JAKARTA – A number of researcher in China managed to find fossils of the oldest marine animals in the world. He is a yunnanozoan which is the ancestor of the water creatures that have inhabited the Earth more than 500 million years ago.
This Yunnanozoan, became the oldest relative of all vertebrates on Earth. Researchers in China have analyzed the fossils of Yunnanozoans, they are part of a soft-bodied organism that became extinct and lived during the Cambrian Period.
Fossils found in Yunnan Province, China, show that the creature is the oldest known vertebrate on Earth, and is closely related to living vertebrates.
Yunnanozoans are also referred to as fish-like organisms with very simple body anatomy that live underwater. But they had a skeleton similar to that of today’s vertebrates.
They are also considered to be deuterostomes, which means their anus is formed in front of their mouth during embryonic development, as reported by the Daily Mail, Saturday (9/7/2022).
The new study has been carried out by experts at the Nanjing Institute of Geology and Paleontology and Nanjing University in China’s Jiangsu province. It was revealed that the yunnanozoa were Cambrian animals with a long-debated taxonomic position.
Scientists have long been puzzled about gaps in the fossil record that would explain the evolution of invertebrates into vertebrates. The evolutionary process of developing the backbone has been a mystery for centuries.
When scientists have studied how vertebrates evolved, the main focus has been on the pharyngeal arch, a paired structure that grows on either side of the future head and neck of the developing embryo and fuses in the middle.
Mammalian embryos have five pairs of these pharyngeal arches. As the mammalian embryo grows, the pharyngeal arch produces parts of the face and neck, such as muscles, bones, and connective tissue.
The authors say it was this pharyngeal curvature that was a ‘key innovation’ that likely contributed to the evolution of the vertebrate jaw and braincase.
It is thought that the pharyngeal arch evolved from the jointless cartilaginous ‘stem’ of vertebrate ancestors, such as the chordate amphioxus, a small ‘fish-like’ organism and close invertebrate relative of vertebrates.
However, did such an anatomy really exist in an ancient ancestor that is not yet known for certain? In an effort to better understand the role of pharyngeal arches in ancient vertebrates, the research team studied fossils from 127 Yunnanozoan specimens.
The specimens had well-preserved carbon residues that allowed the team to carry out detailed analyses, using microscopy, spectrometry and other methods.
The results confirmed that Yunnanozoans had cartilage in the pharynx, a section considered specific to vertebrates, indicating that they were rod vertebrates.
During their study, the team also observed that the seven pharyngeal arches in the Yunnanozoan fossils were similar to one another.
All arches have segments and filaments like bamboo. The arches are all connected by horizontal bars and the top and bottom, forming a basket.
The basket-like pharyngeal skeleton is a part found today in living fish without jaws, such as lampreys and hagfish.
“Two types of pharyngeal skeleton – basket-like and isolated types – occur in Cambrian and living vertebrates. This implies that the shape of the pharyngeal skeleton has a more complex early evolutionary history than previously thought,” said study author Tian Qingyi.
The researchers describe the Yunnanozoans as ‘controversial’, as their classification has been debated for about three decades. But new anatomical observations support the evolutionary placement of Yunnanozoans at the very bottom of the vertebrate tree of life.
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