''Ussuria'' is a genus of Lower Triassic

ammonite Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...

s with a smooth, involute discoidal shell with submonophyllic sutures, belonging to the

ceratitid 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 ammon ...

family

Ussuriidae Ussuriidae is an extinct Family (biology), family of cephalopods belonging to the Ammonite order (biology), order Ceratitida and superfamily (taxonomy), superfamily Noritoidea. References The Paleobiology Database
accessed 9/24/07 Norit ...

. ''Ussuria'' has been found in Russia in

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(original discovery),

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, and

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in the United States.

Description

The shell of ''Ussuria'' is laterally compressed and involute. Whorls are deeply embracing, increasing rapidly in height. Umbilicus is narrow and deep with rounded shoulders. Sides gently convex, converging on a narrow-rounded venter. Sutures are ammonitic, with digitate lobes and submonophyllic saddles. The external, (or ventral), lobe is divided by a broad digitate siphonal saddle with each side of the lobe deeply trifid. The two or three principal lateral lobes on either side that are wide and deeply digitate, followed dorsally by another three or more smaller, also digitate, auxiliary lobes. The first lateral saddle is typically indented only on the ventral (rim) side and the second lateral saddle only of the dorsal side. ''Ussuria'' somewhat resembles '' Sturia'', commonly placed in the

Ptychitidae The Ptychitidae is a family of ceratitid ammonites (''ammonites sensu lato''). They are combined with the Eosagenitidae and Sturiidae in the superfamily Ptychitoidea. Ptychitid genera have compressed, involute shells in which the inner whorls ...

. The early growth stages of ''Ussuria'' are like '' Dimorphoceras'', the intermediate growth stage like '' Thalassoceras''.

Taxonomy

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classified ''Ussuria'' in the Ussuriidae, based on Siberian forms, which is followed by W.J. Akell, et al., in the American Treatise part L, 1957. Related genera include '' Metussuria'', '' Oxyussuria'', and '' Parussuria''. Other classifications place Ussuriidae, including ''Ussuria'', in the Meekocerataceae, an alternative for the Noritaceae.

References

*W.J. Arkell et al.,1957. Mesozoic Ammonoidea. Treatise on Invertebrate Paleontology, Part L. Geological Soc of America. Geological Society of America and University of Kansas Press. * James Perrin Smith, 1932. Lower Triassic Ammonoids of North America, US Geological Survey, Professional Paper 167.
Paleobiology Database-Ussuria
Noritoidea Triassic ammonites Ceratitida genera Triassic animals of Asia {{Ceratitida-stub