The study of the relationship between disparity (occupied morphospace) and diversity (number of taxa) through geological time represents a powerful tool in the macroevolutionary study of groups. In this contribution, this approach is applied for the first time to the cyrtocrinid crinoids, a major clade of mostly Mesozoic articulate crinoids also represented by rare Cenozoic forms (two extant taxa). The analysis of disparity identified two separate evolutionary radiations for cyrtocrinids with maximum morphospace exploration, one at the beginning of the evolutionary history of the group in the Pliensbachian and a second one between the Late Jurassic and Early Cretaceous. On the methodological level, the disparity measured both as total variance and as sum of ranges shows compatible results, with trends well coupled to the diversity curve indicating that, in cyrtocrinid crinoids, an increase or decrease in the number of taxa in the history of the clade corresponds a proportional increase and decrease also in the occupied morphospace. The curves obtained were interpreted in the light of the clade's phylogeny, major oceanographic events, newly available ecological niches and relative key innovations, which would be able to increase the fitness of the group. The group diversity was already in decline starting from the Aptian, and the mass extinction at the K‐PG boundary had no effect on the history of the clade. The results show once again the importance and potential of diversity/disparity studies when put into the light of palaeotectonic, palaeoecological and palaeoenvironmental factors.
Paleontological museums should adopt a code of ethics in order to carry out restorations and to set-up exhibits without any falsification. Indeed, alterations can often be voluntary because an exhibit needs to be 'beautiful', 'realistic' or 'charming' for the public. Therefore, the reconstructed parts are painted and then 'soiled' artfully to look more realistic. An incomplete skeleton might be completed by reconstructing the missing bones, or by adding casts of other bones. Sometimes skeletons are 'created', by assembling together bones from several specimens of the same species. Therefore, the museum staff should also inform visitors if a specimen has undergone such tampering, because otherwise each visitor is convinced that they have seen a 'true' fossil. So all museum staff should be trained not only in the techniques of museums, but also in the ethics of restoration and installation.
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