As Harvard biologists tell us:
Despite their importance for understanding animal evolution, most information about ctenophores comes from living species alone as fossil comb jellies are extremely rare due to their gelatinous bodies. However, some fossil ctenophores have been discovered in early and middle Cambrian sites (about 520-500 million years ago) with exceptional preservation. These fossilized specimens, found around the world in sites including Burgess Shale in Canada and Chengjiang in South China, show that Cambrian ctenophores are a bit different from living representatives. The fossils include features such as a skeleton that supported the ctenes, or comb rows, as well as up to 24 comb rows – many more than the eight comb rows possessed by living species…
The researchers conclude that Cambrian ctenophores had more complex nervous systems compared to those observed today. Living species of comb jellies have a diffuse nervous system similar to the structure of chicken wire, but very thin and transparent. Cambrian ctenophores’ nervous systems were condensed with specific nerve tracks that basically ran along the length of the body and then as a ring around the mouth. This complex system is only seen in one living species, the Euplokamis, which is regarded as potentially being an early branching ctenophore living today. However, while Euplokamis has this elongated nerve structure that runs the length of the body, it does not have the ring around the mouth, so it too is simpler compared to Cambrian ctenophores.
Department of Organismic Evolutionary Biology, “Rare Cambrian fossils from Utah reveal unexpected anatomical complexity in early comb jellies” at Harvard University (August 20, 2021)
A classic example of devolution, as explained in Michael Behe’s Darwin Devolves.
Throwing a horseshoe into the works of Darwinism, many life forms simply reduce their complexity in order to survive. Yes, natural selection works and is real but — because it depends on randomness — it doesn’t produce reliably complexity all by itself any more than winning a lottery ticket reliably produces wealth.
Comb jellies today:
You may also wish to read: Devolution: Getting back to the simple life
Hat tip: Philip Cunningham