Paraceltitidae is a family of

Middle Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (disambiguation) * Middle Brook (disambiguation) * Middle Creek (d ...

and

Upper Permian The Permian ( ) is a geologic period and 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 251.9 Mya. It is the last period of the Paleozo ...

cephalopod A cephalopod is any member of the molluscan class Cephalopoda ( Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, ...

s, that comprise the earliest of the

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 Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from t ...

. Paraceltitidids have variably ribbed, discoidally evolute shells with compressed elliptical whorl sections and simple suture lines. Their origin is most likely in the

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 ...

of the

Prolecanitida Prolecanitida is an order of 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 ...

and they are the apparent source of the

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 we ...

. All together they lived for some 12 million years, from about 270.6 to about 258 million years ago. Paraceltitidae was named by Spath in 1930, however the taxon is omitted in the Treatise on Invertebrate Paleontology Part L, 1957 wherein respective genera are included in the Xenodiscidae. The family has returned to recognition and has been used by Tozer, 1981 and more recently by Leonova in 2002 and by

Korn Korn (stylized as KoЯn, or occasionally KoRn) is an American nu metal band from Bakersfield, California, formed in 1993. The band is notable for pioneering the nu metal genre and bringing it into the mainstream. Originally formed in 1993 b ...

in 2006.

References

GONIAT-online
7/26/11
The Paleobiology Database Paraceltitidae entry
accessed 7/26/11 Xenodiscoidea Ceratitida families Guadalupian first appearances Lopingian extinctions {{Ceratitida-stub