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(invertebrate zoology)
A primitive order of tetrabranchiate cephalopods; shells are external and smooth, being straight or coiled and chambered with curved transverse septa.



a superorder of invertebrates of the class Cephalopoda. The nautiloids appeared in the Cambrian and reached their zenith in the Ordovician and Devonian; they became rare in the Mesozoic and Paleocene. Modern representatives of the nautiloids constitute the single genus Argonauta.

The shell structure of nautiloids is similar to that of the ammonites. The nautiloids, however, have simpler septa to divide the shell into chambers and a siphon that, as a rule, is not situated along the shell wall. The structure of the initial parts of the shell in nautiloids differs from that in ammonites.

The extinct nautiloids made up approximately 700 genera, embracing more than 2,000 species. These predators lived in the sea; their modes of locomotion included creeping, soaring, and swimming.

The Nautiloidea are important in the study of the development of the Cephalopoda and in the stratigraphy of lower Paleozoic deposits.


Osnovy paleontologii: Molliuski-golovonogie, part 1. Moscow, 1962.


References in periodicals archive ?
On the relations of the principal muscles to the shell in Nautilus and some fossil nautiloids. Arkiv for Mineralogi och Geologi, 2, 219-254.
Because fossil nautiloids are common in Ontario's fossil record, the ROM tried for about a year to keep a living nautilus.
Nautiloids are low in richness and abundance in all Cretaceous strata of Texas (Kummel 1953; 1956; Hanger 1989), and the Upper Cretaceous is particularly barren.
Colour pattern polymorphism in Silurian nautiloid Phragmoceras Broderip, 1839.
In the Soeginina Beds distinct transgressive features appear compared to the underlying Vesiku Beds: rich normal marine fauna (corals, nautiloids) and numerous bivalves, gastropods, and calcareous algae (Solenopora).
Class 8 Cephalopoda (Octopods, Cuttlefish, Squids, and Nautiloids)
Theoretical approaches have been applied to fossil nautiloids (e.g., Westermann, 1973) and ammonoids (Westermann, 1975; Hewitt and Westermann, 1986; Jacobs, 1990; Daniel et al., 1997).
At the age of ten, I can remember hiking to those rocky cliffs and collecting fossils of nautiloids and brachiopods.
In another example, Signor and Brett (1984) described the marked increase in sculpture among gastropods, brachiopods, nautiloids and crinoids, paralleled by the subsequent decline of clades without these features.
These "nautiloids," the earliest cephalopods to appear in the fossil record, are thought to be the first organisms with jaws and consequently to be among the first predators, says Saunders, of Bryn Mawr (Pa.) College.
Other macrofossils present, or locally characteristic, within this formation are orbitolinids, nautiloids, brachiopods, vermetid gastropods, solitary corals, serpulids, echinoids, Plicatula placunea and Lithocodium aggregatum (e.g., Bover-Arnal et al., 2010; 2011).