Recent research published in September 2025 in Nature sheds light on the evolution of mammalian jaw joints, revealing a greater diversity in jaw structures during early mammal evolution and highlighting the experimentation that led to the modern dentary-squamosal joint essential for chewing and hearing.

The study emphasizes how this evolutionary experimentation with different jaw joint configurations ultimately resulted in the sophisticated structure supporting both mastication and auditory functions in mammals.

A groundbreaking discovery was made in the Middle Jurassic fossil of Polistodon chuannanensis, which showed a previously unknown secondary jaw joint between the jugal and dentary bones, marking the first such find in four-limbed animals.

Researchers examined fossils of Jurassic mammaliamorphs, including Polistodon chuannanensis and Camurocondylus lufengensis, using high-resolution CT scans to better understand their jaw structures and evolutionary significance.

The Early Jurassic species Camurocondylus lufengensis exhibited a simple articular head of the dentary, indicating an intermediate stage in the evolution toward the modern mammalian jaw joint.

This research fills important gaps in the fossil record, providing new insights into vertebrate evolution and revealing transitional forms that illuminate the development of jaw joints over millions of years.

Overall, these findings challenge previous assumptions about jaw evolution, offering fresh perspectives on how complex structures in mammals emerged through evolutionary experimentation.