A new primitive brachythoracid arthrodire, Uralosteus bashkiricus gen. et sp. nov., is described from two Emsian (late Early Devonian) localities in the Ural Mountains of the Autonomous Republic of Bashkortostan, Russia. The holotype includes bones of the skull and trunk armor associated with numerous scales from one individual, which facilitates the study of isolated microremains. The dermal ornament of distinctive tuberculate ridges suggests a relationship to Errolosteus Young, 1981 from the Emsian of southeastern Australia, but neither form is well enough known for this to be strongly supported in a character analysis. Some isolated placoderm bones with ridged ornament from southeastern Australia are figured, and interpreted to belong to a new form of williamsaspid rather than to Errolosteus. The new genus Uralosteus is referred to the family Buchanosteidae, defined by a unique overlap arrangement of the posterior lateral onto the anterior dorsolateral plate of the trunk armor. Buchanosteids, as a basal brachythoracid group, are a key to understanding the phylogeny of that clade. The type genus Buchanosteus comes from southeastern Australia, but it is now evident that the family was widely distributed in shallow marine environments during the Emsian.
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Vol. 23 • No. 1