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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.

The Paratethyan basins of eastern Europe and western Asia became isolated from marine influence in the Late Miocene, and were the sites of several remarkable endemic radiations of brackish and freshwater organisms. Here I describe the patterns of tempo and mode before and during the radiation of the gastropod Melanopsis in the Pannonian basin of eastern and central Europe, and I explore the underlying mechanisms of evolutionary change.The most ancient melanopsid species in this area, M. impressa, was present in freshwater areas marginal to the basin well before the radiation. Widely spaced samples of M. impressa indicate that this species underwent a period of stasis lasting at least 7 m.y. The end of stasis corresponded with the extinction of the last of the normal marine fauna in the basin, suggesting that the lack of other fauna and/or reduced salinity in the basin permitted expansion of the melanopsids from the basin margins into the basin proper. Stasis ended with the onset of changes in size, shouldering, and ontogeny, which led eventually to M. fossilis. Change occurred over a 2-m.y. interval; a series of intermediates is present for all three characters. Within-sample correlations provide no evidence that the three characters are constructionally linked; instead they appear to be changing independently. The mode of change in the M. impressa–M. fossilis lineage appears to have been anagenetic. Alterations in the rate and direction of selection (and/or genetic links between characters) are probably required to explain the overall slowness of the change.Most Pannonian basin melanopsid species arose by rapid cladogenesis in the Middle Pannonian Stage. Physical factors in the basin probably influenced the timing of this diversification; contrasting patterns of variation and diversity between two melanopsid clades suggest that intrinsic factors influenced the extent of diversification.

Stomatopods (mantis shrimps) are important predators in Recent tropical shallow-water communities. Despite a long geological history, they are poorly preserved as fossils, and traces of their predation have never been identified from the fossil record. Here we report on Plio-Pleistocene gastropods (mostly Strombus) from Florida with distinctive holes “punched” into their body whorls. The similarity of these holes to holes punched into live gastropods by Gonadactylus implicates gonodactyloid stomatopods as the predators that made them. Recent gonodactyloids break gastropod shells as thick and thicker than those of the Plio-Pleistocene strombids that were punched. Because our data underestimate the incidence of stomatopod predation, the frequency of holes in these strombids (8–13 percent) suggests that stomatopod predation may be of considerable importance in the ecological and evolutionary history of tropical benthic assemblages.

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