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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."
You're not a real P.U. grad! Is the basement finished or unfinished? One or two car garage?
You should include a /sarcasm tag in your posting. Otherwise folks might get the wrong idea.
Just can't fool anybody. :)
One or two car garage? You must be joking: Have you seen what I charge for my videos?
My dear sir - if you're going to go all "Patrick Henry for the Hoplite guy", you had best not bring your own cedentials into question with posts which make an Aztek look good.
Cordially yours,
w00t, etc.
2 more gaps.
I am a doctor! You're going to hell. I and the two shi tzus will pray for your soul.
Yeah, not my finest hour.
I guess that lecture hall also doubles as the mail room.
So... why is that flatworm wearing lipstick?
So you're saying God said, "Over the course of the next 50 million years, let there be a sudden appearance of complex multicellular macroscopic organisms with hard parts (as opposed to earlier macroscopic soft organisms)?"
Something like that.........
All the facts are never in, in science. But this finding is being published in Nature, the respected peer-reviewed journal, meaning that independent scientists have vetted the methodology, findings and analysis and found them to be significant. It's irresponsible for you to accuse the researchers in this discovery of fraud, without one shred of evidence, withought having even read the article in question.
That all fossils before the Cambrian were "soft" bodied is an old theory and unprovable, as so many postulations from evos are.
You're sure you're not a creationist?
Don't cry to whom?
It's auditioning for a role on Teletubbies, which has homosexual activists giggling in anticipation of Jerry Falwell's statement denouncing it.
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