Watsonulus is an extinct genus of prehistoric ray-finned fish that lived during the Early Triassic epoch in what is now Madagascar.

[2][1] It may have also existed in what is now Himachal Pradesh, India, during the Induan age (Early Triassic).

Watsonulus belongs to Parasemionotidae, a family of early neopterygians closely related with halecomorphs.

Other members of Parasemionotidae include Albertonia, Candelarialepis, Icarealcyon, Jacobulus, Lehmanotus, Parasemionotus, Qingshania, Stensioenotus, Suius, and Thomasinotus.

Similar to Albertonia (Early Triassic of Canada) and Icarealcyon, the pectoral fins of Watsonulus were fairly large.