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Odd find from Oxford Clay in Dorset England - Crinoid Calyx ?


JamieLynn

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Hi All! Just got back from a lovely trip to England and had a great hunt in Weymouth. Found this odd thing that I thought was a crinoid Calyx, but I am really not sure. I will eventually clean out the center, but was wondering if anyone might be able to tell me for sure what it is. Any help is appreciated! Thanks! 

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7 hours ago, caldigger said:

Brooksella?

Could very well be, although ammonite chamber is another possibility. There are records of Brooksella family members ranging up into the Devonian of which according to the geological map of Weymouth there are outcrops.

 

Greetings from the Lake of Constance. Roger

http://www.steinkern.de/

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I think it's a sponge, probably from the Cretaceous Greensand - perhaps Hallirhoa sp. (I don't believe there are any sponges in the Oxford Clay, although there are in other Callovian deposits.)

 

59 minutes ago, Ludwigia said:

...the Devonian of which according to the geological map of Weymouth there are outcrops.

Roger, I was a bit mystified by that! - maybe you're looking at this Wikipedia map? 

https://en.wikipedia.org/wiki/Geology_of_Dorset#/media/File:Dorset_Geology.png 

The bits that look Devonian brown coloured are all Jurassic, the practically identical brown of the Kimmeridge Clay

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Tarquin

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so we were kind of on the right track with Brooksella....I think sponge is probably accurate. It definitely does not have the same features of any kind of ammonite chamber I've seen, even water worn. So perhaps this washed up from another formation in that location.

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2 hours ago, JamieLynn said:

so we were kind of on the right track with Brooksella....

Yes, it looks very similar, though Brooksella (or some of them) may not actually be a sponge...:wacko:

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Tarquin

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5 hours ago, TqB said:

Roger, I was a bit mystified by that! - maybe you're looking at this Wikipedia map? 

https://en.wikipedia.org/wiki/Geology_of_Dorset#/media/File:Dorset_Geology.png 

The bits that look Devonian brown coloured are all Jurassic, the practically identical brown of the Kimmeridge Clay

Oops!You're right about that. I mistook the Kimmeridge Clay for the Devonian. Well, Brooksella may not be right, but I think that sponge is the right idea.

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Greetings from the Lake of Constance. Roger

http://www.steinkern.de/

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Would Alcyonite be a possibility?

 

 

Mark.

 

Fossil hunting is easy -- they don't run away when you shoot at them!

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Sponge identification is usually a matter for a specialist, with microscopic work and looking at spicules. Overall form is highly variable so not necessarily that diagnostic.

 

Polypothecia hasn't been properly described and there are a number of possible synonyms that should take precedence, including Hallirhoa. See:

https://www.academia.edu/36777066/Where_is_Polypothecia_Benett_1831

 

Tetralithistida isn't a genus but an order, a very large group that contains many sponge genera. Hallirhoa is one of them and is what your illustration shows (as the old label says!).

 

So I still reckon Hallirhoa? is a reasonable ID until you take it to a sponge specialist. :)

 

(I think Alcyonite is an archaic term not in modern use that includes a lot of sponges.)

 

 

 

 

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Tarquin

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thank you for taking the time to explain! As you can tell, i have no experience with sponges- and yes, I did see the Hallirhoa tag on that one so was curious about that. I will just go with Halirhoa! 

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17 hours ago, JamieLynn said:

thank you for taking the time to explain! As you can tell, i have no experience with sponges- and yes, I did see the Hallirhoa tag on that one so was curious about that. I will just go with Halirhoa! 

A pleasure! I'm very much an amateur on sponges. They're an enormous and endlessly fascinating group - in the academic sponge world, each specialist can only concentrate on a particular area within them. I've had a lot of help from @Spongy Joe who hasn't been seen on here for a while...

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Tarquin

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On 9/19/2019 at 1:52 AM, TqB said:

(I think Alcyonite is an archaic term not in modern use that includes a lot of sponges.)

It happens in your late sixties. I'm 68, therefore I am. Archaic that is. :D

 

 

Mark.

 

Fossil hunting is easy -- they don't run away when you shoot at them!

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