Is a Turtle Shell Really Modified Ribs?

It’s thought that the evolution of turtles
A turtle shell is not a shell at all but is made up of specially evolved ribs.

The Eastern Box Turtle

Turtle - Evolution, Adaptation, Conservation

Fact Checks Archive, Page 240

Madison Dapcevich, Author at Page 18

At last, the hard facts on how the turtle got its shell

Vertebral Column and Turtle Shells – Morphology of the Vertebrate Skeleton

Shelly Miscavige Articles

How the turtle got its shell

Eight-year-old boy discovers early turtle fos

Turtle shell - Wikipedia

Turtle shell - Wikipedia

Testudines: More on Morphology