Most animal phyla appeared in the Earth's rock record only during a short period of the Cambrian bio radiation (~540-520 my). Small Shelly Fossils allow us to form conclusions about the sequence of evolutionary events that shaped the Earth's biodiversity, and the existence of stem-group species.
We found exceptionally preserved fossils on two field campaigns in W Mongolia in 2017 and 2019. These astonishing discoveries included the eggs, embryos, and post-embryonic stages of camenellans. Far from being skeletal remains, our newly discovered embryos and post-embryonic stages of camenellans are preserved in soft tissue which was replaced by calcium phosphate during the early sedimentary process of fossilization, conserving them for millions of years.
You can find our publication here
and a blogpost on the fieldwork that leads to the discovery here
