Mollusca		Cephalopoda
CYRTOSOMA		Glossary

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Cephalopoda Glossary

CYRTOSOMA  
|--+--SCAPHOPODA
|  `--CEPHALOPODA  
|     |--Plectronocerida  
|     `--+--Ellesmerocerida  
|        |--Endocerida  
|        |--Actinocerida  
|        |--Pseudorthocerida  
|        |--Discosorida  
|        `--+--NAUTILOIDEA
|           `--NEOCEPHALOPODA
|              |--Ammonoidea
|              `--COLEOIDEA
|                 |--DECAPODIFORMES
|                 `--VAMPYROPODA
`--Gastropoda

parts of a fossil cephalopod graphic from Lake Témiscamingue Fossil Centre	close-up of half of a nautiloid siphuncle graphic from Moore, Lalicker and Fischer, Invertebrate Fossils

Actinosiphonate deposits
- radially arranged longitudinal blades inside the siphuncle. image

adnate, adnation area
- Pertaining to, or area of, contact between a connecting ring and the preceding septum

Annulosiphonate deposits
- calcareous rings inside the siphuncle; they are generally thicker on the ventral (bottom) side. image

apical
- pertaining to, or pointing to, the "rear" or apex of the shell.

Body Chamber
The large undivided (as opposed to the phragmocone), anterior space in shell open at aperture, occupied by the animal's body.

Camerae
Camerae (sing. Camera) are the spaces enclosed between two adjacent septa, but not including the siphuncle.

Cameral Deposits
- Calcium carbonate secreted in the empty chambers of palcephalopod (Nautiloid) shells, for ballast and control of buoyancy.  The nature of the cameral deposits are very useful in nautiloid classification.

Connecting ring
- partly calcareous, partly organic matter, a thin-walled tube tubular membrane with straight or (in cyrtochoanitic nautiloids) bulging sides which extend between perforations of two adjacent septa; it connects a septal neck with the septum immediately behind it.

compressed
- Shell cross-section which is squeezed laterally, so it is taller than it is wide.

cyrtochoanitic
- Type of siphuncle which is expanded in the chambers (camerae) and contracted in passing through a septum.

depressed
- Shell cross-section which is flattened dorso-ventrally, so it is wider than it is high.

Endocones
- apically pointed conical layers which fill the siphuncle; building forwards from the rear. They are known only from endocerids. image

Living Chamber
- the outermost or last chamber of a cephalopod shell.  The body of the animal itself occupies the Living Chamber

orthochoanitic
- siphuncle of tubular form, composed of short septal necks and intervening connecting rings.

Phragmocone
The phragmocone is the chambered portion of the shell or conch, divided by septa into camerae

Septa .  (sing. septum). 
- The thin walls or partitions between the internal chambers (Camerae) of the shell are called the septa.  As an ammonoid or nautiloid cephalopod grew it moved its body forward in the shell secreting septa behind it, thereby adding new chambers to the shell. The septa divide the phragmocone into camerae, and attached to the inside wall of the shell.

Septal Neck
- Extension of septum along the siphuncle; it is the bent portion of septa adjacent to siphuncular cord. Its length is measured parallel to longitudinal axis of the siphuncle.

Siphuncle
- The Siphuncle is a tube - which may be thick or slender - which runs through each of the internal chambers (camerae) of the shell, from the base of the living chamber to the apex.  It consists of soft and shelly parts, including septal necks, connecting rings, calcareous deposits, and siphuncular cord.  Nautiloids are classified by the nature of the siphuncle and its position within the shell.

Sutures
- narrow wavy lines on the surface of a cephalopod shell, which are lines of junction of septum and the inner side of the phragmocone wall, where each septum contacts the wall of the outer shell.   In Nautiloids they are very simple, but in some ammonoids they display astonishing fractal complexity.

Umbilicus
- open space, in the position of axis of coiling, which is left when successive whorls do not reach this axis.