Because we are team members, it is easy to see invertebrates as evolutionists, a group capable of producing bats, birds, and whales larger than us. But when they first appeared, vertebrates were not. They separate from the group that lives in the mud and do not have to separate the top from the bottom or left from the right, so they end up losing a string of organized emotions. Our close relatives who are not spinal cords also developed nerve fibers (naturally on the wrong side of the body) but could not suffer from good things like bone marrow.
How the vertebrates came out of this is still unclear, and our ancestors’ possible lack of skeletal structure has helped to ensure that we do not have too many fossils that can help clarify things.
But in Thursday’s Science magazine, researchers re-examined some of the mysterious remains of the Cambrian period and resolved several controversies over what the nunanozoans possessed. Responses include cartilaginous structures that support gills and spleen that may have been our lower jaw. In this process, they indicate that the unnanozoans are probably the first branch of the spinal tree.
You can get an idea of what yunnanozoan looks like in the picture above. The soft tissues below the sides are divided into segments, a feature in both of our closest non-spinal cord relatives (amphioxus or lancelet) and are present in the embryonic vertebrae. Still, it is often lost as it continues to grow into an adult. Next to the animal’s head — with a clear head and mouth — is a series of structures with almost gill arches found near the head of a modern fish.
If that translation is correct, then the unnanozoans look like amphioxus but have a trait found only in modern vertebrates. This could mean that it retains essential elements in understanding the origin of vertebrates.
But “if” from the previous section is excellent. Many people in this field disagree with this definition and place the nunanoanoans elsewhere. Or in several other places, depending on who was arguing. Others group them with amphioxus. Some support themselves away from vertebrates and place them in a group of mud-dwelling people who do not have two body axes found in vertebrates. Still, some suggest that they are the ancestors of a large group of species that include such things as sea urchins.
A small team from China has now tried to resolve these disputes. It does this in part by capturing more than 100 new remains of this type. But for the most part, they use some of the most sophisticated photographic methods available. That included three-dimensional X-ray imaging, electron microscopy, and a technique that exploded small sample circuits electronically and then used the emission light to determine which features were present.
I will show you one of the pictures from the page below to give an idea of the details provided by these photography methods.