Terrestrial and lacustrine gastropods from the Priabonian (upper Eocene) of the Sultanate of Oman

Abstract

Terrestrial and aquatic gastropods from the upper Eocene (Priabonian) Zalumah Formation in the Salalah region of the Sultanate of Oman are described. The assemblages reflect the composition of the continental mollusc fauna of the Palaeogene of Arabia, which, at that time, formed parts of the southeastern Tethys coast. Several similarities with European faunas are observed at the family level, but are rarer at the genus level. These similarities point to an Eocene (Priabonian) rather than to a Rupelian age, although the latter correlation cannot be entirely excluded. At the species level, the Omani assemblages lack any relations to coeval faunas. This suggests the possible presence of a distinct biogeographic province during the Palaeogene or may simply reflect the extremely sparse non-marine fossil record of the Eocene in the Tethys region. The occurrence of the genera Lanistes, Pila, and Gulella along with some pomatiids, probably related to extant genera, suggests that the modern African–Arabian continental faunas can be partly traced back to Eocene times and reflect very old autochthonous developments. In contrast, the diverse Vidaliellidae went extinct, and the morphologically comparable Neogene Achatinidae may have occupied the equivalent niches in extant environments. Carnevalea Harzhauser and Neubauer nov. gen., Arabiella Kadolsky, Harzhauser and Neubauer nov. gen., Pyrgulella Harzhauser, Kadolsky and Neubauer nov. gen., Salalahia Kadolsky, Harzhauser and Neubauer nov. gen., Omanitopsis Harzhauser and Neubauer nov. gen., Arabicolaria Harzhauser and Neubauer nov. gen., Pacaudiella Harzhauser and Neubauer nov. gen., Goniodomulus Harzhauser and Neubauer nov. gen., Eoquickia Harzhauser and Neubauer nov. gen., Omanillya H. Nordsieck nov. gen. and Omanifera H. Nordsieck nov. gen. are introduced as new genera. Pila neuberti Harzhauser and Neubauer nov. sp., Arabiella arabica Kadolsky, Harzhauser and Neubauer nov. sp., Pyrgulella parva Harzhauser, Kadolsky and Neubauer nov. sp., Salalahia thaytinitiensis Kadolsky, Harzhauser and Neubauer nov. sp., Omanitopsis vandammei Harzhauser and Neubauer nov. sp., Procyclotopsis eocenica Harzhauser and Neubauer nov. sp., Palaeocyclotus kuehschelmi Harzhauser and Neubauer nov. sp., Arabicolaria arabica Harzhauser and Neubauer nov. sp., Pacaudiella omanica Harzhauser and Neubauer nov. sp., Pacaudiella flammulata Harzhauser and Neubauer nov. sp., Goniodomulus solaniformis Harzhauser and Neubauer nov. sp., Cerastus hyznyi Harzhauser and Neubauer nov. sp., Omanillya lunellifera H. Nordsieck nov. sp., Omanillya costellata H. Nordsieck nov. sp., and Omanifera euclista H. Nordsieck nov. sp. are described as new species.

Morphological diversification of ampullariid gastropods (Nsungwe Formation, Late Oligocene, Rukwa Rift Basin, Tanzania) is coincident with onset of East African rifting

“…Furthermore, the basal lip of C. santiapillaii is curved whereas in C. thaytinitiensis it is pointed (Neubert & Van Damme ; Harzhauser et al . ). Due to keeled, nearly planispiral morphology, Carnevalea santiapillaii is distinct from all other ampullariids from the Nsungwe Formation.…”

“…Prior this study, the only known occurrence of Carnevalea was from the paludal biomicritic limestones of the Eocene (Priabonian) Zalumah Formation in Thaytiniti, Oman (see Neubert & Van Damme ; Harzhauser et al . ). The depositional environment of that unit has been interpreted as a freshwater wetland (Harzhauser et al .…”

“…The depositional environment of that unit has been interpreted as a freshwater wetland (Harzhauser et al . ). Similarly, Carnevalea santiapillaii , was collected from Nsungwe 3 locality, which is interpreted as a quiet water environment (Roberts et al .…”

“…The ampullariid genus Carnevalea , which represents an entirely extinct clade, was introduced by Harzhauser et al . () to describe the unique characters of a nearly planisprial, sinistral (hyperstrophic) ampullariid species, C. thaytinitiensis , which was formerly assigned to Lanistes by Neubert & Van Damme (). Carnevalea has previously been documented only from the Eocene of Oman.…”

“…Carnevalea santiapillaii differs from the type (and only other) species, C. thaytinitiensis (see Neubert & Van Damme ; Harzhauser et al . ) because it exhibits an evenly convex outer lip resulting of the slight curvature on the adapical portion of the outer lip; whereas the adapical segment of the outer lip is horizontal in C. thaytinitiensis . Furthermore, the basal lip of C. santiapillaii is curved whereas in C. thaytinitiensis it is pointed (Neubert & Van Damme ; Harzhauser et al .…”