Richard Lein
RIGA (AFP) – Darwinists claim that two small fossil fragments discovered in the Baltic republics of Estonia and Latvia could be the missing link between fish and animals, and help explain the origin of species, scientists claim in a forthcoming article.
However, with only two similar pieces of the lower jawbone of the so-called "Livonia multidentato" to work with, they cannot be sure whether the creatures had fingers or fins when they crawled from the sea to the land. "There's still too little material available to be able to say it is an amphibian," Elga Kurik, a researcher at Tallinn's Geology Institute, said.
The multidentato – an improvised word meaning "many-toothed" – may well have been the earliest tetrapod (backboned animal) to walk out of the sea onto land about 380 million years ago.
Scientists have long been searching for the first tetrapod because all land animals with backbones – including humans – are believed to have descended from the same type of fish. Possibly about 1.5 meters (4.5 feet) in length, the Livonia multidentanto probably looked similar to a short stocky salamander and had a fin instead of a tail, and spent most of its time crawling along the bottom of shallow bodies of water.
But for nearly the past half century the "missing link" has been lying in academic collections as scientists missed its significance. Kurik discovered the first specimen as a student in 1953 near the Piusa River in southern Estonia. The Latvian fragment was found in 1964 in a sandstone cliff-face above the Gauja River by an amateur researcher and reached other scientists only at the end of the 1980s when it was donated to Latvia's Natural History Museum.
However, two years ago, local paleontologists began to put the puzzle together with the help of Dr. Per Ahlberg of London's Natural History Museum. Latvian researcher Ervins Luksevics, who had found a later tetrapod specimen, Ventastega, during a dig in Latvia with Ahlberg in the early 1990s, invited his British colleague back in 1998 to look at the Gauja specimen.
Ahlberg was even more confident than Luksevics that the fossil was an early tetrapod, and on a side visit to Tallinn, he found another specimen in Kurik's collection. "You can't believe how surprised I was when Ahlberg came back from Tallinn and said he had found another one," said Luksevics in his Riga office, surrounded by cabinets and shelves stacked with boxes of specimens. "It was all by chance."
The three have co-authored an article on Livonia multidentato, due to be published in the British journal Paleontology this summer. "I picked the name because I found the fragment in South Estonia, which is part of what is historically known as Livonia, and because the creature had an unprecedented five rows of teeth in the lower jaw," Kurik said.
It is the teeth, the pattern of the small bones, and canals for arteries, veins and nerves that set apart Livonia multidentato from earlier fish and lead the experts to believe the creature was an early tetrapod.
But Livonia multidentato raises other puzzling questions for scientists besides whether it had digits or fins, said Luksevics. The two fossils are about 380 million years old, about 20 million years older than other tetrapods that have been found.
This will prompt scientists to begin looking at older sediments for more clues about the first tetrapods and may indicate that there were several ascents onto land in different places and over a longer period of time than previously believed.
An interesting possibility, says Luksevics, is that Livonia multidentato is really a fish, and then he's got the fish ancestor of tetrapods. "This is a real important find," said Luksevics while affectionately holding the fossil. "But I really don't think we have enough of it to say whether we have a tetrapod or a fish... so it is real important that we find more fossils to tell us more."
|
