The inferior vertebrates (fish) fauna of the Gaspé Sandstone (Quebec, Canada) was almost unknown 50 years ago, except for an Osteostracan Cephalaspis (jawless fish) described by Russell in 1954, which was later referred to a new genus by Belles-Isles in 2011. In 1969, Pageau described many Osteostracans, Arthrodira Placoderms (fish with jaws), Acanthodians (fish with bony spines on fins), and Selacians (sharks). In this article, 2 rare Arthrodira specimens are described in their geological setting, a deltaic environment created by the erosion of a mountain range undergoing active uplift. One is a cephalic shield (dermal skull), the other, a thoracic shield. These are rare because they are articulated (the thoracic shield has the spinal plate in place) and because they represent the first record from the geological York River Formation of Gaspé Sandstone at L’ Anse-à-Brillant (on the south side of Baie de Gaspé). These fossils confirm that the York River Formation at L’ Anse-à-Brillant is Lower Devonian of Emsian age (407-394 Ma), and that the Battery Point Formation at Cap-aux-Os on the north side of Baie de Gaspé is near the top of the York River Formation, therefore also of Emsian age.