How are they reconstructed?

Paleontologists carry out a patient investigating task, in which even the smallest element may be fundamental for the reconstruction of the types and habits of the life of a creature of the past, at times it can be a very small bone fragment.
Generally, even in paleontology, as in geology, the principle of actualism is used, in which it is hypothesized that similar organs (a paw, a skull, a backbone) in organisms of the present day and of the past, had the same purpose and worked in the same way. For this reason the reconstruction of fossil organisms is carried out trying to compare them with present day organisms that are the most similar to the specimen that is being examined. At present the use of computers and new biomechanical and bio-engineering technologies enable reconstructions that were unheard of up to only a few decades ago. Using bone-casts, for example, it is possible to reconstruct the insertions of tendons and muscles, it is possible to determine the development and the arrangement of the mass of muscles, in other words, it is possible to cover the skeletons with muscles and flesh, creating reconstructions of the animals in “flesh and bone”. If, as in some lucky cases, preserved traces of delicate skin or cartilage tissues are found, it is possible to add other details to the “model” such as crests and bone, membrane or cartilage protuberances, the appearance of the skin, either smooth or wrinkled or with scales, the presence of hairs and feathers. In some cases, due to the discovery of traces of the cerebral cortex in the skull it has been possible to reconstruct the size of the brain, and in some exceptional cases, to reconstruct the internal organs. In order to reconstruct and recognize a species, however, it is not necessary to find a complete individual, the characteristics of the species are patiently reconstructed using the parts of various individuals that have been preserved better, as in a complicated puzzle. Naturally when complete individuals are found, which are perfectly preserved, the information provided by these is of particular importance because it is possible to verify the model. However it may occur that, specially for very ancient organisms, belonging to extinct phyla, as for example the bizarre animals of the Burgess fauna, it is not possible to compare these specimens with analogous organisms of the present : in this case the principle of adaptive convergence will be used, based on the assumption that different organisms that live in the same environment eventually have a similar morphology, thus it will become important to understand what environment the discovered fossil lived in.

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