Giant fangs are new developments in this fish clade

From the Lower Jurassic to the present
giant fangs uniquely developed in this small clade of bony fish (compare Figs. 1, 2). Mesozoic members don’t have fangs. Extant members do.

BRLSI M1332 (Cawley et al. 2018; Early Jurassic) reported on 3D specimens (BRLSI M1332) attributed to Pachycormus. You might remember earlier I mistakenly nested the tuna mimic BRLSI specimen with the tuna, Thunnus.  Now the BRLSI specimen nests with Hydrolycus (below), lacking only the hyperelongate teeth.

Hydrolycus armatus (Jardine 1841, up to 1.1m in length) is the extant dogtooth characin or payara of tropical South America. Here it nests with Amia, the bowfin and Salmo, the salmon. The skull is taller and narrower. The anterior teeth are longer. The maxilla extends to the quadrate. The jugal and postorbital are extensive. The intertemporal, supratemporal and tabular are reduced. A parietal crest is present. The long teeth are used for spearing piscine prey.

These are some of the basalmost
teleost fish (orange clade above).

References
Cawley JJ, Kriwet J, Kug S and Benton MJ 2019. The stem group teleost Pachycormus(Pachycormiformes: Pachycormidae) from the Upper Lias (Lower Jurassic) of Strawberry Bank, UK. PalZ 93(2):285–302.