Morphological disparity through time of Calliotropis (Vetigastropoda: Eucyclidae)

PEREZ, D. E.; FERRARI, S.M.; EZCURRA, M. D.

Congreso; Reunión de Comunicaciones de la Asociación Paleontológica Argentina, Puerto Madryn, 2018; 2018

Calliotropis Seguenza is a genus of marine gastropods ranging from the Triassic to Recent, in which modern forms are strikingly similar toMesozoic 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 thephylogenetic matrix using maximum observable rescaled distances and the weighted mean pairwise dissimilarity was used as the pre-ordinationdisparity metric. We analyzed morphological changes through the entire biochron of the clade using three character-sets: the first using allcharacters, 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/Recentspecies, respectively. Disparity curves through time show non-significant differences across time-bins but morphospace occupation showssignificant shifts from the Triassic to Jurassic and from the Paleogene to Neogene. The Paleogene group has a significantly larger morphospacethan Neogene species. The approaches using only characters with paleoecological signal or without them found results very similar to thoseusing all characters. From these results, we can preliminary interpret that the morphological differences observed within Calliotropis alongthe geological record may not be driven by paleoecological constraints, but by intrinsic phenotypic evolution of the group through time.