I Think These Are Some Sort Of Trace Fossil? And Am Wondering What Exactly They Are Burrows? Trackways? And What May Have Made Them?

[claire01]

There are virtually no real fossils up at that level. I have to go dig those imprint? fossils back out of storage where I put them after I sort of gave up on the idea, but here is a photo I still had on my iPad:

*Edited to add a very crude drawing of the area. I don't have a stylus so this is my best attempt at a fingerpainting of the hunting spot:

Edited September 9, 2014 by claire01

[Auspex]

...I have found what looked to me like bird track imprints, but they were dismissed as not possible for my Cretaceous shallow sea environment....

Do you have images of these?

[claire01]

[tmaier]

I'm no expert on surface tracks, but I see two possible canidates on the image you provided.

#1 looks very much like a bird or reptile track, but notice that there are no other footprints contiguous with it, so either the animal had a very long stride or it is just by luck that it had this shape.

#2 Also looks vaguely like a track, but seems to be missing the toe imprints, so I would dismiss that also as a coincidence.

Conclusive proof of muddled tracks would be a series of them with a believable stride distance. Although I can't totally dismiss #1, I find it hard to accept.

[tmaier]

With the second image you provided I see two problems...

- There is only one print that looks like a footprint, meaning the creature was walking, and yet there seems to be no second footprint even though the rock seems long enough to catch the stride.

- The footprint has a round, deep pock mark as it's origin point, with no sign of a bird like reversed toe. This creature would not have been able to stand upright because there is no way to balance if all toes point forward.

So I totally dismiss this second one.

[Auspex]

Pretty suggestive in shape, but the matrix does not look like an emergent surface; too much deep turbation.

[claire01]

Well, I got right with them not being imprints once before, I'm sure I can do it again Thanks VERY much everyone for indulging me. Going back to the original subject of this thread...do y'all think those are those indeed burrows I posted a pic of on the previous page?

[tmaier]

I do... those are definitely feeding burrows in my opinion. Quite a collection, too.

[claire01]

I have many more! Thank you very much tmaier and everyone for your thoughtful responses and willingness to share your expertise. I sincerely appreciate it.

Edited September 9, 2014 by claire01

[Auspex]

...Going back to the original subject of this thread...do y'all think those are those indeed burrows I posted a pic of on the previous page?

Yes, I do, and nice ones! If you find the possible maker in one of them, it will be a strong Find of the Month candidate (so take plenty of 'before' pictures)!

[claire01]

Oh wow, thanks, Auspex! Will do

[tmaier]

... and you are right to be watching out for surface activity on these materials you are looking at. If you see more tracks, consider them carefully so you don't accidentally dismiss a real one.

[claire01]

I just had one more quick question: I was giving these another look and I noticed on the ends of most of these is a visible circle in the center that maybe someone will recognize or may be of help

[tmaier]

At first I was thinking coprolites (poop), but then notice how crystalline they are.

Anybody got any guesses? I've never seen anything like that.

(Hey, this spell checker has the word coprolite in it.)

[tmaier]

If the excrement decayed and created a void, the void could become filled with crystalline growth...

Just an idea...

[BobWill]

Siphuncle!!! Just kidding...I abandoned the idea of cephalopod right after I posted that

[Auspex]

All I can think of is that it is caused by mineral accretion during diagenesis.

[PFOOLEY]

...I noticed on the ends of most of these is a visible circle in the center that maybe someone will recognize or may be of help.

May they have something to do with ventilation?...just a thought.

As a burrow slowly fills with sediment, this last remaining tube of water passing through might crystallize.

Edited September 9, 2014 by PFOOLEY

[tmaier]

How about this idea. The first burrow is a large creature and that burrow fills in with sediment. A second creature comes along and follows the nutrient rich fecal trail of the first one, and that trail doesn't fill with sediment, it becomes a void. The void grows crystals.

Kind of long and complex theory, and thus more prone to failure...

[PFOOLEY]

Well I definitely agree with a void being filled with crystals.

[Auspex]

How about this idea. The first burrow is a large creature and that burrow fills in with sediment. A second creature comes along and follows the nutrient rich fecal trail of the first one, and that trail doesn't fill with sediment, it becomes a void. The void grows crystals.

Kind of long and complex theory, and thus more prone to failure...

<cough-cough> Occam's Razor <cough-cough>

[tmaier]

Ockum's razor is not a burrowing animal. I was thinking some form of annelid.

[Auspex]

Occam's Razor Clam?

[tmaier]

With the second image you provided I see two problems...

- There is only one print that looks like a footprint, meaning the creature was walking, and yet there seems to be no second footprint even though the rock seems long enough to catch the stride.

- The footprint has a round, deep pock mark as it's origin point, with no sign of a bird like reversed toe. This creature would not have been able to stand upright because there is no way to balance if all toes point forward.

So I totally dismiss this second one.

This is in reference to the bird-like tracks on the slabs shown in the previous post...

I'd like to retract my opinion that these are not bird-like prints due to the lack of a reversed toe. Claire pointed out to me that shore birds don't have that reversed toe and they often create a pock-mark right at the center of where the leg meets the toes. A look at tracks of modern shore birds and their toe structure shows this to be true.

Non-shore birds seem to have this reversed toe imprint. Shore birds are not likely to have it.

http://www.google.com/images?hl=en&q=tracks+of+shore+birds&gbv=1&sa=X&oi=image_result_group&ei=BTMQVLnVCYieyATy7oDoDQ&ved=0CBoQsAQ

So I reverse my opinion that these can't be bird tracks because they don't have the correct form. The only thing that would make these more convincing would be to have a series of tracks, instead of just the one imprint of each footprint. Claire might find this series of prints later, so I would hold onto this slab until more evidence is found.

Thanks for pointing that out to me, Claire.

[Auspex]

I have well over a thousand specimens of bird tracks, and so far have differentiated 28 distinct morphologies from the Green River Fm. alone.

Most shorebirds have a hallux, and some don't. Of those that do, an impression is not always made. Some are palmate or semi-palmate or unwebbed. Some leave distinct claw marks, many do not. The angle between the toes and between the hallux and centerline is another variable.