Chiara Sorbini

VOLHYNIAN (EARLY SARMATIAN SENSU LATO) FISHES FROM TSUREVSKY, NORTH CAUCASUS, RUSSIA

Abstract A new fish fauna is described from the late Middle Miocene (Volhynian; early Sarmatian sensu lato) of Tsurevsky, North Caucasus, Russia. Ten taxa belonging to nine families are described, of which two may be new (Micromesistius sp., Bothus sp.), but not formally described awaiting better-preserved material. The predominant faunal element is Sardinella sardinites, including more than 42% of all investigated specimens. The paleoecological analysis reveals a semienclosed marine environment not far from the coast, characterized by shallow depths and a soft bottom. The sedimentological features of the deposits and the preservation of the specimens suggest that periodic oxygen minima affected the bottom waters, causing repeated hypoxic events, probably related to the decay of organic matter previously accumulated in the basin. Paleoenvironmental considerations of fish faunas from several Paratethyan localities suggest that marine waters characterized by a little shift in chemical composition (high alkalinity) filled up the entire basin during the Sarmatian.

OREOCHROMIS LORENZOI, A NEW SPECIES OF TILAPIINE CICHLID FROM THE LATE MIOCENE OF CENTRAL ITALY

Abstract A new species of tilapiine cichlid, Oreochromis lorenzoi, is described from the late Miocene (Messinian) of central Italy. This species is represented by four articulated specimens and a caudal region of a fifth individual. Oreochromis lorenzoi, sp. nov. is the earliest confirmed representative of the genus Oreochromis, and it is the first European fossil cichlid. Oreochromis lorenzoi and additional examples from other fossil fishes provide evidence of faunal exchanges between Africa and the northern coasts of the Mediterranean during the Miocene. Paleoenvironmental implications are also discussed.

Biogeographical significance of northern extraprovincial fishes in the Pliocene of Ecuador

Abstract The biogeographical relationships of a Pliocene (Globigerinoides fistulosus Zone) fish fauna are described. The data here presented show that the Ecuadorian fish fauna has a precise Panamic identity already in the Pliocene. Several (15) northern extraprovincial guests of Californian origin have been identified. The presence of Californian taxa in the Pliocene of Ecuador suggests the existence of faunal relationships between these two areas. The analysis of the California fossil record reveals that the faunal exchange occurred only via north–south. Two dispersal mechanisms have been pointed out by the authors: (1) the flow at lower latitudes of a branch of the California Current, and (2) the activation of coastal upwelling cells beginning from California area.

Late Pliocene fossils of Ecuador and evolution of the Panamic bioprovince after closure of Central American Isthmus

Studies carried on in the last several years allow us to date the Canoa Formation as Late Pliocene. The rich paleontological record (foraminifers, mollusks, and otoliths) allowed us to outline a first articulate picture of the biogeographic relationships in the tropical eastern Pacific during the Plio-Pleistocene. The mollusk fauna shows a Panamic connotation, as the majority (88.7%) of the extant species are present between the Gulf of California and the coasts of Ecuador or northern Peru. Benthic foraminifers assemblages indicate a temperate character with a certain affinity with the Mexican Pacific microfauna. More than 7000 otoliths have been found in the Canoa Formation that are attributed to 105 taxa of 46 fish families. Only 65% of the fossil association is living today along the Ecuadorian coasts, while the association as a whole shows closer relationships with the extant Californian fish community (about 80%). In particular, a conspicuous group of fishes (15 taxa) today spread in the boreal East Pacific (from Oregonian to Californian Province or limited only to the Californian area) has been recorded in the Canoa Formation. We named these taxa “Californian guests.” After the rising of the Central American Isthmus, climatic variations may have caused changes in the pattern of surface currents and (or) activated coastal upwelling cells, supporting the diffusion of a part of the boreal biota toward more southern areas. At the present state of knowledge, both proximal causes seem to be compatible with the data presented.