Protopterus is the genus of four species of lungfish found in Africa. Protopterus is considered the sole genus in the family Protopteridae, which is grouped with Lepidosiren in the order Lepidosireniformes.
Taxonomy
The earliest fossils of the Protopteridae come from the Late Cretaceous (Campanian-Maastrichtian) of Sudan, but phylogenetic evidence indicates that it and Lepidosirenidae split at the very beginning of the Early Cretaceous, around 145 Ma.
Some papers suggest grouping Protopterus and Lepidosiren together in the family Lepidosirenidae, as their Cretaceous divergence is relatively recent compared to the Carboniferous origins of other lungfish families. However, most taxonomic authorities retain them as distinct families. The largest species can reach about in length. The lungfish heart has adaptations that partially separate the flow of blood into its pulmonary and systemic circuits. The atrium is partially divided, so that the left side receives oxygenated blood and the right side receives deoxygenated blood from the other tissues. These two blood streams remain mostly separate as they flow through the ventricle leading to the gill arches. As a result, oxygenated blood mostly goes to the anterior gill arches and the deoxygenated blood mostly goes to the posterior arches.
African lungfishes breed at the beginning of the rainy season. They construct nests or burrows in the mud to hold their eggs, which they then guard against predators. When they hatch, the young resemble tadpoles, with external gills, and only later develop lungs and begin to breathe air. As technology advancements such as longlines and gillnets have been increasingly applied over the past 50 years, the lungfish populations there are believed to be decreasing.
Species and subspecies
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The family Protopteridae and genus Protopterus contain four extant (living) species: