Perisphinctidae
Encyclopedia
Perisphinctidae is a family of Middle and Upper Jurassic
discoidal ammonites in the order Ammonitida
. They have a shell morphology that is mostly evolute, typically with biplicate, simple, or triplicate ribbing. Large forms have simple apertures and smooth body chambers while small forms have lappets and ribbed body chambers.
Perisphinctidae were derived from the Stephanoceratidae
in the Middle Jurassic Bajocian
and ranged into the Tithonian
at the end of the Jurassic. This family forms the root stock of the Perisphinctoidea which gave rise directly or indirectly to the other perisphinctoid families.
The Treatise on Invertebrate Paleontology (Part L, 1957)
includes the subfamilies Leptosphinctinae, Zigzagiceratinae, Pseudoperisphincinae, Perisphinctinae, Aataxioceratinae, Pictoniidae, Aulocostephaninae, Virgostephaninae, Dorsoplanitinae, and Virgatitinae in the Perisphictidae. Donavan et al also recognizes the Leptosphinctinae, Zigzagiceratinae, Pseudoperisphincinae, and Perisphinctinae but leaves out the others, adding instead the Epipletoceratinae, and Idoceratinae
Epipeltoceratinae is based on Epipletoceras, a genus in the Aspidoceratidae in the Treatise, (subfamily Peltoceratinae). The Idoceratinae is based on Idoceras
, a genus in the, according to the Treatise, polyphyletic Ataxioceratinae. Donavan et al separates the Aulocostephaninae, including the Pictoniidae, as the Aulocosphanidae. The Virgostephaninae, Dorsoplanitinae, and Virgatitinae are thereby separated also as separate families. all from the Upper Jurassic.
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
discoidal ammonites in the order Ammonitida
Ammonitida
The Ammonitida is an order of more highly evolved ammonoid cephalopods from the Jurassic and Cretaceous time periods, commonly with intricate ammonitic sutures....
. They have a shell morphology that is mostly evolute, typically with biplicate, simple, or triplicate ribbing. Large forms have simple apertures and smooth body chambers while small forms have lappets and ribbed body chambers.
Perisphinctidae were derived from the Stephanoceratidae
Stephanoceratidae
Sephanoceratidae is a family of planulate and coronate ammonites within the Stephanocerataceae. Shells are evolute so that all whorls are exposed and have strong ribbing that bifurcates, that is splits in two, on the flanks. Many have tubercles at the point of bifurcation...
in the Middle Jurassic Bajocian
Bajocian
In the geologic timescale, the Bajocian is an age or stage in the Middle Jurassic. It lasted from approximately 171.6 Ma to around 167.7 Ma . The Bajocian age succeeds the Aalenian age and precedes the Bathonian age....
and ranged into the Tithonian
Tithonian
In the geologic timescale the Tithonian is the latest age of the Late Jurassic epoch or the uppermost stage of the Upper Jurassic series. It spans the time between 150.8 ± 4 Ma and 145.5 ± 4 Ma...
at the end of the Jurassic. This family forms the root stock of the Perisphinctoidea which gave rise directly or indirectly to the other perisphinctoid families.
The Treatise on Invertebrate Paleontology (Part L, 1957)
Treatise on Invertebrate Paleontology
The Treatise on Invertebrate Paleontology published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and...
includes the subfamilies Leptosphinctinae, Zigzagiceratinae, Pseudoperisphincinae, Perisphinctinae, Aataxioceratinae, Pictoniidae, Aulocostephaninae, Virgostephaninae, Dorsoplanitinae, and Virgatitinae in the Perisphictidae. Donavan et al also recognizes the Leptosphinctinae, Zigzagiceratinae, Pseudoperisphincinae, and Perisphinctinae but leaves out the others, adding instead the Epipletoceratinae, and Idoceratinae
Epipeltoceratinae is based on Epipletoceras, a genus in the Aspidoceratidae in the Treatise, (subfamily Peltoceratinae). The Idoceratinae is based on Idoceras
Idoceras
Idoceras is a genus of perisphictacean ammonite, belonging to the Perisphinctidae subfamily Idoceratinae. The genus is known from the Upper Jurassic, with a widespread distribution. Shells of Idoceras are evolute, with a wide umbilicus; ribbing strong, bifurcate high on flanks. Suture simpler...
, a genus in the, according to the Treatise, polyphyletic Ataxioceratinae. Donavan et al separates the Aulocostephaninae, including the Pictoniidae, as the Aulocosphanidae. The Virgostephaninae, Dorsoplanitinae, and Virgatitinae are thereby separated also as separate families. all from the Upper Jurassic.