Discussion and conclusions
The only level with a diverse herpetofauna is Kä G, which yielded at least seven species, including two salamanders, one anuran, and four lizards (Table 1). Kä H yielded at least one salamander and two lizards, and Kä E produced a single anuran species. The fossil material has been referred to extant species that occur in the area today.
If we assume that extant Pleistocene amphibians and reptiles had similar ecological preferences and tolerances as they do today, herpetological assemblages can be useful to reconstruct the general habitats or even the biotopes present during the time of the deposition of the bones.
The fossils assemblage from Kä G is the only assemblage that is extensive enough from which to draw ecological conclusions. The presence of the amphibians Triturus cristatus, Triturus vulgaris and Bufo bufo indicate that a still-water habitat such as a marsh or pond had to be present near the site for these animals to breed. The presence of Anguis fragilis suggests that low vegetation and ground cover must have been present; and the lizards, especially Lacerta agilis, indicate that a relatively dry, at least somewhat sandy habitat, must have been available. These conclusions are supported by the paleoenvironmental reconstruction based on the accompanying mammalian assemblage. The mammalian fossil record indicates the alternation of forested areas with forest dwellers such as Eliomys quercinus and Apodemus sylvaticus alternated with areas with a prevailing steppic environment in which hamsters such as Cricetus cricetus and Cricetus major occurred. The semi-aquatic water vole, Arvicola terrestris cantianus, indicates the occurrence of slow moving, calm water.
The fact that all of the amphibians and reptiles of the Kärlich localities almost certainly represent extant forms is consistent with previous studies of Pleistocene amphibians and reptiles in Britain, Europe, and North America (see citations in
1998). The stability of Pleistocene herpetofaunas during and at the end of the Pleistocene is a subject of considerable discussion today (e.g.,
1998). This is because the mammalian fauna, and (to a somewhat lesser extent) the avifauna, suffered much familial, generic, and specific extinction during the same time interval. These extinctions in the endothermic fauna were extensively discussed in the past two decades (e.g.,
Martin and Klein 1984).
Holman (1991) posed the questions "What attributes have allowed the herpetofauna to survive the stresses that have caused dramatic extinctions in other classes during the Pleistocene." Beside other suggestions, such as the possible advantages of being ectothermic rather than endothermic, some paleontological evidence has suggested the possibility that amphibians and reptiles might not have been as dependent upon the large endothermic species (mammalian megafauna) that became extinct during the Pleistocene as were certain predators, scavengers, or commensals (Holman
1991). For instance, at the famous Rancho La Brea Late Pleistocene site in California, scavenging or commensal birds and dung beetles became extinct along with the mammalian megafauna, but all of the amphibians and reptiles at Rancho La Brea survived into the present (Holman
1995). On the other hand, in Australia, the gigantic monitor lizard Megalania and the huge snake Wonambi (Murray
1984) were top predators and became extinct during the Pleistocene, presumably because the many large marsupials that they preyed upon died out during the epoch. Oddly, few suggestions have been made in Britain, Europe, or North America about the possible ecological relationships of amphibians and reptiles to the large extinct mammals.
We might suggest here that it is possible that the small, ectothermic amphibians and reptiles of Europe (and elsewhere) were a not significant enough part of the food web of the large mammalian herbivores, predators, and scavengers to have been highly influenced by the disappearance of these mammals.
Based on the evolutionary stasis of most of the Pleistocene herpetofauna (Holman
1995, 1998), one might doubt the usefulness of Pleistocene amphibians and reptiles in Pleistocene stratigraphic studies. Nevertheless, in England certain Pleistocene herpetological species with limited tolerances to cold temperatures (e.g., Hyla arborea, Hyla meridionalis, Emys orbicularis, and Elaphe longissima) are characteristically associated with temperate interglacial stages (e.g.,
Ashton et al. 1994). On the other hand, amphibians and reptiles with broad tolerances to climatic conditions (Bufo bufo, Rana temporaria, and Lacerta vivipara) are the only British amphibians and reptiles (with one exception) to be found in cold, glacial stage faunas (e.g.,
1995). Therefore, in a broad sense, amphibian and reptile faunas are stratigraphically important, at least in indicating whether deposits represent temperate interglacial or cold glacial stages. In the Kä G fauna, for instance, the common European toad (Bufo bufo) and the viviparous lizard (Lacerta vivipara) have broad climatic tolerances and could be representative of either glacial or interglacial stages. On the other hand, the large Lacerta species, perhaps representing the green lizard (Lacerta viridis), could be indicative of a temperate stage of the Pleistocene (Böhme 1996). The fact that all the fossil remains from the Kärlich deposits have been referred to amphibians and reptiles that occur in the vicinity at present would indicate that the climate during Kä G time was rather similar to what it is in modern times, a conclusion supported by the extensive smaller mammal fauna.