Ancestors of modern mammals evolved into one of the most successful animal lineages by starting out small and simple, researchers have found.
A new study, published today in Communications Biology, shows that skull bones were successively reduced in early mammals around 150 to 100 million years ago.
The research further demonstrated that alongside the reduction of skull bones, early mammals also became a lot smaller, some of which had a skull length of only 10-12 mm. This miniaturization considerably restricted the available food sources and early mammals adapted to feeding mostly on insects, allowing them to thrive in the shadows of dinosaurs.
In many vertebrate groups (animals with a back bone), such as fishes and reptiles, the skull and lower jaw are composed of numerous bones. This was also the case in the earliest ancestors of modern mammals over 300 million years ago.

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