Life history of a new Paraceratheriid from the Early Oligocene of Northwest China.

Understanding life history is crucial for elucidating mammalian evolution. Body size and tooth development have long been fundamental parameters in reconstructing the life histories of both fossil and extant species. The superfamily Rhinocerotoidea exhibits a protracted evolutionary history from the Eocene to the present, with its large body sizes and high-crowned teeth providing compelling evidence for such studies. In this research, we describe Turpanotherium qiui sp. nov., a new species within the family Paraceratheriidae, identified from a mandible recovered from the Early Oligocene of Northwest China. Analysis of elemental concentrations revealed insights into both longitudinal life history patterns and discrete developmental events. Significant variations in barium and strontium concentrations in the enamel were associated with neonatal development and breastfeeding phases, whereas zinc, strontium, and barium concentrations in the dentine displayed marked seasonal variability. Analysis of Retzius lines in enamel and annual lines in cementum from tooth histology reveals that this Paleogene species exhibited a life history pace comparable to its Quaternary relatives. The evolution of life history traits in Rhinocerotoidea has been relatively conservative since the Oligocene and does not consistently correlate with shifts in body size. This study establishes a foundation for understanding the evolution of life histories in this group.