Recently, Current Biology published online the results of the large-scale evolution of pterosaur diversity completed by Yu Yilun, doctoral students at the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, and researchers Zhang Chi and Xu Xing. The study explored the evolution of pterosaur diversity from origin to extinction and potential influencing factors. Studies have shown that the evolutionary history of pterosaurs can be roughly divided into two phases, namely the flourishing period of 115 million years and the decline period of 65 million years. The flourishing period was accompanied by the peak of multi-wave net seed rate, high morphological diversity and morphological evolution rate. The decay period is accompanied by a negative net growth rate, a continuous decrease in morphological diversity, and a lower rate of morphological evolution. The macroevolution of pterosaurs was also influenced by factors such as body size , the decorative structure of the head , and the exclusion of competition from birds to small pterosaurs. The study also found that the diversity of many large terrestrial amniotic animals, including pterosaurs, declined in the mid-Cretaceous period, and this diversity decline may be caused by a variety of factors such as land area decline.
As the earliest vertebrate with active flight ability, the macroevolution of pterosaurs has gained attention in academia. However, due to the shortcomings of sample size and research methods, the diversity curves obtained in previous studies are often affected by formation sampling bias, and important macroevolution indicators such as morphological evolution rate and net seed formation rate have rarely been discussed in previous studies. In order to explore the diversity evolution process and potential influencing factors of pterosaurs in more depth, the new pterosaur morphological matrix and appendage skeletal measurement data were collected and integrated to construct the largest pterosaur supertree. A unified Bayesian terminal dating model was used to simultaneously estimate the morphological evolution rate and diversity dynamics with time. Use the time slice model to estimate the change of morphological differentiation over time; Bayesian phylogenetic regression models were used to estimate the body weight of 120 pterosaur species, and body size evolution rate and ancestral state recovery analysis were performed. The correlation between morphological evolution rate and missing data, and net seed rate and number of exposed strata was discussed to exclude the influence of missing data and sampling bias.
Studies have shown that the evolutionary history of pterosaurs can be roughly divided into a flourishing period of up to 115 million years and a decline period of about 65 million years, and the flourishing period basically corresponds to small body size and the decline period corresponds to large body size. The flourishing period is accompanied by the peak of multi-wave net seed rate and high morphological diversity and morphological evolution rate, and almost every increase in net seed rate is caused by the increase of seed rate and the decrease of extinction rate. The decay period is accompanied by a negative net growth rate, a continuous decrease in morphological diversity, and a lower rate of morphological evolution. This shows sufficient robustness in different sensitivity analyses, and the correlation analysis shows that the research results are not affected by missing data and formation sampling bias.
Pterosaur 's late Triassic radiation was accompanied by an increase in the rate of evolution of the shoulder girdle forelimb bones, suggesting that this time the radiation was caused by occupying the sky ecosystem. Continued diversification during the Jurassic period was accompanied by an increase in the rate of bone evolution throughout the body. Early Cretaceous radiation was accompanied by a gradual increase in average body size and an increase in the rate of skull evolution. This radiation may be related to the entry into the "large-scale niche", and the diversification of the skull crown may be the main reason for the increase in the rate of skull evolution. There was a significant decline in the net growth rate of pterosaurs at the boundary between the Late Jurassic and Early Cretaceous and this decline was due to a large increase in the rate of extinction. At the same time, the net breeding rate and morphological diversity of early birds showed an upward trend during this period. This supports the hypothesis that early birds had competitive exclusion of small pterosaurs. Although the large pterosaurs of the Early Cretaceous avoided competition with contemporaneous birds, the morphological diversity and size diversity of birds continued to increase during the Cretaceous period, and the pterosaurs of the Late Cretaceous may still have to face competitive pressure from birds.
The study further showed that the diversity of large terrestrial amniotic animals, including pterosaurs, such as non-avian dinosaurs, beaked dinosaurs, crocodiles, etc., had a downward trend in the middle of the Cretaceous. The number of habitats suitable for animals decreases exponentially with the size of animals, so the impact of habitat loss on large animals is more significant. The loss of habitat population due to the decline of continental area in the mid-Cretaceous period may be the main reason for the decline in the diversity of macroterrestrial amniotic animals.
This research is part of the National Natural Science Foundation of China's Basic Science Center project "Cratonic Destruction and Terrestrial Evolution". The research work is supported by the Chinese Academy of Sciences Strategic Leading Science and Technology Project.
Figure 1." Liaoning pterosaur flying into a flock of birds" (Drawing by Ren Minghui)
Figure 2.Pterosaur net seed rate, seed rate, extinction rate, morphological evolution rate with time
Figure 3.Change in the rate of morphological evolution of pterosaurs on trees
Figure 4.Evolution of morphological diversity of pterosaurs
Figure 5.Body evolution of pterosaurs
Source: Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences
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