Ptomacanthus anglicus

is a species of Acanthodians lived in the Early Devonian, and was found from the Old Red Sandstone known for the Devonian age strata in England ³⁾.

The generic name "Ptomacanthus" is derived from the Greek words "ptoma" and "akantha", meaning "corpse" and "thorn" respectively ³⁾. The specific name "anglicus" is named after the Teutonic tribe "Angle" who lived in England in the 5th century 3).

Ptomacanthus is a relatively large acanthodian, reaching up to 30 cm in length ³⁾, and the dorsal outline is highly arch ¹⁾. The head part is also broad, and the eyes are large as in other acanthodians ³⁾.

There are two dorsal spines, a pair each of pectoral and pelvic spines (webbing are not identified), a anal spine, three pairs of intermediate spines between the pectoral and pelvic spines, two rows of prepectoral spines, and a median spine ^{1), 3)}.

Ptomacanthus probably had lived in the freshwater shallows arround the estuaries ²⁾ and swallowed other animals such as a placoderm Cephalaspis ^{2), 3)}.

Acanthodians, as the early gnathostome, provide a clue to understand the evolution of jawed vertebrates, however, Ptomacanthus has features of both osteichthyans and chondrichthyan, complicating its phylogenetic position ¹⁾. Acanthodian themselves, has a challenge, that is monophyly or not ¹⁾.