Suecoceras
Encyclopedia
Suecoceras is an endoceratid
(a kind of nautiloid cephalopod) that lived during the Middle Ordovician. It is characterised by a long, straight, slender shell with a slightly expanded tip that curves slightly downwards.
The shell is compressed from side to side in the humped apical portion, but circular in the rest. The siphuncle
is proportionally large, 1/3 to 1/2 the shell diameter; ventral at the beginning, becoming subventral in the adult portion. Septal necks are holochoanitic to slightly maxichaonitic, extending back to the previous septum and sometimes beyond. Endocones are long and slender, with a narrow tube running down the middle.
The siphuncle takes up the entire apex, but is not swollen as in Chazyoceras
or Nanno
.
A typical species, S. barrande (Dewitz), whose fossil remains are known from Sweden, has a shell about 15 cm long.
Endoceratidae
The Endoceratidae is a family of large to very large straight shelled nautiloid cephalopods belonging to the order Endocerida that lived during the Middle and Late Ordovician...
(a kind of nautiloid cephalopod) that lived during the Middle Ordovician. It is characterised by a long, straight, slender shell with a slightly expanded tip that curves slightly downwards.
The shell is compressed from side to side in the humped apical portion, but circular in the rest. The siphuncle
Siphuncle
The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and Spirula...
is proportionally large, 1/3 to 1/2 the shell diameter; ventral at the beginning, becoming subventral in the adult portion. Septal necks are holochoanitic to slightly maxichaonitic, extending back to the previous septum and sometimes beyond. Endocones are long and slender, with a narrow tube running down the middle.
The siphuncle takes up the entire apex, but is not swollen as in Chazyoceras
Chazyoceras
Chazyoceras is a moderately large endocerid included in the Endoceratidae with a Nanno type apex and a ventral siphuncle with a holochoanitic wall, characteristic of the family. The siphuncle swelling at the apex is subtriangular in longitudinal profile. Endocones are of medium length.Chazyoceras...
or Nanno
Nanno (animal)
Nanno in cephalopod paleontology, as commonly used, refers to endocerids in which the siphuncle swells to fill the entire apex of the shell leaving septa and camerae to begin a few centimeters forward, having a morphologic rather than a taxonomic connotation.The term is based on the genus Nanno,...
.
A typical species, S. barrande (Dewitz), whose fossil remains are known from Sweden, has a shell about 15 cm long.