Thursday, 19 March 2020

Fish Fingers - Then and Now



I couldn't resist using this photo to illustrate the following, intriguing article on 'fish fingers' from The Times.

 


Fish had fingers 380 million years ago

The elpistostege fish is thought to be among the first to emerge from the sea onto land. Its fossil found in Quebec, Canada has revealed new insights into how the human hand evolved from fish fins - 
JOHN LONG

By Rhys Blakely - The Times

An extraordinary fossil of an ancient fish that had “fingers” has rewritten the story of the origins of humans.

The remains have revealed for the first time how the architecture of our fingers and wrists were present in the pectoral fin of a fierce predatory fish that lived in shallow, tropical waters some 380 million years ago.

The researchers behind the discovery have called it “the missing evolutionary link” that explains how four-legged vertebrates clambered from the seas onto land.

“This finding pushes back the origin of digits in vertebrates to the fish level, and tells us that the patterning for the vertebrate hand was first developed deep in evolution, just before fishes left the water,” Professor John Long, strategic professor in palaeontology at Flinders University, said.

Our dexterity has been key to our success as a species, he added. “Think of Michelangelo’s Sistine Chapel — a human hand touching the hand of God. This is where it begins.”


The skeleton, unearthed in Quebec in Canada, is about 1.6 metres long and includes the first complete pectoral fin of a so-called elpistostegalian fish from the Late Devonian period — a time where only plants and invertebrates, among them scorpions and millipedes, had made it onto land.


The fossil of Elpistostege watsoni that showed bones, the origins of human fingers, inside its fins - NATURE

The fish, named Elpistostege watsoni, was the apex predator of its day, armed with crocodile-like jaws. It also had two holes on the top of its head, apparently for breathing. Using computed tomography scans — a form of x-ray — the researchers were able to reveal an array of bones in its fin. These included a humerus (the equivalent of a human arm), a radius and ulna (a forearm), rows of carpus (a wrist) and two phalanges organised in digits (fingers).

The find revealed “extraordinary new information about the evolution of the vertebrate hand,” Professor Long said.

“This is the first time that we have unequivocally discovered fingers locked in a fin in any known fish. The articulating digits in the fin are like the finger bones found in the hands of most animals.”

The evolution of fishes into tetrapods — the group of four-legged vertebrates to which humans belong — was one of the most significant events in the history of life.

Vertebrates with backbones were then able to leave the water.

Richard Cloutier of the Universite du Quebec a Rimouski, a co-author of a paper published yesterday in the journal Nature, said that over the past decade fossils have improved our understanding of the anatomical transformations associated with breathing, hearing and feeding on land.

The origin of digits would have allowed the fish to support its weight in shallow water or for short trips out on land, he said.

“The increased number of small bones in the fin allows more planes of flexibility to spread out its weight through the fin. The other features the study revealed concerned the structure of the upper arm bone or humerus, which also shows features present that are shared with early amphibians.

“Elpistostege is not necessarily our ancestor, but it is closest we can get to a true ‘transitional fossil’ — an intermediate between fishes and tetrapods.”