Scientists from the United States Museum of Natural History and the Chinese Academy of Sciences have presented in society, through the journal Nature, three hitherto unknown animals that lived about 160 million years ago : Shenshou lui, Xianshou linglong and Xianshou songae .
They weighed between 28 and 280 grams, gave an air to modern squirrels and lived in trees, as can be deduced from the anatomy of their tails and legs.
The most important thing about this discovery is that it considerably delays the origin of mammals, until approximately 208 million years ago. For decades, paleontologists had argued over the classification of an enigmatic group of extinct animals called the Haramiyida, of which they had barely found fragments of jaws and teeth.
The discovery of the new fossils, very well preserved, allows us to reconstruct their complete physiognomy and label them, practically without a doubt, as mammals. Experts are based on details such as the presence of a middle ear with three bones, exclusive to that group of warm-blooded vertebrates to which humans also belong.
This could mean that mammals split from the reptilian lineage in the late Triassic (between 231 and 201 million years ago) and not in the Middle Jurassic (between 176 and 161 million years ago) as many researchers believed. This agrees with other hypotheses based on the study of DNA.
For the three arboreal trees of the Mesozoic they have created a new group or clade in the tree of evolution: Euharamiyida . Regarding their eating habits, it seems that they fed on insects, nuts and fruit, which they devoured with their strange teeth, full of pointed edges.
