More Tracks from the Patuxent Formation of MD!

[patelinho7]

Hi everyone! I have some unexpected footprint-y finds to share . Back in June, June 1st to be exact, I visited the old locality where I found my first dinosaur track which ultimately led me to join this forum, linked below. This is a stream locality in Maryland close to DC that belongs to the Early Cretaceous Patuxent Formation of the Potomac Group.

 

 

I have returned to this locality on occasion when I am in the area. It is very unproductive nowadays. Even back when I found that track, I got very lucky. The site has a limited exposure along a creek that has been reduced due to development. The stream has also significantly changed, covering the beaches where slabs of rock could be found, often bearing tracks. Nevertheless, it was the first Mesozoic locality I ever searched on my own and the site of one of my proudest finds. I occasionally visit it to have lunch after volunteering at Dinosaur Park, where I enjoy some time in a pretty location, as well as beside a memorable locality of sorts. On this day in June, I did just that. However, old habits die hard, and despite not planning to collect, I couldn't help but look around a bit on the limited beach as I enjoyed my sandwich.

 

It was a beautiful early summer day, one of the last ones before it got really hot here on the East Coast. We are finally getting some storms today, though! After just a few minutes of looking around, I identified three possible specimens. One was the cycadeoid fossil I posted in Fossil ID a while back.

I will take a minute to mention that I finally got my items IDed by Dr. Rob Weems last week (he helped me with my old track). I meet with him on occasion and I brought the items from this day with me when I met with him. He confirmed this specimen to be a cycadeoid bark cast.

 

Anyway, I found two other items nearby the plant fossil. Both looked like possible tracks, but I was honestly unsure. The track-collecting game is very difficult, I must say, at least in the Patuxent. So much of the rocks are very vague and difficult to interpret, but very frequently are indeed tracks as the depositional environment was fantastic for the preservation of tracks. You need a lot of imagination to agree you have found a track, at the risk of much pareidolia. The best thing you can do is to show it to a scientist who has more experience reading tracks. In fact, because of the difficulty of track identification at this site, I rarely attempt at explicitly searching for tracks on rocks. I also never attempt to ID them in the field. Instead, I search for anomalous structures on rocks. With experience, you can begin to differentiate geologic sedimentary structures from those that may be created by organisms. Honestly, I use this technique in much of my collecting. Don't look for fossils, look for things that are odd or cannot be explained from an elementary understanding of geology. You notice a lot more when you're not narrowing your vision to one specific area. I find strange specimens that match this description and bag them for later. When I get home, I clean them and complete a more investigative analysis, eventually sending photos to others to get additional opinions. Because so much is left to imagination with track interpretation, I don't like posting them for ID or in a trip report right away. Either I lose myself to pareidolia, or sometimes real tracks could be voted geologic because it's hard to see from a few photos. 

 

I digress. I collected the two possible tracks and thought about returning to my car. However, the weather was nice and the water was cool. I mentally debated for a moment before throwing caution to the wind, taking off my shoes, rolling up my pant legs and wading in. The water was fantastic. I was able to access rocks at the bottom of the creek which provide the greatest selection of large, flat sandstone slabs that typically have tracks. One such rock was quite strange, with an obvious extrusion that looked not at all geologic and definitely the result of a track, at least to me. I thought the extruded portion of this slab was a raised track cast, the negative of an actual track. I carried the heavy rock back through the creek, hunched over and maneuvering through the sharp, rough creek bottom. It was quite a feat of fortitude, staving off mosquitoes and unstable footing while cradling a very heavy rock like a caveman all while muttering to myself, trying to remember how I charted my course through the shallower regions of the creek. Some random guy walked in on me looking very strange like this. All of a sudden, I looked up and locked eyes with a guy who had just witnessed a crazy person ambling through a creek, clutching a rock to his chest, and mumbling intermittently. 

 

I made it back to the shore safely, and contemplated my possible finds as I dried off and put my shoes back on. I had a very interesting set of possible footprint preservation mediums. One was a classic sandstone slab with a footprint-like structure. I have seen many rocks like this, including my previous track find. The next one was a small blob of ironstone, akin to a cowpatty. It had much lumpy layering around the possible track. I have only seen these occasionally, they sometime preserve the cast of tracks. The third item was a classic Patuxent rock. It consisted of a pottery-like shard or siderite, one side preserving the ground from 115 million years ago, the other side retaining a more-granulated concretionized surface, with a few flecks of lignite. I'm not sure why there are so many lithologies that allow for tracks to be preserved, but they are interesting. Anyway, I took all the items back and left for home, where I placed the specimens on a shelf, out of mind until my meeting with Dr. Weems.

