Posted on 07/13/2006 6:12:42 AM PDT by doc30
Mollusk fossils push back evolution, ROM scientists say
Life 560 million years ago more advanced than previously believed, article says.
Two Canadian paleontologists have discovered dozens of fossils of a soft-bodied, deep-sea dweller that lived more than half a billion years ago, adding one more piece to the enigmatic puzzle that is the history of life on Earth.
The 189 well-preserved fossil specimens of Odontogriphus omalus have been interpreted as the world's oldest known soft-bodied mollusk, and were found in British Columbia's mountains in the Burgess Shale, one of the most important fossil sites in the world.
The newly discovered fossils are remarkable, one of the researchers notes, because there are perfect impressions of all of the animal's soft tissues.
The fossils show the early mollusk had an oval body ranging in size from a few millimetres to 20 centimetres with simple gill-like structures surrounding a muscular sole or "foot" on the underside.
The stomach, intestines, outer membrane and mouth are all visible.
This discovery pushes back the history of animal evolution tens of millions of years to 560 million years ago in Precambrian time (543 million years ago and earlier), according to the Royal Ontario Museum's David Rudkin, co-author of the article published in today's issue of the journal Nature.
Very few fossil specimens have been found from that time period. The Cambrian Period (543 million to 490 million years ago) marked the sudden appearance of complex multicellular macroscopic organisms.
In the Precambrian era, before the so-called explosion, organisms were thought to be much simpler, but this study shows that was not the case.
"This is a crucial interval in evolutionary history because it seems to represent a time in which a great deal happened," he said.
"Odontogriphus seems to be a late holdover that somehow got preserved in with the creatures from the Cambrian . . . opening up new windows on evolution for us," Mr. Rudkin said.
The specimens were collected over 15 years in the late 1980s and 1990s by the ROM and, upon closer examination, were found to have distinguishing "molluskan" features including a specialized feeding structure called a radula, made up of short rows of small, tooth-like elements that would wave and sweep food into the mouth.
The shell-less mollusks grazed on seafloor bacterial growths.
Odontogriphus, which translates to "toothed riddle" was originally discovered in 1976 from a single, poorly preserved specimen. Until now, it has been described as an "enigmatic organism," according to the study's lead author, Jean-Bernard Caron, also of the ROM.
"Our study redescribes and reinterprets previously unrecognized features that link Odontogriphus to the mollusks, one of the most diverse and important groups of animals living today," Dr. Caron said.
Odontogriphus predates modern-day mollusks -- with 200,000 living species today including snails, clams, squids and octopuses -- which began to develop hard shells during the Cambrian Period to survive.
"They were the last of their kind and they were dying out because the sea floor was changing and all these other animals started developing hard parts and new strategies for dealing with predators," Mr. Rudkin said. "The successful mollusks are those that branched off and developed shells."
Mr. Rudkin said the fact that many mollusks have survived such a catastrophic extinction could shed light on the evolutionary path many animals may take.
"Those lessons we learn from the past -- about where groups of organisms originated, when they become extinct, how they became extinct, or if they didn't become extinct entirely, how they recovered from extinction -- we use that kind of historical background to help us predict what might happen in modern extinction circumstances. Maybe there's a lesson in there for us."
Ping - this is a good article for the list!
What I'm shocked...scientists wrong about the past. No way but Global Warming is man-made dontcha know. Scientists say so. ;-)
Dynamite! The Cambrian explosion is looking like a dud. I'm cranking up the ping machine.
|
Real scientists don't.
Doesn't sound like evolution to me. Sounds more like GOD!.....
I had a ten dollar bet on that one. Looks like I am out a sawbuck ;)
I see the ;) but I recommend the /sarcasm tag on these threads.
People make the silliest posts and MEAN IT.
:)
Did you forget the "/sarcasm" tag?
Silly posts on FreeRepublic? Shirley you jest.
What are the criteria for being a "real scientist?"
This is a good thing. It shows that scientists know the limits of current knowledge and are capable of recognizing the importance new findings when they occur. When new facts emerge, existing theories are modified or discarded, depending on the nature of the new evidence. This finding of pre-Cambrian complex animal life fits very well with evolutionary theory.
Yup I see your point about silly posts but I usually don't mind clarifying the point for those folk.
ping
This sounds like the defacto definition of scientist to me. Good for them.
THe criteria for being a real scientist in this group is swallowing any evolutionary theory hook line and sinker in lock step without a hint of debate.
Well this finding shows that there really wasn't an explosion of complex multicellular life. The Cambrian explosion seems to be the appearance of organisms that were more easily fossilized. That doesn't mean there weren't complex organisms before the Cambrian Explosion. This very exciting finding shows complex multicellular life predates the Cambrian explosion. We now have data from an epoch where we didn't have it before. This is fantastic news!
"What I'm shocked...scientists wrong about the past."
Actually, this reinforces what they already suspected.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.