Barrandeocerina


The Barrandeocerina comprise a suborder of Early Paleozoic nautiloid cephalopods, primitively coiled but later forms may be cyroconic, gyroconic, torticonic, and even breviconic, all having empty siphuncles with thin connecting rings. The Barrandeocerina were originally defined as a separate order by Rousseau Flower, but since then have been united within the Tarphycerida as a suborder. Derivation is from the Tarphyceratidae.
In early forms the siphuncle is central or subcentral, orthochoanitic, and thin, with tubular segments. Later forms include those with cyrochoanitic septal necks and segments that may be slightly to strongly expanded into the chambers.

Taxonomy

Six families are included in the Barrandeocerina,.
Flower also included the Lituitidae in the Barrandeocerida,, which were found to have more in common with the Tarphycerida in the original Treatise Part K.