Tomognathus was a halecomorph fish related to the modern bowfin that lived in the Cretaceous Period. It was named by Dixon in 1850.

The name Tomognathus was also later applied to a modern species of ant by Mayr in 1861. But since the name was already taken it came instead to be classified as Harpagoxenus.

• Cavin, Lionel; Giner, Stephen (2012). "A large halecomorph fish (Actinopterygii: Holostei) from the Valanginian (Early Cretaceous) of southeast France". Cretaceous Research. 37: 201–208. Bibcode:2012CrRes..37..201C. doi:10.1016/j.cretres.2012.03.020.
• Forey, Peter L.; Patterson, Colin (2006). "Description and systematic relationships of †Tomognathus, an enigmatic fish from the English chalk". Journal of Systematic Palaeontology. 4 (2): 157–184. doi:10.1017/S1477201905001719. S2CID 86028273.