Dermal denticle dilemma

[cck]

Why are these denticles going in opposite directions? It’s got me baffled, but maybe it’s just ignorance.. any help is appreciated 

[minnbuckeye]

Very odd from my uneducated perspective. I will be interested in the explanation!!

[Rockwood]

It might be that they just fit next to each other this way at random. In other words. Why would they be going the same way ?

[cck]

My understanding is that they are a feature of the mid line of the animal… not a random feature … have you seen random dermal denticles in rays ? 

[Rockwood]

Do you see a ray ?

[cck]

Stingray..that’s what it’s from..is that not clear?

[Rockwood]

54 minutes ago, cck said:

Stingray..that’s what it’s from..is that not clear?

Again. Do you see a ray ? From implies the ray is not there any more. No ray. No arrangement.

[cck]

Please I asked a specific question about the fossil posted… 

[Rockwood]

49 minutes ago, cck said:

Please I asked a specific question about the fossil posted… 

Two denticles that are not attached to anything is what I see. I do not think that the original life position has been preserved. The relative positioning is a random positioning which occurred after the animal was long gone. It is a piece of a pile of pieces. They are not articulated.

[Al Dente]

This reminds me of shark teeth in jaws that point the wrong direction. I saw a paper that had a nice example of a Galeocerdo jaw with teeth pointing the wrong direction, but I can’t find that paper now. Here is a similar example from www.elasmo.com.

 

 

[Meganeura]

3 hours ago, Rockwood said:

Two denticles that are not attached to anything is what I see. I do not think that the original life position has been preserved. The relative positioning is a random positioning which occurred after the animal was long gone. It is a piece of a pile of pieces. They are not articulated.

While I understand what you’re saying - the denticles of a Ray aren’t just the little spine, they’re also the base the spine thing sits on, so it does appear that these are in fact articulated and not just 2 denticles in matrix 

[Rockwood]

26 minutes ago, Meganeura said:

- the denticles of a Ray aren’t just the little spine, they’re also the base the spine thing sits on,

Precisely. The base is what was in the body. The body was not preserved.  What proof is there that they were articulated in the living body and not a collection of bases that were dislocated and subsequently cemented in this position ?

[FranzBernhard]

8 minutes ago, Rockwood said:

What proof is there that they were articulated in the living body and not a collection of bases that were dislocated and subsequently cemented in this position?

@cck, please let us have a look at the back side of the specimen!
Franz Bernhard

[cck]

Thanks for the discussion. Here’s the back and one more of the front. I believe they are articulated.

[Rockwood]

Next question. Would they typically be articulated ? I never thought of them as forming a tiled surface.

[Meganeura]

23 minutes ago, Rockwood said:

Next question. Would they typically be articulated ? I never thought of them as forming a tiled surface.

That I agree with, I didn’t think they connected!

[cck]

I’ve seen doubles  before, but oriented the same direction. Here’s a screenshot from the gallery of one with a pathology… perhaps that is to blame? 

[cck]

Another example of multiples

[Rockwood]

2 minutes ago, cck said:

Another example of multiples

 

6 hours ago, Rockwood said:

It is a piece of a pile of pieces.

I think this tends to support my argument. 

[cck]

And they do appear in groups on modern rays and skates…perhaps someone else has another fossil example?

[Rockwood]

45 minutes ago, cck said:

And they do appear in groups on modern rays and skates

Can you point out a modern example ? The ones I see in an image search look to be relatively isolated from each other.

[cck]

Many examples in the field guide to the skates of the Canadian Atlantic… Rajella fyllae, Bathyraja bigelowi, Leucoraja erinacea… all have clusters of thorns on various parts

[Mahnmut]

Intriguing piece!

Although obviously not the same kind, this is what I bought under the name of " fossil ray denticle cluster from Florida"

It does look like in life-position to me. Would be grateful for any further information.

The squares are 5mm each. Sorry for bad lighting.

Best Regards

J

[Rockwood]

51 minutes ago, cck said:

Many examples in the field guide to the skates of the Canadian Atlantic… Rajella fyllae, Bathyraja bigelowi, Leucoraja erinacea… all have clusters of thorns on various parts

But if all that appear to be clusters were fused like this the fish would be unable to move its tail.

[cck]

Clusters are on the snout, behind the eyes, on the pectoral fins… depending on species