Letognathus is a genus of rhizodont tetrapodomorph that lived during the Carboniferous period.[1] Its remains come from the Blue Beach Member of the Horton Bluff Formation, near Hantsport, Nova Scotia. Like most rhizodonts, it was of relatively large size, had a large recurved fang at the symphysis of the lower jaw, and a row of three coronoid fangs along the length of the jaw in addition to its marginal dentition. Letognathus is important for rhizodont systematics because it retains a number of primitive features, such as ossified Meckel's cartilage, are not found in the genera Rhizodus and Strepsodus.
The members of the Rhizodontida have nearly all had complex taxonomic histories[2] due to earlier use of the genus Strepsodus as a wastebasket taxon. The taxon was originally assigned to the genus Rhizodus by John William Dawson and later to Strepsodus by Arthur Smith Woodward. A new genus was erected for the Horton Bluff material based on a number of differences from either Strepsodus or Rhizodus.