 

  ------------------------------------------------------------------------------------------------------------------------------------------------------------------

 

I have rambled on too long without showing any of the fossils! I just felt this specific report fit into two "episodes" since the collecting was very separate from the study and IDing of the specimens. I am trying to be more descriptive with my reports, providing more of a story along with the fossils. I have taken much inspiration from members like @SPrice, @Mikrogeophagus, and @Jared C, whose reports I greatly admire. Let me know if I'm being too wordy, or if I have glossed over details that require more explanation.

 

 

Now, into the fossils! First up, we have the sandstone slab: 

 

 

Can you see it? Here, the black lines represent the extruded portion that I thought was part of a track. But instead, it's the red outline, with the blue lines representing the impression! Never even saw this shape at first. 

 

 

Ornithopod Track cf. Caririchnium kortmeyeri

Patuxent Fm., Aptian/Albian

Prince George's County, MD

 

This track likely belongs to an ornithopod dinosaur. Similar tracks can be found by googling the genus Caririchnium, including some at the famous Dinosaur Ridge in Morrison, CO, like this one:

 

The ichnospecies I listed above was created by an Iguanodontid dinosaur, one of the last few which were dying out right as the basal hadrosaurs were starting to emerge. On to the next track!

 

 

 

 

Possible Turtle Track cf. Emydhippus ichsp.

Patuxent Fm., Aptian/Albian

Prince George's County, MD

 

This is a very small track created by a small creature like an early mammal, lizard, or turtle. The rock may have other residual scratch marks, but this is the main one, though the heel is cut off. Based on the size and morphology (spacing of the claw marks), we think the track belongs to a turtle. I should mention that the ichnospecies that I am "cf."ing are the reported ichnospecies that match the trackmaker closest based on our analysis. Please let me know if I'm using my taxonomic vocabulary incorrectly.

 

 

Lastly, we have my personal favorite! Palm-sized, rather uncommon, and adorable... Please meet (drumroll, please):

 

 

 

Juvenile (!!!) Basal Tyrannosauroid Track cf. Tyrannosauripus bachmani

Patuxent Fm., Aptian/Albian

Prince George's County, MD

 

This one is quite cute, but you need a few lighting angles to see all the toes just right. This likely belongs to a baby theropod, and not just any theropod, a basal tyrannosauroid! You can see the little toes, though the leftmost digit is not fully preserved. You can see it branch off before it stops. The middle toe is most clear, complete with knuckle marks and a pointed claw mark, but not as sharp as older theropods and the tyrannosaurs that would come later on in time. I was incredulous that a track so small could be preserved like this, but it really is unmistakable when you get the light on it. It's so satisfying that I've been carrying around the little guy in my pocket all week, pretending I have a baby pet dinosaur. Until I find my first osteological theropod fossils, I will be quite content with this track. And unlike most tracks which are hard to distinguish for non-paleo people and quite large and heavy, I can carry this one around and brag to my friends .

 

Anyway, that is all for now. I don't know when I will have another chance to go looking in the Patuxent again as I am quite busy with the Culpeper Basin in VA, where I am slowly making progress I can hopefully share soon. I hope everyone enjoyed reading and looking at these tracks as much as I have! Let me know if I have made any egregious errors. Have a good night.

 

 

 

 

 

References (used for ID purposes):

Weems, Robert. (2021). ADDITIONS AND A TAXONOMIC UPDATE TO THE DINOSAUR ICHNOFAUNA FROM THE PATUXENT FORMATION IN VIRGINIA, USA. 82. 475-485. 

 

Edited July 14 by patelinho7

[SPrice]

Yep...this right here says it all...Thanks for the putting us in the creek with you!

