Researchers say 165-million-year-old fossil from China shows chewing, suckling

Researchers said a small fossil from the middle Jurassic provides some of the oldest evidence of chewing and swallowing, and also of suckling, traits shared by mammals. The animal, named Megacauda sungei, lived about 165 million years ago, according to NPR. The team described the find in the journal Nature.

The fossil came from the Inner Mongolia region of China, an area NPR reported has produced many fossils, from feathered dinosaurs to flying reptiles. Zhe-Xi Luo, a paleontologist at the University of Chicago, said of the area: "To say it's [a] hot spot is actually [an] understatement." Many such fossils go to the nearby Paleontological Museum of Liaoning, which Luo and his colleague Thomas Martin of the University of Bonn visit each year to examine new finds.

Luo said early fossil mammals are "exceedingly rare." The fossil was about the size of a chihuahua and hard to discern from the dark rock around it. Chang-Fu Zhou of Shandong University of Science and Technology used a technique called X-ray fluorescence spectroscopy, which Luo said "would make this bone pop out in different colors." The resulting image rendered the skeleton bright yellow.

The back end, which includes the pelvis, hind limbs and tail, resembles a modern-day platypus. The researchers said these features suggest the animal was likely semi-aquatic, meaning it lived partly in water, and foraged there. "The big tail is good for swimming," Luo said. He added that its teeth and jaw would be very different from a platypus, so "the head is very much of a predator."

Luo and his colleagues found several small salamander bones inside the fossil that they suspect the animal had eaten. They conclude that these traits among ancient mammalian relatives extend back to at least the middle Jurassic.