Carboniferous Arthropod?

[Omnomosaurus]

Evenin' all!

 

Am I going a little bit doolally, or is this impression a fossil?

 

It's situated between a couple of thin plant fossils either side, on a piece of siderite from Duckmantian Carboniferous deposits in North Wales, UK.

 

I've played with the lighting a bit to try and bring the details out....

 

 

It's not noticeable to the naked eye, but the photos seem to be showing up spines/protrusions in one area?

 

 

It's probably nothing, but worth a double check.

 

Cheers!

[Omnomosaurus]

It's shape matches quite well to this spider fossil:

 

 

Possible arthropod?

[Omnomosaurus]

Sooooo, nobody have any ideas on this one?

[Rockwood]

A little cleaver prep. work might convince me that it is a fossil of some creature with an exoskeleton. The texture of what is exposed leaves doubt though.

[Plantguy]

Interesting...does have some symmetry but you got me...I dont immediately recognize it either...good sized at 1cm+...

 

Does it look like further prep can expose anything as Rockwood was asking? 

 

Do the plants have the same carbonaceous (shiney black) looking type of remains/preservation as this object?  Do you have photo of all of them for comparison? 

 

I noticed some very small circular/elliptical areas on the left side...is that just my photo enhancement creating something and playing with my eyes? 

Got a tough one there. Might be worthy of bouncing off the local folks at the National Museum of Wales for their thoughts? 

 

Regards, Chris 

 

 

[Fossildude19]

I'm thinking mineral stain. I do not seeing any morphology consistent with arthropods.

 Reverse black and white: 

 

[hndmarshall]

could be a little jelly fish of some type look at the little darker T shape inside it

 

[Omnomosaurus]

1 hour ago, Rockwood said:

A little cleaver prep. work might convince me that it is a fossil of some creature with an exoskeleton. The texture of what is exposed leaves doubt though.

 

It's an impression from a split siderite nodule, so I'm not sure what prep I'd be able to do on this one? 

 

47 minutes ago, Plantguy said:

Interesting...does have some symmetry but you got me...I dont immediately recognize it either...good sized at 1cm+...

 

Does it look like further prep can expose anything as Rockwood was asking? 

 

Do the plants have the same carbonaceous (shiney black) looking type of remains/preservation as this object?  Do you have photo of all of them for comparison? 

 

I noticed some very small circular/elliptical areas on the left side...is that just my photo enhancement creating something and playing with my eyes? 

Got a tough one there. Might be worthy of bouncing off the local folks at the National Museum of Wales for their thoughts? 

 

Regards, Chris 

 

 

 

Thanks, Chris!

 

There is a lot of plant material from this locality, and it tends to vary; I've found plenty of carbonaceous remains, and other forms of preservation in the past.

 

Here's a small example:

 

 

And here are some leaves and a possible 3D stigmaria specimen from the same trip that I found the "thing":

 

 

Now you mention it, that does look like a little elliptical area in the photo. Hadn't noticed that previously.

 

If there's any consensus on this being an actual fossil (I'm still not 100% convinced myself), then I may fire off an email to the NMoW.

 

24 minutes ago, Fossildude19 said:

I'm thinking mineral stain. I do not seeing any morphology consistent with arthropods.

 Reverse black and white: 

 

 

Ooh, good photo! My first thought was possible stain, but some of the features started to look suspicious after I stared at it for a bit too long.

 

Here are a couple more face-on shots (one with some enhancement):

 

 

You can make out the plant impressions either side here too.

 

19 minutes ago, hndmarshall said:

could be a little jelly fish of some type look at the little darker T shape inside it

 

 

I'm not too familiar with jellyfish fossils....to my knowledge, none have been discovered from this area previously, but it's a good suggestion!

[Rockwood]

21 minutes ago, Omnomosaurus said:

an impression

Could you define that more precisely ?

If you are suggesting it is a mold fossil I just don't think so.

[Plantguy]

Thanks for the additional photos. That staining/type of preservation does seem to be a bit different than those from most of the plant material. I suppose it could be just staining but it seems to be something more...just my opinion....Do both sides look identical? 

 

Just PM'd you with possible museum contact info...

 

Regards, Chris 

[hndmarshall]

enhanced photo have arrows to suspicious parts one the definitely interesting inner marking and second the ringlike rim?...still looks jelly to me

[Omnomosaurus]

18 minutes ago, Rockwood said:

Could you define that more precisely ?

If you are suggesting it is a mold fossil I just don't think so.

 

Sorry, I wasn't particularly specific there, was I!

 

The "impression" (not sure what better to describe it as) is almost two-dimensional. There is a slight raising/difference in texture compared to the surrounding rock.

