Wednesday, November 3, 2010

Very Old, Quite Small, Lamprey: A Big Deal for Scientists

"Discovery of the oldest fossil lamprey in the world"
Science in Africa (February 2007)

"Scientists from the University of the Witwatersrand and the University of Chicago have discovered a 360 million-year-old lamprey, from Witteberg Group rocks near Grahamstown, in the Eastern Cape, demonstrating that modern lampreys are remarkable living fossils. The report is published in Nature.

"This jawless fish fossil was discovered by Robert Gess, a PhD student at the Bernard Price Institute for Palaeontological Research at Wits, under the supervision of Prof. Bruce Rubidge of Wits and Dr Mike Coates of the University of Chicago.

"Scientists from around the world are currently engaged in reconstructing the evolutionary tree of life, combining data from the structure of living organisms, the fossil record and the analysis of DNA. In ancient seas, jawless vertebrate fish predated and gave rise to jawed fish, from which all vertebrates, including humans, descended. The only surviving group of jawless vertebrates are the lampreys which, as a result, are attracting intense scientific interest. Only in living lampreys may jawless vertebrate embryology or DNA be studied, resulting in lampreys being increasingly used as surrogate ancestors in researching jawed vertebrates...."

This newly-discovered fossil is a big deal, since lampreys haven't left much evidence of their existence:

"...Knowing when lampreys acquired this specialization, would suggest how representative they really are of ancient fish.

"The boneless cartilagenous skeletons of lampreys have, however, left virtually no fossil record - only three fossil species having previously been described, in none of which is a sucker-disc visible...."

And now, there are four.

Back to that article:

"...The remarkably well-preserved new fossil, described in the prestigious scientific journal Nature, published today, is older than any previously discovered fossil lamprey by 35 million years. Only 42mm long it reveals details of its fin, gill basket and, most importantly, its mouth region. It's circular mouth, situated at the center of a large sucker disk and encircled by small teeth, is remarkably like that of living lampreys, revealing that lamprey adaptations for a blood-sucking lifestyle were acquired in ancient seas, before modern fish faunas arose. Lampreys are therefore 'living fossils' that have remained largely unaltered through more than 360 million years and four major extinction events...."

This ancient lamprey species has been dubbed Priscomyzon riniensis. The article explains that it's taken from Latin prisco (ancient), myzon (a lamprey), and Rini, the Xhosa name for Grahamstown and surrounds).

Lampreys aren't likely to show up in, say, a list of cute Disney cartoon characters. Between their eel-like appearance, that mouth, and their eating habits, they're - well, just not that conventionally endearing. The term 'disgusting blood-sucker' comes to mind.

That said, they're impressive critters - for their durability, if nothing else. And, as the article points out, lampreys are useful tools for studying other critters that didn't leave living descendants.

Now, this little fossil lamprey gives paleontologists and others some concrete evidence to work with.

"Little" is a comparative term. The Lemming checked - and that 42mm length works out to just over one and five eighths inches.

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