Jurassic Mammals Were Picky Eaters: Shrew-Sized Animals Munched Insects

It turns out that Jurassic mammals were pickier eaters than once thought. Scientists have taken a look at tiny fossil mammals and have found that during this time period, the animals developed new characteristics, such as teeth capable of precise chewing.

"None of the fossils of the earliest mammals have the sort of exception preservation that includes stomach contents to infer diet, so instead we used a range of new techniques which we applied to our fossil finds of broken jaws and isolated teeth," said Pamela Gill, one of the researchers, in a news release. "Our results confirm that the diversification of mammalian species at the time was linked with differences in diet and ecology."

The researchers used both synchrotron X-rays and CT scanning in order to examine the internal anatomy of fossil jaws of two of the earliest shrew-sized mammals, Morganucodon and Kuehneotherium. The jaws themselves were only 2 cm in length, making them extremely delicate. In fact, the jaws were in many pieces, so these scans were pieced together to create a complete digital reconstruction.

In the end, the researchers found that these two mammals had teeth that had very different patterns of microscopic pits and scratches, known as "microwear." This indicated that they were eating different things; Morganucodon favored harder, crunchier food items such as beetles while Kuehneotherium preferred softer foods, such as scorpion flies.

"This study is important as it shows for the first time that the features that make us unique as mammals, such as having only one set of replacement teeth and a specialized jaw joint and hearing apparatus, were associated with the very earliest mammals beginning to specialize their teeth and jaws to eat different things."

The findings are published in the journal Nature.