The discovery of two lower jaw fragments from a 1.3 meter crocodile-like creature that lived 370 million years ago was announced last week by Dr. Pers Ahlberg from the Natural History Museum of London and could be the missing link that reveals how our ancestors paddled out of swampy shallows to live on land.
Ahlberg, together with Baltic researchers Dr. Ervins Luksevics from the Natural History Museum of Latvia in Riga and Dr. Elga Kurik from Tallinn's GeologicalInstitute, have affectionately named the creature "Livonian multidentato" for now because of its unprecedented five rows of lower teeth.
The ancient land of Livonia, where the specimens were unearthed from sandstone deposits left over from a world-wide climate shift, included central Latvia and southern Estonia.
"I was very very surprised by the discovery," said Luksevics. "The fossil has been in a drawer in our museum for about 11 years. It was originally found in 1964 by Teodors Kams, a private collector, whose collection was donated to the museum upon his death."
Ahlberg discovered a second jawbone fragment from Estonia at the Estonian Geological Institute, where it had been stowed away unrecognized for nearly 50 years.
Such discoveries come rarely in a lifetime.
"It took me about a minute from taking one of those bones in my hands to realizing that this was what I had been searching for all this time," said Ahlberg, who had looked at thousands of specimens and hundreds of collections before he came across these two priceless pieces of the puzzle. He is convinced they came from the same species.
The Latvian fossil is a particularly good specimen and according to Ahlberg, shows just about a perfect intermediate condition between fish and amphibian.
"The jawbone carries the signature of the creature and this jaw carried the perfect intermediate features between land and sea," Ahlberg said.
It may be seen at the Natural History Museum in Riga.
The other specimen which is not in such perfect condition, but is excellent for comparison, remains at the Geological Institute in Tallinn.
Fossils of backboned land animals are rare but a sequence can show lineage, and according to Ahlberg, the lower jaw carries a signature for the entire species. This jaw carried the features intermediate between land and sea and fills a 10 million year gap in the family tree of land animals with backbones and helps to piece together the order of the evolutionary chart.
It has long been scientifically accepted that all land animals with backbones, including humans, are descended from one small group of fish that left the water about 365 million years ago.
"The question we cannot yet answer is whether this creature had paired fins or legs," Dr. Ahlberg told BBC News.
"It can be called a fish with limbs," said paleontologist Mark-Kurik, who participated in the NATO-funded research project in 1997 and 1998 with Ahlberg and Luksevics.
Nevertheless, Mark-Kurik admitted that now that the fossil has been identified, a more difficult question -how the tetropod itself first appeared -has yet to be answered. Newly-backboned fish could not have simply crawled out of the water without suffocating from fresh air entering their gills. She theorizes that the tetropod must have lived in tidal pools along the beach that are in between a land and water environment.
The emergence of the tetropod, no doubt, sheds light on how fish evolved as well as prompts rethinking of where existing fossils fit into the evolutionary jigsaw puzzle.
"It is a very mysterious event," she continued, "and by the way, it is the most important event for you and me." The next step, said Mark-Kurik, is to dig through rocks in Eastern Europe to find more fragments of the skeleton.
A whole fossilized skeleton of one of these animals would be one of the great discoveries of the century.
"After this discovery our territory is a safe bet for digging and searching," said Luksevics.
Details of the findings and the new scientific name of the creature will be published in August in the journal Paleontology.
This article includes information also from ABCNEWS.COM and The Associated Press.
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