New data on the structure of the Early Devonian lungfish,Dipnorhynchus

A skull of a young specimen of Dipnorhynchus sussmilchi (Etheridge Jr), from the base of the Bloomfield Limestone Member (mid-Emsian, probably perbonus Zone) at Taemas, has both sides of the skull roof preserved, but the cheeks are missing. The posterior end of the endocranium, up to its dorsal extremity, provides new data on the endolymphatic sacs, and the attachment of the epaxial muscles. The endolymphatic region is compared with that of Chirodipterus australis. The palate is not fully formed and the marginal ridges are not fully developed. The fine structures around the dermopalatines and the pterygoids are preserved, indicating the manner in which the plates grew. The position of the parasphenoid is clearly outlined against the pterygoids, and confirms the view that this primitive genus of dipnoans did not have the pterygoids divided by the parasphenoid. All these features provide new information and comparison with Dipterus valenciennesi, the next oldest genus on which the same regions are preserved. In addition, a new mandible from a horizon low in the Cavan Bluff Formation is well preserved and provides information on the external bones of Dipnorhynchus.