Evolutionary-developmental biology (Evo-Devo) is a new field of biology that emerged from the fusion of Evolutionary and Developmental biology and aims to study the mechanisms underlying biological diversity. Evolution is marked by the apparition of many morphological innovations that have permitted organisms to adapt to diverse environments. Some of these innovations evolved several times in distantly related organisms, as for example the wings that were developed independently by birds and bats. Explaining how these evolutionary convergences occur is another focus of the Evo-Devo research. Given that animals share a very similar set of developmental genes, the question that arises is whether similar characters are produced by the same or distinct mechanisms. The new molecular classification showed that some of the mammalian groups of morphological character-based phylogenies were not monophyletic and revealed several cases of evolutionary convergences. The particular case we are interested in is the transition from hair follicles to spine- producing organs that occurred independently in some rodents, such as spiny mice and porcupines, in hedgehogs and in tenrecs. So as to understand how mammalian spines evolved and if they have convergent generative bases, new model organisms are used in our lab: the spiny mouse, Acomys dimidiatus, the hedgehog, Atelerix albiventris, and two tenrecs, Echinops telfairi and Setifer setosus. Analyses have also been initiated on the Old World porcupine: Hystrix cristata. The laboratory mouse hair follicle system is used as reference in our study. The results presented here contribute to: (1) the histological description and comparison of spine follicle structures by classical- and immuno-staining and three-dimensional reconstructions of these appendages, (2) the cloning and sequencing of genes likely to be involved in spine development, and (3) the exploration of the spines' structural proteins, by protein extraction and one-dimensional separation. From our results, it appears that different strategies were used by mammals to evolve spines, which constitute thus distinct evolutionary novelties.