Brachythoraci is an extinct suborder of arthrodire placoderms, armored fish most diverse during the Devonian.

Arthrodira is divided into three main groups: the paraphyletic Actinolepida and Phlyctaenii, and then the monophyletic Brachythoraci.

Brachythoraci is then further divided into the large derived clade Eubrachythoraci and several basal groups: Buchanosteoidea, Homosteidae, and Holonematidae.

[1] (Although Holonematidae's membership in Brachythoraci is disputed.

)[2] Below is a cladogram from the 2016 Zhu et al. phylogenetic study:[2] Elvaspis tuberculata Dicksonosteus arcticus Turrisaspis elektor Groenlandaspis antarcticus Holonema westolli Homostius sulcatus Antineosteus lehmani Buchanosteus confertituberculatus Goodradigbeeon australianum Parabuchanosteus murrumbidgeeni Dhanguura johnstoni Gemuendenaspis angusta Xiangshuiosteus wui Millerosteus minor Coccosteus cuspidatus Dickosteus threiplandi Watsonosteus fletti Protitanichthys rockportensis Plourdosteus canadensis Panxiosteus ocullus Janiosteus timanicus Harrytoombsia elegans Torosteus tuberculatus Torosteus pulchellus Mcnamaraspis kaprios Compagopiscis croucheri Trematosteus fontanellus Incisoscutum ritchiei Incisoscutum sarahae Rolfosteus canningensis Tubonasus lennardensis Fallacosteus turneri Camuropiscis laidlawi Latocamurus coulthardi Rhachiosteus pterygiatus Eastmanosteus calliaspis Eastmanosteus pustulosus Kiangyousteus yohii Golshanichthys asiatica Westralichthys uwagedensis Dunkleosteus raveri Dunkleosteus terrelli Dunkleosteus amblyodoratus Heterosteus ingens Yinosteus major Tapinosteus heintzi Bullerichthys fascidens Kendrickichthys cavernosus Bruntonichthys multidens Dinichthys herzeri Hadrosteus rapax Gorgonichthys clarki Heintzichthys gouldii Pachyosteus bulla Gymnotrachelus hydei Stenosteus angustopectus Brachyosteus dietrichi Melanosteus occitanus Rhinosteus parvulus