ON THE NOMENCLATURE OF THE ROOFING AND CHEEK BONES IN PRIMITIVE DIPNOANS

An attempt is made to examine the problem of the nomenclature of the r oofing bones in the most primitive dipnoans, which is still a matter o f contention. The letter and number system that has been in use for th e last half century was based on Dipterus, a Middle Devonian genus tha t has a reduced number of bones and a greatly shortened cheek in compa rison with the Early Devonian Dipnorhynchus. Several attempts have bee n made to expand the Dipterus nomenclature to accommodate the more pri mitive condition in Dipnorhynchus and Uranolophus, but none has yet be en generally accepted. The most recent attempt by Westoll (1989), whic h involves errors of reconstruction and interpretation, is discussed i n this paper. The matter is of importance because assessment of the re lationships of primitive dipnoans to other groups depends to a substan tial extent upon these homologies.