 

" It was quite a feat of fortitude, staving off mosquitoes and unstable footing while cradling a very heavy rock like a caveman all while muttering to myself, trying to remember how I charted my course through the shallower regions of the creek. Some random guy walked in on me looking very strange like this. All of a sudden, I looked up and locked eyes with a guy who had just witnessed a crazy person ambling through a creek, clutching a rock to his chest, and mumbling intermittently."

 

Steve

[Mikrogeophagus]

Very nice and unusual finds! I think you are quite good at the whole narrative style trip report! Footprint ichnofossils boggle my mind. I think I would go crazy of pareidolia trying to find those. 

25 minutes ago, patelinho7 said:

Dr. Weems thinks it is likely the ichnospecies I listed above, which was created by an Iguanodontid dinosaur, one of the last few which were dying out right as the basal hadrosaurs were starting to emerge. On to the next track!

This is interesting. The Middle Cenomanian Woodbine here in TX has footprints from said basal hadrosaurs!

 

Thanks for the fun read as usual  

[Andúril Flame of the West]

Congratulations on a fantastic assortment of finds! It seems that you have become a true track connoisseur - hopefully that also carries into the Culpeper Basin. I second @Mikrogeophagus that I'd be fighting an unshakable case of paredolia all the way. I am glad to hear that you have had success in hunting the largely unexplored Cretaceous of Maryland. 

 

1 hour ago, patelinho7 said:

 

I have rambled on too long without showing any of the fossils! I just felt this specific report fit into two "episodes" since the collecting was very separate from the study and IDing of the specimens. I am trying to be more descriptive with my reports, providing more of a story along with the fossils. I have taken much inspiration from members like @SPrice, @Mikrogeophagus, and @Jared C, whose reports I greatly admire. Let me know if I'm being too wordy, or if I have glossed over details that require more explanation.

 

 

I respectfully disagree - I don't think you rambled on too long! Every piece of that was enjoyable to read and you certainly put us there in the moment hunting alongside you. The narrative style was executed very well and I hope to see similar reports in the future. 

[patelinho7]

Thanks everyone! I appreciate the kind words.
 

I will also add that I tried to do the fancy thing with the hyphens to visually split the report but it seems to not have worked on mobile. On computer I think it may look alright.

Edited July 14 by patelinho7

[Fossil_Adult]

Congratulations on the finds! Ichnofossils are my favorite fossils to find by far. Those are definitely Cretaceous dinosaur trackways, I have been looking for those for a very long time. No luck, unfortunately. Ichnofossils in the DMV area has to be some of the toughest to find, with many preferring shark teeth, which are much easier to find and much more abundant. 
 

@patelinho7and @Andúril Flame of the West we oughta meet up sometime and put our heads together on this. I have been searching for trackways for the majority of my life, but together, I think we’d be unstoppable. There is so much Cretaceous formation out there in Maryland that hasn’t been touched yet. And I’m sure dinosaur park is not the only vertebrate cache. If nothing else, I’d just love to meet fellow collectors who are interested in DMV ichnofossils. 
 

great finds, man. Congrats! 

[Jared C]

Enjoyable report- ID’ing tracks is too daunting a task for a simpleton like myself, I would go crazy with pareidolia. The early Cretaceous of Texas has a few that I’ve probably missed before

[NickG]

Lucky dog

[patelinho7]

On 7/14/2024 at 2:13 PM, Fossil_Adult said:

Congratulations on the finds! Ichnofossils are my favorite fossils to find by far. Those are definitely Cretaceous dinosaur trackways, I have been looking for those for a very long time. No luck, unfortunately. Ichnofossils in the DMV area has to be some of the toughest to find, with many preferring shark teeth, which are much easier to find and much more abundant. 
 

@patelinho7and @Andúril Flame of the West we oughta meet up sometime and put our heads together on this. I have been searching for trackways for the majority of my life, but together, I think we’d be unstoppable. There is so much Cretaceous formation out there in Maryland that hasn’t been touched yet. And I’m sure dinosaur park is not the only vertebrate cache. If nothing else, I’d just love to meet fellow collectors who are interested in DMV ichnofossils. 
 

great finds, man. Congrats! 

Thank you! I agree, the DMV Mesozoic fossils are something else. The elusiveness adds so much excitement. I’d much rather find a dinosaur out here than out west, though I would never pass that opportunity up. 
 

