Morphological diversity evolution of major taxa of Mesozoic birds. Courtesy of Wang Min
BEIJING, Feb. 3 (Xinhua) -- How did some of the mesozoic Cretaceous Cretaceous (about 130 million to 65 million years ago) escape the extinction of Cretaceous organisms 65 million years ago and gradually evolve into modern birds?
For the first time, Chinese scientists have studied the diversity and evolution of Mesozoic bird characteristics ("morphological space") and body size ("body space"), and found that the two main groups of Mesozoic birds, anti-birds and modern bird-type species, which also constitute sister groups, show very different evolutionary trajectories.
Spatial distribution of mesozoic bird body types. Courtesy of Wang Min
It is the different evolutionary trajectories of the two that may have contributed to their different responses during the Great Extinction of Cretaceous organisms: all anti-birds were extinct, while some of the present-day bird-type species survived and evolved at the beginning of the new era after the Great Extinction, eventually forming all modern birds.
This paper on the important achievements of modern bird traceability research, jointly completed by Wang Min, Zhang Chi and Zhou Zhonghe, researchers from the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences (Institute of Paleovertebrates of the Chinese Academy of Sciences), was published in the nature index journal "Proceedings of the Royal Society b" on February 3, Beijing time.
Researcher Wang Min, the first author of the paper, said that through the measurement of the limb bones of a large number of Mesozoic birds, the "body space" is defined by the length of the limb bones, and the "morphological space" is quantified according to the anatomical characteristics, and the change of the two over time. In addition, the principal component analysis method based on phylogenetic relationships is used to eliminate the kinship relationship, which ensures the independence of the sampling points to the greatest extent, and restores the ancestral nodes to show the evolutionary trends of different taxa.
Spatial distribution of mesozoic bird morphology (discrete features). Courtesy of Wang Min
The results of the study showed that the main taxa of Mesozoic birds— anti-birds, avian-type birds, and more primitive "basal birds" ("basal birds" were not a monophyletic group, but included Confucius birds, Hui birds, Rehe birds, and Archaeopteryx birds) did not distinguish significantly in body size space.
However, the ecological habits of these three taxa are significantly different, such as anti-birds are arboreal, today's bird-type species are mostly ground-dwelling, and the "basal birds" of the hot river bird and Archaeopteryx also have long tail bones typical of reptiles. Such "contradictions" indicate that the "body space" is relatively conserved in evolution, which may be the result of selective effects, including flight. In comparing these three taxa, the present ornithischia are higher than the other two groups in quantitative measures of all diversity, reflecting that in the evolution of the present ornithischia, its body size has become more diverse, which is also consistent with the diverse ecological types of this group in the Late Cretaceous.
Wang Min pointed out that in the "morphological space", the three taxa of Mesozoic birds were significantly different, and the differences between anti-birds and present-day bird-type groups became larger over time: in the process of its evolution, the increase in characteristic diversity of anti-birds was almost stagnant, and even had a tendency to become smaller; the diversity of bird-type species increased, and very different morphological characteristics (such as fish and birds) appeared. "Although anti-avians are currently the mesozoic bird clade with the largest number of species found, the present-day ornithics are the highest in all diversity indicators, reflecting the heterogeneity of species and morphology in the evolution of some taxa."
Wang Min said that in summary, this study has obtained a completely different evolution trajectory between anti-birds and modern bird types, which are mainly reflected in: anti-birds are in the existing "body space" and "form space" to increase the number of species, while today's bird types are constantly expanding the scope of "body space" and "form space"; the relatively cramped evolution of anti-birds is also reflected in their single ecological habits, in contrast, the current bird type has appeared including diving, arboreal, ground habitat and other ecological habits. (End)
Source: China News Network