not all sponges are sessile how do they move

reconstructed a phylogenetic tree using 1719 genes of 97 animal species, and applying new and more congruent methods. A study published this month on Current Biology by Simion et al. However, now things appear to be settled. The nervous system of comb jellies is indeed quite unusual, but not so much that it needs an independent origin. This was highly unexpected, as comb jellies are far more complex than sponges and placozoans, which would suggest that muscles and a nervous system evolved twice in the animal kingdom, or that sponges are some weird simplification of a more complex ancestor, which would be very hard to explain. However, some recent molecular studies have put the comb jellies as the most primitive animals. Traditionally, sponges were always seen as the most primitive animals due to their lack of true tissues, muscular cells, nervous cells and all that stuff. All sponge cells can change from one type to another and migrate from one layer to another, so there are no true tissues. The choanocytes capture organic particles in the water and ingest them by phagocytosis. They simply live by beating the flagella of the choanocytes (the cells of the inner layer), creating a water flow entering through the pores and exiting through the osculum. Sponges lack muscles, nervous system, excretory system or any other kind of system. Some species also secrete an outer calcium carbonate skeleton over which the organic part grows. Between the two cell layers there is a jelly-like mesohyl containing unspecialized cells, as well as the skeleton structures, including fibers of spongine and spicules of calcium carbonate or silica. There are several small openings connecting the cavity to the outside, called pores, and one or more large cavities, called oscula (singular: osculum). Their body is consisted of a kind of tube, having a large internal cavity and two layers of cells, an outer one and an inner one around the cavity. They have a very simple anatomical structure. Sponges (phylum Porifera) are always sessile, i.e., they do not move and are fixed to the substrate. It is clear that there are five animal lineages that are usually regarded as monophyletic: sponges, placozoans, comb jellies, cnidarians and bilaterians.

What animal group is the earliest of all? Who came first?

The endless question is here again, but this time it appears to be settled.

Not all sponges are sessile how do they move