Fig. 3 in Morphogenetic gradients in graptolites and bryozoans

Fig. 3. Variation of morphological characters of zooidal tubes (thecae) along the colony axis. A. Didymograptus pakrianus Jaanusson, only one branch of the biramous colony presented. B. Monograptus clingani (Carruthers). C. "Monograptus" (= Pernerograptus) argenteus (Nicholson). A, B belong to uniform type and exhibit mainly size gradient, while C represents a biform type, with distinct differences in morphology of proximal and distal thecae. Not to scale. From Urbanek (1973).