Figure 17 in Comparative morphology of the finlet spines of the extant Polypteridae (Osteichthyes; Cladistia). Systematic interest

Figure 17. – Basal view of the articular head of the finlet spines, showing the glenoid cavity and the processes. The posterior and anterior sides are respectively lower and upper. The basal surface of the articular head can be inserted either in a rectangular frame (Polypterus b. katangae, P. ansorgei, P. b. lapradei, P. ornatipinnis, P. palmas, P. polli, P. weeksi), a square frame (P. retropinnis) or a round frame (Erpetoichthys). Scale bars = 0.5 mm.