Its leaders, a team of scientists from the Universities of Chicago, Harvard and Brown, analyzed a specimen from Haramiyavia with unprecedented detail using high-resolution computed tomography. Thanks to these images, the complex dental mechanism and chewing movements adapted to a herbivorous diet have been revealed, indicating that various evolutionary adaptations in feeding already occurred among the early proto-mammal lineages. However, the primitive structure of the jaw, associated with a primary type of middle ear, suggests that Haramiyavi a and its relatives were not mammals. Rather, they occupied a more ancient niche in the evolutionary tree.
The study, published in the Proceedings of the National Academy of Sciences , confirms the previous idea that diversification among mammals occurred in the Jurassic, about 175 million years ago, 30 million years after the Haramiyavia and other similar links. on the evolutionary path they will diversify in the Triassic. For Neil Shubin, author of the research and Professor of Anatomy and Biology of Organisms, “ this fossil is the only representative of a very important era in the evolution of mammals ; ecosystems changed throughout the planet during the transition between the Triassic and the Jurassic.
If you examine the jaw of Haramiyavia , with its primitive features, it seems clear that this group of animals sits at the foot of the tree of the mammal family, just as Tiktaalik roseae sits at the base of the tetrapod tree. ” The Haramiya form one of the earliest lineages of proto-mammals. They emerged in the Triassic about 210 million years ago. We knew them only dimly from isolated dental fossils, until the very well-preserved jaw of Haramiyavia , with its intact molars and part of the skull bones, was discovered in Greenland in 1995.
Initial studies, done by hand, did not reveal much, but the new examination with modern technology, such as high-resolution computed tomography and 3D reconstructions, has been key to carrying out a much more detailed description of Haramiyavia . Thanks to this technology, it has been seen that the species was not related to multituberculate mammals, but occupied an earlier position in time , in a separate branch that preceded mammals. It also confirms that the emergence of modern mammal diversification did not occur in the Triassic, but 30 million years later, in the Jurassic.
Image : Analysis of the jaw of Haramiyavia clemmenseni. Courtesy of The University of Chicago Medicine & Biological Sciences.
