Early Ordovician – Late Ordovician, ?Middle Silurian
Endocerida is an extinct order of nektobenthic carnivores
Characteristics of the Order
- Conchs curved, breviconic, longiconic, or endogastrically
- Septal necks ranging from nearly achoanitic to macrochoanitic
- Siphuncles small to large, generally marginal more rarely subventral
Treatise on Invertebrate Paleontology, Part K (1964):
- Breviconic, longiconic, or endogastrically curved conchs with small to large, generally marginal, more rarely subventral or central siphuncles with posterior part filled by simple or complex endocones. Septal necks ranging from nearly achoanitic to macrochoanitic.