The Discovery
International researchers have unveiled a newly identified relative of modern mammals, named Megacauda sungei, which lived around 165 million years ago during the Middle Jurassic period. Discovered in rock strata within China's Inner Mongolia Autonomous Region, the fossil belongs to the mammaliaform group—an evolutionary line encompassing modern mammals and their extinct early relatives. The research was published in the journal Nature by a team including Professor Li Kun of Shenyang Normal University and Professor Luo Zhe-Xi of the University of Chicago.
What Scientists Found
Estimated to have weighed between 1 and 2 kilograms, Megacauda sungei is the largest known Jurassic mammaliaform discovered to date. The specimen features several adaptations for a semi-aquatic life:
- A broad, flattened tail combined with short hind legs and long feet, ideal for swimming.
- Pelvic and ankle structures that resemble those of the modern platypus.
- Sharp canines and molars suited for cutting meat, suggesting it hunted fish, salamanders, and invertebrates before retreating to burrows on land.
Using computed tomography (CT) imaging, the team analyzed the fossilized hyoid bones and pharyngeal skeletal structures. By comparing these features with living mammals, they reconstructed the soft palate and pharyngeal muscles. The analysis revealed a saddle-like hyoid arrangement similar to that found in living placental and marsupial mammals.
Why It Matters
Soft throat tissues rarely survive fossilization, making it difficult to trace when mammals developed the capacity to nurse and swallow. The well-developed hyoid apparatus in Megacauda sungei shows that the anatomical structures required to regulate oral pressure while suckling and to shield airways during swallowing were already present in the Middle Jurassic, well before modern mammals evolved. Furthermore, the discovery proves that early mammalian ancestors in the Mesozoic era occupied diverse ecological niches, including positions as semi-aquatic predators alongside dinosaurs.
Source: dinosaur fossil discovery - BingNews · Published October 31, 2026 · Photo by Jan Allbeck on Unsplash
