Section through an Indonesian fossil coral

Bruce Williams · Post by **Bruce Williams** » Wed Mar 07, 2007 12:49 pm

Hi folks,

Section through an unidentified fossilised coral sp. from Indonesia. Each individual waggon-wheel shaped corallite (polyp skeleton) is ~5mm in diameter. I am still in the process of researching this piece - so far I have from a somewhat questionable commercial source that this type of agatized coral is "probably" Devonian (c. 360 mya).

I have produced a very simple diagram to try and make sense of the corallite structure see here.

All 3 pics are CombineZM stacks taken through my Meiji CMZ-5TR. Pic1 is of the unpolished side and I was surprised to see that turned out the sharpest image. Pics 2 and 3 are of the more colourful polished side of the slab. Much of what we are looking at is being viewed through various translucent silicas and is therefore not intrinsically "pin sharp" even through the microscope eyepiece - of course surface structure can be highly detailed.

Just to be clear on scale (sorry I forgot scale bars): Pic1 and Pic2 are approximately 10mm X 7.5mm and Pic3 is approx. 3.75mm X 5mm.

Bruce

MacroLuv · Post by **MacroLuv** » Wed Mar 07, 2007 1:28 pm

Very interesting Bruce!

I think #1 appears sharper because of ridge surface and less direct reflections.
Have you any data about dating or similaritiy with today corals?

beetleman · Post by **beetleman** » Wed Mar 07, 2007 2:44 pm

Great pictures Bruce. Modern corals are identified by their polyp skeletons. I am sure somewhere there is a key to the structures of these fossil corals. They are amazing little animals

.

Ken Ramos · Post by **Ken Ramos** » Wed Mar 07, 2007 3:40 pm

That diagram was really helpful there Bruce, because for a moment I really had no idea of exactly what I was looking at. Some very interesting little creatures these coral polyps. Very nice and detailed images.

Bruce Williams · Post by **Bruce Williams** » Thu Mar 08, 2007 3:49 am

Nikola - I'm still getting nowhere fast on identifying species and a confident age (350 million years is best I have so far). Based on structure of the fossil corallite there seems to be a very close similarity to present day species. There is an official "body" investigating how modern corals can be distinguised from non-agatized fossil corals for purpose of protecting endagered species from over collecting.

Doug - Thanks for that info. - I'll follow up on your suggestion.

Ken - I'm glad you found the diagram helpful. Things look so different when highly magnified and of course we are used to seeing coral in huge colonies rather than the minute, individual polyp and even less so an individual corallite.

Bruce

Hairyduck · Post by **Hairyduck** » Thu Mar 08, 2007 5:34 am

Hi Bruce, your diagram seems to have disappeared

I'd be interested to see the rest of the colony that it came off, I may even be able to give you some sort of ID as I have a reef tank full of SPS corals and have many books on identifying them, it'd be interesting to see how closely it compares with todays corals.

Kev

Bruce Williams · Post by **Bruce Williams** » Thu Mar 08, 2007 7:42 am

Kev - A warm welcome to the Forum. Thanks for pointing out the problem with the link. I've now changed the host to one I know to be reliable (although it costs £'s) so you should find it ok now - btw it's a VERY simple diagram.

My photos were taken from a very small piece of fossil coral - maybe 3cm X 2cm - I'll take a photo of the whole piece and provide a link to it later today.

Bruce

Bruce Williams · Post by **Bruce Williams** » Thu Mar 08, 2007 12:29 pm

Kev - Photo of the fossilised coral cab can be seen here.

http://www.tal-handaq.co.uk/fos_coral_cab.jpg

Not sure there's enough more of it to help much in identification, but would appreciate any help in narrowing it down. What I have found out is that colonial forms of rugose corals did not appear until end of Silurian and more likely age for this piece is Early Carboniferous thru Late Permian (say 250 - 350 mya).

Bruce

Hairyduck · Post by **Hairyduck** » Thu Mar 08, 2007 2:43 pm

It looks very similar, and it's scale is similar also, to specimins from the Galaxea genus, here's a picture of Galaxea fascicularis which bears some resemblance to it, there are several corals in this Genus that are of the same scale and polyp spread.

Skeleton:

]

and when it was alive

and a close up

Unfortantelt the skeleton came about after my whole tank wiped out whilst I was on holiday

Ken Ramos · Post by **Ken Ramos** » Thu Mar 08, 2007 4:06 pm

Hi Kev and welcome to the forums, good to have you here and I hope that you will enjoy all that the forums have to offer. I hate to be pushy right at the start but we need to stick to the forums criteria, which is, in this case, microscopy. Your images are great and well defined but images such as these belong in the Macro Forum side of the house. However just about every new member makes a mistake or two so don't be put off, we are used to it

You may want to familarize yourself with the sites guidelines to make things a bit easier.

Anyway Kev, as I said, it is great to have you aboard as a member and we look forward to seeing your posts and having you as a participant in the forums.

Bruce Williams · Post by **Bruce Williams** » Thu Mar 08, 2007 4:33 pm

Kev,

Those photos are just SO HELPFUL - thanks a million! Your pic1 of the corallite skeleton is so similar to my fossilised cab image it's amazing when you consider the hundreds of millions of years that separate the two corals. The pic also helps to make more sense of my fossil images too.

Pics 2 and 3 are very interesting and add greatly to the overall appreciation of the structures in the fossil images.

The generic name led me to this website showing a Galaxea sp. from the Miocene (between 7 and 23 mya). The septa count is within limits too. So I'm pretty sure that you have put me on the right track

Thanks again.
Bruce

Hairyduck · Post by **Hairyduck** » Fri Mar 09, 2007 1:37 am

Great stuff Bruce, glad I could be of some assistance!

Ken, I'll post links next time if that's more appropriate, my microscope only arrives next week so you'll have to wait for my microscope pics

Bruce Williams · Post by **Bruce Williams** » Sat Mar 10, 2007 2:31 am

Kev - Concerning identification - another factor (ex. Google) supporting Galaxea as genus is that your coral G. fascicularis is often imported from Indonesia (same general location as this fossil).

Bruce

Ken Ramos · Post by **Ken Ramos** » Sat Mar 10, 2007 4:56 am

Hairyduck said:

Ken, I'll post links next time if that's more appropriate, my microscope only arrives next week so you'll have to wait for my microscope pics

Links are fine Kev, use them myself from time to, to time

A new microscope eh? Oh boy!

Hairyduck · Post by **Hairyduck** » Sun Mar 11, 2007 11:16 am

Great stuff Bruce, I knew it was from Indonesia just forgot to tell you

, most corals that come into the UK are collected/maricultured in Indonesia

Ken: Yep I thought it was about time to get rid of my old chinese monocular that I've had for the last 20 years so I've just aquired myself a nice Olympus BHS trinocular from Ebay