125-million-year-old mammal fossil discovered in Spain

Scientists have found fossilized remains of a 125-million-year-old rat-sized mammal in Spain, pushing back the earliest record of preserved mammalian hair structures and inner organs by more than 60 million years. The microscopic structures of hair and spines in the specimen, named Spinolestes xenarthrosus, are the earliest-known examples in mammalian evolutionary history. Spinolestes xenarthrosus lived in the Cretaceous period and belonged to an extinct lineage of early mammals known as triconodonts. 
Its teeth and skeletal features indicate it was a ground-dweller that ate insects. Its soft tissues, with discernable microscopic structures, were preserved through a rare process known as phosphatic fossilization.Individual hair follicles and bulbs, as well as the composition of individual hair shafts, could be identified using an electron scanning microscope. 
Spinolestes had remarkably modern mammalian hair and skin structures, such as compound follicles in which multiple hairs emerge from the same pore. It had small spines around a tenth of a millimetre in diameter on its back, similar to modern hedgehogs and African spiny mice, which appeared to be formed by the fusion of filaments at follicles during development.