Quote:
The earliest evidence of the Cambrian organisms dates back to nearly 700 million years ago, which is about 130 million years before the Cambrian Explosion. During the period between the earliest animal evidence and the Cambrian, there are three primary assemblages of pre-Cambrian fossils: the Avalon Assemblage (571-555 million years ago), the White Sea Assemblage (560-551 million years ago), and the Nama Assemblage (555-541 million years ago). Together, these assemblages are known as the Ediacaran biota. The vast majority of the fossils found in these assemblages share striking similarities with the forms that emerged during the Cambrian period. The Ediacaran biota was dominated by ancestral stem groups of the animal groups that appeared during the Cambrian period (Wan et. al, 2016).
The claim that the Ediacaran biota contained ancestral stem groups of the animal phyla that emerged in the Cambrian period is highly speculative and unproven. The article you cite by Wan et. al does not support this claim. They discovered a new genera of organisms they named
Lantianella which was "
morphologically, remarkably very similar to Flabellophyton", an organism that is interpreted as an
algae. They were intrigued, however, at the possibility that Lantianella was related to, and perhaps a precursor of, animals called cnidarians due to their conical and pyramidal shape and the tentacle-like structure. Though, they noted that the tentacles could have been blades that algae use for photosynthesis (amazing that an incredibly complex system like photosynthesis could have appeared so quickly, but I guess that's another topic) and thus the similarity may be the result of convergent rather than divergent evolution. And although they were similar in shape and size to cnidarians (
Corumbella and
Conotubus) they noted that they had completely different structures. Compared to other cnidarians with the same similarity in conical structure,
Protoconites and
Thectardis, they noted that they were either much bigger or much smaller in size. And Lantianella differed from all of them by having a globose holdfast structure, which is characteristic of algae of the time. Another possible interpretation that was entertained, was that
Lantianella was an early
conulariid, a kind of marine animal, due to the tentacles, tripartate body plan, and pyramidal theca. But the authors note that this due to ONE specimen having a pyramidal theca. None of the other specimens had it, so they believed it was due to a preservation artifact. Also, the tripartate body plan was likely due to convergent evolution, they concluded, because of a lack of "diagnostic fusellar structures".
So, no, I wouldn't characterize this as "striking similarities" or that the Ediacaran biota "was dominated by ancestral stem groups of the animal groups that appeared during the Cambrian period." The authors of this article were intrigued by the possibility, but at this point it's all just unproven speculation and hypothesis. As the authors noted, "
The phylogenetic interpretation of Lantianella remains uncertain....Lantianella remains an enigmatic Ediacaran fossil with intriguing but unproven affinity to cnidarian animals."