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Mystery Fossil Found At Mannum


CalGregg

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Hi Fossil Forum!

I was down at the Mannum Cliffs in South Australia today collecting some wonderful Lovenia Forbesi and brachiopod specimens. I came across this odd looking rock, I I picked it up and saw that this indent was on it. It very much reminded me of 'Dickinsonia', but what do you guys think?

post-11376-0-31777000-1363507705_thumb.jpg

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It's very unusual. I didn't think Dickinsonia could be found in the Mannum area. And note the indent line in the centre.

This is a view from the side

post-11376-0-18813500-1363508097_thumb.jpg

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Interesting.. it sure does look like a Dickinsonia given the symmetry but maybe it's a slightly deformed negative (imprint) of the top of a horn coral? I dont know the geology of your area but it might help to narrow down the possibilities if we knew.

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It looks like the internal mold of a coral similar to Flabellum.

Ahh yes!

The area I collected it in has thousands of Lovenia Forbesi fossils among it, but they all differed in colour compared to this fossil. This is what I found c2a.jpg

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Looks like an obvious coral to me. Actually it's a cast (impression) of the calyx, the opening on top where the coral polyp lived . You can see primary and secondary septa clearly, maybe tertiary septa too. There doesn't seem to be any actual shell left, just rock that filled the calyx, which may account for the color difference from other local fossils. The resemblance to Dickinsonia is superficial; Dickinsonia was a flat organism with wrinkles on it's surface, whereas the fossil in question is clearly fairly 3-dimensional judging from the side view. Also Dickinsonia, like all the other Ediacarian organisms, was apparently soft bodied and was preserved only as an impression in very fine grained rock, whereas the the fossil in question is preserved in a fairly coarse sandstone so it was evidently fairly hard shelled.

Isn't Lovinia a Miocene echinoid? Dickinsonia is an Ediacarian (late Precambrian) fossil of uncertain affinities. There is approximately a 600 million year difference in age. Finding a Miocene Dickinsonia would be like finding a fossilized bird on a slab with an Olenellus trilobite, except the age gap for the bird/trilobite would be less.

Don

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  • 1 year later...

Well, if it was dickinsonia… explain the brachiopods :P Brachiopods appeared in the cambrian… whereas dickinsonia is ediacaran (Late precambrian)

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coral to me also.

"Absence of evidence is not evidence of absence"_ Carl Sagen

No trees were killed in this posting......however, many innocent electrons were diverted from where they originally intended to go.

" I think, therefore I collect fossils." _ Me

"When you have eliminated the impossible, whatever remains, however improbable, must be the truth."__S. Holmes

"can't we all just get along?" Jack Nicholson from Mars Attacks

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Isn't Lovinia a Miocene echinoid? Dickinsonia is an Ediacarian (late Precambrian) fossil of uncertain affinities. There is approximately a 600 million year difference in age. Finding a Miocene Dickinsonia would be like finding a fossilized bird on a slab with an Olenellus trilobite, except the age gap for the bird/trilobite would be less.

Don

Spot on. Mannum fossils are Miocene, there have even been whale fossils recovered from the cliffs.

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