Other than that set of giant teeth, these two taxa resemble one another

More work needs to be done on the LRT,
but this current pairing of time-separated extinct fish seemed worth sharing.

Not the origin of the preopercular (Fig 1, light yellow) in this clade from a larger cheek cover in tiny toothless and unnamed ANU V244 from the Early Devonian that breaks into three parts in larger toothier Calamopleurus from the Early Cretaceous.

At the same time, note the genesis of the jugal (cyan) splitting and expanding to form a tripartite operculum in just a few hundred million years.

Figure 1. The tiny unnnamed genus (ANU V244) from the Early Devonian compared to the much larger Cretaceous predator, Calamopleurus. Note the extreme width of the skull in both along with the large coverage of the postorbital (light yellow) covering most of the cheek. The former is virtually toothless, the later is blessed with long, sharp teeth. Note also the expansion and splitting of the jugal to form a three-part operculum, convergent with several other fish clades.

References
Agassiz L 1833-43. Recherches sur les poissons fossiles. Imprimerie de Petitpierre et Prince, Neuchâtel.

wiki/Calamopleurus