Xenodiscoidea, formerly Xenodiscaceae, is a superfamily within the
ammonoid order
Ceratitida
Ceratitida is an order that contains almost all ammonoid cephalopod genera from the Triassic as well as ancestral forms from the Upper Permian, the exception being the phylloceratids which gave rise to the great diversity of post-Triassic ammon ...
. The superfamily was named by Frech in 1902, presently contains ten families, only one of which was included in the original Otocerataceae of Hyatt, 1900, the remaining having been added.
The Xenodiscoidea has its origins in the Middle
Permian
The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...
in the
prolecanitid Daraelitidae through the ancestral Xenodiscidae. According to Kummel (1952) and Arkell et al. (1957) the Xenodiscidae gave rise to the
Otoceratidae and
Ophiceratidae. The Ophiceratidae in turn gave rise to the Dieneroceratidae which is considered the source for all remaining ceratitid stocks. All four families made up the original Otocerataceae
The Xenodiscidae is removed from the Otocerataceae as originally perceived (Arkell et al. 1957) to become the root of Xenodiscoidea, as emended. The Otoceratidae remains the type family of the Otocerataceae as revised. The Ophiceratidae is reassigned to the Noritaceae along with the Dieneroceratidae.
The Huananoceratidae, Liuchengoeratidae, Plueronodoceratidae, and Tapshanitidae, described by Zhao et al. 1978, include Late Permian and Early Triassic genera from Asia. The Xenoceltitidae, established by Spath in 1930 are included in the Treatise in the superfamily Noritaceae
The Xenodiscoidea gave rise through the Ophiceratidae to the Noritaceae. and through the Paraceltitidae to the revised Otocerataceae
References
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Ceratitida superfamilies
Guadalupian first appearances
Early Triassic extinctions
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