Complex sentence: The unusual and varied characteristics of these creatures were at the time of discovery startling and the fossils, when described, helped to demonstrate that the soft-bodied Burgess fauna was more complex and diverse than had previously been anticipated.
Split into simpler sentences: The unusual and varied characteristics of these creatures were startling at the time of discovery. The fossils, when described, helped to demonstrate that the soft-bodied Burgess fauna was more complex and diverse than had previously been anticipated.