Quantitative Analyses Reveal the Katian Cephalopod Palaeobiogeography

As key predators during the Great Ordovician Biodiversification Event (GOBE), cephalopods evolved diverse and complex morphologies. Despite yielding abundant Ordovician fossils, the Eastern Anti-Atlas (Morocco) and the Northern Qilian (China) lack detailed systematic studies on cephalopod faunas. We describe Katian cephalopod fossil assemblages from these two localities. The Eastern Anti-Atlas assemblage consists of Tafadnatoceraselfechtense Fang et al., 2025 and Isorthoceras sp., whereas the Northern Qilian assemblage comprises Anaspyroceras sp., Geisonocerina sp., Paradnatocerasnyalamense Chen, 1983, along with several oncoceratoid and orthoceratoid taxa. These findings enhance understanding of Katian cephalopod diversity in the Eastern Anti-Atlas and Northern Qilian. Based on their global palaeogeographical distribution, Katian cephalopods flourished at low latitudes with high biodiversity, but declined at high latitudes. This pattern is consistent with the Latitudinal Diversity Gradient (LDG). Using the software packages PAST (version 4.13) and EDENetworks (version 2.18), we perform cluster analysis and weighted network analysis to investigate the palaeobiogeographical significance of Katian cephalopods. Our quantitative analyses demonstrate distinct provincialism among Katian cephalopods, recognizing two provinces: Mid–Low Latitude Province and High Latitude Province. We propose that global oceanic currents were a primary driver for this faunal differentiation.