In soil biology studies, vertebrates have received the importance they deserve only in recent years. The fact that these animals have on average a much greater mobility respect to invertebrates has probably made some of their adaptations to life underground be overshadowed, but nowadays their importance is being rediscovered. In the course of time, biologists realized that even though they were endowed with great ecological flexibility, many vertebrates had very strong connections with the soil environment.
It must be said that even the vertebrate soil fauna, at times called megafauna by soil biologists, shows significant variations in its dimensions, that vary from a few cm of the insectivores (such as the shrewmouse) and of the small amphibians, to the much greater dimensions of the cusk-eels and of the bigger rodents.
As can be imagined, vertebrates that have adapted to an underground existence include all the groups that are comprised in the entire series of tetrapods. Many of the latter, for example, spend a part of their life-cycle in natural cavities or in shelters dug in the ground for this purpose because of the advantages that this type of life style offers both in terms of protection from predators and in terms of a better regulation of some physiological functions (for example thermoregulation and water saving). Contrary to what one might expect after what has been stated with regard to ecological flexibility, vertebrates include some animals that can, or rather, must live in very limited ecological conditions such as those typical of some hypogeal habitats of tropical ecosystems. Amphibians with a worm-shaped body bear witness to this – the adaptations to life in the soil of the so-called caecilians have reached a formidable level of specialization. These animals, besides having eliminated their limbs completely, are often characterized by a regression of their eyes and a reduction of their skin pigments. Hence, their life style is very similar to that of many invertebrates which they resemble due to ‘adaptive convergence’.

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