SAHRA REPORT ON LOAN 7454 The Evolutionary Origin of Hearing in Archosauria Student: Gabriela Sobral Advisor: Johannes Müller Museum für Naturkunde Berlin The aim of my PhD project is to recover when in the evolutionary history of Archosauria impedance matching hearing appeared. This morphological change in the braincase avoids loss of energy during sound transmission and is regarded as a key feature for improvement of hearing sensibility of terrestrial vertebrates. We are also trying to link this transformation to the tempo of other major biological and geological events. The material of Mesosuchus (SAM-PK-6536) permitted very high-resolution scans of its braincase, providing a handful of new information on its anatomy. The material had been scanned on a previous loan to Gaberiel Bever from the New York College of Osteopathic Medicine, and we agreed on a collaborative study on early rhynchosaur braincase evolution together with Dr. Richard Butler from the University of Birmingham, who is providing data for Howesia , which has also been scanned in the facilities of the MfN. This project is advancing rather quickly as segmentation and description of both braincases is almost complete. Hopefully, a manuscript should be ready for submission later next year. The exceptional preservation of Euparkeria (SAM-PK-7696) also allowed for a high-quality scan which facilitated the segmentation of inner ear structures and some of the sutures between bones. Roland Sookias, one of the PhD students of Dr. Butler is currently working on a reevaluation of the family Euparkeriidae. We have decided to collaborate with them, sharing the CT data for Roland’s thesis and, in the future, working on a more detailed description of Euparkeria braincase anatomy and inner ear structures. Anjan Bhullar from Harvard University will also participate and provide further CT data on the braincase of Euparkeria . The materials of Prolacerta (SAM-PK-K10018 and SAM-PK-K10797), on the other hand, were more difficult to scan given that densities between matrix and materials were too similar, but they also provided good data for early archosaur braincase anatomy. The data might be merged with those acquired for another Prolacerta material scanned here, loaned from the Council of Geosciences in Pretoria by the other PhD student of Dr. Butler, Martin Ezcurra. The Notochampsa material (SAM-PK-K4639) also yielded good results, but scans have not yet been completely worked out. All scans were performed by me at the Museum für Naturkunde Berlin using the micro-computed tomographer Phoenix Nanotom. The data acquired will be incorporated into my thesis, which will be published as a review paper after defense, in September next year. Furthermore, as mentioned, separate parts of the data will be used in different collaborative works. An electronic copy of all publications will be sent to the curator of the South African Museum Sheena Kaal once authorized, together with a copy of the CT data used in these studies. .