Since we are a member of the group, it is easy to see vertebrates as the pinnacle of evolution, capable of producing bats, birds, and giant whales in addition to ourselves. But when vertebrates first evolved, it was a solid thing. They separated from a group that lived in the mud, not to mention top from below, or left from right, thus losing their organized nerve tendons. Our closest invertebrate cousins have recreated a nerve cord (on the wrong side of the body, naturally), but skeletal knights can’t be bothered.
It’s unclear exactly how vertebrates evolved from this, and the lack of a skeleton in our direct ancestors helped ensure there weren’t too many fossils to make matters clear.
But in Thursday’s journal Science, researchers reassessed some puzzling fossils from the Precambrian and settled many arguments regarding what makes them unique. Unanozoans You answers include the cartilaginous structures that support the gills and a possible predecessor to what became the mandible. In practice, they show it Unanozoans The spine may be an early branch of the tree.
Greeks?
You can get an idea of what it is Unanozoan As can be seen from the image above. The soft tissues on either side of it are divided into segments, similar to those of the closest living invertebrate relatives (amphioxus or lancelet) and is present in vertebrate embryos, but is usually lost when they develop into adulthood. Near the head of the animal – it has a pronounced head and mouth – are a series of curved structures similar to similar gill arches found near the head of modern fish.
If this interpretation is correct, then it makes sense Unanozoans It is similar to amphioxus, but has a feature found only in modern vertebrates. This means that it preserves features important for understanding the origin of vertebrates.
But “if” starting from the previous paragraph is written in capital letters. Many in this field disagreed with this interpretation, and they maintained it Unanozoans in another place. Or in many other places, depending on who is rightly arguing. Some put them in the same group as Amphioxus. Others have supported them beyond vertebrates and included them in a group of mud dwellers who lack the body axes found in vertebrates. However, others have suggested that it was an ancestor of a larger species that included sea urchins.
A small team from China has now attempted to address these arguments. It does this in part by photographing more than 100 new fossils of the species. But the great part is that they used some of the most advanced imaging technologies available. This includes 3D X-ray imaging, electron microscopy, a technique that bombards small parts of the sample with electrons, then uses the emitted light to identify which elements are present.
Tian et al. The.
Show one of the images in the paper below to understand the details offered by these imaging techniques.