Reconstructing Integumentary Innovation in Mammals and Dinosaurs from the Lower Cretaceous: Insights from Las Hoyas Fossils

The Lower Cretaceous was a period of major evolutionary innovation for plants and animals, especially in wetlands. The Las Hoyas fossil site (125–129 Mya) provides an exceptional record of this, preserving a nearly complete wetland ecosystem with detailed bone and soft tissue fossils.This project focuses on reconstructing unique integumentary microstructures from two Las Hoyas fossils—a triconodont mammal (Spinolestes) and an undescribed maniraptoran dinosaur—using X-ray phase-contrast imaging. Both fossils exhibit extraordinary soft tissue preservation, with keratinous structures about 400–500 µm in size. In Spinolestes, these "protospines" have unknown structure and functions, while the dinosaur's structures are completely new to science. By scanning and reconstructing these structures in 3D, we aim to uncover their function, providing insights into the animals' evolution and ecology, while deepening our understanding of integumentary complexity in early mammals and dinosaurs.