Fossil marine 'thingy'

Beatsy · Post by **Beatsy** » Tue Aug 26, 2014 1:27 pm

From a strew of cleaned Oamaru diatomite. A relatively unproductive sample holding a sparse mix of diatom species with stephanodiscus, sponge spicules and battered radiolarians dominating. And this thing (pictured alongside a sand grain). I have no idea what it is.

Stack of 45 images using a 40/0.95 'corr' objective with NA0.63 condenser.

carlos.uruguay · Post by **carlos.uruguay** » Tue Aug 26, 2014 5:21 pm

Impressive!!!
Thanks for sharing it!
http://news.mongabay.com/2009/0729-extinction.html
(see the photo)

Cactusdave · Post by **Cactusdave** » Wed Aug 27, 2014 12:01 am

Very nicely photographed indeed Beats. I have also seen and photographed similar structures in Oamaru fossil diatom strews. As to what they are, Carlos' suggestion is an interesting one, but I think these may be fossil gemmules of sponges. With your permission I could post my own image in this thread. They need high power oil objectives and stacking to resolve the structure.

Beatsy · Post by **Beatsy** » Wed Aug 27, 2014 12:49 am

Sure - post away Dave. Sponge parts make sense, given all the spicules in there. Cheers

Cactusdave · Post by **Cactusdave** » Wed Aug 27, 2014 1:17 am

Thanks Beats. This is my effort. Zeiss Planapo X63 1.4 oil. Non optimal 0.52 LWD condenser on a Nikon Diaphot, so this objective is more than a little 'hobbled' here. 38 image stack with Zerene PMax.

Black and white version.

Beatsy · Post by **Beatsy** » Wed Aug 27, 2014 1:55 am

Certainly looks the same structure, albeit different surface texture. So gemmules (baby sponge 'seeds') it is. The bryozoan pics you linked Carlos have some surface similarities, but I think Dave has the ID here. Thanks both.

René · Post by **René** » Wed Aug 27, 2014 3:25 am

The internal lines in a radial (starlike) pattern are typical, I have seen things like it. There doesn't seem to be anything alive internally?!

Thanks for the ID, brings me also a bit further.

Best wishes, René

Beatsy · Post by **Beatsy** » Wed Aug 27, 2014 3:42 am

No, nothing alive Rene. It's 35 million years old and been boiled in conc. sulphuric acid

René · Post by **René** » Wed Aug 27, 2014 6:03 am

I'll keep an eye out for them in my samples!

Best wishes, René

BJ · Post by BJ » Wed Aug 27, 2014 6:18 am

Hi,

99.99% certain that it is a sponge spicule. Spherical / ovoid spicules are termed "sterrasters". Do an image search for this term and you will see many like your specimen.

thanks for posting!

Brian

René · Post by **René** » Wed Aug 27, 2014 7:03 am

Righto, exactly what I have come across in one of my samples: http://www.microscopy-uk.org.uk/mag/art ... query.html. Thanks Brian! Dotted on the outside, radially structured inside. Not birefringent, not alive. And therefore neglected...

Best wishes,
René

Cactusdave · Post by **Cactusdave** » Wed Aug 27, 2014 9:27 am

Sterrasters -- that's a new one on me. I always think of spicules as needle shaped or hooky things. That Microscopy-uk article is very informative. I have genuinely learnt something and its interesting to know that Beats and I have both stumbled on something that has been a mystery to many, and little researched. Beats' example is a really intriguing shape and texture, and fits well with the SEM in that article.

Beatsy · Post by **Beatsy** » Wed Aug 27, 2014 11:12 am

Indeed - something new learned for me too! Thanks Brian for the ID and Rene for the link to the very interesting article.

Of course, I'm seeing sterrasters all over the shop now and found several more in that same strew

I composited a few into a single image for posting. Stephanopixis and a radiolarian top left and the other four are sterrasters, I think.

Cactusdave · Post by **Cactusdave** » Wed Aug 27, 2014 12:17 pm

Excellent picture again Beats. That's a really attractive goblet shaped radiolarian, very nicely imaged. The sterrasters are also very nice, one very similar to mine. They are fascinating to look at in detail. I assume they are unique to Oamaru diatomite? I don't think I have seen them in other samples.

Beatsy · Post by **Beatsy** » Wed Aug 27, 2014 1:34 pm

Thanks.

I assume they are unique to Oamaru diatomite? I don't think I have seen them in other samples.

To be honest, I can't remember. After several hundred hours poring over open strews selecting diatoms, I visually' filter out' spicules and other stuff and don't really notice them. I only paid these any attention because the small mounted strew I was examining didn't hold much else of interest!

Having said that, sponges have been around 1.5 billion years or more, so I very much doubt that sterrasters (word of the day

) are limited to Oamaru diatomite.

PS. That's not a radiolarian after all. It's Pyxilla johnsoniana - a diatom!