Pseudonautilidae is a family of
Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...
and Lower
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
nautilid cephalopod
A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head ...
s belonging to the same superfamily as modern ''
Nautilus
The nautilus (, ) is a pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina.
It comprises six living species in t ...
'',
Nautilaceae
The Nautilaceae form one of five superfamilies that make up the Nautilida according to Bernard Kummel (1964), and the only one that survived past the Triassic. The Nautilaceae comprise six families: Nautilidae, Paracenoceratidae, Pseudonautilidae ...
, but forming a different branch from the family
Nautilidae
The nautilus (, ) is a pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina.
It comprises six living species in t ...
. Pseudonautilids, together with other nautilids, were contemporary with the
ammonoids
Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...
, which comprise an entirely different set of shelled cephalopod stocks more closely related to octopus and squid.
Pseudonautilids are characterized by an involute, generally compressed, nautiliconic shell; highly sinuous "goniatitic" sutures; and
siphuncle
The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and ...
generally located between the center and venter. Three genera are included.
* '' Pseudonautilus'': Shell involute, compressed; whorl section higher than wide, flanks flattened; venter broadly arched; umbilicus small and deep; suture with deep narrow ventral lobe, large V-shaped lateral lobes on either side followed by rounded saddles then smaller lobes just above the umbilical seam; siphuncle subventral. Found in Europe and North Africa. An almost perfect homeomorph of the Permian ''
Permoceras
''Permoceras'', the sole member of the family Permoceratidae, is a genus of coiled nautiloids with a smooth, compressed involute shell, whorls higher than wide, earlier whorls hidden from view. The venter is rounded as are the ventral and umbili ...
''. Range as for family.
* '' Pseudaganides'' Nautiliconic; whorl section subrectangular to compressed with flattened flanks converging toward a flattened to rounded venter; suture with ventral lobe and broad deep lateral lobes; siphuncle central to subcentral.. Found in the Jurassic of Europe and Pakistan.
* ''Xenocheilus'' Like ''Pseudonautilus'' but with subangular ventral shoulders and rounded, rather than pointed, lateral lobes. From the Upper Jurassic and Lower Cretaceous of Europe and north Aftrica.
References
* Bernhard Kümmel, 1964. Nauiloidea -Nautilida.
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 K. Geological Society of America and University of Kansas Press, Teichert and Moore, (eds).
Pseudonautilidae -PaleodbDec 2010
{{Taxonbar, from=Q7255163
Prehistoric nautiloid families
Jurassic first appearances
Early Cretaceous extinctions