Search results
Results from the WOW.Com Content Network
The other three unite related orders which share a common ancestor and form a branch of the nautiloid taxonomic tree: Plectronoceratoidea, which consists mostly of small Cambrian forms that include the ancestors of subsequent stocks; Orthoceratoidea, which unites different primarily orthoconic orders (including the ancestors for Bacritida and ...
Nautilus (from Latin nautilus 'paper nautilus', from Ancient Greek ναυτίλος nautílos 'little sailor') [3] are the ancient pelagic marine mollusc species of the cephalopod family Nautilidae. This is the sole extant family of the superfamily Nautilaceae and the suborder Nautilina .
Unlike most modern cephalopods, most ancient varieties had protective shells. These shells at first were conical but later developed into curved nautiloid shapes seen in modern nautilus species. It is thought that competitive pressure from fish forced the shelled forms into deeper water, which provided an evolutionary pressure towards shell ...
Volborthella, some fossils of which predate , was long thought to be a cephalopod, but discoveries of more detailed fossils showed its shell was not secreted, but built from grains of the mineral silicon dioxide (silica), and it was not divided into a series of compartments by septa as those of fossil shelled cephalopods and the living Nautilus are.
Nautilus are unable to easily move across areas deeper than 800 metres, and most of their activity occurs at a depth of 100–300 metres deep. [4] Nautilus can occasionally be found closer to the surface than 100 metres, however, the minimum depth they can reach is determined by factors such as water temperature and season. [4]
When motionless, Nautilus can only extract 20% of oxygen from the water. [62] The jet velocity in Nautilus is much slower than in coleoids, but less musculature and energy is involved in its production. [75] Jet thrust in cephalopods is controlled primarily by the maximum diameter of the funnel orifice (or, perhaps, the average diameter of the ...
The 2nd-century Alexandrian Greek writer Ptolemy, one of the most important geographers, mathematicians and astronomers in the ancient world, refers to Ireland in two of his works. In the astronomical treatise known as the Almagest he gives the latitudes of an island he calls Mikra Brettania (Μικρὰ Βρεττανία) or "Little Britain ...
Driscoll, K. The Early Prehistory in the West of Ireland: Investigations into the Social Archaeology of the Mesolithic, West of the Shannon, Ireland (2006). Flanagan L. Ancient Ireland. Life before the Celts. (1998). ISBN 0-312-21881-8; Thompson, T. Ireland’s Pre-Celtic Archaeological and Anthropological Heritage. (2006) Edwin Mellen Press.