Daily News B1 · Intermediate 4 practice tests

A Jurassic fossil offers clues about when mammals learned to chew

2 min read 263 words Published Oct 11, 2026

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Intro

New evidence from a fossil found in Inner Mongolia suggests that mammals may have been chewing at least 165 million years ago.

Vocabulary

Word	Part of speech	Meaning	Example
preserved adjective	adjective	Meaning: kept in good condition for people to study	Example: The preserved letter showed how people lived long ago.
specimen noun	noun	Meaning: a plant, animal, or object studied as an example	Example: The museum displayed a rare bird specimen.
delicate adjective	adjective	Meaning: easily damaged because it is thin or fragile	Example: Please carry the delicate glass carefully.
reconstruct verb	verb	Meaning: to build or understand something again from available information	Example: Scientists used old maps to reconstruct the village.
machinery noun	noun	Meaning: a system of parts that works together for a purpose	Example: The factory uses modern machinery to make cars.

The story

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Chewing may be much older than scientists once understood. New evidence from a fossil found in Inner Mongolia, China, suggests that mammals had this ability at least by the middle Jurassic period, when dinosaurs still ruled much of Earth.

The fossil belonged to a small ancient mammal that lived roughly 165 million years ago. It was about the size of a Chihuahua and was preserved in a thick slab of shale. The specimen included bones and fur, but it was difficult to see clearly against the rock.

A colleague of University of Chicago paleontologist Zhe-Xi Luo used X-rays to make the bones easier to study. The image showed an unusual mix of features. The animal’s back end looked similar to that of a modern platypus, suggesting that it may have spent time in water. However, its teeth and jaw looked very different from a platypus. Its head appeared to be built for hunting.

The fossil also preserved tiny hyoid bones. In people, the hyoid bone is in the throat and helps support the back of the tongue. Scientists later used CT scans to study the underside of the animal’s skull. They found a delicate roof of the mouth and other small bones and ridges.

Together, these features gave the researchers a way to reconstruct parts of the animal’s mouth and throat. The results point to an early form of the machinery needed for chewing and swallowing. Because early mammal fossils are rare, this specimen offers an important look at how a basic part of eating developed long before modern mammals appeared.