Palaeoecological and palaeoenvironmental influences revealed by long-bone palaeohistology: the example of the Permian branchiosaurid Apateon

Abstract

AbstractApateon, a small temnospondyl from the Permian freshwater-lake deposits of the Saar-Nahe Basin (SW Germany), is known by exceptionally well-preserved material. Here we report the first palaeohistological analysis of Apateon that focuses on its life-history traits and palaeoenvironments. Different samples (different localities and horizons) of Apateon caducus and Apateon pedestris have been analysed. Their stylopod histology shows different growth rhythms that might be correlated to changes in palaeoecosystems: food availability and/or presence of predators. Palaeoenvironmental influences are also recognized during the limb-bone osteogenesis by the expression of simple and/or double patterns of Lines of Arrested Growth (LAG). A double-LAG pattern expresses hibernating and aestivating arrests of growth in extant newts. The fossil samples from the two stratigraphically oldest horizons preserved a similar double-LAG pattern, suggesting that they may have hibernated and aestivated every year because of harsh climatic conditions. The Saar-Nahe lake system probably passed from a higher altitude zone into a lower one, possibly because of subsidence and/or erosion. It could also be correlated to the size of the lakes that differs from one locality to another, inducing different responses of the organisms to the climatic variations.