31. It lived from 501 to 497 million years ago during the Guzhangian of the late Cambrian Period . 32. It dates to the early Cambrian period , and is the earliest known fossil of the cephalochordate lineage. 33. Good evidence exists for the appearance of gastropods, cephalopods and bivalves in the Cambrian period } }. 34. Good evidence exists for the appearance of marine gastropods, cephalopods and bivalves in the Cambrian period } }. 35. The earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period . 36. It lived from 501 to 490 million years ago during the Dresbachian faunal stage of the late Cambrian Period . 37. It lived from 501 to 497 million years ago during the Dresbachian faunal stage of the late Cambrian Period . 38. Isham Park is noted at its southern end for some exposed marble outcroppings which date from the Cambrian period . 39. It lived about from 501 to 497 million years ago during the Guzhangian faunal stage of the late Cambrian Period . 40. From the Cambrian Period , the Candana Quartzite is equivalent to the Herreria Formation and is 1 to 2 km thick.
