they are essentially non-fossiliferous excepting a few preserved remains of fish and plant fossils.
(they; are; essentially non-fossiliferous excepting a few preserved remains of fish and plant fossils) (they; excepting; a few preserved remains of fish and plant fossils)
they they
are excepting
essentially non-fossiliferous excepting a few preserved remains of fish and plant fossils
a few preserved remains of fish and plant fossils