Moythomasia is one of the most speciose and completely known of all Devonian actinopterygian genera and has been incorporated into numerous phylogenetic studies. However, several species remain incompletely documented despite being known from excellent fossil material. Specimens from the Late Devonian of Germany and Australia are described herein. A form from Bergisch Gladbach, Germany, previously described by Jessen as Moythomasia cf. striata, is recognized as a new species: M. lineata, sp. Nov. Newly prepared specimens of Moythomasia durgaringa from the Gogo Formation, Western Australia, allow for the first rigorous full-body reconstructions of this species. Aspects of the dermal skeleton and body shape of this form are updated over previous descriptions. The genus is currently problematic owing to the highly fragmentary nature of the type species, M. perforata from Kokenhusen; however, it is considered provisionally valid owing to distinctive cranial ornamentation. The three completely known species (M. durgaringa, M. Nitda, and M. lineata, sp. Nov.) do not share any unique squamation-based characters exclusive to other Devonian actinopterygians, invalidating purely scaled-based referrals to this genus.