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| Fossils of bryozoans appeared 530 million years ago |
| The three-act Cambrian explosion hypothesis has new evidence |
When did bryozoans originate? There is new evidence for the Cambrian explosion hypothesis in three acts?
Researchers from Northwest University and other units have studied the micro-fossils found in the Dengying Formation of the Baxiaoyang Section in Southern Shaanxi, and found that the bryozoans originated in the early Cambrian outbreak 530 million years ago, instead of the previously thought 480 million.
Ordovician years ago
.
This finding further supports the Zhong Keyuan academician Shu Degan team proposed three-act formula Cambrian explosion hypothesis, revealed in 4000 million years, based on animal Cambrian animal kingdom from the mouth to the original animal, and then to the mouth The escalating evolution of animals reflects the continuity and stage of the Cambrian explosion
Zhong ASTRI ASTRI academicians
Bryozoans are euphorbias with tentacle crowns.
They are a type of aquatic group of fixed benthic animals.
They are mostly marine, living in groups, presenting a branch-like shape and resembling bryophytes, so they are called bryozoans, also known as bryozoans.
A typical "grassroot animal"
.
Bryozoans, together with brachiopods and broom worms, are called tentacle crest animals.
They belong to the protomouth subunit.
They have a horseshoe-shaped tentacle crest feeding structure.
Their digestive tract is U-shaped, and the anus is located outside the tentacle crest, hence the name external anus.
Animals
.
The body of bryozoans has calcium, glia or chitin chambers secreted by surface cells, which can be preserved as fossils, but soft body information is difficult to preserve
About 540 million years ago-518 million years ago, the early Cambrian was a magical period of geological history
.
At that time, the early ancestor representatives of almost all living animals including vertebrates suddenly appeared on the earth, including large predators and various strange animal types
However, "bryozoa, a very important animal phylum in geological history, has been lacking conclusive fossil records in the Cambrian.
They have small individuals, group living, modular growth, and complex ecology, so they are considered to be Austrian.
The product of Tao Ji's big radiation
.
" Zhang Zhifei, the corresponding author of the thesis and professor of the Department of Geology of Northwest University, introduced
Recently, Zhang Zhiliang, a doctoral student under the guidance of Professor Zhang Zhifei, discovered several millimeter-level microfossils in the clastic limestone of the Xihaoping section of the Dengying Formation, Xiaoyang Section, Xiaoyang Section, Xiaoyang Town, Ba County, South Shaanxi
.
Studies have found that these micro-fossils are the earliest known bryozoan fossils on earth
"This result pushed the geological history of bryozoans from the pre-Ordovician to the early Cambrian explosion, and pushed the geological history of bryozoans forward by at least 50 million years
.
" Zhang Zhifei said
Researchers using scanning electron microscopy and X-ray tomography technology analysis found that these fossils present a two-way thin plate mesh, back to back covered with epidermal cells secreting chitin chambers
.
The insect chamber lacks obvious mineralization.
At the same time, through 52 features, 18 taxa and 2 outer groups, the largest parsimony method and Bayesian clade system analysis showed that Cambrian bryozoans were the backbone group of bryozoans, representing the most primitive ancestor type
.
In this regard, Zhang Zhifei explained: "This means that the modular growth and regular community distribution of animals on both sides is much earlier than imagined.
Zhang Zhifei said that the fossils found in the argillaceous limestone in the Xihaoping section of the Dengying Formation indicate that the Cambrian bryozoans are similar to the later species and are suitable for living in a clear hard bottom environment, thus revealing the preservation in shale.
The reason for the lack of bryozoan fossils in the special-type fossil library
.
"This discovery provides new evidence for the formation of the earth animal tree and the Cambrian life explosion.
It shows that the study of peculiar fossils cannot fully reveal the historical process of life evolution in earth history.
It also needs the constraints and supplements of other fossils.
The discovery provides a new time frame for the origin and evolution of the Earth metazoan phylum
.
" Zhang Zhifei said
.
