Plio-Pleistocene non-marine Ostracoda from Central Apennines intermontane basins in the frame of the taxonomic harmonistation of subfamily Candoninae (Kaufmann, 1900)

Abstract

This thesis concerns the study of non-marine Ostracoda from different Pliocene-Early Pleistocene intermontane basins of central Italy. In detail, in central Apennines, the Neogene Quaternary extensional tectonics gave origin to several basins filled by continental deposits but much of their tectono-stratigraphic evolution is still unknown. The analysis of the non-marine ostracod assemblages recovered from the early infilling (Piacenzian and Gelasian) deposits of three different central Apennines intermontane basins (Tiberino, L’Aquila, and Rieti basins) and the Middle Tiber Valley merged with the previously known data, gives a good framework of the non-marine ostracod palaeobiodiversity. Ostracods species found in the studied Plio-Pleistocene sequences mainly belong to the subfamily Candoninae and some of them are referable to the genus Caspiocypris that originated in the Paratethyan domain, a huge epicontinental brackish sea that extended across central Europe and western Asia. Neogene and Quaternary ostracods from the Paratethys bioprovince originated through huge adaptive radiations, which gave rise to endemic brackish genera and species. Unfortunately, much confusion surrounds their taxonomy, due to the low quality of information and images in the original old literature and the incompleteness of the type material, a taxonomic revision was necessary. The systematic revision of Paratethyan endemic genera included in the subfamily Candoninae was performed. 33 genera were taken into account: Advenocypris, Candoniella, Graviacypris, and Telekia were considered to be junior synonyms of Typhlocypris, Pseudocandona, and Candona; Moesiella is a nomen nudum; Caspiollina, Dacicandona, Liventalina, and Turkmenella lacks of material and the poor descriptions prevented us from performing a full revision; and the monospecific genus Thaminocypris possibly includes a teratological form. Finally, the remaining 23 genera were merged into nine endemic, valid genera (Bakunella, Camptocypria, Caspiocypris, Hastacandona, Lineocypris, Pontoniella, Propontoniella, Typhlocyprella, and Zalanyiella). Emended diagnoses and descriptions are proposed for these genera. The Tiberino Basin sedimentary infill is made of a thick succession of Pliocene–early Quaternary continental deposits. We analysed the deep lacustrine ostracod assemblages from the Fosso Bianco Fm. and provided descriptions of five new species included in the subfamily Candoninae (Caspiocypris basilicii Spadi & Gliozzi sp. nov., Caspiocypris perusia Spadi & Gliozzi sp. nov., Caspiocypris posteroacuta Spadi & Gliozzi sp. nov., Caspiocypris tiberina Spadi & Gliozzi sp. nov. and Caspiocypris tuderis Spadi & Gliozzi sp. nov.) and one new species included in the subfamily Limnocytherinae (Paralimnocythere umbra Spadi & Gliozzi sp. nov.). The five species of Caspiocypris seem to represent a species flock because Caspiocypris includes a group of closely related species characterized by monophyly, endemism and speciosity, confirming the ‘ancient lake’ nature of the Palaeolake Tiberino during the Piacenzian–Gelasian. The marginal lacustrine ostracods collected from Fosso Bianco Fm. and from the alluvial fan-related Ponte Naja Fm. were represented by 17 species with two new species (Paralimnocythere sp. nov. and Hemicypris sp. nov.), which could be divided in different cluster groups linked to different palaeoenvironments along the swampy lacustrine margins of the Palaeolake Tiberino. Overall, the ostracod from the Tiberino Basin were referable to 14 genera split into 24 species, eight of which resulted endemic. For the L’Aquila Basin, the palaeontological and facies analyses were carried out on the San Demetrio-Colle Cantaro Synthem. The ostracods were collected in the deep lacustrine silts of the San Nicandro Fm. and the Gilbert-type delta system conglomerated of Valle Orsa Fm. Thirteen species were recognised, six of which are new: Caspiocypris amiterni Spadi & Gliozzi sp. nov., C. bosii Spadi & Gliozzi sp. nov., C. nicandroi Spadi & Gliozzi sp. nov., C. vestinae Spadi & Gliozzi sp. nov., Cypria bikeratia Spadi & Gliozzi sp. nov., and Ilyocypris ilae Spadi & Gliozzi sp. nov.. Conversely, the ostracod assemblages of the Valle Orsa Fm., due to the co-occurrence of Ilyocypris, Candona and Cypria, suggested a shallow water environment with flowing waters possibly linked to a nearby river delta. Overall, the ostracod from the San Demetrio-Colle Cantaro Synthem were referable to 13 species pertaining to 10 genera, eight of which resulted endemic species. At the confluence between the Rieti Basin and the Middle Tiber Valley only one species, Qinghaicypris cf. Q. riojensis, was found in the Monteleone Sabino Unit related to the deposition of a braided plain with some small lake, ponds and swampy areas. In the same unit, previous papers reported other ostracods, in total, 28 species pertaining to 14 genera were recovered from the Gelasian of Monteleone Sabino Unit. In summary, during the Piacenzian-Gelasian interval, the continental aquatic environments of central Italy were characterised by the occurrence of 60 different species referable to 24 genera. This is due to the rich-in-species genus Caspiocypris that gave rise to two species flocks in the deep lacustrine environment of Palaeolake San Nicandro and Palaeolake Tiberino. The ostracod assemblages studied show affinity at generic and specific level with the Neogene and Quaternary Paratethyan and Balkan realms. This contrasts with the pattern seen in the other central Italian Pliocene and Early Pleistocene assemblages related to shallow water environments where the taxa show a clear Palaearctic or Holarctic distribution and were widely distributed in central and western Europe at least until the Early Pleistocene. The presence in the Plio-Pleistocene of the central Italy basins of some Paratethyan ostracods species or some shallow freshwater species from “Paludinian Beds” can be explained as the consequence of the passive dispersal through aquatic birds along a westward path from the Balkan area or with the evolution in the Mediterranean area of Lago Mare ostracods that occurred at the end of the Messinian. According to our palaeontological analyses, the early infill of the Tiberino (Fosso Bianco and Ponte Naja Fm.) and L’Aquila (San Demetrio-Colle Cantaro Synthem) basins must be dated to Piacenzian-Gelasian, due to the presence of Caspiocypris in both basins. Similarly, the oldest deposits of the Rieti Basin (Monteleone Sabino Unit) resulted to be at least Gelasian in age, owing to the occurrence of large mammals and other biostratigraphical proxies. The late Piacenzian (ca. 3 Ma) onset of the Tiberino and L’Aquila extensional basins calls into question previous suggestions that the onset of these basins becomes younger from the Tyrrhenian toward the Adriatic side of the central Apennines.