Cranial morphology of the Silurian sarcopterygian Guiyu oneiros (Gnathostomata: Osteichthyes)
QIAO Tuo1,2 & ZHU Min1*
1 Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China;
2 Graduate School of Chinese Academy of Sciences, Beijing 100049, China
Cranial morphological features of the stem-group sarcopterygian Guiyu oneiros Zhu et al., 2009 provided here include the dermal bone pattern and anatomical details of the ethmosphenoid. Based on those features, we restored, for the first time, the skull roof bone pattern in the Guiyu clade that comprises Psarolepis and Achoania. Compari-sons with Onychodus, Achoania, coelacanths, and actinopterygians show that the posterior nostril enclosed by the preorbital or the preorbital process is shared by actinopterygians and sarcopterygians, and the lachrymals in sarcopterygians and actinopterygians are not homologous. The endocranium closely resembles that of Psarolepis, Achoania and Onychodus; however, the attachment area of the vomer possesses irregular ridges and grooves as in Youngolepis and Diabolepis. The orbito-nasal canal is positioned mesial to the nasal capsule as in Youngolepis and porolepiforms. The position of the hypophysial canal at the same level or slightly anterior to the ethmoid articulation represents a synapmorphy of the Guiyu clade. The large attachment area of the basicranial muscle indicates the presence of a well-developed intracranial joint in Guiyu.
This work was supported by National Basic Research Program of China (Grant No. 2006CB806400), Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-156), National Natural Science Foundation of China (Grant No. 40930208), and the CAS/SAFEA International Partnership Program for Creative Research Teams.