While the progenitor cells that contribute to vertebrate skeletal tissues are known to have two embryonic origins, the mesoderm and neural crest, the evolutionary origin of their developmental process remains unclear. Mineralized skeletal tissues of vertebrates are an evolutionary novelty within the chordate lineage. 4Marine Research Station, Institute of Cellular and Organismic Biology, Academia Sinica, Yilan, Taiwan.3Department of Anatomy and Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.2Department of Aquatic Biology, Chia-Yi University, Chia-Yi, Taiwan.1Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan.Luok Wen Yong 1, Tsai-Ming Lu 1, Che-Huang Tung 1,2, Ruei-Jen Chiou 3, Kun-Lung Li 1 and Jr-Kai Yu 1,4*
