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Any Ideas - Blastoids?


Rick_Jo

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Does anyone know what this is?

These small fossils (size 7-10mm) are from the Braxton Formation in the Maitland Group based of the Sydney Basin somewhere during the mid Permian.

The formation is marine, below wave base and the majority of the fossils found are brachiopods and flourishing bryozoans.

I was fortunate enough to visit the site on the weekend and am currently going through my fossil finds photographing and ID-ing.

I have not seen this before.

post-8539-0-53761400-1376638427_thumb.jpg

post-8539-0-13679800-1376638441_thumb.jpg

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They are an odd shape, aren't they?

To me, they look like misshapen crinoid columnals.

Weird.

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Ya, that's what I'm thinking as well.
Here's why...

* grooves on outer end of each one look like the crenella that help the individual columnals stay in place on the crinoid's column
* dot/point/knob in the very middle of each one seems like the ossicle's lumen which, together, make up the crinoid's axial canal

The main thing that throws us off is the fact that, for the most part, the individual ossicles of a crinoid column are usually circular, whereas these (if that's what they are) are oval. Given the fact that all of the pieces are oval, individually, I'm inclined to think that they were so in life as well (or at lesat that somethig happened to the crinoid immediately prior to final burial).

It seems like, if it were a normal-shapped column (with circular ossicles), whatever pressure came upon them would have squished them all in the same direction, and they'd all be arranged similarly, but they are all as if they were oval prior to burial here, by the way they are all sitting in different directions/orientations.

If anyone has a good explanation for how they could all get 'squished' like this (or if you happen to know iof a species that grew oval-shaped columnals), please do tell.

.

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"Being genetically cursed with an almost inhuman sense of curiosity and wonder, I'm hard-wired to investigate even the most unlikely, uninteresting (to others anyway) and irrelevant details; often asking hypothetical questions from many angles in an attempt to understand something more thoroughly."

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I agree ...

Similar to a Platycrinites saffordi crinoid stem segment

Link

I agree with Indy. The oblong shape allows the "stem" to spiral.

Doh, I missed both of those posts because I was still typing. :lol:

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scale in avatar is millimeters

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Come visit Sandi, the 'Fossil Journey Cruiser'

____________________

WIPS (the Western Interior Paleontological Society - http://www.westernpaleo.org)

____________________

"Being genetically cursed with an almost inhuman sense of curiosity and wonder, I'm hard-wired to investigate even the most unlikely, uninteresting (to others anyway) and irrelevant details; often asking hypothetical questions from many angles in an attempt to understand something more thoroughly."

-- Mr. Edonihce

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I've come across similar crinoid ossicles in the Brigantian (U. Mississippian) in northern England - I've mislaid the specimen :( but here's a pic, the ossicle is about 5mm across the long axis. Sorry, no name for it!

post-4556-0-54862900-1376663885_thumb.jpg

Tarquin

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I certainly don't have a better idea than crinoid but can anyone see crenella groves on both sides of any of those? The groves seem to curve around the ends of the ovals but I'm unable to see any with groves going down the opposite side. This could just be a trick of the light or angle of the photo...

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Not sure. We find fossiliferous plates from the Tournasian with similar type shapes. Sometimes blastoids in the matrix. The Blastoids are not studied (they aren't in most places) but are similar to 'Schizoblastus'. This blastoids type extends into the Permian.

Anyways it looks a bit like a side plate from a disarticulated schizoblastus-type blastoid. All speculation.

If this is something from the Echinodermata it should be calcite and the calcite crystal surface should be reflective if wetted and held at a horizontal angle to the light..

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Although these crinoid ossicles have not been officially recorded in the Branxton Formation they are described from the lateral eqiuvalent Berry Siltstone. Attached are some examples of Neocamptocrinus for comparison. The specialist on this material has suggested Neocamptocrinus bundanoonensis to be the likely species for the posted examples. Congrats on a great discovery!

 

Neocamptocrinus.jpg

 

Willink, R.J. (1980)

A new coiled-stemmed camerate crinoid from the Permian of eastern Australia.

Journal of Paleontology, 54(1):15-34

 

 

 

image.png.a84de26dad44fb03836a743755df237c.png

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Great find and ID! So it wasn't a trick of the light. Now I'm very curious to know why grooves were not needed on both sides. It doesn't seem likely they would be worn off with such regularity so they must have grown that way :unsure:

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On 8/16/2013 at 0:24 PM, BobWill said:

Great find and ID! So it wasn't a trick of the light. Now I'm very curious to know why grooves were not needed on both sides. It doesn't seem likely they would be worn off with such regularity so they must have grown that way :unsure:

 

 

According to the paper:

 

"For convenience the side of the stem facing the axis of coiling will be termed the inner side, and that facing away from the axis, the outer side. Columnar articular facets consist of: 1) a fulcral ridge oriented parallel to the long axis of the facet; 2) a very small (<1 mm diameter) circular lumen, the external expression of an axial canal, located medially on the fulcral ridge; 3) two shallow, semi-circular areolar areas (bifascial fields), one on either side of the fulcral ridge; and 4) a crenularium along the inner facet perimeter whose culmina are closely spaced, moderately high and vary in length according to position."

 

Neocamptocrinus Morphology.jpg

 

 

 

image.png.a84de26dad44fb03836a743755df237c.png

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My take = coiled-stemmed crinoids developed the coiling tendency as a means of helping them wrap around another object.

Simple example with our own bodies...
If you put your two hands together with the fingers interlocking (um....the traditional 'prayer' pose), it is still possible to move the proximal ends of your hands side to side, whereas, for the most part, the portion of the hands from the start of the fingers on out are sort of locked in place. If the 'free' end of the hand was then connected to a locked end of another, there could be a very flexible structure, even though it were still a stack of hands connected by a central axis.

I don't know if that's really what they were trying to say there or not, but it makes sense to me.

What I want to know is how the crenulated sides are organized. Is it always on the same side, so that one entire hemisphere of the column is like this, or does it alternate from one side to the other from one columnal to the next?

It would seem to result in a more flexible structure, overall, if it was alternating. Otherwise, it would seem to only allow the column to flex in one plane.

Don't mind me.....I'm just thinking out loud....

.

____________________

scale in avatar is millimeters

____________________

Come visit Sandi, the 'Fossil Journey Cruiser'

____________________

WIPS (the Western Interior Paleontological Society - http://www.westernpaleo.org)

____________________

"Being genetically cursed with an almost inhuman sense of curiosity and wonder, I'm hard-wired to investigate even the most unlikely, uninteresting (to others anyway) and irrelevant details; often asking hypothetical questions from many angles in an attempt to understand something more thoroughly."

-- Mr. Edonihce

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Thank you to everyone for helping me solve this, I have learnt much about crinoids and ossicles in the process.

If anyone is interested in learning more about the 'Permian fossils and palaeoenvironments of the northern Sydney Basin' I have included a link to an interesting publication. I read it before visiting the site and should have investigated it further as it does mention crinoids such as Neocamptocrinus sp., I was always under the impression that crinoid ossicles where round, not anymore.

thanks again

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Thank you to everyone for helping me solve this, I have learnt much about crinoids and ossicles in the process.

If anyone is interested in learning more about the 'Permian fossils and palaeoenvironments of the northern Sydney Basin' I have included a link to an interesting publication. I read it before visiting the site and should have investigated it further as it does mention crinoids such as Neocamptocrinus sp., I was always under the impression that crinoid ossicles where round, not anymore.

thanks again

Most crinoid stems are round...

however some have different shapes.

Flash from the Past (Show Us Your Fossils)
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