Global distribution of the genus Macrophyllum macrophyllum in the Late Triassic and its possible radiation migration routes. Courtesy of Nangu Institute
Nanjing, September 6 (Reporter Yang Yanci) According to the news of the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences on the 6th, the Chinese and foreign research teams involved in the Institute have carried out research on new materials of the genus Macrophyllum newly discovered from Sichuan, China, and carried out classification revision and spatio-temporal distribution characteristics from the perspective of global stone records, refreshing the new understanding of the plant morphology of the genus for more than a hundred years.
The results were published in the international academic journal Review of Palaeobotany and Palynology.
According to researchers, the genus Macrophyllum is a representative gymnosperm of the Late Triassic. Since its establishment in 1878, it has a research history of more than 140 years, and has been popular and widely distributed around the world.
A new specimen of large net feather leaves from the Guangyuan region of Sichuan was found, showing different degrees of missing inscriptions at the leaf margins. Courtesy of Nangu Institute
However, the genus is an extinct morphological genus that is considered to be cycad or seed ferns, and there is still much controversy about its taxonomic location; especially due to the incomplete preservation of specimens, the long-term understanding of changes in its morphological characteristics is relatively limited, and it has been difficult to make a breakthrough.
Recently, Xu Yuanyuan, a doctoral student at the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences, under the guidance of supervisor Wang Yongdong and Researcher Zhu Youhua, collaborated with Professor Mihai E. Popa of the University of Bucharest in Romania and Professor Zhang Tingshan of Southwest Petroleum University to conduct in-depth systematic research on the newly discovered new materials of the genus Macrophyllum in Sichuan, China.
Through this study, the team found a large number of well-preserved fossils of the genus Macronetosa in the Upper Triassic Xujiahe Formation in the Guangyuan region of Sichuan. These specimens were produced in the same layer and showed different morphological changes in the leaf margins.
Morphological restoration diagram of the large net feather leaf shows the leaf margin reticules and the missing engravings of different degrees. Courtesy of Nangu Institute
Based on this, the researchers conducted a more in-depth study of the morphological characteristics of the genus, and revised its genera, revealing that the leaf margins of the plant had deep or shallow missing or occasional pinnate morphological characteristics, highlighting the atypray of the leaf-shaped characteristics of the genus.
This feature has never been reported in long-term studies, refreshing the new understanding of the morphology of the genus for more than a hundred years.
The research team also conducted a comprehensive assessment and revision of published fossils of the genus Macrophyllum around the world.
The results show that only 3 of the 16 species fossil records that have been reported can be identified as valid species, and their mold selection and sub-mold specimens are specified respectively. Another 4 are in doubt pending further revision, and 9 are invalid.
A new specimen of large net feather leaves from the Guangyuan region of Sichuan province was found, showing the morphology of the deep lobed leaf margin of the thick midrib and the knotted network. Courtesy of Nangu Institute
Through the analysis of the spatio-temporal distribution characteristics of the global stone record, the researchers believe that the distribution era of the genus Macrophyllum is limited to the Late Triassic, and the earliest fossil is the Carney period, which is about 230 million years old, and is the most prosperous in the Rhettian period, which has important stratigraphic indicative significance.
It is an important paleoclimate indicator plant in China, which is limited to the southern flora of the Late Triassic period, and there is no conclusive fossil record in the northern flora, which confirms that there are significant differences in paleoclimate characteristics in the flora of northern and southern China during this period.
The researchers deduced from paleogeographic analysis that the plant originated in the South China Plate in the early Late Triassic period, and the radiation migrated to the Middle East and Europe and Africa during the Reti period. (End)
Source: China News Network