The Shell Punctation of Dicoelosia Biloba (Linnaeus)

Abstract

Abstract That all the punctate articulate brachiopods possess puncta with the simple pattern of many Recent terebratuloids is a widespread but incorrect belief; attention is drawn to the fact that puncta of arborescent form exist in articulate shells as well as in some inarticulates such as Crania. Previous conflicting views on the form of puncta in articulate stocks are briefly reviewed, and conclusive evidence of multiple branching of the puncta presented for species of Dicoelosia, with particular reference to Dicoelosia biloba (Linnaeus). In view of the doubts cast on the validity of the evidence of thin sections, the branching is here demonstrated by means of iron oxide infillings of the puncta which have been extracted from the shells and also by relative density counts of the puncta taken on the internal and external valve surfaces. Whilst it is considered that the style of the puncta may prove to be important at generic and even familial level, counts of punctation density are not considered a desi...