Study: Megacauda sungei pushes back mammal-like throat evolution

Megacauda sungei, a semiaquatic, otter-size mammaliaform that inhabited the freshwater lakes and rivers of what is now Inner Mongolia, China, approximately 165 million years ago, pushes the earliest known evolutionary evidence of mammal-like swallowing, drinking, and suckling back to the Middle Jurassic period. Published on October 7, 2026, in the journal Nature, a study led by researchers including University of Bonn paleontologist Dr. Thomas Martin reveals that this ancient creature possessed an anatomical hyoid bone apparatus and pharynx configuration capable of swallowing against gravity long before modern mammals ever diversified.

Discovering the Largest Jurassic Mammaliaform in Inner Mongolia

Excavated in the Inner Mongolia region of China, the fossil of Megacauda sungei measures roughly 0.5 meters, or 1.6 feet, in length and weighed between one and two kilograms, placing it at about the size of a modern platypus or a Chihuahua. As Live Science reported, its name translates to big tail, reflecting its wide, flattened tail, which paired with short hindlegs and relatively long feet to give the animal a lifestyle analogous to a living platypus or an otter. Most contemporary mammaliaforms during the dinosaur-dominated Mesozoic era weighed only a few grams, making this species the largest known Jurassic mammaliaform.

According to NPR, researchers used X-ray imaging and CT scans to examine the delicate underside of the fossilized skull. The scans exposed a preserved roof of the mouth and a series of rare bone hooks and ridges that mapped out the animal’s musculoskeletal machinery.

Megacauda Sungei Fossil Reveals Early Mammal Food Processing

The most significant evolutionary finding centers on the exceptionally well-preserved pharynx and throat bones of Megacauda sungei. Phys.org noted that the animal shared space in the scientific spotlight with another newly described Chinese fossil, Dongoconodon platycauda, which also exhibited semiaquatic traits alongside a third generation of teeth. However, the Megacauda sungei specimen provided distinct anatomical details regarding how early mammal relatives processed food.

Many species of animal do not have a soft palate and only have a simple hyoid bone apparatus without a swallowing mechanism. Crocodiles, for instance, raise their head up and use jerky movements to make their unchewed prey slide down their throat. This is achieved with the aid of gravity.

Dr. Thomas Martin

In contrast to reptiles, mammals evolved a complex hyoid structure in the pharynx that permits swallowing against gravity, an adaptation that allows humans to drink upside down through a straw while breathing.

This ability is a key adaptation that allows mammals to feed on nutrient-rich milk and swallow it safely without it entering their nose. It was this adaptation that made brain development, eventually leading to humans, possible.

Dr. Thomas Martin

Megacauda sungei belonged to the docodonts, an extinct group of early mammaliaforms that lived between roughly 200 million and 120 million years ago. As Live Science detailed, docodonts adapted to a wide variety of habitats, including tree-dwelling shrews like Microdocodon gracilis and tunnel-diggers like Docofossor brachydactylus. The discovery confirms that multiple docodontans exploited diverse niches with semiaquatic and other ecomorphotypes long before modern mammals diversified.

Paleontologists noted that finding these complex anatomical features in a Middle Jurassic species pushes the evolutionary timeline of lactation and modern feeding mechanics back before marsupials and placental mammals diverged approximately 160 million years ago.