The endemic molluscs of the Late Miocene Lake Pannon: their origin, evolution, and family‐level taxonomy

Abstract

I. 1999 04 15: The endemic molluscs of the Late Miocene Lake Pannon: their origin, evolution, and family-level taxonomy. Lethaia, Vol. 32, pp. 47-60. Oslo. ISSN 0024-1 164.Long-lived lakes are often sites of spectacular endemic radiations. During the Oligocene to recent history of the Paratethys, large, long-lived (more than a million years) lakes with endemic faunas formed three times, in three different basins: the first in the Pannonian basin, the second in the Euxinian (Black Sea) basin, and the third in the Caspian basin. Because the Euxinian lake inherited much of the fauna of Lake Pannon, the three lakes together hosted two endemic radiations of molluscs. The most long-lived lake in the region was Lake Pannon, which persisted approximately seven million years from the late Middle Miocene to the Early Pliocene. Lake Pannon was formed by isolation from the sea. Changes in hydrological regime and/or water chemistry in addition to the relative lowstand which accompanied (or caused) the isolation almost completely exterminated the restricted marine fauna of the basin. A few highly euryhaline and marginal marine cardiids, dreissenids, and hydrobiids survived this environmental change. As in other fossil and extant long-lived lakes, the originally low-diversity fauna radiated into a high number of related endemic species ('species flocks') and genera in the expanding and ecologically vacated lake. Many originally freshwater taxa (unionids, sphaeriids, viviparids, valvatids, melanopsids, lymnaeids, planorbids) entered the lake as well, and some of them also gave rise to endemic clades. Evolution in both relict and freshwater immigrant groups led to the appearance of highly unusual shell shapes. Many lineages exhibit gradual morphological changes over one to several million years. More than 900 endemic mollusc species have been described from Lake Pannon, although this number includes junior synonyms, invalid species names, and highly similar chronospecies. Applying a conservative taxonomy, all these species belong to four bivalve and eight gastropod families. The high degree of endemism, however, is reflected by proposals of some authors to establish as many as five new families based on Lake Pannon endemics.

Loss of 40Ar(rad) from leucite-bearing basanite at low temperature: implications on K/Ar dating.

“…In the Neogene, shortly before the volcanism started, a large lake, Lake Pannon, occupied the Pannonian Basin [46][47][48][49]. The lacustrine sandstones, mudstones and marls of the brackish Lake Pannon are the base of the immediate underlying pre-volcanic substrate of the BBHVF [48,[50][51][52][53][54]. Prior to the volcanism the BBHVF area was most likely an alluvial plain [38,48].…”

Comparative phylogeography of two sister (congeneric) species of cardiid bivalve: Strong influence of habitat, life history and post-glacial history

“…This divergence was probably the result of the Messinian salinity crisis during which the Mediterranean was split into a number of isolated basins and lagoons with different salinity conditions (Hsü et al, 1977). These paleogeographic and paleoclimatic events have played an important role in the evolutionary history of several marine taxa (Hanel et al, 2002;Costagliola et al, 2004 and references therein; Valsecchi et al, 2005) including cardiids (Müller et al, 1999). According to the allopatric speciation scenario, which is the most likely for the two cockles, C. glaucum evolved in the area of the present Mediterranean Sea in basins with changing salinity and became adapted to a great salinity range.…”

The paradox of gradualism: phyletic evolution in two lineages of lymnocardiid bivalves (Lake Pannon, central Europe)

“…By the beginning of the late Miocene, a combination of tectonic activity and eustatic sea-level fall had effectively isolated the Pannonian Basin fauna from that of other paratethyan basins and from the marine system (Kazmer 1990;Rö gl 1998;Magyar et al 1999a;Harzhauser et al 2004;Popov et al 2004Popov et al , 2006). Following this isolation, a nearly complete turnover in the faunal assemblages indicates that the environment shifted from marginal marine to lacustrine brackish (Papp et al 1974(Papp et al , 1985Nagymarosy and Mü ller 1988;Mü ller et al 1999;. Brackish conditions prevailed until the Early Pliocene in open lake environments; fresh (or considerably less brackish) water characterized the deltaic environments that became widespread by the middle of the late Miocene (Geary et al 1989;).…”