Which phylum first branched off from the animal phylogenetic tree is a contested issue. A new analysis challenges the proposal that comb jellies are the sister group to all other animals, and emphasizes a ‘sponges-first’ view. Three evolutionary biologists weigh up the evidence.
THE PAPER IN BRIEF:
●●There are five major branches of animals: Porifera (sponges), Cnidaria (jellyfishes, corals and related species), Ctenophora (comb jellies), Placozoa (Trichoplax) and Bilateria (all other animal phyla).
●●Writing in Proceedings of the National Academy of Sciences, Pisani et al.1 reanalyse some existing data and support the case that Porifera are the sister group to all other animals.
●●The authors propose that this conclusion fits with the fact that sponges lack features present in the other phyla, such as a nervous
system and muscles.
●●However, other recent genomic analyses have suggested that the more complex Ctenophora are the sister group.