Origins of Vertebrates :
Chinese paleontologists at Chengjiang fauna have discovered the fossils of
two fish species that are claimed to be approximately 530 million years old ( this is according to evolutionary timeline ) , this period is known
as the Lower Cambrian . Therefore , it became vey clear that along with
all other phyla , the subphylum Vertebrata (VERTEBRATES) was also
present in the Cambrian , WITH NO EVOLUTIONARY ANCESTORS .
The two distinct fish species of the Cambrian, Haikouichthys ercaicunensis and Myllokunmingia fengjiaoa. Therefore
there is no transitional form between chordates and invertebrates , so it can not be said "there is no doubt that chordates evolved from
invertebrates?" Accepting assumptions with a severe lack of supporting
evidence, without entertaining doubts , is certainly not a scientific approach, but a dogmatic one , which is faith based . But it is claimed in the following quote .
There is no doubt that chordates evolved from invertebrates. However, the lack of transitional forms between invertebrates and chordates causes people to put forward many assumptions.
Mustafa Kuru, Omurgali Hayvanlar (Vertebrates), Gazi University Publications, 5th ed., Ankara, 1996, p. 21.
At least he is honest concerning the fossil findings for the transitional examples which are NIL .
The views stated above about the origins of chordates and evolution are always met with suspicion, since they are not based on any fossil records.
Mustafa Kuru, Omurgali Hayvanlar (Vertebrates), Gazi University Publications, 5th ed., Ankara, 1996, p. 27.
Often the claim for the reason that there exist no fossil records regarding the origin of vertebrates is due to invertebrates having soft tissues and consequently they leave no fossil traces. But this explanation is unrealistic , there is a clear abundance of fossil remains of invertebrates throughout the fossil record. Most organisms in the Cambrian period were invertebrates, and tens of thousands of fossil examples of these species have been collected . Canada's Burgess Shale beds. contain many fossils of soft-tissued creatures.
Rober Carrol :
We still have no evidence of the nature of the transition between cephalochordates and craniates. The earliest adequately known vertebrates already exhibit all the definitive features of craniates that we can expect to have preserved in fossils. No fossils are known that document the origin of jawed vertebrates.
Robert L. Carroll, Patterns and Processes of Vertebrate Evolution, Cambridge University Press, 1997, pp. 296.
Gerald T. Todd :
All three subdivisions of bony fishes first appear in the fossil record at approximately the same time. They are already widely divergent morphologically, and are heavily armored. How did they originate? What allowed them to diverge so widely? How did they all come to have heavy armor? And why is there no trace of earlier, intermediate forms?
Gerald T. Todd, "Evolution of the Lung and the Origin of Bony Fishes: A Casual Relationship," American Zoologist, vol. 26, no. 4, 1980, p. 757.