The taxonomy of the Lampreys Geotria and Mordacia and their distribution in Australia

The taxonomy of the Southern Hemisphere lampreys, Qeotria and Mordacia , is reviewed. Many invalid species have been created within these genera due to a lack of knowledge of the great morphological changes that take place during development. The sequence of changes in the dentition of Mordacia is described in detail.
Geotria is now considered to be monotypic, containing only Q. australis Gray, which is found in Australia, New Zealand, and South America. Caragola is regarded as a synonym of Mordacia , and thus the exclusively South American C. lapicida becomes M. lapicida (Gray). The other Mordacia species, M. mordax (Richardson) and M. praecox Potter, are found only in Australia. All these species are anadromous and parasitic, except M. praecox , which is nonparasitic and never leaves fresh-water.
A comparison of anatomical features indicates that living lampreys (Petromyzonidae) are best separated into three subfamilies: Petromyzoninae to contain all Northern Hemisphere genera, Geotriinae for Geotria , and Mordaciinae for Mordacia.
A record of the Australian rivers in which lampreys have been found, shows that both genera are sympatric in South Australia, western Victoria, and Tasmania, and that only Qeotria is found in Western Australia, and only Mordacia in south-eastern Australia.