Xenodiscidae

Xenodiscidae Temporal range: M-U Permian
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Xenodiscus besairiei on display at the Museo Civico di Storia Naturale di Milano
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Ammonoidea
Order:	Ceratitida
Suborder:	Paraceltitina
Superfamily:	Xenodiscaceae
Family:	Xenodiscidae Frech 1902
Genera
Aldanoceras Arctotirolites Glyptophiceras Hanielites Hemilecanites Hypophiceras Iranites Kaibinoceras Kelteroceras Metophiceras Penglaites Phisonites Pseudoceltites Shevyrevites Sutchanites Tompophiceras Tozericeras Xenodiscus

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.

The Xenodiscidae, which are part of the superfamily Xenodiscaceae, 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.

References

• Arkell et al., 1957; Mesozoic Ammonoidea, Treatise on Invertebrate Paleontology, Part-L, Ammonoidea; Geological Soc. of America, reprinted 1990.
• The Paleobiology Database July 2009