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Temporal range: Late Devonian-Early Carboniferous
|An artist's interpretation of Stethacanthus|
| †Stethacanthus altonensis|
It was 2 too 3 feet long, and was possibly 10 to 20 pounds. Stethacanthus that were male had an iron board on top with small spikes on top; females on the other hand just had mini spikes on top.