| Named By: | Rich et al. in 1999 |
| Time Period: | Early Cretaceous |
| Location: | Australia, Victoria |
| Size: | Estimated at around 10 centimetres long (based upon comparison to similar mammals) |
| Diet: | Insectivore |
| Fossil(s): | Partial left dentary (lower jaw bone) |
| Classification: | | Chordata | Mammalia | Monotremata | Platypoda | Steropodontidae | |
Teinolophos trusleri was a prehistoric species of 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.
The species name honours 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. It is usually listed as a steropodontid, though it may be more basal.
The holotype is a partial left dentary known as NMV P208231. An age of approximately 123 million years makes this the earliest known monotreme. The lower molar is broadly similar in morphology to the m2 of Steropodon. The trigonid is compressed and the talonid has no basin. The dentary is about one sixth the size of Steropodon's, and wear facets indicate an "orthal" occlusion with the upper molars.