Project Details
Projekt
Ontogeny and evolution of perception in temnospondyls
Subject Area
Geology
Term
since 2024
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 508778113
Temnospondyls, ranging from the Mississippian to the late Lower Cretaceous, are a group of ecologically highly diverse early tetrapods that occupied a variety of niches in aquatic, semiterrestrial and terrestrial habitats. Their life cycles often involved habitat shifts, e.g., from aquatic to terrestrial. Moreover, they span a huge range of body sizes from only a few centimeters to more than five meters. Given this wide range of lifestyles and ecologies, temnospondyls are most suitable to shed light on how early tetrapods were able to modify and adapt their sensory organs to different environments during their ecological and phylogenetic diversification. The goal of the proposed project is to gain a physiological perspective on the life history of temnospondyls based on evolutionary changes in three sensory systems whose well-preserved osteological correlates permit investigations into the evolution of sensory perception. These are: (1) the hearing system, which is preserved as the squamosal embayment, middle ear cavity and stapes, (2) the visual system as represented by the orbits, scleral rings and palpebral bones, and (3) the mechanoreceptive lateral line system that - in aquatic taxa - formed canals or sulci in the dermal bones of skull and mandible. The project encompasses a systematic, detailed study of the three sensory systems in a large number of species from all main groups of temnospondyls and with different ecologies and life styles. For outgroup comparison, stem-tetrapods and stem-amniotes will be considered. Because the phylogenetic relationships of temnospondyls with other early tetrapods and especially lissamphibians are still a matter of debate, the results will be discussed in the light of alternative phylogenetic hypotheses. Our approach utilizes a breadth of methods, including classical morphology, histology, landmark-based geometric morphometrics as well as 3D surface scanning, synchrotron X-ray phase contrast tomography and micro-CT scans. These studies will be performed against the background of the paleoenvironments and habitats in which the particular taxa lived in, as well as the presumed lifestyle based on general proportions of the skeleton. An integral part of the project will be comparison with the morphology and sensitivity of the same sensory organs in extant lissamphibians and bony fishes based on literature and first-hand studies. In the last phase of the project, the obtained data concerning the osteological correlations of visual and hearing capabilities and lateral line responsiveness in temnospondyls will be merged to get a holistic view on the evolution of sensory organs in temnospondyls. We will assess how phylogeny and ecological factors (e.g. habitat) influenced the relative investment in hearing, vision and lateral line perception and their interaction with each other.
DFG Programme
Research Units
