Osteostraci
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The class Osteostraci is an extinct taxon of bony-armored jawless fish, termed "ostracoderms", that lived in what is now North America, Europe and Russia from the Middle Silurian to Late Devonian.
Cephalaspis species
Parameteoraspis fossilized headshield
Gnathostomata
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Gnathostomata are jawed vertebrates. Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all extant vertebrates, including all living bony fishes and cartilaginous fishes
Osteostraci
…jawed vertebrates. They are thought to be the sister-group to pituriaspids, and together, these two taxa of jawless vertebrates are the sister-group of gnathostomes. Several synapomorphies support this hypothesis, such as the presence of: sclerotic ossicles, paired pectoral fins, a dermal skeleton with three layers…
Dunkleosteus terrelli skull, Royal Tyrrell Museum, Drumheller, Alberta, 2025 07 13
Wikilemon Nbrevirostris 1 Terry Goss
Pygocentrus nattereri Karlsruhe Zoo 01
Nile crocodile head