New cranial remains of neoceratodonts (Osteichthyes: Dipnoi) from the late Oligocene to middle Miocene of northern Australia, with comments on generic characters for Cenozoic dipnoans

ABSTRACT

Fossil lungfish skull and jaw bones from Riversleigh Station in North Queensland, though not found associated with each other, have well preserved articular facets for adjoining bones. The skull of the new Cenozoic neoceratodont, Mioceratodus anemosyrus can be reconstructed with reasonable accuracy, and compared with those of the Recent lungfishes Neoceratodus forsteri from Australia and Protopterus annectens and P. aethiopicus from Africa. In N. forsteri the ascending process of the pterygopalatine bone is angled, flattened and slightly twisted at the distal extremity, and fits within a socket on the descending process of the JLM bone. M. anemosyrus has a short, angled ascending pterygopalatine process with two lateral suture facets that fit within a matching groove in the descending process of the JLM bone. In protopterid species the descending process of the JLM bone is a simple peg fitting within a groove in the elongate ascending pterygopalatine process. A pterygopalatine/calvarial suture appears to be reduced or absent in more primitive dipnoans, and to have a different form in gnathorhizids. It is therefore possible that the structure of this suture is of use in the characterization of some dipnoan taxa.