The age of the oldest species with a backbone is more than 500 million years.

The oldest known relative of all vertebrates on Earth swam in the oceans 518 million years ago, according to a new study.

Researchers in China analyzed the fossils of the Yunnanozoic, an extinct soft-bodied organism that lived in the Cambrian period of our planet’s history.

Fossils found in the Yunnan province of China show that this creature belongs to the Earth. the oldest known “stem vertebrate” is a vertebrate that is extinct but very closely related to modern vertebrates.

The Yunnanozoa were very simple fish-like organisms that lived underwater, but they had “basket” skeletons similar to modern vertebrates.

They are also thought to have been deuterostome, meaning that their anus formed in front of their mouth during embryonic development.

An artistic reconstruction of the underwater inhabitants of the Yunnanozoic shows “basket” skeletons similar to modern vertebrates.

Vertebrates, including fish, amphibians, reptiles, birds, mammals, and humans, share unique features such as a backbone and skull, while invertebrates are animals without backbones.

WHAT WAS THE UNNANOZOA?

The Yunnanozoa are extinct soft-bodied fish-like organisms that lived 518 million years ago.

The Yunnanozoa are the oldest known “stem vertebrates” – vertebrates that are extinct but are very closely related to modern vertebrates.

They are considered deuterostome – their anus formed in front of the mouth during embryonic development.

Fossils of the Yunnanozoic have been discovered in the Chinese province of Yunnan.

The new study was conducted by experts from the Nanjing Institute of Geology and Paleontology and Nanjing University in China’s Jiangsu province.

“The Yunnanozoi are Cambrian animals with a taxonomic position that has long been debated,” their article says.

“Our phylogenetic analysis confirms that the Yunnanozoans are stem vertebrates.”

Scientists have long puzzled over a gap in the fossil record that could explain the evolution of invertebrates into vertebrates.

The evolutionary process that led invertebrates to develop backbones, and what these earliest vertebrates looked like, has remained a mystery for centuries.

As scientists have studied vertebrate evolution, the focus has been on the pharyngeal arches, paired structures that grow on either side of the future head and neck of the developing embryo and fuse in the middle.

Mammalian embryos have five pairs of these pharyngeal arches. As the mammalian embryo grows, the arches of the pharynx form parts of the face and neck, such as muscles, bones, and connective tissue.

The authors say the pharyngeal arches are a “key innovation” that likely contributed to the evolution of vertebrate jaws and skulls.

The pharyngeal arch is thought to have evolved from a “bar” of non-articulated cartilage in vertebrate ancestors such as the chordate amphioxes, small “fish-like” organisms, and close invertebrate relatives of vertebrates.

In an effort to better understand the role of the pharyngeal arch in ancient vertebrates, the research team studied soft-bodied Yunnanzoan fossils found in Yunnan, China.

In an effort to better understand the role of the pharyngeal arch in ancient vertebrates, the research team studied soft-bodied Yunnanzoan fossils found in Yunnan, China.

But whether such anatomy really existed among ancient ancestors is not known for certain.

In an effort to better understand the role of the pharyngeal arch in ancient vertebrates, the research team examined the fossils of 127 Yunnanozoic specimens.

The samples have well-preserved carbonaceous residues, allowing the team to conduct detailed analysis using microscopy, spectrometry and other methods.

The results confirmed that the Yunnanozoans have cellular cartilages in their pharynx, a feature that is thought to be characteristic of vertebrates, suggesting that they are stem vertebrates.

During their study, the team also noticed that all seven pharyngeal arches in the Yunnanzoic fossils are similar to each other.

All arches have bamboo segments and threads. Neighboring arches are all connected by horizontal rods both above and below, forming a basket.

The basket-shaped pharyngeal skeleton is a feature found today in modern jawless fish such as lampreys and hagfish.

The pharyngeal arches are paired structures that grow on either side of the future head and neck of the developing embryo and merge in the middle.  Shown here is a rat embryo with pharyngeal arches.

The pharyngeal arches are paired structures that grow on either side of the future head and neck of the developing embryo and merge in the middle. Shown here is a rat embryo with pharyngeal arches.

“Two types of pharyngeal skeletons – basket-shaped and isolated – are found in Cambrian and living vertebrates,” said study author Tian Qingyi.

“This means that the shape of the pharyngeal skeletons has a more complex early evolutionary history than previously thought.”

The researchers describe the Yunnanozoans as “controversial” because their classification has been debated for about three decades.

But new anatomical observations confirm the evolutionary position of the Yunnozoic at the very bottom of the vertebrate life tree.

New study published in the journal The science.

DIFFERENCES BETWEEN INVERTEBRATES AND VERTEBRATES

A vertebrate is an animal whose spinal cord is covered by a backbone or cartilage. The term comes from the word vertebrae, the bones that make up the spine.

Animals that do not have a backbone or have a spinal cord covered with cartilage are called invertebrates. Vertebrates include birds, fish, amphibians, reptiles, and mammals.

Approximately 97 percent of the animals on our planet are invertebrates or animals without backbones, although when we think of “animals” we tend to think of vertebrates.

Invertebrates are sometimes mistakenly considered primitive due to their lack of developed organs.

Their simple internal systems include respiratory systems such as gills or tracheae, and they often use an open circulatory system to pump blood.

Because invertebrates lack an internal skeletal structure, they sometimes have an external skeleton that protects their soft bodies, called an “exoskeleton”.

In general, the success of invertebrates is often due to their ability to reproduce very quickly, unlike many vertebrates, which take years to become fully mature.

On the other hand, vertebrates have a backbone that develops from a notochord that they possess in embryo.

They also have certain internal systems such as complex respiratory structures, a closed circulatory system, and sensory organs that make up the nervous system.

Vertebrates tend to be larger than invertebrates due to their backbone, which allows their bodies to grow larger and move faster than many invertebrates.

Source: Ellen Eisenbeis / Butterfly Pavilion