Ussuritidae are ancestral,

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

Phylloceratina The Phyllocertina comprise a suborder of ammonoid cephalopods, belonging to the Ammonitida, whose range extends from the Lower Triassic to the Upper Cretaceous. Shells of the Phylloceratina are generally smooth with small to large umbilici and c ...

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'' (or ''TIP'') 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 co ...

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. D ...

. Seven genera are included: *'' Ussurites'' *'' Palaeophyllites'' *'' Monophyllites'' *'' 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