Guess how some fossils are a lot like Elvis
by Ed Willett, Special to The Leader-Post
Elvis lives! Well, kind of. Way back in 1991 I wrote a column on taxonomy -- which is not, as you might suppose, the scientific study of taxes. (And yes, I used that same joke 16 years ago.)
It's just barely possible you don't remember that original column, so first, a quick taxonomy refresher.
Taxonomy is the science of classifying living organisms into hierarchical groups that represent the relationships among them. The system we use was invented by Swedish botanist Carl von Linne (although, since he wrote in Latin, he's better known as Linnaeus).
The fundamental group is the "species." Related species are grouped into a "genus." Thus, horses and zebras are two different species, but they belong to the same genus, Equus.
Related genera, such as the asses and onagers, are grouped into "families" -- in this case, Equidae. Equidae is then grouped with two other families, the rhinoceroses and the tapirs, to make up an "order," Perissodactyla, the odd-toed ungulates. (Odd in that they all have one or three toes per foot, not odd in that their toes look funny. Although they do.)
Perissodactyla and all the other orders of hair-covered, milk-producing animals are grouped together in a "class," Mammalia. Mammals are then grouped with the classes of other backboned animals, such as reptiles, into a "subphylum," Vertebrata, which is part of the "phylum" Chordata, containing all animals which have a nerve chord at some time in their life cycle.
Finally, the Chordata are placed with all the other phyla of living creatures that are multicellular and "heterotrophic" (meaning they have to eat), into a "kingdom," Animalia.
The first word of a species' name is the genus, while the second is species-specific. Thus, the common European starling is Sturnus vulgaris, Sturnus being the genus of starlings and vulgaris meaning common.
So what does all this have to do with Elvis?
Well, as a recent issue of New Scientist explained, the difficulties inherent in deciding where an animal fits taxonomically are magnified when all you've got to work with are a few fossilized bones.
You may be convinced that the particular taxon (any type of biological group) you're studying went extinct 60 million years ago, only to have someone turn up a fossil from the same taxon that's 20 million years younger.
In 1983 David Jablonski and Karl Flessa dubbed such taxons "Lazarus taxons," after the man Jesus raised from the dead. No miracles are involved -- just gaps in the fossil record, caused by the animal becoming rare or relocating to a habitat where it left no fossils.
The best-known example is the coelacanth, a fish closely related to amphibians that had been thought to have died out with the dinosaurs--only to turn up in the net of a South African trawler in 1938.
Sometimes, though, what looks like a Lazarus taxon isn't. Instead, it's a completely different taxon that has evolved to look very much like another. For example, some invertebrates have shells that look like the shells of earlier forms. At first glance, a scientist might think that an invertebrate thought to have become extinct millions of years ago had actually survived into the recent past -- but further study will reveal that she's not dealing with a Lazarus taxon at all. Instead, the more recent animal is, in a sense, an impersonator of the long-dead original.
Which is where Elvis comes in. Doug Erwin and Mary Droser coined the term "Elvis taxons" for such look-alike taxons in 1993, choosing to go with a topical, rather than biblical reference (unless you belong the Church of Elvis, in which case I suppose it is a biblical reference).
There are other similar terms. There's the "Zombie effect," which is when hard fossils are washed out of sediments and deposited in rocks millions of years younger, making them a kind of walking dead. And a recent suggestion is the "Jimmy Hoffa taxon": so-far-undiscovered bones that must be hidden somewhere.
To all of these scientists, working so hard to untangle the fossil record and come up with snappy catch-phrases at the same time, there's just one thing I want to say:
Thank you. Thank you very much.
- Edward Willett is a Regina freelance writer. E-mail comments or questions to firstname.lastname@example.org. Read this and past columns online at www.edwardwillett.com or edwardwillett.blogspot.com.
(News, Source: Leader-Post, 2 Feb 2007)