Richmondoceras is an extinct genus of nektonic carnivores
Identification in Hand Sample:
- Medium to large, slender, gradually expanding orthoconic longicones
- Circular in section with straight, transverse sutures
- Body chamber long and tubular, at least one-fifth the total length of the shell
- Siphuncle segments highly compressed, the length of the phragmocone
- Siphuncle midventral in position to the length of the phragmocone
- Medium to large, slender, gradually expanding orthoconic longicones; circular in section with straight, transverse sutures. Cameral chambers short, cameral lengths decreasing with ontogeny. Body chamber long and tubular, at least one-fifth the total length of the shell, aperture unknown. Periphract dorsomyarian. Shell exterior unknown, apparently smooth.
- Siphuncle midventral in position the length of the phragmocone. Siphuncle segments greatly expanded with camerae having segment diameter decompressing with ontogeny from one-third to one-sixth the diameter of the shell. Segments highly compressed, the length of the phragmocone. Septa foramina broad, averaging half the total diameter of the siphuncle segment. Septal necks cyrtochoanitic and recumbent dorsally and ventrally in more adapical portions of the phragmocone; septal neck, highly curved and short with free brims adorally in large specimens. Connecting rings thin, adnate adapically and ventrally to free part of the septa. Endosiphuncular deposits greatly retarded in their development, consisting of thin adapical parietal deposits. Episeptal and hyposeptal cameral deposits restricted to adapical portions of phragmocone.