Advances of Cranial Morphology of Silurian Sarcopterygian Guiyu Oneiros(25122)

Drs QIAO Tuo and ZHU Min, from Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, recently described cranial morphology features of the stem-group sarcopterygian Guiyu oneiros including the dermal bone pattern and anatomical details of the ethmosphenoid, as reported in the latest issue of Scinece China. They restored, for the first time, the restoration of the skull roof bone pattern in the Guiyu clade (including Guiyu oneiros, Psarolepis romeri and Achoania jarviki) based on some newly-prepared disarticulated assigned to Guiyu oneiros as well as those illustrated in the earlier report (see ZHU et al., 2009. Nature).

The primitive fish Guiyu oneiros from the Silurian of China represents the oldest articulated osteichthyan, and has a mosaic of primitive osteichthyan features, which were thought of derived features of different gnathostome groups.

QIAO and ZHU compared the materials assigned to Guiyu with Onychodus, Achoania, coelacanths andactinopterygians. The comparisons show that the posterior nostril enclosed by the preorbital or the preorbital process is shared by actinopterygians and sarcopterygians, andthe lachrymals in sarcopterygians and actinopterygians are not homologous. The large attachment area of the basicranial muscle indicates the presence of a well-developed intracranial joint in Guiyu.

"The endocranium of Guiyu 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." QIAO and ZHU said, " the position of the hypophysial canal at the same level or slightly anterior to the ethmoid artculation represents a synapmorphy of the Guiyu clade. "

Advances of Cranial Morphology of Silurian Sarcopterygian Guiyu Oneiros