CHEIRACANTHIDAE Berg, 1940

Burrow, Carole & Newman, Michael, 2020, A redescription of the three longest-known species of the acanthodian Cheiracanthus from the Middle Devonian of Scotland, Palaeontologia Electronica (a 15) 23 (1), pp. 1-43 : 9

Family CHEIRACANTHIDAE Berg, 1940

Diagnosis. Acanthodiforms with a short branchial region completely covered by slender branchiostegal rays; jaw cartilages formed of a single mineralisation composed of calcified cartilage blocks; palatoquadrate with median fenestra; mandibular splints absent; 4-6 sclerotic bones; multicuspid denticles/gill rakers on some of the branchial arches; high slender scapular shaft; ossified coracoid and procoracoid; in spines with smooth rounded leading edge ridge separated by groove from smooth or ridged lateral surfaces; dorsal spine with mineralised basal cartilage; no prepelvic or admedian fin spines; polygonal tesserae on cranial roof; ornamented scale crowns.

Remarks. Denison (1979) assigned all acanthodiforms to the one family Acanthodidae , following the suggestion by Miles (1966) that the previous division of the group into the Mesacanthidae , Cheiracanthidae , and Acanthodidae represented a grade, rather than clade, classification. Our observations show that the endoskeletal tissue structure in the Cheiracanthidae (i.e., Cheiracanthus and Homalacanthus , excluding Protogonacanthus ), and their ornamented rather than smooth scales, indicate this family is not intermediate between the Mesacanthidae and Acanthodidae and should be considered a legitimate clade.