Teinolophos is a genus of prehistoric monotreme, or egg-laying, mammal. It is known from a lower jawbone found in Flat Rocks, Victoria, Australia. It lived during the Aptian age of the Lower Cretaceous. It is the earliest known relative of the Platypus. The species name honors the artist Peter Trusler. The genus name, Teinolophos, means 'extended ridge', a reference to its tooth structure. Originally, Teinolophos was thought to be a eupanthothere. Further research revealed similarities to Steropodon, except in size: the animal was around 10 cm long.