What are living fossils?
A living fossil is a species that looks basically like a species that is known only from fossils that have remained largely unchanged from earlier geologic periods. The term was originally used by Charles Darwin in his book On the Origin of Species, published in 1859.
What evolutionary insights do ancient fossils offer?
According to long-running research, it has been established that both climate change and asteroid impacts contribute to the creation and extinction of species. However, fossil discoveries are now showing that tectonics also plays a role in the evolution of species.
Ancient ‘Primitive’ Devonian Coelacanth‘Fish were recently found at the surface in the interior of Western Australia, dating to a period of intense tectonic activity (movement within the Earth’s crust). A study published earlier in Nature Communications reveals exciting new discoveries about the evolutionary history of ancient organisms.
The only fossil of the world’s oldest animal found in Bhimbetka caves of Madhya Pradesh
Coelacanths are often referred to as living fossils, as their lineage dates back an incredible 420 million years. The discovery, called ‘Ngamugavi Wirngari’, was found in the Gogo formations in Goonyandi Country (Kimberley region of Western Australia). Researchers from Flinders University, together with international colleagues, have suggested that the evolution of coelacanths was largely influenced by the movements of tectonic plates.
This discovery advances our understanding of the evolutionary history of coelacanths and how geological events have influenced life on Earth. The study thus sheds light on periods of tectonic activity as they cause change in an evolutionary context and informs new ideas that link Earth’s physical changes to the evolution of its inhabitants.
Does it fill an important gap in the history of fossils?
The fossil, recovered from the Gogo Formation in Western Australia, has been described by researchers from Flinders University, including experts from Canada, Australia and Europe. ‘Ngamugavi wirngari’, the newly discovered coelacanth species is an extinct form that fills a very important gap between primitive coelacanth forms and ‘anatomically modern ones’.
“We are thrilled to work with the people of the Mimbi community to give this beautiful new fish a first name, derived from the Guniyandi language,” says Dr Alice Clement, evolutionary biologist and palaeontologist at Flinders University, in a new study published in Nature Communications “While paying respect to the cultural heritage of the region, the scientific value of this discovery is also boosted through this partnership,” says first author and evolutionary biologist Dr Alice Clement.
The fossil fills a crucial gap in the history of coelacanths, between their earliest known forms and more advanced descendants. She adds, “Our analyses revealed that tectonic plate activity had a profound effect on rates of coelacanth evolution. That is, new species of coelacanths were more likely to evolve during periods of high tectonic activity as new habitats were divided and created”.
This study confirms that the Gogo Formation of the Late Devonian is one of the richest and best-preserved collections of fossil fishes and invertebrates on Earth.
The modern-day coelacanth and its ancestral journey:
The coelacanth is a remarkable deep-sea fish found off the coasts of East Africa and Indonesia, down to 2 metres. They are “lobe-finned” fish, in other words, their fins have strong bones, much like the bones in our own arms, and thus they are much more closely related to lungfish and tetrapods – vertebrate animals with arms and legs, such as frogs, emus and mice – than to most other fish.
Coelacanths have been living on Earth for the past 410 million years; a total of over 175 species have been discovered. Although coelacanths diversified greatly during the Mesozoic Era, often referred to as the age of the dinosaurs, with some species evolving into peculiar body forms, they inexplicably disappeared from the fossil record at the end of the Cretaceous Period, 66 million years ago.
The Cretaceous extinction, caused by a large asteroid impact, wiped out about 75% of life on Earth, including all non-avian (bird-like) dinosaurs. Therefore, it was assumed that coelacanth fishes were swept up as victims of the same mass extinction event.
But in 1938, the Lazarus fish gained cult status in the world of evolution after fishermen off the coast of South Africa pulled up a large, mysterious fish from the depths of the ocean.
Rethinking the ‘living fossil’ concept:
Professor Richard Cloutier, another senior author and vertebrate paleontologist from Canada, UQAR Rimouski, believes that the new study in Nature Communications refutes the opinion that the surviving organisms are the oldest ‘living fossils’.
“They first appear in the geological record more than 410 million years ago, and their fragmentary fossils have been recovered from places such as China and Australia. Yet, most early forms are still poorly known, making Ngamugavi wirngari the best-known Devonian coelacanth.”
“As we gradually fill in the gaps, we can begin to understand how the living coelacanth species of Latimeria, commonly regarded as ‘living fossils’, are actually evolving and perhaps do not deserve such an mysterious title,” said Professor Cloutier in his ‘Comparative Study of Fossil Sites of the Devonian’. He is a former Honorary Visiting Scholar at Flinders University.
