The figure for ‘Recent’ is too large because we do not have any fossils for most of those phyla - the animals are all small squishy marine worms and similar with no hard parts.
This is the claim that the fossil record is “imperfect” – which was refuted in the original article posted in this discussion. Beyond that, with the whole world of evolutionary biology and paleontology for support, this is all that they can come up with.
As for the suddenness of the appearance of the fossils, we could try more credible sources than the Encyclopedia article I found quickly :
Fossils, molecules and embryos: new perspectives on the Cambrian explosion.Valentine JW, Jablonski D, Erwin DH. Collaborators (1) Erwin DH.
Department of Integrative Biology and Museum of Paleontology, University of California, Berkeley, CA 94720, USA.
jwv@ucmp1.berkeley.edu
The Cambrian explosion is named for **the geologically sudden appearance **of numerous metazoan body plans (many of living phyla) between about 530 and 520 million years ago, only 1.7% of the duration of the fossil record of animals. Earlier indications of metazoans are found in the Neoproterozic; minute trails suggesting bilaterian activity date from about 600 million years ago. Larger and more elaborate fossil burrows appear near 543 million years ago, the beginning of the Cambrian Period …
All living phyla may have originated by the end of the explosion.
The cambrian evolutionary explosion recalibrated
Richard A. Fortey 1, Derek E. G. Briggs 2, Matthew A. Wills 2
1Department of Paleontology, Natural History Museum, Cromwell Rd, London SW7 5BD, UK
2Department of Geology, University of Bristol, Queens Street, Bristol B58, UK
**The sudden appearance in the fossil record **of the major animal phyla apparently records a phase of
unparalleled, rapid evolution at the base of the Cambrian period, 545 Myr ago. This has become known as the Cambrian evolutionary explosion, and has fuelled speculation about unique evolutionary processes operating at that time.
Early evolution of animal cell signaling and adhesion genes
Scott A. Nichols*, William Dirks†, John S. Pearse‡, and Nicole King
University of California, Berkeley, CA, and approved June 28, 2006
The fossil record from ≈540 Mya documents **the abrupt appearance of fully diversified eumetazoan body plans **during the “Cambrian explosion.” In contrast, fossil evidence of sponges dates to ≈580 Mya and reveals that **their simple body plan predates the Cambrian and has since remained relatively unchanged **(1, 2).
Towards a new evolutionary synthesis
Robert L. Carroll
Robert Carroll is at the Dept of Biology and is Curator of Vertebrate Paleontology, Redpath Museum,
McGill University, 859 Sherbrooke St. West, Montreal, PQ, Canada H3A 2K6
(
robertc@shared1.lan.mcgill.ca).
The most conspicuous event in metazoan
evolution was **the dramatic origin of
major new structures **and body plans documented
by the Cambrian explosion10,11.
Until 530 million years ago, multicellular
animals consisted primarily of simple,
soft-bodied forms, most of which have
been identified from the fossil record as
cnidarians and sponges. Then, within less
then 10 million years,
almost all of the
advanced phyla appeared, including
echinoderms, chordates, annelids, brachiopods,
molluscs and a host of arthropods.
The extreme speed of anatomical
change and adaptive radiation during this
brief time period
requires explanations
that go beyond those proposed for the evolution
of species within the modern biota.