Sea urchins, sand dollars and brachiopods, Aireys Inlet, Victoria, Australia

[Oli_fossil]

Hi all,

 

See attached - most of these are 5-10mm in size (cm/mm ruler in background). Found at/near base of sandstone cliffs near Aireys Inlet, Victoria, Australia. I have previously found Lovenia fossils in the area (and found a couple more today), but these are much smaller and flatter - more like sand dollars?

 

IDs appreciated, and also suggestions re further cleaning - I just soaked them in water (~30min) and tried to remove loose material, but haven't done anything further. Would it be worth soaking/cleaning them further to try to remove more matrix?

 

Also, do you think the small spines/tripods in 2a/2b/23c are the original spines of the sea urchin?

 

I think 4 is probably the top lid of a similar brachiopod to 3/3a - does that seem reasonable?

 

Cheers & thanks in advance,

Oli

Edited January 31 by Oli_fossil

[Yoda]

@Oli_fossil

 

Nice finds 

[Coco]

I’m not sure they’re sea urchin spines. Indeed, this type of sea urchin has "silks", which is comparable to the hair of pigs, that is to say very fine and very flexible. These seem too thick.

 

That said, I would like to see a closer look of photo 2B, from the article to the right of the three-pointed element.

 

Coco

[Oli_fossil]

Thanks! The thinnest "spine" in 2b is I would estimate ~0.1mm thick - the entire urchin in 2x is ~13mm wide. Is that too thick? What do you think the three-pointed things are? I will try taking a close-up of the region you suggest tomorrow - I am just soaking them in water overnight to see if I can clean them up a little more.

 

Also, the urchins here are mostly ~2mm thick at maximum, if that helps.

[Coco]

According to your rule in the first photo, the sea urchin measures 8 mm. I did not understand if besides all your sea urchins are of the same species: the 1st look very round while the last seem more oval.

 

For the thorn, I rely on its proportion compared to the sea urchin. I have often seen "silks" on current sea urchins and it is very very fine.

 

For the 3-point element, I don’t know what it is.

 

Coco

[Oli_fossil]

Oh sorry - the numbers refer to individual specimens - so 1/1a are the same specimen, 2/2a/2b/2c are the same specimen, etc. So urchin 1 is ~8mm, whereas urchin 2 is ~13mm. I am not sure if they are all the same species or not - they look a but different to me. #1 has very thin edges, whereas #2 is more rounded at the edge.

[Coco]

I don’t really see a difference between 1 and 2. I was comparing 1 - 2 with 5 and 6.

 

I don’t have any austraulian sea urchins that look like this in my collection, I doubt that I’m of much help. But to help identify them by other more experts, we need to see where the periproct (small hole for the anus) is located on the lower part.

 

We see well the peristom (the mouth) in the center of the underside. The periproct can be located near the peristom, on the edge of the sea urchins or anywhere between these two parts, but in any case necessarily visible from below.

 

Here is a recent sea urchin with a part of its silks

 

 

Coco

Edited January 31 by Coco

[Oli_fossil]

Interesting thanks! 1 and 2 are visually quite distinct, but you probably need a side view to appreciate it. 1 has tapered, very thin edges, whereas 2 is even thickness, with rounded edges. Looking up diagrams of Lovenia, which I am more familiar with, I now understand what you mean about the periproct - thanks!

 

In 1a, the periproct is visible at the SSW position, and matches the underside position that lacks evidence of thorn attachment.

 

in 2, the periproct is harder to see, but I think is in the NE position (the darker patch corresponds to a small depression.

 

In 5a, the periproct is directly East, near the edge.

 

In 6, it is directly north, also near the edge of the urchin.
 

I'll try to take some pictures of the side views, if that helps?

[Coco]

Thank you for all this interesting information.

 

On 1, are you talking about the broken area? The perirocte must be represented by a small regular hole with well-defined edges.

 

Same for the 2, I do not see a clear hole, but it is difficult on the photos.

 

OK for 5a and 6. I had not paid attention but the perirocte and clearly visible on the upper part. Both seem to be of the same species.

 

In addition, for these two, the 4 holes on the top (gonopores) will help to find the genre, because some have 5.

 

As for profile views, I think they are not all at the same stage of erosion. I don’t know if it helps, but we’ll only know when we see the pictures

 

Coco

[Oli_fossil]

Here are some more pictures:

 

9824: Shows same specimen as 2 in previous post, but with light better highlighting the putative periproct at the SSW position.

 

9814: Shows four individuals that I believe are the same species as 1, with the periproct at the edge, facing down.

 

9819: profile view of individual previously labeled as 2.

 

9821: profile views of the four individuals in 9814.

[Oli_fossil]

Also somewhat unrelated, but found this beautiful sea urchin spine in the same location - ~5mm thick with beautiful patterning on the surface

 

[Coco]

9824 : I think I see the periroct, at the end of the small crack. Right ?

 

9814 : How old is the sediment they were found in ? They remind me of a small species found in department 44 in France, Lutetian [Proescutella caillaudi (Cotteau, 1861)]. They are very fine like this. You will notice that their periproct is really on the margin of the sea urchin, while for 9824 it is a little behind. Those four are thinner than 9824, so I think they’re two different species.

 

In my opinion, the spine comes from a regular sea urchin (round globular).

 

Coco

Edited January 31 by Coco

[Oli_fossil]

2 hours ago, Coco said:

9824 : I think I see the periroct, at the end of the small crack. Right ?

Yes exactly!

 

2 hours ago, Coco said:

9814 : How old is the sediment they were found in ? They remind me of a small species found in department 44 in France, Lutetian [Proescutella caillaudi (Cotteau, 1861)]. They are very fine like this. You will notice that their periproct is really on the margin of the sea urchin, while for 9824 it is a little behind. Those four are thinner than 9824, so I think they’re two different species.

Estimated ~20-25Mya

 

Thanks!

 

Just found another lovely specimen similar but not identical to 6 (similar but more elongated), along with this beautiful little thing, maybe a foram?

 

These last ones were found in freshly eroded material on a sheltered (under sandstone overhang) platform above the high tide line, so I would estimate also ~20-25Mya for these. The little columnar thing is ~2-2.5mm in diameter (maybe a columnar crinoid?).

Edited February 1 by Oli_fossil

[oyo]

I think that last specimen you illustrate is a fragment of a coral from the Isididae family.

[Oli_fossil]

Thanks @oyo - yes looks reminiscent (though smaller) to the calicular structures of deep sea corals described here (Fig 14.1): 

[oyo]

You have chosen an example with a septal organization (Plan Pourtales) different from that of the Isididae family. Not exactly what your specimen shows.
In any case you have a beautiful coral there, congratulations on your find.
Greetings.

[Oli_fossil]

Thanks - yes I couldn't find a comparable picture of Isididae to compare with but I trust your expertise! Thank you for the ID