Polypterus is a genus of freshwater fish in the bichir family (family Polypteridae) of order Polypteriformes. The type species is the Nile bichir (P. bichir). Fishes in this genus live in various areas in Africa (as the species' common names would indicate). The etymology of the genus name derives from a combination of the Greek prefix πολυ-, poly- (many) and the root word πτερον, pteron (wing or fin) – "many fins." The polypterus is the only discovered vertebrate to have lungs, but no trachea.
Polypterus was discovered, described, and named in 1802 by Étienne Geoffroy Saint-Hilaire as a genus of 10 green to yellow-brown species. Naturalists were unsure whether to regard it as a fish or an amphibian. If it was a fish, what type was it: bony, cartilaginous or lungfish? 
Some regarded Polypterus as a living fossil. They thought it was part of the missing link between fishes and amphibians, helping to show how fish fins had evolved to become paired limbs.
In 1861 Thomas Huxley created an order Crossopterygii to house animals, fossil and living, that possessed lungs and fleshy pectoral fins with Lepidoptera. He placed Polypterus and Calamoichthys within this order, allocating them to a new tribe Polypterini which he created especially for them. The weight of Huxley’s authority allowed this allocation to last in textbooks and lectures long after it had been disproved.
In the 1870s and 1880s, Francis Balfour and his students had shown that embryology could help to answer questions about the evolution of species. No one had studied the embryology of Polypterus. If someone could do this he might prove the “missing link” theory and be greatly honoured. It was a tempting prospect for an ambitious young zoologist. On the other hand it would be a dangerous quest. The only breeding Polypterus were in swampy parts of African rivers. Africa was a turbulent place and swamps were rich breeding grounds for mosquitoes carrying malaria.
Two men: Nathan Harrington and John Samuel Budgett attempted to answer this question by making repeated expeditions to Africa. Harrington failed on his first attempt in 1898 and died early on his second in 1899 before he could reach his destination. Budgett failed three times: in 1898/9, 1900 and 1902. He finally succeeded in 1903 but died of Blackwater Fever shortly after his return to England. He left excellent samples and drawings but his only writing was a diary. Consequently his results on Polypterus were written up and published by his friend John Graham Kerr.
Drawing on this work, in 1907 E.S.Goodrich reported to the British Association the then current state of evidence ‘’against’’ Polypterus being a Crossopterygian, placing it within the Palaeoniscids, the most primitive Actinopterygians. 
Much later, in 1946, Romer, confirmed this view but he also wrote,"The weight of Huxley's  opinion is a heavy one, and even today many a text continues to cite Polypterus as a crossopterygian and it is so described in many a classroom, although students of fish evolution have realized the falsity of this position for many years.... Polypterus...is not a crossopterygian, but an actinopterygian, and hence can tell us nothing about crossopterygian anatomy and embryology." (Romer 1946, pp. 60-61), quoted by Hall.
Hall (2001), relying on Patterson (1982) and Noack et al. (1996), writes "Phylogenetic analyses using both morphological and molecular data affirm Polypterus as a living stem actinopterygian".
Research is ongoing. Most of the conclusions drawn by Kerr from Budgett’s specimens have been confirmed but many questions remain.
Zoo Basel was successful in breeding this rare fish in captivity. In December 2005 several eggs were laid and at the beginning of 2006 six young polypterus' hatched. Within 2 months they reached 10 cm (about 4 inches).
- Polypterus ansorgii Boulenger, 1910 (Guinean bichir)
- Polypterus bichir Lacépède, 1803
- Polypterus delhezi Boulenger, 1899 (Barred bichir)
- Polypterus endlicheri Heckel, 1847,
- Polypterus mokelembembe Schliewen & Schäfer, 2006 (Mokèlé-mbèmbé bichir)
- Polypterus ornatipinnis Boulenger, 1902 (Ornate bichir)
- Polypterus palmas Ayres, 1850 (Shortfin bichir)
- Polypterus retropinnis Vaillant, 1899 (West African bichir)
- Polypterus senegalus Cuvier, 1829 (Gray bichir)
- Polypterus teugelsi Britz, 2004 (Cross River bichir)
- Polypterus weeksii Boulenger, 1898 (Mottled bichir)
- Hall (2001)
- Kerr, J.G. (1907)
- Goodrich (1908)
Goodrich, E. S. (1908). On the systematic position of Polypterus. Report of the 77th Meeting of the British Association for the Advancement of Science (1907): 545-546. Quoted by Hall
Hall, B. K. (2001) John Samuel Budgett (1872-1904): In Pursuit of Polypterus, BioScience, Vol. 51, No. 5 (May, 2001), pp. 399-407
Kerr, J.G. (1907), The development of Polypterus senegalus Cuv., Pages 195-290 in Kerr, J.G., (ed. 1907), The Work of John Samuel Budgett, Balfour Student of the University of Cambridge: Being a Collection of His Zoological Papers, together with a Biographical Sketch by A . E. Shipley, F.R.S., and Contributions by Richard Assheton, Edward J.Bles, Edward T. Browne, J. Herbert Budgett and J. Graham Kerr. Cambridge (UK): Cambridge University Press.
Noack K, Zardoya R, Meyer A. 1996. The complete mitochondrial DNA sequence of the bichir (Polypterusor natipinnis), a basal ray-finned fish: Ancient establishment of the consensus vertebrate gene order. Genetics 144:1165-1180, cited by Hall
Patterson C. (1982). Morphology and interrelationships of primitive actinopterygian fishes. American Zoologist 22: 241-260, cited by Hall.
Romer, A S. (1946). The early evolution of fishes, Quarterly Review of Biology 21: 33-69, cited by Hall