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West African Lungfish

 Dear Fellow Readers,

This post talks about the African lungfish, specifically its classification within the Chordata phylum and its characteristics that demonstrate vestigiality.

African Lungfish/ Protopterus annectens
Phylum: Chordata

Order: Dipnoi

Family: Lepidosirenidae

Genus: Protopterus

Per the name, the African Lungfish is distributed throughout Africa. Being an obligate air breather they are seen in basins and rivers. As of today, there are only seven known species of lungfish, being found in Africa, South America, and Australia. Being abundant since the Triassic geologic period they are thought to be over 250 million years old (phylogenetically speaking).

While they do retain marginal teeth and an ossified braincase it has been significantly reduced in size due to vestigiality. This is also visible in something called the cosmine which has been lost in post-Devonian (between ~419-358 million years ago) lungfishes.

While called Lungfish they are actually able to live on land for months and sometimes even years on end.

Lungfishes are thought to be the closest living relatives to tetrapods. with a brain that demonstrates certain similarities with lissamphibians, internal nostrils, and the four similarly sized limbs like tetrapods it is easy to believe this as true. While there are other similarities 400 million years ago the evolution of limbs from fish fins happened allowing vertebrates to leave the water. This allowed tetrapods (amphibians, reptiles, birds, and mammals) to live on land.

Until next time,

Sol

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