Intejocerida

Systematic Paleontology Class Cephalopoda Subclass Nautiloidea Order Intejocerida

The Intejocerida, an order of nautiloid cephalopods from the lower and middle Ordovician proposed by Balashov in 1960. Shells most often straight, longiconic, more rarely slightly cyrtoconic. Exteriors smooth, chambers short, sutures straight, cross sections generally circular. Siphuncles are large, as much as 1/2 the shell diameter, and are located from marginal to sub-central. Septal necks vary from short, barely present to holochoanitic, reaching to the previous septum. Siphuncle interiors are filled with longitudinal, radially arranged lamellae, resembling the actinosiphonate deposits found in the Oncocerida.

In part K of the Treatise, 1964, the Intejocerida is combined with the Endocerida in the Endoceratoidea, differing by the presence of radial lamellae rather than endocones. Both orders have shells that are rather large, with large siphunles.

Two families, the Intejoceratidae and Padunocertidae are included in the Intejocerida, which except for the radial lamellae and large siphuncles, differ significanly. In the Intejoceratidae siphuncles are central to moderately eccentric, with almost negligible septal necks, and filled with thick radial lamellae. Includes Intejoceras and Evenoceras. In the Padunoceratidae the siphuncle is ventral, with necks that vary from hemichoanitic to holochoanitic, reaching from half way into the previous chamber to the previous septum, and filled with thin radial lamellae. Is established for the genus Padunoceras. A third family, Bajkaloceratidae for Bajkaloceras is tentativley included.

References: Curt Teichert 1964. Endoceratoidea. Treatise on Invertebrate Paleontology Part K.