Turtle shell evolution

This March 2018 video is called How the Turtle Got Its Shell.

From Discovery in the USA:

How the turtle got its shell

Fossil discovery could help put an end to mystery vexing scientists

By Michael Reilly

Oct. 8, 2008

Famous for carrying its shelled “home” on its back, the humble, plodding turtle has also been toting around one of the biggest mysteries of the animal kingdom. Paleontologists have now unearthed a bizarre fossil beast in the eastern New Mexican desert that might put that mystery to rest.

A foot long and armored from head to tail, the 215-million-year-old fossil Chinlechelys tenertesta is a missing link in turtle evolution that promises to finally settle a controversy that’s been raging for the past two centuries over how turtles got their shells.

There are two camps in the debate. As turtle embryos develop, their shells grow directly from the animals’ ribs, and adult turtles’ ribs are fused to the shell carapace. Some scientists conclude this must have been how the shells originally developed in antiquity, too — normal rib bones gradually flattened out and spread until they formed a complete shell.

But animals like armadillos have shells that aren’t attached to their ribs. Instead the shell is skin that has thickened and hardened to provide protection. This so-called “dermal armor” is also prevalent among ankylosaurs, a group of stoutly built dinosaurs that lived in the Jurassic and Cretaceous eras.

Walter Joyce of Yale University was the first to identify the new fossil as a primordial turtle from just a few bits of the neck and shell. “It’s a pretty ugly fossil, really,” Joyce said of the jumbled pieces he examined, “almost like a shoebox full of crud.”

But the key, Joyce said, was an intact series of three neck spines, a small piece of the belly shell, and a fragment of the back shell with ribs attached.

“That’s what really gave it away,” Joyce said of the final piece. “You can see that the ribs are not fused to the shell.”

Covered in dermal armor, the ancient turtle probably looked a lot like an ankylosaur, though the two species are unrelated. It couldn’t yet retract its neck or feet, and its shell was thinner than a modern turtle’s, but Chinlechelys tenertesta was bristled with sharp spines along its neck and tail.

“This is very clear evidence that the shell is a composite structure,” James Parham of the Field Museum in Chicago said. “It is a missing link. This is one of the most important turtle fossils ever found, I think.”

By observing the development of different animal species and confirming their results with fossil analysis and genomic data, researchers from the RIKEN Center for Developmental Biology show that the shell on the turtle’s back derives only from its ancestors’ ribcage and not from a combination of internal and external bone structures as is often thought. Their study is published today in the journal Nature Communications: here.

Eastern box turtle: here. And here.


Jellyfish wins chemistry Nobel Prize

Aequorea victoria

From the BBC:

‘Glowing’ jellyfish grabs Nobel

A clever trick borrowed from jellyfish has earned two Americans and one Japanese scientist a share of the chemistry Nobel Prize.

Martin Chalfie, Roger Tsien and Osamu Shimomura made it possible to exploit the genetic mechanism responsible for luminosity in the marine creatures.

Today, countless scientists use this knowledge to tag biological systems.

Glowing markers will show, for example, how brain cells develop or how cancer cells spread through tissue.

But their uses really have become legion: they are now even incorporated into bacteria to act as environmental biosensors in the presence of toxic materials.

Colour palette

Jellyfish will glow under blue and ultraviolet light because of a protein in their tissues. Scientists refer to it as green fluorescent protein, or GFP.

Shimomura made the first critical step, isolating GFP from a jellyfish (Aequorea victoria) found off the west coast of North America in 1962. He made the connection also with ultraviolet light.

See also here.

Today we consider chemistry to be a science, but its roots, back in Ancient Egypt, lie in art and the creation of synthetic pigments: here.

Summary executions in Bush’s ‘new’ Iraq

This video from the USA is called The Ghosts of Abu Ghraib.

From The Independent daily in Britain:

Secrets of Iraq’s death chamber

Prisoners are being summarily executed in the government’s high-security detention centre in Baghdad. Robert Fisk reports

Tuesday, 7 October 2008

Like all wars, the dark, untold stories of the Iraqi conflict drain from its shattered landscape like the filthy waters of the Tigris. And still the revelations come.

The Independent has learnt that secret executions are being carried out in the prisons run by Nouri al-Maliki’s “democratic” government.

The hangings are carried out regularly – from a wooden gallows in a small, cramped cell – in Saddam Hussein‘s old intelligence headquarters at Kazimiyah. There is no public record of these killings in what is now called Baghdad’s “high-security detention facility” but most of the victims – there have been hundreds since America introduced “democracy” to Iraq – are said to be insurgents, given the same summary justice they mete out to their own captives.

The secrets of Iraq‘s death chambers lie mostly hidden from foreign eyes but a few brave Western souls have come forward to tell of this prison horror. The accounts provide only a glimpse into the Iraqi story, at times tantalisingly cut short, at others gloomily predictable. Those who tell it are as depressed as they are filled with hopelessness.

“Most of the executions are of supposed insurgents of one kind or another,” a Westerner who has seen the execution chamber at Kazimiyah told me. “But hanging isn’t easy.” As always, the devil is in the detail.

“There’s a cell with a bar below the ceiling with a rope over it and a bench on which the victim stands with his hands tied,” a former British official, told me last week. “I’ve been in the cell, though it was always empty. But not long before I visited, they’d taken this guy there to hang him. They made him stand on the bench, put the rope round his neck and pushed him off. But he jumped on to the floor. He could stand up. So they shortened the length of the rope and got him back on the bench and pushed him off again. It didn’t work.”

There’s nothing new in savage executions in the Middle East – in the Lebanese city of Sidon 10 years ago, a policeman had to hang on to the legs of a condemned man to throttle him after he failed to die on the noose – but in Baghdad, cruel death seems a speciality.

“They started digging into the floor beneath the bench so that the guy would drop far enough to snap his neck,” the official said. “They dug up the tiles and the cement underneath. But that didn’t work. He could still stand up when they pushed him off the bench. So they just took him to a corner of the cell and shot him in the head.”

Obama-McCain election debate

This video from the USA says about itself:

McCain Thinks Iraq Borders Pakistan

On Good Morning America, McCain warned of the “hard struggle,” “particularly given the situation on the Iraq-Pakistan border.” Iraq is nowhere near Pakistan; in fact, Baghdad is more than 1,400 miles from Kabul.

Comments on the second Obama-McCain presidential election debate in the USA are here.

And here. And here.