Researchers have identified a 165-million-year-old mammaliaform, Megacauda sungei, that provides evidence for the early evolution of structures necessary for suckling and swallowing.

An international team of scientists has discovered a new Jurassic-era species, Megacauda sungei, that sheds light on the origins of mammalian suckling. The findings, published in Nature, indicate that key anatomical structures for breastfeeding and swallowing evolved nearly 165 million years ago. This discovery suggests these traits appeared long before the rise of modern mammals.

Anatomical Discoveries

Using high-resolution microCT imaging, researchers reconstructed the skull and skeleton of the fossil, which was found in what is now Inner Mongolia, China. The analysis revealed bony projections on the roof of the mouth and specialized hyoid bones in the throat, both of which resemble features in modern therian mammals used to support the soft palate and muscles for suckling.

Evolutionary Significance

The discovery challenges the theory that modern suckling structures evolved directly from primitive bony ridges, as Megacauda possessed both the new therian-like hooks and older, primitive ridges simultaneously. Furthermore, the findings suggest that monotremes, such as platypuses, may have lost these ancestral suckling features over time, rather than never having developed them.

Ecological Context

Megacauda sungei was a large mammaliaform, roughly the size of a modern otter, and is considered one of the earliest examples of a semiaquatic mammal. It possessed blade-like cheek teeth, a platypus-like pelvis, and an otter-like tail, suggesting it was a predator that hunted small vertebrates and invertebrates in freshwater environments.