A Cretaceous eutriconodont and integument evolution in early mammals

Area of Science:

• Paleontology
• Evolutionary Biology
• Mammalian Evolution

Background:

• The Mesozoic era saw significant ecomorphological diversity in early mammals.
• Key mammalian characteristics evolved during this period, crucial for post-dinosaur extinction success.
• Many modern mammal-like forms evolved independently early in mammalian history.

Observation:

• A 125-million-year-old eutriconodontan mammal fossil was discovered in Spain.
• The specimen exhibits exceptional preservation of skin and pelage, including features like fur, a mane, and external ears (pinna).

Findings:

• The fossil displays advanced mammalian integumentary features, such as keratinous dermal scutes, protospines, and compound hair follicles.
• It also shows evidence of alveolar lungs, a liver, and a muscular diaphragm, alongside specialized vertebral articulations convergent with modern xenarthran mammals.

Implications:

• This discovery pushes back the record of complex mammalian integumentary features into the Mesozoic era.
• The findings demonstrate that diverse mammalian traits evolved much earlier than previously thought, showcasing convergent evolution in skin structures and locomotion.