Monday, April 30, 2012

Fossil Fish Found Alive: Discovering the Coelacanth.

I read the book Fossil Fish Found Alive: Discovering the Coelacanth by Sally M. Walker, and it was very informative about Coelacanths. It didn't take long to read and it was great.

The book talks about how the earliest modern day Coelacanth to be found was caught in 1938 off the Camoros Islands, which are a French colony off the coast of Africa. This Coelacanth was named Latimeria chalumnae, after the person who discovered it, who had the last name Latimer. 

Latimer had no idea what the fish in her net was, so she took it to several places and asked what it was. They all said that they did not know. The last place she took it to said it looked like a Coelacanth, which at the time was thought to be extinct. The Coelacanth was believed to have gone extinct 65 million years ago, and at the time, the last Coelacanth fossils were 70 million years ago. No Cenozoic fossils of Coelacanths have ever been found, so to date the prehistory of Coelacanths stops in the Cretaceous. 

Prehistoric Coelacanths, from top to bottom: Allenypterus, Hoplophegis, Mawsonia, Axelrodicthys, and Miguashaia

Somebody named Smith came to see the Coelacanth and proved its identity. Smith wanted to find another Coelacanth. He caught an unusual fish in his net in the Camoros Islands. He thought it was a new species and named it Malania anjouanae. But then he realized his mistake. It was a Coelacanth. The dorsal fins and epicaudal fins were missing from this fish, so he thought it was a new species. The fins were probably just bitten off by another fish when the Coelacanth was young, or another such accident. It was not a different species. 

The modern day Coelacanth Latimeria

A new species of Coelacanth was described around 1998 and it was named Latimeria menadoensis. It was found in Indonesia, which is in Asia. That's unusual because so far Coelacanths had only been found in Africa and Madagascar, never in Asia. 

Scientists were desperate to find a live Coelacanth in its natural habitat. They started diving down in submersibles to habitats of Coelacanths. On October 29, 2000, they were finally successful and found live Coelacanths in South Africa. At first they found one, but then, on the next dive, they found many. They noticed that when the submersible got close, the Coelacanths did bizarre headstands. It was later found out that these were probably because the Coelacanths use the earth's electrical field to navigate, and in the disturbance of the electrical field they automatically did the headstands because of disorientation. 

It was found out that in the daytime Coelacanths rest in caves and only come out at night. When scientists started tagging Coelacanths, they found that they drifted around in the current, and when prey such as small fish got near, the Coelacanths sucked them in. This is another adaptation that conserves energy. 

Latimeria resting in a cave in the daytime

The largest Latimeria chalumnae ever found was 6-1/2 feet long. This population of Coelacanths was also the shallowest-living ever found, with depths of 344 feet. They were filmed by divers, but diving at that depth can be dangerous. Coelacanths usually live at about 700 feet down, so normally they would never be filmed by scuba divers. 

Coelacanths are one of the two groups of lobe-finned fish, or sarcopterygians, alive today. The other group are the famous lungfishes, which have the ability to breath air and can live under dried-up lakes for years. Unlike lungfish, Coelacanths, or at least modern day Coelacanths, live in salt water. There were a few prehistoric Coelacanths, like Undina from the Jurassic, that spent their lives in fresh water. The largest Coelacanth ever was Mawsonia gigas, from the Cretaceous from Egypt and Niger. Mawsonia was also found in South America, but this makes sense if you know that Africa and South America were joined together in the Cretaceous (which also explains the distribution of lungfishes in South America and Africa).

I learned that Coelacanths are full of oil, which helps them maintain balance just above the sea floor without having to actually move. The oil also makes the Coelacanth very disgusting to eat, which is why fisherman don't usually fish for Coelacanths as food. The reason why Coelacanths are fished is normally for maintaining specimens. 


  1. Great illustrations! And the part about coelacanths doing bizarre headstands in response to electric fields is pretty cool.

  2. Comoros put the coelacanth on one of their coins. You can see it here.

  3. If you haven't seen them the NOVA episode and related sites are well worht your time (although the book was probably more in depth, and up to date).

  4. Coelacanths have their own website:

  5. Make sure to wish your mom a Happy Mother's Day, Art!

  6. Coelacanths are one of my favorite kinds of fish. I remember when I was young I watched a documentary on the discovery of living Coelacanths and I've loved them ever since. They are such amazing fish. Thanks for the great blog posts, and keep it up!