New evidence of the evolution of the association between the bird fortress module and the rear limb module.

Unlike other quadriplegic movements, birds' forebrains and back limbs are adapted to different functions, such as forebrains, which are commonly used for flight, while in the process of adapting to radiation evolution, the rear limbs of birds evolve into different functions in different groups of habits, such as running, predation, grasping, climbing, swimming, or perching.
the front and rear limbs are generally thought to be independent of each other during evolution and are therefore also known as fortress modules and post-limb modules.
In recent years, studies have shown that the mutual influence of the two modules plays a key role in the evolution of bird movement, such as developmental correlation, resource allocation and the influence on the position of the center of gravity, so it is assumed that the two modules have some correlation in evolution, but the details of this association are not very clear.
As an important part of the fortress module and the back limb module, the morphological changes of the corset and shin bone in the origin and evolution of birds are very significant, and the fossil record of early birds also shows that in the course of the origin of modern birds, the growth trend of the corset of the corset and the tibrae are.
to verify whether these two features are related in the evolution process, researchers from the Institute of Paleontology and Paleomanology of the Chinese Academy of Sciences and Nanjing University used systematic comparison methods based on measurements of a large number of living birds and some fossil birds to calculate the correlation between the two features on the basis of controlling kinship and weight size.
results showed that there was a significant positive correlation between the length of the chest bone and the length of the tibrae.
this positive correlation is not only applicable to modern birds, but has been shown in meso-generation birds.
evidence, the researchers speculate that this positive correlation may be used to alleviate problems caused by the distribution of muscle mass between foreclosure modules and post-limb modules.
the front limb module is the burden of the rear limb module during walking, while the rear limb module is the burden of the fortress module in flight.
The trade-off between the two modules on muscle mass means that modules with reduced muscle mass have to cope with a greater burden in their movements, and the increased arm, which is the length of the associated bone, can alleviate the problem to some extent.
By Zhao Tao of Nanjing University and Liu Di and Li Zhiheng, co-editors of the Ancient Spine Institute, published the results online in the open source journal PeerJ.
the study was funded by the National Natural Science Foundation of China.
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