How the turtle got its shell: Not a just-so story - Today's news, tomorrow's lesson - 31 May 2013

The scientific riddle behind how the turtle came to have its shell finally might have been solved by a group of American scientists.


How the turtle got its shell: Not a just-so story

Today's news, tomorrow's lesson - 31 May 2013


Richard Vaughan

The scientific riddle behind how the turtle came to have its shell finally might have been solved by a group of American scientists.

The team of palaeontologists claims an already well-known reptile fossil in South Africa dating back 260 million years provides the missing link as to how the turtle’s shell was formed.

It has long been considered an evolutionary gap.

The scientists have identified that the fossil, called Eunotosaurus africanus, is the earliest known version of the turtle due the presence of telltale T-shaped ribs. According to the team, led by Yale University’s Tyler Lyson, the T-shaped ribs were the first evolutionary step to the development of the hard shell worn by turtles.

Unlike armadillos’, which are made of bony scales, the turtle’s shell is made up of about 50 ribs, vertebrae and shoulder bones all fused together.

For many years the oldest turtle fossil was from 210 million years ago and showed a fully-formed shell similar to those found in turtles today. Then in 2008, a fossil dating from 220 million years ago called Odontochelys semitestacea was found in China, which showed a reptile had existed with a full shell on its belly but only a partial shell, or carapace, on its back. Its discovery was believed to be the earliest ancestor of the turtle we know today.

But the team from Yale, the Smithsonian Institution and the New York Institute of Technology has pushed back the evolutionary line of the turtle by between 30-55 million years by linking it to the Eunotosaurus, which they claim shares many common features with the modern turtle.

The Eunotosaurus had no shell or carapace and nor did it have broad spines on its vertebrae, which turtles have today but broadened ribs provide the first step on the evolutionary chain to the turtle’s shell.

“This helps fill the morphological gap between a lizard body plan and the highly modified body form found in turtles today,” Dr Lyson said.

“This is the first real, detailed study of Eunotosaurus and it fills a gap in the turtle fossil record,” Dr Lyson added.



Questions for discussion or further research:

  • What is ‘evolution’?
  • Why do scientists continue to study extinct species? What do you think we might be able to learn from them?
  • What evolutionary advantages do you think having a hard shell might provide?
  • What do you know about turtles? Where could you find out more?

Resources for you


Turtle life cycle

  • Explore the life cycle of a turtle and get students to play a turtle-inspired board game.

Evolution

  • What is Homer Simpson’s theory of evolution? Find out with this lesson activity.

Extinction

  • Explore the causes of extinction with a thought-provoking lesson.

Survival of the fittest

  • Help students to understand how natural selection works with this entertaining game.


Further news resources


First News front page

  • Help your pupils understand the features of the front page of a newspaper.

Write all about it

  • Get students creating their own news report with this step-by-step guide.

What is the News?

  • A sociological and media perspective on what makes an event 'newsworthy'.

On the box

  • Help pupils to write their own TV news broadcast with this handy PowerPoint.

Structuring stories

  • A scheme of work to help students structure news stories.

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