Cranial morphology of the Silurian sarcopterygian Guiyu oneiros (Gnathostomata:Osteichthyes)

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.Comparisons 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.

Postnatal ontogenetic size and shape changes in the craniums of plateau pika and woolly hare(Mammalia: Lagomorpha)

In the present study, postnatal ontogenetic size and shape changes in the cranium of two lagomorph species, the plateau pika （Ochotona curzoniae） and woolly hare （Lepus oiostolus）, were investigated by geometric morphometrics. The ontogenetic size and shape changes of their cranium exhibited different growth patterns in response to similar environmental pressures on the Qinghai-Tibetan Plateau. The overall size change in the cranium of the plateau pika was slower than that of the woolly hare. The percentage of ontogenetic shape variance explained by size in the woolly hare was greater than that in the plateau pika. The overall shape of the cranium was narrowed in both species, and morphological components in relation to neural maturity showed negative allometry, while those responsible for muscular development showed isometric or positive allometry. The most remarkable shape variations in the plateau pika were associated with food acquisition （temporalis development）, though other remarkable shape variations in the incisive and palatal foramen in the ventral view were also observed. The most important shape change in the woolly hare was demonstrated by the elongation of the nasal bones, expansion of the supra-orbital process and shape variation of the neurocranium.