The Burgess Shale faunas ( ~530 Ma) are unusual because they consist mainly of soft bodied animals at a time in evolutionary history when most animals had acquired hard parts.
(The Burgess Shale faunas; are; unusual; because they consist mainly of soft bodied animals at a time in evolutionary history) (they; consist mainly; of soft bodied animals; T:at a time in evolutionary history) (most animals; had acquired; hard parts; T:a time in evolutionary history)
The Burgess Shale faunas they most animals
are consist mainly had acquired
unusual because they consist mainly of soft bodied animals at a time in evolutionary history
of soft bodied animals T:at a time in evolutionary history
hard parts T:a time in evolutionary history