The basal opening of conodonts

Observations on a number of different species, which range in age from Cambrian to Triassic, confirm that conodonts have at least two kinds of basal openings. The primitive type is a basal cavity which increased in size as the specimen grew larger. The second variety is defined as a pit; its size was relatively constant after the initial stages of growth, although the total size of the specimen bearing it may have increased several times.