No, I'm not. You are asserting that there are precursors to Cambrian organisms that have been discovered, and further, that such fossils were not discovered earlier because they were soft bodied and thus not easily fossilized. I am assuming that you mean some sort of transitional precursors in the sense of lineage, ancestry, or common descent.
I think the implication that the fossil record is incomplete because soft bodied organisms are not easily fossilized is belied by the tremendous variety of soft bodied fossil finds in the Burgess Shale and elsewhere, such as the Wheeler and Marjum Formations in Utah, and Early Cambrian Chengjiang China Fossils
"The Maotianshan shale known as Chengjiang ranks as one of the most important Lagerstätten fossil sites in the world. The Chengjiang site is located in the Yunnan Province of China in the villages of Ercaicun and Chengjiang near the city of Kunming. Some 50 meters of mudstone sediment are exposed, yielded many excellently preserved soft-bodied creatures of the Cambrian Explosion. Dated at 525 million years ago, it lies just above the Precambrian-Cambrian boundary at 544 million years ago."
Fossil evidence of purported transitional forms is lacking, not because the organisms were soft bodied, but because the theory requires major phyla to have supposedly appeared very deep in the Precambrian, hundreds of millions of years before the oldest fossils in the fossil record. And some of these alleged "precursors" fossils that are being found are further compounding the problem, not only by complete absence of fossil evidence of the origin of these complex invertebrates, which by themselves constitute about 95% of the entire fossil record, but by compressing the available time for invertebrate to vertebrate evolution down to an incredible 2 or 3 million years.
If there is evidence for these purported transitions, it is not in the fossil record, and the reason is not because the organisms were soft bodied.
Cordially,
Are you of the opinion that every thing that dies gets fossilized? If not, what percentage of things would you guess get fossilized, and why?
Since many fossils are found on ancient seacoasts, and seacoasts are changing at a rather constant and measurable rate, what effect do you suppose this has on on the availability of fossil finds as we go back billions of years.
Have you done any math to estimate the effects of subduction on seacoasts? Have you given any consideration to the percentage of seacoasts that have been lost to tectonics?
You seem open minded on this, so I assume you have studied these factors and would like to share your findings with us.
The Cambrian explosion has previously been thought to be the time of origin of multiple body plans and metazoan life. It used to be thought that the Mediacaran lifeforms were a sister clade. However, now several types of Precambrian organisms are thought to be ancestral to later forms, and we have fossils of metazoan embryos going back into the Precambrian.
"However, there is a growing body of evidence that many so-called vendobionts may actually belong to established metazoan phyla, although debates about the proper assignment of individual taxa continue. At the very least, we consider that there are strong arguments against the application of the vendobiont hypothesis to all the Ediacaran taxa (Gehling, 1991). The Cnidaria is almost certainly represented in the Precambrian (Conway Morris, 1993b). Amongst Ediacaran genera Spriggina has been interpreted as an annelid (Jenkins, 1992), Arkarua as an echinoderm (Gehling, 1987), and Parvancorina (considered again below) and Praecambridium (Jenkins, 1992) as arthropods. Other taxa have attracted more diverse speculation, Dickinsonia being variously interpreted as cnidarian, flatworm or annelid (see discussion in Valentine, 1992)."
Fortey, R. A.; Briggs, D. E. G.; Wills, M. A. "The Cambrian evolutionary ‘explosion’: decoupling cladogenesis from morphological disparity." Biological Journal of the Linnean Society (1996), 57: 13–33.
This is not saying that there was no Cambrian explosion, just that some major groups appeared earlier than that. The Cambrian explosion definitely was a dramatic event.
This next article I'd really encourage you to find, copy or print out, and read five times! I wish I could post the whole thing.
"Extant monophyletic groupings are always morphologically distinct from their extant sister-group, and that distinctness is brought about by subsequent extinction of the lineages (plus its offshoots) that led to each of them, away from their last common ancestor. As random extinctions through time slowly remove lineages, the most basal taxon of a clade will sometimes be the victim, thus widening the path-length between the surviving most basal members of extant sister clades (Fig. 3). The bases of clades are therefore eroded by extinction, and, as only living members of the clade can rediversify, this is a permanent loss. These extinct basal taxa will not possess all of the apomorphies that define the basal node of the surviving clade. It should be noted that this process will occur whether or not basal members of clades are particularly prone to extinction or not; there does not have to be anything ‘‘special’’ about basal taxa. One further aspect about these now extinct basal taxa is that they would have accumulated their own autapomorphies not possessed by the extant taxa. As a result, these basal fossil taxa are bound to differ from the extant clades: they will not be diagnosable as members of those clades; and they will show a confusing mixture of some but not all features of those clades, together with a set of features absent from them. It should be noted that this characteristic mix has been repeatedly noted in Cambrian fossils. For example, Hughes (1975) said of the Cambrian arthropod Burgessia: ‘‘what is apparent from this restudy is that Burgessia did possess a mixture of characters . . . many of which are to be found in modern arthropods of various groups’’ (Hughes, 1975, p. 434). . . .
"One example of the sorts of possibilities that stemgroup reconstruction offers is provided by the arthropods (e.g., Budd, 1998, 2001b). Optimization of the terminal character states of the various stem-group demonstrates the most parsimonious reconstruction of the evolutionary stages passed through by ancestral arthropods. A remarkably complete series is now available, demonstrating how the most basal, worm-like taxa of the entire Arthropoda sequentially acquired the important features characteristic of their clade, including the sclerites and lever-style musculature (Budd, 2001b), components of the biramous limb (Budd, 1996), and even how the complexities of the arthropod head were assembled (Budd, 2002), a construction that can be corroborated by the recent fauna (Eriksson et al., 2003)."
Budd, G. E. "The Cambrian Fossil Record and the Origin of the Phyla." Integrative and Comparative Biology, 43:157–165 (2003).
As I said before, we do have some deposits with excellent soft-bodied fossils, but these are the exception rather than the rule. As js1138 pointed out, we can tell that soft-bodied creatures (and creatures with other characteristics and from other environments) are under-represented in the fossil record by examination of fossils of living species and genera. Typical fossilization conditions preclude the preservation of details of soft flesh. Heck, we don't even need to check and see which modern organisms are missing or underrepresented in the fossil record, just look at the fossils that are available of hard-shelled and bony remnants. Trace fossilization of soft flesh around an organisms bones or lining its shell are extremely rare.