Untangling phylogenetic, geometric and ornamental imprints on Early Triassic ammonoid biogeography: a similarity-distance decay study

摘要: Ammonoids are diverse and widespread fossil, externally shelled cephalopods that flourished for more than 300 Myr before their total extinction 65 Ma ago. In spite of two centuries intensive scientific studies, mode(s) life long-distance dispersal abilities remain poorly known. Here, we address this by focusing on the latitudinal distribution Early Triassic (approximately 250 Myr) ammonoids through similaritydistance decay analyses. We examine compare rates similarity-distance between various groups with respect to systematics, shell geometry ornamentation untangle phylogenetic, geometric ornamental imprints observed biogeographical pattern. Our data do not support any phylogenetic influence, but rather demonstrate significant effect (sub-)adult decay: most evolute morphs tend have been endemic involute forms. This contrasts classic hypothesis ammonoid mainly occurred during earliest planktonic stages, thus morphological characteristics should constrain large-scale patterns ammonoids. Although direct control Sea Surface Temperature can be discarded, result may indicate at least some adult were skilled active swimmers capable achieving migration, as present-day coleoid cephalopods.