The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles...

typically had ventral siphuncles like ammonites, although often proportionally larger and more internally structured. The word "siphuncle" comes from the Neo-Latin...

perforated by the siphuncle, a fleshy tube which runs through each of the internal chambers of the shell. Surrounding the fleshy tube of the siphuncle are structures...

sections, straight to sinuous sutures, and a tubular, generally central siphuncle. Having survived relatively unchanged for hundreds of millions of years...

release of egg and sperm, in the nautilus a string of tissue called the siphuncle goes through all the chambers, and the eight plates that make up the shell...

body chamber transversely constricted, and a subcentral orthochoanitic siphuncle. The surface is ornamented by a network of fine lirae (Sweet 1964:K224)...

Agonititida. Agoniatitids are primitive ammonoids with a ventral retrochoanitic siphuncle (septal necks point to the rear) reflective of their nautiloid ancestors...

to some gastropods was used to support this view. The development of a siphuncle would have allowed the shells of these early forms to become gas-filled...

cephalopods from the Lower Paleozoic with cone-like deposits in their siphuncle. Endocerida was a diverse group of cephalopods that lived from the Early...

the genus Nanno in that the siphuncle in Nanno fills the entire apical portion of the shell while in Endoceras the siphuncle is ventral even there with...

some gastropods was used in support of this view. The development of a siphuncle would have allowed the shells of these early forms to become gas-filled...

Pseudactinoceratinae). The siphuncle is central or located between the center and venter. Necks are cyrtochoanitic, otherwise siphuncle shape and structure are...

shell with an exogastric curvature, such that the lower side with the siphuncle is convex in profile and the opposite, upper, side is concave in profile...

ventral siphuncle instead. The siphuncle in Loganoceras is subcentral. The related Romingoceras is more curved, also with a ventral siphuncle. All three...

twists the internal organs so the anus lies above the head.   = Septa   = Siphuncle Volborthella, some fossils of which predate 530 million years ago, was...

of the siphuncle. The surface of the siphuncle is supported by septal necks which are holochoanitic, meaning that they fully sheath the siphuncle and extend...

On the ventral (bottom) side of the cuttlebone is the highly modified siphuncle; this is the organ with which the cuttlebone is filled with gas or liquid...

externally, but has a siphuncle with a trapezoidal aspect to its siphuncle segments. Perimecoceras has similar concave siphuncle segments but is tubular...

orthoconic to cyrtoconic shells that may be long or short with a narrow siphuncle invariably in contact with the ventral wall and sutures uniformly with...

in the siphuncle, reaching as much as halfway between septa in the chambers; sparse cameral deposits and apparently none within the siphuncle. The inclusion...

from North America, belonging to the family Endoceratidae, in which the siphuncle takes up the entire apex. Foestellites, named by Kobayashi, 1940, is based...

ammonoid. The body of the animal occupies the living chamber, apart from the siphuncle which extends through the rest of the septa (the phragmocone) to provide...

as endogastric, assuming the small siphuncle on the inner margin to be ventral. Known for sure dorsal siphuncles do not appear until later in the Early...

Rayonnoceras is characterized by large straight shells with a large subcentral siphuncle composed of subglobular segments, as for the family. The endosiphuncular...

from the side) that has no hyponomic sinus and a central to subcentral siphuncle composed of subquadrate to nummuloidal segments in which the septal necks...

proportionally large ventral siphuncles that contain numerous diaphragms. Orders are determined principally by differences in siphuncle detail. Mutvei, Harry...

changing the gas-to-liquid ratio in the chambered cuttlebone via the ventral siphuncle. Each species' cuttlebone has a distinct shape, size, and pattern of ridges...

only those ellesmerocerids that have straight transverse sutures and siphuncles with concave segments and thick connecting rings. Protocycloceratidae...

shells are endogastric and strongly compressed, such that the ventral or siphuncle side is curved inward and the dorso-ventral height is greater than the...

of concavo-convex chambers linked by a centrally-placed tube called a siphuncle. There is a tendency for the chambers to develop cameral deposits, which...