They had a culticular ornament of scales or mucrones and unlike the hibbertopterids , appendage IV was non-spiniferous .
Mycteroptids were medium medium - sized to fairly large mycteropoids with parabolic prosoma and a hastate telson with paired ventral keels .
Mycteroptids had a culticular ornament of scales or mucrones and unlike the hibbertopterids , appendage IV was non-spiniferous .
Mycteroptids were medium medium - sized to fairly large mycteropoids with parabolic prosoma and a hastate telson with paired ventral keels .