The Ceratitida is a diverse order that comprizes most of the ammonoid fauna of the Triassic, which diversified at various times into distinct groups generally thought of as superfamilies, and sharing that period with the early Phyllocerida and last of the medlicottiacean Prolecanitida.
Ceratitids produced a variety of shells, varying from thinly discoidal evolute to subglobular involute, and from smooth to variably sculpted with ribs and/or nodes. Sutures are generally ceratitic with smooth saddles and serrate lobes, but may be goniatitic or variably ammonitic. Some species even became uncoiled, like the earlier nautiliod Lituitidae and later ammonoid Baculitidae.
The Ceratitida began in the Late Permian with the evolute, discoidal Xenodiscidae, derived from the prolecanitid Daraelitidae, and seem to form a monophyletic group. Sixteen superfamilies are recognized, as shown, beginning with the earliest as arranged in more or less temporal sequence. Further indented taxa are derived from the preceding taxa where they had been included as families.
Ceratitida, Paleobiology Database.
Classification of E.T, Tozer 1981.  E. T. Tozer. 1981. Triassic Ammonoidea: Classification, evolution and relationship with Permian and Jurassic Forms.
Arkell et all, 1957 Mesozoic Ammonoidea, Treatise on Invertebrate Paleonology, Part L, R.C. Moore (ed); Geological Society of America and University of Kansas Press.
Credits, John M, Apr 30, 2011.