Turtle’s shell is an excellent protection from an enemy’s attacks but it wasn’t originally developed for that purpose, a new study suggests.

The development of turtle’s shell originated from the need of digging, a group of palaeontologists has found. The conclusion was made by examining a fossil of the earliest known species that resemble turtles. The most notable was the fossil of Eunotosaurus arficanus, a species believed to be the turtle’s ancestor.

Eunotosaurus africanus had a broad ribcage that developed the base that is now the protective shell that turtles have. As time passed, the bones of the ribcage broadened and slowly started to form a solid plate.

The ancient turtle-like creature had broad ribcage that is believed to later developed into a shell. Photo: Tyler Larson/ Sci-News

The most notable fossil was found by an 8-year-old Kobus Snyman at his father’s farm in South Africa. The discovery was the remains of a turtle’s ancestor that lived some 260 million years ago. The fossil, only the length of 15 centimetres, shows well-reserved ribcage, front legs and back legs. The fossilised animal also had strong claws that were suitable for digging.

Turtles have a ribcage under their shells that has formed into one smooth plate, unlike most animals. The fossils show that the development may have started from the animal’s need to dig underground to take cover from the heat.

The broad ribs slowed the animal’s movements and hampered its breathing but also made its core strong and suitable for digging.

The development of the shell and claws likely facilitated the formerly terrestrial animals into aquatic environments, according to the palaeontologists.