 

The area circled in red has an even greater raised texture than the rest of the thing. The thin protusion-like shapes circled in blue are most like stains (I still think they might point to something):

 

 

12 minutes ago, Plantguy said:

Thanks for the additional photos. That staining/type of preservation does seem to be a bit different than those from most of the plant material. I suppose it could be just staining but it seems to be something more...just my opinion....Do both sides look identical? 

 

Just PM'd you with possible museum contact info...

 

Regards, Chris 

 

Thanks very much for that contact info!

 

It is a tough call, isn't it?! I'm being dense here, not sure what you mean about "both sides"?

 

2 minutes ago, hndmarshall said:

enhanced photo have arrows to suspicious parts one the definitely interesting inner marking and second the ringlike rim?...still looks jelly to me

 

I can definitely see the ring-like markings on the inside of the "dome". It does appear that there might be a rim where your lower arrow is too - that lower rim is on the edge of where the "impression" is more raised/rough in texture.

[connorp]

My vote goes to mineral stain, probably an iron oxide. It's not a jellyfish, the morphology isn't really right. There is also no evidence of segmentation, so unlikely an arthropod.

[Rockwood]

1 hour ago, Omnomosaurus said:

(not sure what better to describe it as)

Precisely the distinction between being a fossil and not being a fossil ?

[Rockwood]

A better sense of just how the plants are preserved might be helpful ?

[Omnomosaurus]

3 hours ago, connorp said:

My vote goes to mineral stain, probably an iron oxide. It's not a jellyfish, the morphology isn't really right. There is also no evidence of segmentation, so unlikely an arthropod.

 

Thanks, connorp. I've been thinking it was probably nothing more than a stain, but that little bit of doubt has kept me spitballing, just on the off-chance that I shouldn't throw it away.

 

1 hour ago, Rockwood said:

Precisely the distinction between being a fossil and not being a fossil ?

 

As I'm more comfortable dealing with theropod dentition, I think in this case it's more down to a terminology-fail on my part.  

 

1 hour ago, Rockwood said:

A better sense of just how the plants are preserved might be helpful ?

 

If it helps, this is a generalised sequence of the geology from the site:

 

The specimen in question and plant fossils originated from this exact sequence, but were collected from scattered nearby surface-level locations, as part of the fossil bed was heavily disturbed by road construction.

 

The "fine-grained, iron infiltrated sandstone" would fit well with the iron oxide mineral stain theory?

[paleoflor]

Can you post a picture of the specimen's edge? I would like to have a look along the surface and see the rock's face oriented towards the bottom in the current photographs. Anything visible where the mystery shape meets the rock edge?

[Rockwood]

6 hours ago, Omnomosaurus said:

The "fine-grained, iron infiltrated sandstone" would fit well with the iron oxide mineral stain theory?

Agreed.

The plants being mold fossils would also tend to make me think a body fossil would be absent or have a texture that was more distinct from the matrix.

[Omnomosaurus]

8 hours ago, paleoflor said:

Can you post a picture of the specimen's edge? I would like to have a look along the surface and see the rock's face oriented towards the bottom in the current photographs. Anything visible where the mystery shape meets the rock edge?

 

Sure thing, it's quite difficult to see, but there is I'd say roughly a .05 to 1mm thickness to the stain where it meets the rock.

 

This photo is with the previous front-face of the rock orientated to the bottom, with the previous bottom oriented forwards. I've circled the edge of the stain in red:

 

 

Here are a couple more from different angles:

 

 

7 hours ago, Rockwood said:

Agreed.

The plants being mold fossils would also tend to make me think a body fossil would be absent or have a texture that was more distinct from the matrix.

 

It would be safe to assume so. Though there is an abundance of plant material, evidence of fauna at the site is very scarce, so I sadly don't have a wide enough experience with animal preservation from this site to say anything with certainty.

 

To my knowledge, there have been a very small number of shrimp and a single trilobite fossil discovered at the locality, though I haven't seen these in person. 

[Rockwood]

7 minutes ago, Omnomosaurus said:

a single trilobite fossil

Maybe a hypostome ? The texture would seem a better fit.

[piranha]

Most Pennsylvanian trilobites are approximately the same size of this object .. definitely not a hypostome.

[Rockwood]

[abyssunder]

To be honest, I'm not seeing fossils, but the mineral features might be there.  Maybe it's something close to the formation of the Liesegang rings?

[paleoflor]

Thanks for the additional photographs. Based on all the images, I am in the mineral-camp. The rock texture (grains) also appears to continue underneath the darker coloured areas, suggesting it is a relatively thin film. Concentric patterns can be the result of the interplay between mass transport via pore fluids and mineral growth kinetics (intermediate between dendritic and euhedral growth forms).