The Coelacanth is a prehistoric fish that was once thought to be extinct along with the dinosaurs about 65 mya (million yrs ago). But, in 1938 the species was discovered very much alive and well in the waters around South Africa and Madagascar. Presently, there are two known species of this creature. One lives near the Comoros Islands off the east coast of Africa and the other lives in the waters near Sulawesi, Indonesia. Evolutionists believe that the Coelacanth represents an early step in evolution of fish evolving into land-dwelling four legged amphibians. Today the Coelacanth is conidered a “living fossil.”
The Coelacanth is an elusive creature living in depths up to 2300 feet (700 m). They can grow to be huge with some reaching as large as 6.5 feet (2 m) or more and they can weigh around 198 lbs (90 kilograms). Some scientists believe the creature can live up to 60 years or more. In terms of population we don’t really know just how many of these creatures still exist but some estimates put their number at about 1000. Logically, these “living fossils” are considered an endangered species today.
Prior to 1938 we only knew about the Coelacanth through fossil remains. It is believed that it evolved into its present form around 400 mya. It’s story begins with the Cretaceous Period (145–66 mya). The first specimen of this alleged extinct fish was discovered by a museum curator named Marjorie Courtenay-Latimer who found the fish among the catch of a local fisherman on the east coast of South Africa near the Chalumna River (today known as the Tyolomnga River). When living specimens of this creature were discovered it rocked the world of Paleontology to say the least. Suddenly, a creature believed to be extinct 66 mya was discovered living and very much alive! However, the Coelacanth is not the only “living fossil” around thought to have gone extinct but, in fact, did not.
When paleontologists talk about “extinction” most people think it means the absolute end of a species. That’s known as “biological extinction” but there is also something known as “functional extinction.” A species that is biologically extinct is a species that no longer exists. A functionally extinct species is a species that is still around although small in numbers and rare. In the case of the Coelacanth we once thought it to be biologically extinct but after 1938 when living specimens were discovered we know that it was only functionally extinct.
The creatures appearance is very primitive. It has lobe-fins which some other fish have/had too but there are some things that make the Coelacanth distinct. For instance, they have a trilobate fin or diphycercal tail. A secondary tail extends past the primary tail. It has cosmoid scales which act like armor as a means of protection. At the back of the skull is a hinge known as an intracranial joint which allows the Coelacanth to open its mouth extremely wide. Additionally, the Coelacanth heart is shaped different from most other fish as the heart chamber is arranged in a straight tube. They also retain an oil filled notochord, a hollow pressurized tube, which is replaced by the vertebral column early in the embryonic stage in most other fish and vertebrates. Further, its brain case is composed of 98.5% filled with fat and only 1.5% of the braincase actually contains brain tissue. Finally, the Coelacanth has two kidneys that are fused into one! All in all, the Coelacanth is a strange looking creature with some rather odd features.
The Coelacanth has 8 fins. It has rather large eyes and a small mouth that can be opened widely. In terms of locomotion the Coelacanth is unique. They take advantage of up or down current and drift wellings. They create thrust with their caudal fins and in full motion the creature is highly maneuverable. They can also swim standing on their heads and belly up.
The Coelacanth genome has been studied. It was thought that the Coelacanth was the closest living relative to the tetrapod but genetic evidence revealed this not to be so as the closest is the Lung Fish. The vertebrate land transition theory is on of the most important steps in evolution as it postulates the transition from sea creature to land creature. Some believe the Coelacanth is a transitional species which may or may not be so.
Genetic analysis of today’s living Coelacanth reveals that the current species evolved around 390 mya during the Cretaceous–Paleogene Extinction Event. This extinction event is also known as the Cretaceous–Tertiary or K-T extinction. It was a mass extinction of about 3/4 of all plant and animal species on Earth at the time. It included the extinction of the non-avian dinosaurs. This event is thought to have taken place about 66 mya, It is used as a marker for the end of the Cretaceous Period and the end of the entire Mesozoic Era. It is also used as the marker for the beginning of the Cenozoic Era that continues into our present time.
In terms of fossils, the first Coelacanth fossil was discovered in Australia. It consisted of a jaw dated at 360 myr (million yrs old). The most recent Coelacanth in the fossil record is from a sister species of the modern-day species with a separation of about 80 million years. The first live specimen was actually caught in Indonesia in 1998. The fossil record reveals that there were about 80 species of Coelacanth. Many people believe the fossil remains are the same morphology as seen in the fish today but there are in fact some slight differences. Those differences could be nothing more than individual or species variations, however. In general, however, the ancient Coelacanth looks pretty much the same as the living specimens today.
The Coelacanth’s evolutionary relationship is, frankly, a matter of considerable controversy. As expected there are several competing hypotheses along with many unanswered questions. Some believe it is a “transitional species” (read missing link) between the tetrapod (4 legged land dwellers) and and sea dwelling creatures but there is really very little if any evidence of this at all.
The bottomline on the Coelacanth is this…..there has been very little if any change in its morphology since prehistoric times and that is not supportive of evolutionary theory. Genetic analysis as I mentioned earlier indicate that the Lung Fish is more closely related to the tetrapods (amphibians, reptiles, birds, mammals).
So what we once thought might possibly be a “missing link” (transitional species) from sea dwellers to 4 legged land dwellers turns out NOT to be so. But what is intriguing about the Coelacanth is the lack of any significant change in morphology since its supposed extinction 66 mya. They are almost identical today as those found in the fossil record. It seems to be a species that never evolved beyond what it was originally and that evidence is not supportive of the theory of evolution. And the Coelacanth is not the only species that contradicts evolution. I’ll post about some of those in future posts. For now, the Coelacanth is certainly a “creature out of time”….or….maybe NOT. In fact, maybe it is a creature very much IN time as are some others once thought to be extinct but, in fact, are still very much alive in our own 21st century.