break into separate teeth. These teeth are pointed, unlike the other southern hemisphere lamprey Geotria australis which has spatulate (broad and rounded) teeth. The eyes of Mordacia are dorsolaterally located, which is unlike the other known lamprey species, and they contain a photoreceptor that has both rod and cone characteristics. This photoreceptor is also unique to M. mordax and enhances vision in darkness by optimizing photon reception. It is not unlike deep sea fish eye anatomy, in that sense as M. mordax only comes out of the sediment of rivers at night to travel. The posterior and anterior dorsal fins of Mordacia are continuous to the caudal fin, unlike G. australis. When M. mordax is fully developed those anterior and posterior dorsal fins are well separated, which distinguishes them from northern hemisphere lampreys. Lampreys have been established as worthy models in understanding the development of higher vertebrate anatomy and physiology, with one such experiment determining that major classes of lipoproteins are similar in Mordacia to those found in humans. M. mordax and the lamprey group have also been shown to be the lowest vertebrate to have clear roles for neurohormones in the hypothalamic-pituitary-gonadal axis. References mordax Freshwater fish of Australia short-headed lamprey