Brachythoraci is an extinct suborder of arthrodire placoderms, armored fish most diverse during the Devonian.
Brachythoraci
Arthrodira is an order of extinct armored, jawed fishes of the class Placodermi that flourished in the Devonian period before their sudden extinction, surviving for about 50 million years and penetrating most marine ecological niches. Arthrodires were the largest and most diverse of all groups of placoderms.
The pelagic selenosteid Amazichthys trinajsticae
Lower jaw plate of Eastmanosteus pustulosus from the Middle Devonian of Wisconsin
Heterosteus ingens from the Middle Devonian of Estonia