Pronunciation: [fɹˈaɡmɐkˌə͡ʊn] (IPA) 
The word "phragmacone" refers to the chambered shell of a cephalopod. Its spelling can be a bit confusing as it contains several silent letters. The first syllable is pronounced with the "f" sound rather than the "ph" sound due to the Greek origin of the word. The "g" is also silent, and the "a" in the second syllable is pronounced like the "a" in "bat." The IPA phonetic transcription for "phragmacone" is /ˈfræɡməkoʊn/.
Phragmacone is a term used in the field of paleontology and zoology to describe a specific structure found in the internal shell of ammonites, which were a group of ancient marine mollusks. More specifically, the phragmacone refers to the chambered portion of the shell that houses the animal's soft body, including the head, tentacles, and other internal organs.
In ammonites, the phragmacone is formed by a series of interconnected chambers, known as septa, that are separated by thin, curved walls called septal walls. As the ammonite grows, it continuously adds new chambers to the phragmacone, each larger than the previous one, forming a spiral-shaped shell. The septal walls serve as partitions between the chambers, strengthening the shell structure and providing buoyancy control.
The phragmacone plays a vital role in the life of an ammonite. The animal is able to control the amount of water and gas within the chambers, allowing it to adjust buoyancy and move up or down within the water column. This adaptation was crucial for the ammonite's survival, enabling it to find optimal depths for feeding, avoiding predators, or reproducing.
Although ammonites went extinct millions of years ago, the study of their phragmacone has provided valuable insights into ancient marine ecosystems and evolutionary patterns. By examining the size, shape, and arrangement of chambers and septal walls in phragmacones, scientists can classify different species of ammonites and trace their evolutionary relationships.
The chambered cone of the shell of the belemnite cephalopods.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.
The word "phragmacone" is derived from the Greek words "phragma" meaning "fence" or "partition", and "konos" meaning "cone". The term refers to a specific part of the internal shell of ammonites, which is divided into chambers by calcified partitions. These partitions help the ammonite control its buoyancy and depth in the water by adjusting the amount of gas in each chamber. Thus, the word "phragmacone" essentially describes the cone-like structure with partitions found in the ammonite shell.