You’re right, there’s so much Cretaceous to explore but believe it or not, the Patuxent is very present in VA as well on the coastal plain. Take a look at the paper I put at the end of the post, it shows the outcrop belt and a few old localities. I don’t know where you are in VA/MD, but it’s much closer to access the MD sites for me than the VA ones. 

[cck]

I’d be hesitant about these as trackways.. maybe ichno of some sort… 

[cck]

The pictures have a lot of  suggestions in the editing which I don’t think are valid

[Andúril Flame of the West]

1 hour ago, cck said:

I’d be hesitant about these as trackways.. maybe ichno of some sort… 

 

Personally I also tend to be very skeptical of trackways and ichnofossils, particularly when I have tried finding some myself. I usually reason that any strange or suggestive features are just sedimentary structures or erosional features. In my case, I have very little confidence in my ability to identify tracks.

 

However, @patelinho7 brought the tracks to Dr. Weems who is very knowledgeable on tracks, particularly those from the DMV area. To my knowledge he has written (or coauthored) several papers on track assemblages from the Patuxent formation of Maryland and Virginia and from several basins in the Newark Supergroup. IMHO I am naturally skeptical of trace fossils and can see how some of these pieces might be interpreted as being of geological/erosional origin, but I would also place trust in Dr. Weems' assessment. 

[patelinho7]

22 hours ago, cck said:

I’d be hesitant about these as trackways.. maybe ichno of some sort… 

@cck, you bring up a fair claim. With ichnos such as these, very often you have to go along with whatever the poster is preaching. However, let me provide some extra information to assure you that I’m not trying to blindly assert my fossils as tracks. I think it’s totally fair to be skeptical of tracks, as was I until I showed these to an expert. 

 

First off, as @Andúril Flame of the West already stated, Dr. Weems is a knowledgeable individual on tracks in general, but also ones from the Patuxent Formation in Maryland and Virginia. As mentioned, he has written and coauthored papers regarding tracks from the Patuxent spanning two states. In particular, he coauthored a paper covering many notable fragmentary tracks from the Patuxent with Martin Lockley (LINK). I also believe he worked on or at least aided excavation with the famous trackway slab found near the Goddard space facility in Greenbelt, MD. He also has great experience with tracks from the Newark Supergroup. 
 

That’s the easy answer, but I’ll also add my perspective into the research and collecting that I’ve done on this formation so far. Hopefully I can prove why I’m attempting to collect these fossils objectively without trying to “see” things, which is how many track collectors fall to pareidolia. A collector’s perspective from one collector to another, especially since you have great experience with Newark Supergroup ichnos, so nobody has to blindly trust the assessment above. 
 

I’d hope to say that I have accrued a significant knowledge of the Patuxent Formation in the last few years by way of reading papers, books, and other material written by paleontologists with knowledge of the formation. In addition, I’ve studied many pictures of past finds in the aforementioned papers as well as in person, seeing finds or casts of finds. I’ve also been to my locality many times. The locality is also a known track locality which has historically been incredibly productive, though in recent years not so much. In other words, I have a large sample set of  information to base my collecting off of. More specifically, I have learnt the characteristics beyond the track itself that indicate the presence of a trace fossil. This is an interesting formation in the way that it was deposited, and there are likewise interesting features in terms of lithology, coloration, layering, and other sedimentary processes that are tell-tale signs for when a rock has a track, as well as when it 100% does not. 
 

For example, the turtle track above has lighter coloration within the track marks. It’s not a trick of the light, it really is tan-colored. This is a classic Patuxent feature- it is not guaranteed, but often accompanies the track. I’m not sure what causes it, my guess is that the trackmaker left micro grooves and facets on the surface of the track that accumulate dust and other material which don’t easily blow away. When I have wet tracks like this, the lightness goes away, but returns when the specimen dries. If you look at the paper I linked in this comment, you can see similar tracks with light coloration in the positive impression. Note: this is specific to positive tracks, not negative casts.

 

Another characteristic I look for is the layering and folding/bulging around the track. I have not attached photos in this thread because I don’t have a good way to take clear photos from side angles, but the layering around/under tracks vs. pseudotracks are quite different. There are LOTS of geologic oddities and pseudo tracks and other strange rocks that resemble ichnos in this formation. It is something to do with the large presence of siderite, which formed in strange ways, undergoing chemical processes in some instances. Keep in mind that I look through many, many rocks across several visits to this locality until I find a few that are worth taking home. It’s not an easy locality. 
 

