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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 ?
Knowing that the chambered shells represent cephalopods also helps us to interpret the ancient environments inhabited by nautiloids.
Breed, "The Discovery of Orthocone Nautiloids in the Redwall Limestone, Marble Canyon, Arizona," in C.
Twenty-five million years ago, nautiloids occurred in seas around the world, but now they are restricted to a region from the Philippines south through Indonesia to Australia and eastward to the Fiji Islands.
Stephenson (1941) described only one nautiloid species from the Navarro Group.
Reconstructing the life history of modern and fossil nautiloids based on the nitrogen isotopic composition of shell organic matter and amino acids.
Among the fossils are a variety of creatures from sponges, worms and nautiloids to solitary hydroids, also known as the flowers of the sea.
Fossils of nautiloids (an ancestor of the giant squid) dug up during the building of the new centre are set into the floor of the building; a reconstructed Stone Age roundhouse sits on the site of a crannog (a prehistoric dwelling built on an artificial island in a lake); and the reserve's spectacular new glass-sided bird observatory sits above lime kilns that provided many of the bricks that built Belfast.
Dick's Ganymedian slime-mold Lord Running Clam; Octavia Butler's gigantic tentacled Oankali slugs; Hal Clement's Mesklinite centipedes; the ichthyoids, arachnoids, nautiloids, and echinoderms of Star Maker; the sublime jellyfish of The Abyss.
5 + m--microlaminated, silty, argillaceous eurypterid-dolostone with Eurypterus remains, nautiloids, and ostracods (Herrmannina).
Manda and Turek discuss colour ornamentation in straight-shelled nautiloids in the Ordovician and Silurian, and Szaniawski describes Early Palaeozoic conodont-like fossils of uncertain affinity.