POLYPTERIFORMES

The bichirs (Polypterus) and the rope eel (Erpetoichthys) comprise the living members of the actinopterygian
order Polypteriformes. They are distributed with around 16 species in the freshwaters of Africa and range in
size from 15-70 cm. Polypteriformes have sometimes been considered living fossils, because of their large
number of primitive morphological characters, e.g. presence of thick ganoid scales, paired lungs, and holoblastic
eggs.

Polypterus delhezi (Photo courtesy E. Hilton)

They also show numerous autapomorphic features that make them easily recognizable even to the non-scientist, most notably their dorsal finlets, the muscular base of the lobe-like pectoral fins, and the confluence of the dorsal and caudal fins. The systematic position of polypterids has been highly controversial, although recent consensus suggests that they belong to the Actinopterygii, among which they form the most basal clade of living ray-finned fishes.
Polypterids are of no economic importance and are rarely used as food fishes, but they have received considerable attention from numerous scientists because of their unusual anatomy and their key phylogenetic position.

Polypterus bichir lapradei (Photo courtesy P. Bartsch)

The fossil record of Polypteriformes is scarce and articulated skeletons were reported from the Cretaceous of Morocco and the late Miocene of the Chad. Fragments of skull bones, vertebrae, scales and fin spines assigned to polypteriforms are known from different localities in Africa. Fragments of fin spines from Bolivia are believed by some paleontologists to have belonged to polypteriforms.
New living species of polypterids are still being discovered, although the taxonomy of the family is confused and in need of a comprehensive revision.

Polypterus ornatipinnis (Larva, Photo courtesy P. Bartsch)

Not much is known about the biology and reproduction of polypterids. They feed on small vertebrates and invertebrates, with the larger species being mainly piscivorous. Males have an enlarged anal fin, which they use to cup the females genital opening during mating. Eggs are released into this cup and fertilized by the male. The egg chorion (egg shell) is covered by numerous, short, highly adhesive threads, which attach the egg firmly to aquatic plants or gravel. Egg development strongly resembles that of other basal actinopterygians, as well as lungfishes and amphibians. Hatched larvae have paired attachment organs at the tips of their upper lips, and well-developed external gills. The latter are usually reduced in juveniles, but may persist beyond 15 cm length in the larger species. (Ralph Britz)