MrDarwin

Try asking a creationist to name just one animal that is alive today that is represented by fossils during or immediately after the "Cambrian explosion".

Then try asking why fossils of sponges and coelenterates (although again, not representing any species that are alive today) are found in precambrian sediments. (Coincidentally enough, these two groups have long been considered to be the oldest and most primitive of all living phyla, even before their fossil record was known.)

Non-praying Mantis

I assume that when you talk about "pollen" in the above post, you mean angiosperm pollen. Pollen was an earlier development as gymnosperms (pine trees, cycads, etc) also have pollen, and they first evolved sometime in the Permian, approx. 260 mya, IIRC.

Also, is it possible to distinguish angiosperm pollen in fossils from gymnosperm pollen?

NPM

Shpongle

http://news.nationalgeographic.com/n...rustacean.html

This is an interesting article I found awhile back that discusses the possibility that the Cambrian "explosion" may not have been as rapid as previously thought.

MrDarwin

It seems to me that if creationists accept the Cambrian explosion as a real event, then they must think that a phylum is roughly equivalent to a "kind" and that all the dozens of classes, hundreds of families, thousands of genera, and millions of species must have "microevolved" from just a couple of dozen original "kinds".

Joe Meert

JM: HOW can they consider a creation event? The 'explosion' is a bunch of dead animals in the fossil record. It cannot be the evidence for sudden creation, for them it MUST represent sudden death. If I were a young earth creationist, there would be no doubt in my mind that the Middle Cambrian marks the onset of the flood. This is one of the reasons I am so perplexed that creationists argue that the Noachian flood was THE defining event in geological history, but they cannot unequivocally document the onset, peak and post flood strata on a global basis. Even secular geologists are able to point to the K/T boundary around the globe to identify a major extinction. If we can establish reliable correlation based on evolutionary criteria surely they can do a better job when they only have to deal with a single catastrophic event?

Cheers

Joe Meert

Kevin

Jeffrey Levinton's Genetics, Paleontology and Macroevolution contains a very good scholarly discussion of the Cambrian explosion (he devotes his entire chapter eight to the subject):

Genetics, Paleontology and Macroevolution

Oolon Colluphid

Yup. Pretty much as I said in the first paragraph.
Yup.
I’m certainly no expert on fossil pollen, but I somehow doubt that those who are would be so certain that angiosperms -- ie the flowering plants of Gen 1:20 -- don’t appear until the early Cretaceous (or very late Jurassic) unless it were distinguishable!

See for instance:

http://www.ucl.ac.uk/GeolSci/micropal/spore.html
I note that this means that, even if we take ‘pollen’ to include spores and such, there’s still at least a sixty million year gap between the ‘Cambrian Explosion’ and the Silurian.
See also
Origins of Angiosperms
and
Another page titled ‘Origins of Angiosperms’

This Letter to Nature is also interesting.

However, I could be (somewhat) wrong... Bruce Cornet for one disputes a Cretaceous angiosperm flourishing (pun intended). See:

Fossil Evidence for Rapid Orderly Genetic Evolution: The first detailed fossil record of microevolution with missing links

Why do Paleobotanists Believe in a Cretaceous Origin of Angiosperms?

His original paper, from Palaeontographica, 213B: 37-87, is: Late Triassic Angiosperm-Like Pollen from the Richmond Rift Basin of Virginia, U.S.A.

Further research inclines me to take his stuff with a pinch of salt, since it seems he’s a defender of John Mack and alien abductions... but hey, even Linus Pauling went a bit doo-lally with the vitamin C thing . I’m not qualified to judge it, but the Triassic angiosperm-like pollen thing looks a bit persuasive (but then, it would, wouldn’t it?). Is this a job for MrDarwin? Any thoughts, MrD?

But even if Cornet is correct though, the Triassic is still 250 million years too late to fit with a Genesis / Cambrian creation!

TTFN, Oolon

pz

Ooooh, that looks very interesting...how could I have missed that?

Of course, you realize you have just cruelly added another 600 page book to my already excessively long reading list this summer, don't you?

ps418

Regarding the request for information, there are a couple of interesting articles and resources online:

Precambrian to Cambrian Fossil Record and Transitional Forms

International Subcommission on Cambrian Stratigraphy

Phylum Level Evolution

PNAS: Cambrian explosion: slow fuse of megatonnage?

Early Animal Evolution: Emerging Views from Comparative Biology and Geology

The Ediacara Biota: A Terminal Neoproterozoic Experiment in the Evolution of Life

A Review of The Evidence For Trilobite Predecessors in the Fossil Record

Patrick

MrDarwin

Oolon, we have a pretty good idea of the relationships of living taxa but when we start looking at fossils, the older they are, the less like modern angiosperms they are (as would be expected) and in particular, when we start looking at fossils of plants that may have been on or close to the line to angiosperms before any of the modern taxa originated, i.e., pre-Cretaceous angiosperms, there's a serious problem of both recognizing them and defining them as angiosperms. I think right now the early Cretaceous is the earliest that there is any consensus for an unequivocal appearance of angiosperms, but there are some older things that are candidates for pre- or proto-angiosperms--the problem then becomes defining "angiosperm".

I'm not intimately familiar with Cornet's research; he's doing some very, very interesting work and his plants may well be on the line to angiosperms but the early evolution of angiosperms is still rather contentious. Many of the major groups apparently began their evolutionary radiations shortly before or shortly after the K/T extinction event, but it's clear that several lineages (including some archaic families still alive today) of angiosperms were already in existence at that point, and had already diverged quite a bit. One thing is clear: if Cornet's fossils are angiosperms, they existed long before any of the modern groups appeared, and they lack most of the characters that we now associate with angiosperms. In other words, whether or not to classify them (and some other angiosperm-like fossils) as angiosperms may boil down to circumscriptional semantics. It's an increasingly common problem with stem group vs. crown group taxa; cladistics may tell us relationships, but it can't tell us what names to put on taxa.

Regarding pollen: I'm not an expert on the subject either. One very distinctive pollen type is associated with a major group of angiosperms (eudicots) that diverged after several other lineages of angiosperms had already appeared. The apperance of such pollen in the fossil record marks the absolute latest that any angiosperms could have appeared, but also indicates that angiosperms must have originated sometime before the appearance of such pollen. In addition, certain other groups (like grasses) likewise have distinctive pollen and are easily recognized as fossils, but monocots are also somewhat derived within the angiosperms.

Caveat: I'm not a paleobotanist and certainly not an expert on pollen (fossil or otherwise) so what I've written off the top of my head should probably be checked against a more authoritative source.

Edited to add that after checking my facts, it looks like I got them mostly right. I re-read Cornet's website and the guy does seem a bit nutty and he hurts his own credibility with his hyperbolic and rather hysterical writing style. It wouldn't surprise me if he's a conspiracy theorist. I don't think there's any conspiracy or blind dogma to suppress or deny pre-Cretaceous angiosperm fossils; I think most botanists just want to see better and stronger evidence. I certainly think that botanists are more open to pre-Cretaceous angiosperms, and alternative theories of angiosperm origins in general, than they were even 10 years ago.