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Fish with fingers missing link in evolution of human hand

Harry Pettit and Reuters, March 23, 2020 8:00AM The Sun

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Artist’s impression of an ancient Elpistostege fish fossil found in Canada with fin bones like human hands. Picture: Katrina Kenny media_cameraArtist’s impression of an ancient Elpistostege fish fossil found in Canada with fin bones like human hands. Picture: Katrina Kenny

animals

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A fish with fingers that lurked in lagoons 380 millions years ago could teach us about the origins of the human hand.

The 1.6m-long, shark-like Elpistostege watsoni was a slippery predator that lived in what is now eastern Canada.

Australian and Canadian scientists studying a fossil of the fish say its fin has similarities with the human hand, with the skeleton featuring an arm, a forearm and finger-like parts.

Researchers say their findings reveal “extraordinary new information” about how the human hand evolved.

Professor John Long, of Flinders University, South Australia, said: “This is the first time that we have unequivocally* discovered fingers locked in a fin with fin-rays in any known fish.

“The articulating* digits in the fin are like the finger bones found in the hands of most animals.

“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.”

Evidence of Elpistostege was first found in 1938 in the cliffs of Miguasha National Park in Quebec, Canada.

It was only in 2010 a complete specimen was discovered.

Supplied Editorial Fwd: Ancient fossil reveals evolutionary origin of human hands- Flinders Uni media_cameraFlinders University’s Professor John Long with an ancient Elpistostege fish fossil found in Canada. Picture: supplied

The unique predator is believed to have lived in a shallow, tropical marine habitat with brackish* water in the Quebec region during the Middle and Upper Devonian period, about 393-359 million years ago.

Researchers believe fish such as Elpistostege are “transitional fossils” which could help understand how vertebrates, or backboned animals, were able to transition from water to land.

Palaeontologists* from Australia and Canada used high-energy CT scans to study the pectoral* fin, used to control the direction of movement.

The fin skeleton revealed the presence of an arm (humerus), a forearm (radius and ulna), a wrist (rows of carpus) and fingers (phalanges organised in digits).

Lead author, palaeontologist Dr Richard Cloutier, of the University of Quebec, Canada said humans come from a long line of evolution and “that every part of our body, like our fingers, has a long evolutionary history”.

“This is true for Homo sapiens but it is also true for all living organisms,” Dr Cloutier added.

This marks the first time such traits have been found in a fish rather than in the earliest amphibians – the first land vertebrates – that later evolved from fish with sturdy fins like Elpistostege. It had two explicit* digits and three other apparent* digits.

“The origin of digits relates to developing the capability for 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 created more flexibility to spread the fish’s weight out on dry land when not supported by the buoyancy of water.

The research was published in the journal Nature.

Hands playing piano close-up media_cameraHuman hands are incredibly complex. The many small bones help us move the fingers independently of the others and this complex design has a long evolutionary history.

This article was first published on The Sun and is republished with permission.

MEET THE FISH WITH FINGERS
Elpistostege was mostly aquatic with a crocodile-like body shape and flat triangular head, eyes on the top the skull and many teeth around the jaws and in the palate*.

Its slender body was covered in thick scales.

It likely was the top predator in its habitat during the Devonian Period.

It is unclear whether it occasionally emerged onto land, but the structure of its fins would have enabled it to do so, according to Prof Long.

Its fingers were contained within the fin; the skin was not separated around them.

The digits of the 30,000-plus living species of tetrapods — four-limbed animals, including humans — all share the same basic pattern found in Elpistostege.

girl's hand holds an old woman's hands media_cameraFour-limbed animals, including humans, all share the same basic pattern found in Elpistostege. Picture: iStock

GLOSSARY

  • unequivocally: without doubt
  • articulated: able to move independently of the things around it
  • brackish: a bit salty
  • palaeontologists: experts in fossils
  • pectoral: chest
  • explicit: stated clearly without room doubt
  • apparent: looks to be that way, but not certain
  • palate: roof of the mouth

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QUICK QUIZ

  1. What is similar about the fish and modern humans?
  2. When did this live and where?
  3. What does a palaeontologist do?
  4. What were small bones useful for?
  5. What is a tetrapod?

LISTEN TO THIS STORY

CLASSROOM ACTIVITIES
1. Summarise the Information
There is a lot of information in this article. Interesting detail has been added to give further information for those that want to know more. Your job is to read through the article and determine what are the most important pieces of information and what are the ‘extra’ details. Note down or highlight the most important information and then rewrite this into a succinct paragraph. Make sure you use correct punctuation.

Time: allow 15 minutes to complete this activity
Curriculum Links: English, Science

2. Extension
An artist’s impression
When we read, we create an image inside our head of what we are reading about.

Try not to look at the picture in the article. (If you have already seen it that is OK) Using only the explanation in the article, draw an ‘artists impression’ of what you think the Elpistostege watsoni would have looked like. Include the typical environment you might have expected to find one. How does your picture compare to the one used in the article?

Label the significant physical traits that palaeontologists believe the Elpistostege watsoni had.

Time: allow 15 minutes to complete this activity
Curriculum Links: English, The Arts – Visual Arts, Science

VCOP ACTIVITY
Punctuation Thief
Pick a paragraph from the article, or about 3 sentences together if that’s easier, and rewrite it without the punctuation. At the bottom of the page write a list of all the punctuation you stole and in the order you stole it. For example; C , . C .

Then swap your book with another person and see if they can work out where the punctuation needs to go back to.

Make it easier: Underline where you stole the punctuation from but don’t put the list at the bottom in order.

Make it harder: Don’t put the punctuation in order at the bottom.

Underline where you took the punctuation from, but don’t tell them what pieces you took.

Just tell them how many pieces you took, but not what they are.

Don’t give them any clues!

HAVE YOUR SAY: Give Elpistostege an easier name.
No one-word answers. Use full sentences to explain your thinking. No comments will be published until approved by editors.

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