegia nov. gen. The latter experienced a last radiation during the Sarmatian. With the onset of the late Miocene, the brackish Lake Pannon established in the study area and Clavatulidae disappeared from the region.

The strong increase of clavatulid diversity after the early Miocene is also documented from the ProtoMediterranean Sea, where Bellardi (1877) recorded about 28 Burdigalian species and 37 Tortonian species. Landau et al. (2013) (as revised herein) reported additional 15 clavatulid species from the Serravallian of the Turkish Karaman Basin. In the northeastern Atlantic, in contrast, the clavatulid diversity was generally slightly lower and the middle Miocene boom is much weaker. Peyrot (1931) listed about 13 Burdigalian species, about 17 Langhian and Serravallian species from the Aquitaine Basin and Landau et al. (2020) described only seven clavatulid species from the Tortonian of the Loire Basin. High endemism was documented by Landau et al. (2013) for the Serravallian of the eastern Proto-Mediterranean Sea, by Davoli (1990) for the Tortonian of the central Proto-Mediterranean Sea and by Landau et al. (2020) for the Tortonian of the northeastern Atlantic Loire Basin. Due to the revisions proposed herein, the endemicity of the assemblages from the Serravallian Karaman Basin, described by Landau et al. (2013), increased from 57% to 73%.

The paucispiral protoconch of most clavatulid species suggests direct development or only a short planktotrophic phase, which restricts geographic distribution and supports endemic radiations. Therefore, we interpret the observed peaks in Paratethyan clavatulid diversity during the late Burdigalian (Karpatian) and Langhian (early-middle Badenian) as endemic radiations. This hypothesis is supported by the occurrence of groups of morphologically closely related species such as the ‘ Clavatula ’ interrupta group, the Perrona perron group, the Perrona eleonorae group and as represented by the Megaclavatula polonica and M. suturalis , and by all species of Olegia . Only one of the Paratethyan species is also recorded form the Proto-Mediterranean Sea: ‘ Clavatula ’ romana ( Defrance, 1826) . This results in an extremely high endemicity of 98.8% for Paratethyan Clavatulidae .

Tortonian records from Italy suggest persisting high diversities in the Proto-Mediterranean Sea up the late Miocene (e.g., Davoli 1990), although Messinian assemblages already seem to be poor in species (e.g., Harzhauser et al. 2013). The Clavatulidae started to decline distinctly everywhere in Europe during the Pliocene. Only a single species reached to the Loire Basin during the early Pliocene ( Ceulemans et al. 2018) and only about nine species occurred in the central Mediterranean Sea ( Malatesta 1974; Chirli 1997; Spadini & Manganelli 2010; Landau & Harzhauser 2022). Only ‘ Clavatula ’ and Granulatocincta managed to spread throughout the entire Mediterranean during the Pliocene, whereas Tomellana re-invaded only the western Mediterranean adjacent to the Strait of Gibraltar ( Landau & Harzhauser 2022). Pusionella did not enter the Mediterranean at all during the Pliocene.