Shell severely restricts the evolution of turtles
Published: Wednesday, Nov 20th 2024, 12:40
Updated At: Thursday, Nov 21st 2024, 00:59
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The shell of turtles has severely restricted their evolutionary development. This explains their low species diversity compared to other animal groups, as two researchers from the University of Freiburg shed light on in their study in the journal "Ecology & Evolution".
Although turtles originated 230 million years ago in the Triassic period, there are only around 350 species today. In comparison, there are 10,000 bird species. The two researchers investigated the relationship between body size and limb length in turtles and how these proportions limit the evolutionary possibilities of the animals, as the University of Fribourg (Unifr) announced on Monday.
Turtles show a fixed body-limb proportion, while in other animals the limbs grow and adapt flexibly with body size. "Our measurements on over 200 species of turtles, both living and extinct, show that the ratio of shell to limb length has hardly changed for millions of years," scientist Guilherme Hermanson was quoted as saying in the press release. The shell acts as an evolutionary dead end. Turtles could not develop new body forms such as flightless or limbless variants.
Sea turtles show slight deviations as they use their front flippers for locomotion in the water. Using statistical scaling models, the researchers were also able to estimate the size of extinct species and assume that the maximum carapace length of sea turtles is around 2.2 meters, wrote Unifr.
Sea turtles may not be able to grow larger because they have to return to land to lay their eggs, where larger animals would overheat more quickly, the report added. Marine animals such as whales and dolphins do not have this limitation. They give birth to their young in the water and could grow much larger as a result.
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