Turtles have an important place in many cultures because of their long-lived and extraordinary body structures. You will all remember the story of the Turtle and the Rabbit, the derivative of this story has been created in other cultures and has survived to the present day. Again , it would not be wrong to say that in most cultures turtles are depicted as slow-moving wise animals carrying their homes on their backs . So why are turtles so different from other animals today? Why do turtles have shells?
To answer this question, we first need to understand tortoise shell structure and evolution. For example, turtles cannot come out of their shells, as we have seen in cartoons, because their shells do not form when their skin hardens or ossifies as is observed in some other crustaceans. Turtle shells are formed by the enlargement and thickening of the ribs and parts of their backbones [1]. It's not like breaking your dreams, but the tortoiseshell is not the animal's home, it's actually a modified rib cage!
There are three different types of tortoises today: sea, land and freshwater turtles. While all land turtles have thick and hard shells, soft shells can be observed as well as thick shells in marine and freshwater turtles. Soft or thick, it is an indisputable fact that these shells serve as physical protection for animals. Is this the case when we look at the fossil record? So has the tortoise shell functioned as a protection for turtles throughout their evolutionary history? Dr. Tyler R. Lyson answers this question "Probably not" and adds.“The widening of the ribs means that breathing becomes difficult in animals [you can try this at home by trying to breathe without moving your ribs] and therefore the movement is slowed down; Moreover, the full shell is not observed in the pioneer turtle species as in the current turtles, you can think of the pioneer turtles as large lizard-looking animals with a flat body ”. If the benefit of the expansion of the ribs in the predatory turtles is not physical protection, what then?
The oldest known pioneer turtle fossil dates back about 260 million years. Looking at the partially preserved specimens of this fossil species, called Eunotosaurus africanus, we could infer that it was less enlarged than current turtles, but still had a flat rib sequence [2]. While playing on his father's farm in South Africa, the person who found the first * nearly complete * preserved fossil of this fossil species was an 8-year-old boy .! Thanks to the contributions of this curious boy, Dr. Lyson et al conducted a study in 2016 and, in addition to the body form information above, suggested that Eunotosaurus africanus's forelimbs were much more developed than their hind legs, they had a strong tail, and even examining their fossilized eyes, the animal had poor eyesight. . Let's combine all these findings now: a flattened body, slowed motion, low vision, strong forearms… Dr. All these findings suggest that the pioneer turtles are good diggers, according to Lyson et al. Given the climatic conditions of South Africa 260 million years ago, the animals probably needed to be protected from the heat, digging a hole with their strong forearm, entering it and waiting for the air to cool.Their flat bodies probably provided an advantage for them to get into the holes they dug more easily. Sharp eyesight and speed were not necessary for animals that would spend a long time in pits [2].
For now, all the findings are Dr. It backs up the arguments of Lyson et al., That turtles' shells do not appear to have evolved to protect them from physical influences. As a result, although shells act as protection for current tortoise species, the origin of tortoise shell is for other reasons!
You know, birds' feathers did not evolve to facilitate flight either, but the contribution of feathers to flight aerodynamics is huge in present-day flying birds! Let this be the subject of another post
Before finishing the article, I would like to thank the young South African scientist for his contribution to science at the age of 8 and remind us that we should not stop encouraging our children to wonder.
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