Xenodiscidae
Encyclopedia
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.
Ceratitida
The 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 ammonites....
and comprise Middle and Upper Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "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
Xenodiscaceae
The Xenodiscaceae is a superfamily within the ammonoid order Ceratitida. The Xenodiscaceae, 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 Xenodiscaceae has its origin in the...
, are derived from the Daraelitidae
Daraelitidae
The Daraelitidae form a family in the ammonoid order Prolecanitida from the Upper Mississippian - Middle Permian characterized by discoidal shells with no prominent sculpture, moderately large umbilicus, and goniatitic or ceratitic sutures with a trifid ventral lobe and few auxiliary lobes.The...
, a family in the Prolecanitida
Prolecanitida
The Prolecanitida are extinct ammonoid cephalopods with discoidal to thinly lenticular shells with goniatitic or ceratitic sutures and which retained the simple retrochoanitic siphuncle with backward extending septal necks. As typical for ammonoids the siphuncle is along the ventral margin...
(ibid). In turn, the Xenodiscidae provided the root stock for the subsequent expansion and diversification of the Ceratitida in the Triassic.