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- proper noun A taxonomic
genuswithin the orderAcanthodiformes — an extinctspiny shark from the Permian.
from Wiktionary, Creative Commons Attribution/Share-Alike License
Prior to this study, the only acanthodian whose braincase has been studied is the genus Acanthodes, which is a group that appears late in acanthodian history, Brazeau explained.
Ptomacanthus is about 100 million years older than Acanthodes and Brazeau's study has shown that its braincase shares little in common with those of bony vertebrates and is more similar to those of early shark-like fishes.
The braincase of Acanthodes resembles those of early bony vertebrates, a lineage that includes humans and other land vertebrates (for this reason, acanthodians are thought to be more closely related to bony fishes than to sharks).