However, that isn’t to say that this locality rarely produces trace fossils. On the contrary, it is a hotbed of activity if you’re looking at the right rocks. If you’ve found a weird groove, bump, or impression on a flat slab, it probably is a track or other trace. The deposition environment was very favorable to the formation of traces. The trouble is figuring out what you have and proving it to others. This is where more imagination is required, and where you cross the line of reality at times. To avoid this, I try to find really interesting specimens that show clear, distinguishable features that could be interpreted as a fossil by an expert. I got really lucky with my first find being so clear. Since then, I’ve gone through hundreds of “maybe”s and “definitely-not”s before coming across these three, which I wasn’t initially too sure of either.

 

When I am searching for tracks, I make a strong policy of not attempting to interpret rocks in the field, and instead searching for the base characteristics as I mentioned. This helps me keep from drawing crazy conclusions from each rock. I mentioned the light areas on the turtle track. That and its overall lithology is why I picked it up. After I noticed the scratch marks, I thought it had a decent chance at being a track, but I did not expect it could be IDed. 
 

The large iguanodontid track showed very interesting layering around the base of the extruded region I used blue markings on. This one was a prime example of my collecting strategy. I could not visualize a track for the life of me until Dr. Weems pointed it out, I merely thought the slab was noteworthy because it resembled other tracks in the way the extruded portion was raised above the rest of the rock.

 

The tyrannosauroid track is the most obvious, I think. The layering around the sides also matched negative track casts I’ve seen pictures of as well as being different from geologic items that are not tracks. The morphology was also very clear here. There are 3 toes of reasonable proportions present, even if cut off. There is a segmented appearance to the clearest digit, the middle one, which makes sense since it’s the biggest digit on the animal. The nail is also present. Morphology is key for the successful ID of tracks from this formation. It’s already been proven to yield many specimens, so if a rock that matches the lithological characteristics of a track also has a reasonable track visible, it is a very strong candidate. It’s not like other pseudo tracks, where there are alien-like proportions to the toes, or missing toes, or no nails, or other biologically inaccurate characteristics. These tracks in my report are not out of the ordinary for the formation. A lot of track ID is based on precedence. That used to bother me, but as I learned about the characteristics that allowed these tracks to be preserved, I found that my anal-retentive, sometimes-cynical analysis matched with the precedence. 

Anyway, I have gone on long enough. Let me know if you have any other questions! 

 

23 hours ago, cck said:

The pictures have a lot of  suggestions in the editing which I don’t think are valid

I’m curious as to what you mean here. I didn’t edit the photos other than adding duplicates with the track outline highlighted to help members see the track clearly in case they can’t.

 

I didn’t draw the lines to exaggerate the details, and I made sure to leave a margin between the drawn line and the actual track outline so it’s clear I’m not drawing over the rock and muddling the actual details. The only mistake I made was for the Iguanodontid track, where I accidentally curved off the leftmost toe. The original rock does NOT have this curve, that side of the track has eroded and does not continue very clearly. It doesn’t need this toe, however, it has the middle and right toes present.

 

 

[patelinho7]

A few last notes in passing:

 

The paper I linked in the above comment discusses the presence of hatchling dinosaurs creating tracks, which supports the idea that the tyrannosauroid track was created by a juvenile, an otherwise bold claim. 
 

Also, I cannot prove this with certainty, but I’m pretty sure that my locality sourced some of the specimens written up in this and possibly other papers. It was a known site that had been collected in the past by at least one of the authors of that paper. If my guess is correct, it even further establishes the precedence of the locality yielding studiable tracks.

Lastly, I hope that my notes here can be of some use to collectors trying to determine whether the rocks they found are tracks or not. That was one of the goals of my report here, though I didn’t do it very clearly. I was hoping to provide some insight into my strategy and thinking when I try to find these tracks, and how I avoid the pitfalls of pareidolia. Maybe, with some more experience in the coming years, I will try to make a track ID guide 

 

[NickG]

One thing that might help skeptical readers is providing multiple photos showing different oblique lighting to help enhance details that you're seeing.