Xenacanthus, meaning “strange spine”, was a 3 foot long shark-like freshwater fish which lived in North America, South America, Europe, and Asia from the second half of the Carboniferous Period to the end of the Permian Period, approximately 323-251 million years ago.

Xenacanthus was named in 1848 by Heinrich Ernst Beyrich, and since its official naming, over twenty different species have been ascribed to this genus. Xenacanthus was the namesake genus of the family Xenacanthidae, which includes Xenacanthus, Plicatodus, and Triodus. The family Xenacanthidae is part of the much larger group Xenacanthiformes, which includes genera like Barbclabornia (which might be the biggest xenacanthiform, estimated to measure almost 15 feet long), Sphenacanthus, and Orthacanthus. Most xenacanthiforms went extinct at the end of the Permian Period. Species dating to the middle and late Triassic Period which were formerly ascribed to Xenacanthus have been reclassified as a new genus called Mooreodontus, which was named in 2010.

Xenacanthus decheni. © Jason R. Abdale (August 7, 2025).

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Categories: Paleontology, Uncategorized

Tags: art, Asia, Carboniferous, Carboniferous Period, Europe, fish, Mesozoic, North America, paleo-art, paleontology, Paleozoic, Permian Period, Prehistoric, shark, South America, Triassic Period, xenacanthid, Xenacanthus