Xenodiscidae
The Xenodiscidae are the earliest of the Ceratitida and comprise Middle and Upper Permian genera characterized by compressed, discoidal, evolute shells with rounded to acute venters and commonly with lateral ribs. Sutures are goniatitic to weakly ceratitic.Arkell et al, 1957 The Xenodiscidae, which are part of the superfamily Xenodiscoidea, are derived from the Daraelitidae, a family in the Prolecanitida (ibid). In turn, the Xenodiscidae provided the root stock for the subsequent expansion and diversification of the Ceratitida in the Triassic. Notes References * Arkell et al., 1957; Mesozoic Ammonoidea, Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ..., Part-L, Ammonoidea; Geological Soc. of America, reprinted 1990. The Paleobiology Databa ...
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