The Clydonautilidae are Middle and Upper Triassic
nautiloid cephalopods, which are derivatives of the
clydonautiloidean family
Liroceratidae
Liroceratidae is an extinct family of nautilids, shelled marine molluscs, belonging to the Clydonautiloidea, consisting of generally smooth, involute, nautiliconic forms with a small umbilicus. The whorl section is usually depressed and broad ...
, that have generally smooth, involute, globular to compressed shells, characterized by a
suture with prominent lobes and saddles. The family is known to contain five genera, These are:
*''
Clydonautilus
''Clydonautilus'' is a genus of nautiloids and type for the Clydonautilidae that has been found in the Upper Triassic of Europe, India, and Timor. Its type is ''C. noricus''.
''Clydonautilus'' is the most derived of the Clydonautilitidae, evide ...
''
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Callaionautilus''
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Cosmonautilus''
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Proclydonautilus''
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Styrionautilus''
Of these only ''Styrionautilus'' is known from the Middle Triassic. The other four are so far restricted to the Upper Triassic.
The five genera in the Clydonautilidae form a sequence of increasing sutural complexity, beginning with ''Styrionautilus'' and ending with ''Clydonautilus''. ''Styrionautilis'', which has the simplest suture of the five, has a broad ventral saddle with a flat bottom and a gently curved lateral lobe. ''Clydonauatilus'' at the opposite extreme has a secondary ventral saddle within the ventral lobe modifying the primary ventral saddle and a deep, asymmetric lateral lobe. ''Callaionautilus'', ''Cosmonautilus'', and ''Proclydonautulus'' fall in between.
References
* Bernhard Kummel, 1964. Nautiloidea -Nautilida;
Treatise on Invertebrate Paleontology, Part K. Geol Soc of America and Univ of Kansas press, R.C. Moore (ed)
{{Taxonbar, from=Q5137094
Prehistoric nautiloid families
Middle Triassic first appearances
Late Triassic extinctions