They mean, presumably, that early animals resemble modern embryos, pointing to 609 mya Caveasphaera:
Co-author Zongjun Yin, from Nanjing Institute of Geology and Palaeontology in China, added: “Our results show that Caveasphaera sorted its cells during embryo development, in just the same way as living animals, including humans, but we have no evidence that these embryos developed into more complex organisms.”
Co-author Dr John Cunningham, also from University of Bristol, said: “Caveasphaera had a life cycle like the close living relatives of animals, which alternate between single-celled and multicellular stages. However, Caveasphaera goes one step further, reorganising those cells during embryology.”
Co-author Stefan Bengtson, from the Swedish Museum of Natural History, said “Caveasphaera is the earliest evidence of this most important step in the evolution of animals, which allowed them to develop distinct tissue layers and organs”.
Co-author Maoyan Zhu, also from Nanjing Institute of Geology and Palaeontology, said he is not totally convinced that Caveasphaera is an animal. He added: “Caveasphaera looks a lot like the embryos of some starfish and corals – we don’t find the adult stages simply because they are harder to fossilise“Animal embryos evolved before animals” at University of Bristol
Well, now that Zhu mentions it, hadn’t we better be sure that there are no adult stages before we make such dramatic claims? Otherwise, what we really have is another early Ediacaran complex animal which, while a marvellous find, is certainly not the one Darwinians would be hoping for.
The paper is open access.