CONICET | Buscador de Institutos y Recursos Humanos

Calliotropis Seguenza is a genus of marine gastropods ranging from the Triassic to Recent, in which modern forms are strikingly similar to Mesozoic species. Previous authors suggest a distinction between living and fossil representatives, with possible paleoecological differences (shallow/deep waters, respectively). A recent quantitative phylogenetic analysis of Calliotropis (36 terminals and 85 shell-characters) allows performing a morphological disparity analysis of the group based on discrete characters. A distance matrix was calculated from the phylogenetic matrix using maximum observable rescaled distances and the weighted mean pairwise dissimilarity was used as the pre-ordination disparity metric. We analyzed morphological changes through the entire biochron of the clade using three character-sets: the first using all characters, the second using only characters with paleoecological signal, and the third using characters excluded from the second approach. Three clusters are clearly separated in the morphospace using all the characters, representing Triassic, Jurassic/Paleogene and Neogene/Recent species, respectively. Disparity curves through time show non-significant differences across time-bins but morphospace occupation shows significant shifts from the Triassic to Jurassic and from the Paleogene to Neogene. The Paleogene group has a significantly larger morphospace than Neogene species. The approaches using only characters with paleoecological signal or without them found results very similar to those using all characters. From these results, we can preliminary interpret that the morphological differences observed within Calliotropis along the geological record may not be driven by paleoecological constraints, but by intrinsic phenotypic evolution of the group through time.