Fig. 4

Myoanatomy of the digestive tract of selected ctenostomes. a Paludicelloidea, Paludicella articulata. Dissected zooid and overview of the main regions of the gut and its musculature. Volume rendering. b Vesicularioidea, Cryptopolyzoon wilsoni. Lateral view of a zooid showing a distinct prominent cardiac proventriculus. Volume rendering. c Arachnidioidea, Nolella dilata. Detail of the cardia showing more prominent circular musculature. Volume rendering. d Arachnidioidea, Nolella(?) sp. Detail of the gut with distinct concentration of cardiac circular musculature. Volume rendering. e Vesicularioidea, Amathia verticillata, showing the prominent cardiac sphincter. Volume rendering. Abbreviations: a – anus, ca – cardia, cae – caecum, ds – diaphragmatic sphincter, es – esophagus, int – intestine, l – lophophore, lb – lophophoral base, pb – parieto-vaginal band, ph - pharynx, pm – parietal muscles, py – pylorus, pv – parieto-vestibular muscles, rm – retractor muscle, tm – tentacle muscles, tsm – tentacle sheath muscles, vm – vestibular wall muscles