Qin-Wei Wu1, Josef P Kapfhammer2. 1. Institute of Anatomy, Department of Biomedicine, University of Basel, Pestalozzistr. 20, 4056 Basel, Switzerland. Electronic address: qinwei.wu@unibas.ch. 2. Institute of Anatomy, Department of Biomedicine, University of Basel, Pestalozzistr. 20, 4056 Basel, Switzerland. Electronic address: Josef.Kapfhammer@unibas.ch.