Ussuritidae are ancestral,

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

Phylloceratina The Phylloceratina comprise a suborder (biology), suborder of Ammonoidea, ammonoid cephalopods, belonging to the Ammonitida, whose range extends from the Lower Triassic to the Upper Cretaceous. Shells of the Phylloceratina are generally smooth w ...

characterized by generally smooth, discoidal, evolute shells with rounded venters and little or no ornamentation and by sutures with primitive monophyllitic saddles with a single terminal branch or leaflet.

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ...

Part L Mollusca 4, Ammonoidea The Ussuritidae are most likely derived from the Dieneroceratidae and give rise to the

Discophyllitidae Discophyllitidae are discoidal, generally evolute Phylloceratina from the Upper Triassic, derived from the Ussuritidae, in which the principal saddles of the suture have bifurcated or trifurcated endings, described as being di- or triphyllic. Di ...

. Seven genera are included: *''

Ussurites ''Ussurites'' is an extinct ammonoid cephalopod genus belonging to the suborder Phylloceratina and is included in the family Ussuritidae. Its range is restricted to the early Middle Triassic, (Anisian) As with the family, the shell of ''Ussurit ...

'' *'' Palaeophyllites'' *''

Monophyllites ''Monophyllites'' is an extinct cephalopod genus belonging to the family Ussuritidae that lived during the Triassic period, from Anisian to Ladinian age. Description "Form evolute laterally compressed. Whorl low and increasing slowly in height, ...

'' *'' Majsvarites'' *'' Leiophyllites'' *'' Eopsiloceras'' *'' Eophyllites'' Genera are distinguished on the basis of shell morphology and characteristics of the suture. Ussuritidae are also known as the Monophyllitidae, a junior synonym. Palaeophyllitidae, for ''Palaeophyllites'', is sometimes found in the literature.Paleobiology Database
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References

Ammonitida families Triassic first appearances Triassic extinctions {{Ammonitida-stub