In this study, we describe the carapace ornamentation found in species of Lithodidae (Decapoda, Anomura), focussing primarily on the genus Paralomis, which displays the greatest diversity of forms, globally. Evidence of ontogenetic change in the surface ornamentation of lithodids has previously been highlighted for one species of Paralomis (P. granulosa Jaquinot, 1847); however, its wider occurrence within the family has never been formally examined. Growth-related change in dorsal spines and tubercles was considered using growth-series from eight species of Paralomis (P. mendagnai, S Pacific; P. multispina, N Pacific; P. spinosissima, P. granulosa, S Atlantic; P. inca, SE Pacific; P. erinacea, E Atlantic; P. cubensis, Caribbean; P. stella, S Indian Ocean). Tubercular structures from adult specimens of 24 additional species of Paralomis are figured in order to provide a reference for future diagnosis. This study shows that ontogenetic changes should be considered when identifying specimens of Lithodidae to species level.