Could this be a small dinosaur or an early mammal track?

[MS3]

Hi Everyone,

 

I'm very excited to have found and have an opportunity to post on this forum.

 

The rock with a potential fossil was found by my six year old son while we were hiking along a riverbed (Paint Branch watershed) within greater Silver Spring, Maryland area.  The rock was in a shallow stream.  My son was pulling me by the sleeve to show me a "fox track".  He loves nature and always draws my attention to various tracks and animal bones on the ground so I didn't think much of it at first until I realized this time the track was in stone instead of the usual sand/mud.  I'm wondering if it could be an early mammal, a small dinosaur track, or some other type of fossil?

 

I attached several photos that I hope are helpful and show the rock with the potential footprint/track form various distances.  One of the photos is showing the size (about 1.5 inches or 3.8 cm long), and one is a close-up showing what seems like a "thumb" imprint with a claw and even something that looks like a thenar/pad area of the bottom of hand/foot.  The bottom of each of the "toes" appears rounded, as one would see on animal tracks- this cannot be seen in the photos.

 

Any help is greatly appreciated.

 

 

 

 

 

 

Edited May 1, 2021 by MS3

[Lone Hunter]

I think it's just geological and coincidental but wait for expert opinion.

[Rockwood]

Sorry. I see the resemblance to a track, but I'm quite certain it is not. Several details about the appearance and position on the rock surface don't quite fit.

[Fossildude19]

This doesn't look like the correct sedimentary rock for footprints.

My vote is for geological.

[val horn]

as you may know multiple foot prints have been found in paint branch creek., however this creek has also been  treated by the government to control erosion by reshaping banks and importing stones to stabilize the banks in areas, making finding anything less likely.  This does not look like a foot print to me ( and I have several pseudo tracks in my own collection).   Look for tracks on flatish surfaces that would have been formed in clay and mud at the edges of water when they were laid down.  Unfortunately I am not the expert, and am still looking for my first local track.  There are people at the Laurel dinosaur park who could help when it reopens.

[Myrmica]

I agree that this is unlikely to be a real footprint.  As val horl wrote, we would expect tracks to be preserved in rocks that are relatively soft, and your specimen appears to be something hard that has weathered out.

[Rockwood]

There are many factors that affect the hardness of rock. It would seem difficult to use as an indicator. 

[jpc]

I find not-so-obvious fossilized footprints tough to buy into unless there is a series of them lined up in a trackway.  This one is one such... I don't think it is a track.  

[ClearLake]

I see what you are seeing, and it certainly has the general look of a paw print, but I'm thinking the rock is not right.

 

Maybe I am not interpreting the pictures correctly, but in the last two I believe I see crystalline texture with light and dark minerals.  This might indicate an igneous or metamorphic rock, rather than a sedimentary.  I'm not even sure if that is feasible where you found this.  If that is the case, you can certainly rule out tracks or footprints.  Maybe if the rock were cleaned up some it might be easier to tell, it can be very difficult with just a few pictures of a small hand sample.

[MS3]

Thank you all who have replied thus far.  Based on what I hear, the rock doesn't seem to be of the correct type.  I have found and broken a rock of similar appearance- photo attached.  I think it may be either a sandstone, a quartzite, or a sandstone turning to quartzite.  When broken, the rock was grainy and crumbly and seems to break around the crystals rather than through them which perhaps may mean it's more sedimentary than metamorphic(??) 

 

When attempting to power-wash the back side of the original stone, it started to flake off so I stopped the process, concluding that the stone is not as dense as it appears to be.  It is certainly much less dense than quartzite I've encountered in the area.  As far as fossils in the area go, I read that they are mostly found in the rocks of the so-called Potomac Group (Cretaceous) which, among other, is defined as "...interbedded quartzose gravels, protoquartzitic to orthoquartzitic argillaceous sands..." and, specifically for Patuxent Formation (of the Potomac Group): "...white or light grey to orange-brown moderately sorted, cross-bedded, argillaceous, angular sands and subrounded quartz gravels..."

 

I was hoping someone would further comment on the following:

 

• If this rock is a sandstone, could this be a track preserved in sandstone?

 

• While it is generally thought that metamorphic rocks don't retain fossils due to temperature and pressure changes, how about in cases where the rock undergoes a slight       metamorphic change?  In this case, would it be possible for the track to have been preserved in sandstone which then underwent a light metamorphic change that could still preserve a fossil?

Thank you very much for your assistance.

[Plantguy]

Neat curious find--welcome to the forum! 

 

Your son has very good eyes for catching something that subtle. I think he has a tremendous future using those skills--tell him nice job for wondering!

But I'm afraid I'm going to agree though with the others that its not a track although it does kind of look that way. I dont think its sandstone either. 

 

Here's one of your photos and I rotated it and zoomed in a bit. I dont know the geology of your area and havent collected there so this is up for validation by others here. 

To me it appears you are looking at an area in the rock where some minerals/grains have simply fallen out. Note the sharp edges where I've got the arrows.  The one looks particularly rectangular so I dont know if it shows the edge of a quartz crystal (which are usually hexagonal) or some other mineralogic impurity that has a rectangular mineral form that is now gone. 

 

Your other specimen appears to be the same type of rock...Nice weathered rind with staining and looks remineralized with many sharp quartz crystals/facets. I say its weathered quartzite and no longer of granitic origin/or sandstone. 

 

Yes there are fossils found occasionally in slightly metamorphosed rocks. I dont think this is the case for your example. 

 

This may unintentionally cloud the issue as its not from your locale but for comparative purposes here is a very fine grained Permian-aged sandstone from Arizona that I have that shows a track/subtle trackway.  

Continued hunting success! Thanks for showing us the find! 

Regards, Chris 

 

[Rockwood]

Sandstone is very capable of preserving tracks. That is not the problem.

Grain size can appear to be the opposite of what actually was deposited. Smaller particles coalesce in the lithification process.

The more important aspect is the nature of the particles which cover the track. Plate shaped minerals which align to form a bedding plain are usually necessary to allow the track to be exposed on a surface. That is where the angular look of the track becomes problematic. Without the indication of the right sedimentary context, or additional tracks in the expected alignment there is little to base a track identification on. 

[val horn]

You may want to check these out,  referring to dino tracks found in Maryland.

 

Spectacular dinosaur stomping grounds discovered just ...https://www.washingtonpost.com › news › 2018/01/31
 

MNCPPC, MD - Parks & Recreationhttp://pgparks.com › Blog
 

[MS3]

Thank you all - this was very, very helpful!