Nice Legs

by Jennifer Frazer on June 28, 2009

. . . and he knows how to use them. The harvestman (daddy long legs) Phalangium opilio. Credit: Dschwen/Creative Commons Attribution Sharealike 2.5 License. Click for link.

. . . and she knows how to use them. The harvestman (daddy long legs) Phalangium opilio. Credit: Dschwen/Creative Commons Attribution Sharealike 2.5 License. Click for link.

Sometimes evolution moves quickly and groups of organisms change radically over very short spans of geologic time. Think of modern horses, which evolved from dog-sized creatures over the course of the last few tens of millions of years. Or take humans — we only evolved about 150,000 years ago, and if you look at our ancestors ca. 3 million years BP, you’d find yourself looking at an unfamiliar face indeed. But sometimes, when a particular organism hits on a successful niche, it changes hardly at all.

I’ve previously mentioned that sharks and mosses fall into this category. But this week I found an interesting story about some amazing harvestman fossils that show they are in the same boat. Harvestmen, also called daddy long legs, are arachnids like spiders or scorpions. Scientists recently found two new species in fossils from north central China that date from 165 million years ago. That’s right — the Jurassic, When Dinosaurs Ruled The Earth.

The two new species, described by Selden and his colleagues in an upcoming Naturwissenschaften, were entombed in fine-grained volcanic ash that fell in what is now north central China about 165 million years ago. The harvestmen — and the ash — either dropped into a lake or were washed there soon after the ash fell, Selden notes. Little is left of those ancient harvestmen: The fossils are, for the most part, 3-D outlines of fragile bodies that disappeared long ago. Those tiny molds, however, preserved even small details of the creatures, including their mouthparts, genitals and the joints of their legs.

You just gotta love German science journal names. Wait . . . genitals? Yes. According to scientist Paul Selden, one of the authors of the paper, the details are so fine and the organism so similar to existing harvestmen, we can tell that if you saw one of the fossilized species wander through your back yard today, you wouldn’t even look at it twice. And this is a creature that once may have scuttled underneath T. rex or Stegasaurus!

I can’t publish the photo here for copyright reasons, but head on over to Science News to see the fossil and read the rest of the article and make sure to embiggen that fossil photo — twice.  With enough time, it is amazing what low-probability events can happen.

{ 2 comments… read them below or add one }

Reed July 2, 2009 at 12:56 am

Wikipedia pushes back the harvestmen even further to the Devonian…

“Well-preserved fossils have been found in the 400-million year old Rhynie cherts of Scotland, which look surprisingly modern, indicating that the basic structure of the harvestmen has not changed much since then.”

Who’d have guessed that our little friends are living fossils?!

Solius July 14, 2009 at 3:06 pm

The lowly(to some) lingulid brachiopods have changed little since the Cambrian. If nothing else, the little buggers are persistent.

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