Isotelus was named by Dekay (1824). Its type is Isotelus gigas.It was reranked as Asaphus (Isotelus) by Owen (1852).It was assigned to Asaphus by Owen (1852); to Asaphinae by Phleger (1933) and Whittington (1941); to Isotelinae by Henningsmoen (1960) and Owen (1981); to Asaphida by Sepkoski (2002); and to Asaphidae by Jell and Adrain (2003) and Owens and Fortey (2009).I. aktchokensis, I. bradleyi, I. copenhagenensis, I. frognoensis, I. gigas (type species), I. harrisi (syn. I. platymarginatus), I. iowensis, I. kimmswickensis, I. maximus, I. megistos, I. parvirugosus, I. platyrhachis, I. skapaneidos, I. spurius, I. susae, I. violaensis, I. walcotti (syn. I. planus)1824 Isotelus Dekay1852 Asaphus (Isotelus) Owen1933 Isotelus Phleger, Jr. p. 181941 Isotelus Whittington p. 5121960 Isotelus Henningsmoen1981 Isotelus Owen2002 Isotelus Sepkoski, Jr.2003 Isotelus Jell and Adrain p. 3892009 Isotelus Owens and Fortey
