I'm one paragraph in and the article has immediately contradicted itself saying animals first appear in the fossil record 574mya and their arrival appears as a sudden explosion 539 to 485mya, which 574mya is outside of. It then says people believe animals evolved before the Cambrian period but can't explain why they're missing from the fossil record. Except there are plenty of known fossils from the Ediacaran, the period directly preceding the Cambrian. That's a helluva lot of problems in one paragraph so I think I'm gonna stop reading there.
> Estimates for animal antiquity exhibit a significant disconnect between those from molecular clocks, which indicate crown animals evolved ∼800 million years ago (Ma), and those from the fossil record, which extends only ∼574 Ma. Taphonomy is often held culpable: early animals were too small/soft/fragile to fossilise, or the circumstances that preserve them were uncommon in the early Neoproterozoic. We assess this idea by comparing Neoproterozoic fossilisation processes with those of the Cambrian and its abundant animal fossils. Cambrian Burgess Shale-type (BST) preservation captures animals in mudstones showing a narrow range of mineralogies; yet, fossiliferous Neoproterozoic mudstones rarely share the same mineralogy. Animal fossils are absent where BST preservation occurs in deposits ≥789 Ma, suggesting a soft maximum constraint on animal antiquity
> contradicted
There is no contradiction in saying that the earliest found occurrence of x is at some point in time and the first high concentration of x is at some other later point in time. It is actually expected.
E.g.: First tablets found in Sumer: -3500 ; bulk of earlier found tablets in Sumer: -3300.
The prose is unclear, but I expect by arrival they mean success/dominance, in the sense given by the phrase "truly arrived." See the definitions given at https://idioms.thefreedictionary.com/have+arrived. Seems like poor phrasing rather than straight up contradiction.
Moreover, while most animals preserved in fossils after the start of Cambrian (540 million years ago) can be clearly identified as relatives of known animals, most of the fossils dated before the start of Cambrian and presumed to be of animals cannot be determined with any certainty as relatives of known animals. There are various hypotheses about the nature of the Ediacaran animals, but none of them is reasonably certain.
The exception is that some Precambrian fossils come without doubt from some kind of sponges.
Unlike multicellular animals, which have appeared much later, multicellular red algae and green algae were already widespread one billion years ago.
