Pups nesting with wolves. Imagine that…
I googled ‘pupfish, wolffish’ looking for a prior hypothesis of relationship between these two fish. Apparently, there is none (See below), despite the obvious and overall similarities, other than size.
According to Wikipedia
Anarhichas belongs in the Anarhichadidae (nothing but wolffish and wolf eels), then the Perciformes (a huge clade of ray fin fish).
Another traditional member of the Cyprinodontiformes,
Anableps, the four-eyed fish, nests elsewhere in the LRT, with sea robins, like Prionotus. Perhaps that nesting will change when I can find some guppy skulls, which seems not very likely, at present.
Pseudorestias brings new insights
into the very weird cranium of Anarhichas.
Anarhichas vomerinus (Linneaus 1758; 1.5m length) is the extant Atlantic wolffish. The marginal and vomer teeth are robust. The conjoined temporal fenestra meet dorsally along a thin ridge. Pelvic fins are absent.
Pseudorestias lirimensis (Arratia, Vila, Lam, Guerrero & Quezada-Romegialli 2017) is a tiny, newly discovered pupfish, a traditional member of the Cyprinodontiformes (killifish), but here related to the much larger wolffish. The skull is broad, as in other teleost fish. Pelvic fins are tiny.
The teleost subset of the LRT is undergoing review and reinterpretation. This is not easy, but parts are working out. I will let you know when the whole clade is better supported at every node.
Arratia G, Vila I, Lam N, Guerrero CK and Quezada-Romegialli C 2017. Morphological and taxonomic descriptions of a new genus and species of killifishes (Teleostei: Cyprinodontiformes) from the high Andes of northern Chile. PLOS ONE 12(8): e0181989. doi:10.1371/journal.pone.0181989
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.