an autodidact meets a dilettante…

a dialogue/monologue promoting humanism, science, skepticism, globalism and femocracy, and demoting ignorance, patriarchy, thuggery and zero-sum game nationalism

Posts Tagged ‘compound eyes

Kangaroo Island – Emu Bay’s Burgess Shale-type fossils

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Emu Bay, a lovely beach with hidden secrets. The 500 million-year-old fossils were found on the far, eastern side of the bay

Canto: We have a slightly disappointing tale to tell about Emu Bay, famous site for fossils from the so-called Cambrian explosion of some 500 million years ago.

Jacinta: Yes we went there in the naive expectation of ‘seeing something’ – not so much Cambrian-era fossils sticking out of the rocks, but a housed display, perhaps of a touristy nature, of at least photos of the many species of trilobite as well as an endemic species to Emu Bay, Anomalocaris briggsi.

Anomalocaris briggsi, named for famed Burgess shale paleontologist, Derek Briggs. Note the length, indicated by the scale

Canto: ‘Anomalocaris’ means ‘abnormal shrimp’. I recall using the term shrimp to indicate and abuse a small person, so when is a shrimp not a shrimp? I presume abnormal means rather large, as shrimps grow.

Jacinta: Well before we go into all that, let’s say that our trip was a disappointment because there was nothing on site to indicate, or celebrate, the place as one of the most important shale fossil deposits on the planet. Still, it was a nice beach. And I must say the weather here has been more than kind, so far.

Canto: Yes, after driving around for a bit in the tiny township of Emu Bay, we gave up and returned to Kingscote. On visiting the museum there, I asked the caretaker if he knew anything about Emu Bay’s fossils. Were any to be found on the island? He very much doubted it, and said that the exact location of the fossil deposits is not let out to the public – as fossil-fossickers were liable to desecrate the site, so to speak. In fact they’d already done so, it was said. Adelaide would be the most likely destination of the precious fossils, he said, or other parts unknown.

Jacinta: So, yes, in some respects a waste of time, but it was exciting to be so near the site of so many, and such old, fossil finds.

Canto: I’ve decided to return. Just to get a little closer, and fossick about.

Jacinta: Fossick – is that related to fossil?

Canto: Haha, good question – actually fossicking is probably related to fussing, but etymology, as I’ve learned from John Simpson – is often a fruitless endeavour. At least if you want to find definitive answers. But the word fossil has a much clearer etymology, ultimately from Latin fossilis, ‘something which has been dug up’.

Jacinta: But arguably the most important finding with respect to Anomalocaris was made in 2011, in Emu Bay. Six fossil finds of compound eyes belonging to Anomalocaris, which proved that it was an arthropod (as are shrimps), and that these eyes, which were 30 times more  powerful than those of trilobites, had developed very early in the evolutionary process. They dated back 515 million years! Trilobites were previously though to have the best eyes of the period!

Canto: I can see you’re impressed. In fact the Anomalocaris eye contained 16,000 lenses, which makes for pretty impressive resolution. But then, the modern  dragonfly has 28,000.

Jacinta: Hmmm, highly evolved eyes don’t seem to go with highly evolved brains. I’m sure there’s a lesson there…

artist’s impression of the sharp-eyed predator Anomalocaris, found fossilised at Emu Bay

Written by stewart henderson

April 2, 2018 at 8:05 pm