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

[tmaier]

I don't know that much about vertebrate fossil trace tracks. Most of what I know is from tracking while hunting.

Grouse and pheasant fear me...

[claire01]

No worries y'all, I promise I have moved on as far as the bird track goes Tom was just responding to a pm I had sent him with an image showing that the lack of a "reversed toe" in a bird track imprint doesn't necessarily preclude it from being one. Thanks again everyone!

[tmaier]

... and you should not be apologetic about correcting me, Claire.

I've worked in many areas of scientific and engineering research over many decades and you learn to follow the data and not my emotions. When enough data is presented to sway an argument, I will quickly abandon my opinion and join the other side. I don't follow what I WANT to believe and I don't follow people, I just follow what the data says. It's like juggling the coefficients of a probability equation to find the answer, or the probability of an "answer" being right.

... and that has worked very well for me for many decades.

Most of my experience is in physics, chemistry, electronics, and programming. So don't take me too seriously for paleontology or biology, those are my hobbies.

And never accept that an "expert" is always right. Question authority. I also taught college for some years, and when I had students who questioned my presentation I knew that person had the ability to go far.

[claire01]

Sorry to revisit this, but I have been looking at cross section images of cephalopods and the crystalline circle at the ends of these really does have me thinking it might be a siphuncle. Could these somehow be some sort of actinocerid cephalopod? Or some other living creature rather than a burrow? I don't want to destroy them looking for something inside if they aren't burrows after all.

[tmaier]

Notice that the crystalline circle is asymmetrically located in the burrow, and is not in the same place between the ones that you show. An anatomical feature like a siphuncle would not be wandering around like that. They are two independent features.

[caldigger]

Tmaier, I wouldn't exactly call two lines on a page "a long and complex theory". lol!

[BobWill]

. Could these somehow be some sort of actinocerid cephalopod?

The Actinocerids were Paleozoic so too old for your Cretaceous site. Also tmaier is correct about the location of the sipuncle. It is always central in the nautiloids and ventral in ammonites. After seeing your newer photos I agree about burrows. Ammonites would not have the irregular bumps or branching seen on those.

[claire01]

Okay, thanks you guys. I just had a moment of doubt when I started to clean one up a little

[claire01]

I saw this post today and it has me wondering if mine are protovirgularia: http://www.thefossilforum.com/index.php?/topic/49536-late-ordovician-trace-fossil/

I know it's a different time period, but it shouldn't matter in this instance, should it? I also saw this paper online: http://paleoneomed.blogspot.com/2009/02/protovirgularia-pistas-fosiles-de.html

And while my Spanish isn't very good, I think I get the gist of it and the description and image seem to fit my trace fossils. Also, I basically destroyed one today (for science) and there was nothing inside. So maybe these are just bivalve locomotion trace fossils? There are lots of bivalve fossils here.

[tmaier]

Here's a translation of that spanish website

In this paper we describe for the first time in the Neogene Protovirgularia of the Iberian Peninsula, particularly in langhienses marine sediments (Middle Miocene) of the Vallès-Penedès basin. This ichnogenus designated tracks generated by the movement of bivalve nuculoideos through the sediment. These molluscs burrow using the well-known mechanism of "double anchor". The animal starts the process intruding your foot in the sediment making use of the shell as a first "anchor" that is fixed on the substrate. Subsequently expands the foot (the second "anchor") so that you can stretch your body forward with the shell. In the case of nuculoideos (as in arcáceos and scaphopods) the foot is forked so that fixation is achieved by the separation of its two terminal halves. The result of this behavior is the formation of a track with a herringbone structure.

The particularity of the material in this paper is that in some cases these tracks are preserved as full relief at the base of the pin structure on a track apparently meniscada probably left by the passage of the animal body appears is identified. Depending on the position of the producer in relation to the interface sand / mud, conservation varies substantially what has led us to characterize 3 distinct morphotypes.

The presentation that you can see below was exhibited at the International Congress on Bivalves Bivalvia 2006, which took place just over two years ago organized by the Universitat Autònoma de Bellaterra. The article can be downloaded freely shortly on the website of the Spanish Society of Paleontology.

Your burrow does resemble that one a bit. So it might be a clam pulling its way through the sediment.

[claire01]

Thanks for the translation! I wanted to show exactly what I found inside for anyone interested.

I chose one that had the crystalline tube end showing on one end but ended in a sort of bulbous shape at the other in the hope that the fatter end was a resting place for whatever might be inside. There were no obvious signs anywhere on the outside that indicated a good starting point so I just picked a spot and started scraping. After hours of this and still not seeing anything, I decided on a more drastic approach and took a hammer to it I wanted to follow that crystalline tube all the way to its end to make absolutely sure there was nothing there. Here's what I found:

[tmaier]

This burrow isn't the clam type that we were discussing in the previous post.

Notice that at the bulbous end of this one the crystalline tube wanders out of the bulb end and leaves the burrow. That is looking like an annelid trail, a worm, that was following the burrow and then left it to continue on to somewhere else.

[claire01]

I was just looking annelid fossils up! I'm afraid I scraped away any distinguishing features on one side, but I will try to be a little more delicate and expose another portion of what I am now also thinking is a worm !

*Edited to say:

Sorry, I just retread your post and realize you still think its a track, not the worm itself. I thought maybe it was the actual worm because the tube seems to widen out in places there at the bulbous end and it's got a slightly different look than the rest of exposed portions of the tube. Not as crystaline.

**also, there was no obvious exit. I suppose I could have missed it, but I don't think so. Here is a picture of this one before I started scraping.

I originally thought the tube was going to go straight back toward the back end of the fossil so that's what I scraped away, but was surprised to find it actually made a curve just after that break.

I'm in a good 1/8 to 1/4 inch from the original outside of the rock.

Edited September 16, 2014 by claire01

[tmaier]

You are unlikely to find the worm, but it doesn't hurt to look.