Revealing the hidden patterns of shark and ray diversity over the past 145 million years

Neoselachians (a monophyletic group including modern sharks, rays, and skates and their extinct relatives) 1 , 2 have an extensive fossil record and a long evolutionary history, 1 , 2 , 3 with over 1,100 extant species today. 4 Previous reconstructions of their evolutionary history suggest a diversity peak in the Cretaceous, a severe decline across the Cretaceous-Paleogene (K/Pg), 5 , 6 , 7 , 8 , 9 and a prolonged stability thereafter, 7 , 8 aside from a small decline in the Pliocene. 10 However, our knowledge of past neoselachian diversity has been mostly based on high taxonomic levels (e.g., genera or families), 8 or from studies restricted to particular regions, 11 , 12 , 13 time periods, 5 , 9 or shark orders. 14 , 15 This is further complicated by spatiotemporal biases, 16 , 17 which can lead to apparent diversity changes, even when bias-correction methods are employed. 16 , 17 Using an extensive dataset of fossil occurrences 18 and a deep-learning model that explicitly accounts for spatiotemporal and taxonomic sampling variation, 19 we reconstruct the neoselachian diversity trajectory over the past 145 million years. We found a long-term increase during the Cretaceous, in which neoselachians reached modern diversity levels. Throughout the K/Pg, we recovered only a small (10%) decline, suggesting high turnover rather than a major extinction. Diversity then surged, culminating in a mid-Eocene peak, when neoselachians reached maximum richness. This peak was followed by a fluctuating yet downward trajectory toward the present, which overall resulted in a 41% loss of species and left modern diversity depleted compared to their thriving past. Together, our results reveal patterns hitherto obscured by multiple biases, challenging previous paradigms about neoselachian diversity.