What do you believe is the single most important factor driving up the cost of living in Nigeria?

Newly discovered fossils, belonging to the mammal-precursor species Brasilodon quadrangularis and Riograndia guaibensis, offer critical insights into the development of the mammalian jaw and middle ear, revealing evolutionary experiments that occurred millions of years earlier than previously thought.

Mammals stand out among vertebrates for their distinct jaw structure and the presence of three middle ear bones. This transition from earlier vertebrates, which had a single middle ear bone, has long fascinated scientists. The new study explores how mammal ancestors, known as cynodonts, evolved these features over time.

Using CT scanning, researchers were able to digitally reconstruct the jaw joint of these cynodonts for the first time. The researchers uncovered a 'mammalian-style' contact between the skull and the lower jaw in Riograndia guaibensis, a cynodont species that lived 17 million years before the previously oldest known example of this structure, but did not find one in Brasilodon quadrangularis, a species more closely related to mammals.

The work, published in Nature, indicates that the defining mammalian jaw feature evolved multiple times in different groups of cynodonts, earlier than expected.

These findings suggest that mammalian ancestors experimented with different jaw functions, leading to the evolution of 'mammalian' traits independently in various lineages. The early evolution of mammals, it turns out, was far more complex and varied than previously understood.

• Read More