phragmocone การใช้

• The chambered part of the ammonite shell is called a phragmocone.
• The phragmocone is usually only found with the better preserved specimens.
• Actinosiphonate deposits in the siphuncle are confined to early part of phragmocone.
• Description is based on an incomplete immature phragmocone with a 5mm cross section.
• Periodic constrictions may be present on the phragmocone.
• The phragmocone is rapidly expanding and strongly exogastric.
• In the early juvenile stage the living chamber is about as long as the chambered phragmocone.
• The short phragmocone is poorly known.
• The chambered phragmocone is finely ribbed.
• Both belemnotheutids and belemnites resembled modern squids except that they had chambered internal skeletons called phragmocones.
• Siphuncel segments in this genus tend to become strongly elongated in the mature part of the phragmocone.
• The holotype of " Microbaltoceras minore " is only 10mm long, essentially all phragmocone.
• Projecting forwards from one side of the phragmocone is the thin " pro-ostracum ".
• The septa are attached to the inside wall of the shell, thus dividing the phragmocone into camerae.
• Like " Juvavites " except has nodes or clavi on the ventrolateral area of the phragmocone.
• At the very tip of the phragmocone beneath the rostrum is an embryonic shell known as the protoconch.
• The early coleoids and belemnoids adopted a different approach : the phragmocone was retained but became internal and reduced.
• The rostrum is in turn attached to a chambered conical shell known as the " phragmocone ".
• The venter, especially of the chambered phragmocone is convex in profile; the body chamber long and tubular.
• Some nautiloids, such as the Silurian Ascocerida, dropped the phragmocone upon maturity, presumably to increase speed and maneuverability.