Patterns of life history recorded in the dorsal rib histology of amniotes

Abstract

Dorsal ribs of tetrapods for centuries have never been in focus of scientific interest in any of the main areas of research in biology or paleontology. However, new insights into rib inner structures reveal the importance of these underestimated skeletal elements that yield information about life history, ontogeny, ecology, and taxonomic assignment. Especially for extinct taxa this data stored in dorsal ribs often remains the only way to reconstruct the life history and mode of life of an animal.This dissertation analysis the potential of dorsal ribs to provide information of ecology and life history traits on both, individual and taxonomical level, mainly using the tool of bone histology. The growth record stored in the dorsal ribs provides information about ontogenetic stage, age at sexual- and skeletal maturity, and in some cases age at death and sex of an individual. The advantages of rib histology in contrast to the normally sampled long bones are especially important for studying sauropods that are primarily in focus of this study. Dorsal ribs of different sauropod taxa from different localities were sampled because the usual sampled long bones like humeri and femora do not develop and preserve cyclicity in all but the outermost cortex. Thus, growth record preservation in ribs that has been proven to be the most complete of all skeletal elements is the best approach to analyze growth of these largest terrestrial animals of all times.