Hunting for Ammonites in the Rio Puerco Valley

[historianmichael]

Last weekend I made a trip to New Mexico to hunt the Rio Puerco Valley with @PFOOLEY in search of Upper Cretaceous ammonites, mostly in the middle Turonian Carlile Shale. Mike is incredibly knowledgeable about the Upper Cretaceous of New Mexico and the stratigraphy of the area and I had a blast collecting alongside him. Before making my way to New Mexico I had told Mike that my goal was to find a Placenticeras. Placenticeras and Sphenodiscus are my two favorite Upper Cretaceous ammonite genera. Despite Mike's warning that the areas we would look had been consistently collected over the years, I was excited to explore a new area and collect some new fossils for my collection. Going into the trip, I had told myself that if anything I would get to spend a weekend collecting amongst a beautiful surrounding. 

 

I met Mike early on Saturday before we made our way to the Carlile Shale. After we exchanged some quick pleasantries, Mike gifted me an amazing Placenticeras pseudoplacenta embedded in a large concretion. At the very least, I was not going to leave New Mexico without my Placenticeras!

 

Once we arrived at the site, Mike explained to me which horizons hold the best fossils and what color concretions I should be looking for. He also said that rattlesnakes can be found out here and that he hoped we would see one -- that made one of us. I am happy to report that we did not see one! With Mike's two dogs guiding the way, we found ourselves over the next several hours climbing up and down several slopes on the hunt. Given that we were in the Prionocyclus hyatti zone, Prionocyclus hyatti made up the majority of our finds, but to both of our surprise, we were still able to find quite a variety. I found a couple Placenticeras pseudoplacenta of my own as well as two "Franken-ite" ammonites that I wrapped and glued back at home, including an uncommon Romaniceras mexicanum. Mike found his first ever Scaphites carlilensis, which was cool to see. 

 

Prionocyclus hyatti

 

Placenticeras pseudoplacenta

 

Romaniceras mexicanum

 

 

Indeterminate Collignoniceratid

 

While the ammonites were the obvious draw to the site, I also enjoyed picking up a couple of the other invertebrates lying around the hills, including a double valve Inoceramus howelli.

 

Cameleolopha bellaplicata

 

Cyprimeria sp.

 

Nuculana sp.

 

Inoceramus howelli

 

 

After walking the full stretch of the exposure, Mike said that he wanted to check out one more site, an exposure of the Santonian Satan Tongue, before heading home. Once again Mike gave his fair warning that he had only found a few fossils in the past from this formation but that he had always thought it worthwhile to check it out as a last stop before calling it a day. As we walked around I could see why he had given his warning. I could find nothing! Mike came up to me to ask how I was doing and when I said I was empty handed, he handed me to my surprise two Baculites codyensis and showed me an interesting oyster he had picked up. I have no idea how he could find these things! 

 

Baculites codyensis

 

 

We walked around a little bit more, and just as Mike said "I hope this stop was not a waste of time," I spotted a Placenticeras syrtale peeking out of the ground. I quickly called Mike over, and as soon as I looked at the ground again, I saw another one less than half a foot away from the first. We spent a few more minutes searching this horizon and each collected a few more pieces.

 

Placenticeras syrtale

 

 

Shortly thereafter Mike left me to head home for dinner, but before he did, he pointed me in the direction of another area worth checking out. Mike must have the magic touch for ammonites, because after he left I did not find much else. Nonetheless I still managed to find another Prionocyclus hyatti and a couple other invertebrates. 

 

Prionocyclus hyatti

 

Pecten sp.

 

Cardium sp.

 

Eoacteon sp.

 

Before flying back home in the afternoon on Sunday I wanted to make one more effort at finding some ammonites. Returning to an area Mike and I had visited the day before I decided to go right while we had gone left. That decision turned out to be a poor one. I spent the next hour hiking with nothing to show for it except a few isolated broken Prionocyclus hyatti chunks that I left where I found them. Believing that I might not find anything for my day, I made my way back towards my starting point, and just as I arrived there, I spotted an interesting concretion on the ground. Crouching down to examine it, I decided to split it open. No luck. Just more tiny Prionocyclus hyatti fragments. But as I spun around from my seat I saw what looked like the shell of a decapod. Mike had joked with me the day before that he had found a crab in association with an ammonite several years ago and when he donated it the researchers had wanted to break off the ammonite to preserve the crab. He said that decapod material is rare, so I did not have much hope of finding one myself. The concretion had broken into four pieces so I made sure to collect everything and wrap them appropriately. Since returning home and consolidating the specimen, I have struggled to identify it. Yesterday I spoke with one academic who asked to see it in-person. I will report back once I have a definitive identification.

 

Unidentified Decapod

 

 

All in all, I had a great time in my short visit collecting from the Upper Cretaceous of New Mexico. I found some great fossils and multiple personal trip makers. I cannot thank Mike enough for his hospitality and generosity. I cannot wait to pay him back on a potential trip to the Upper Cretaceous of the Atlantic Coastal Plain.

 

As a funny aside, I did not have enough space in my checked bag for all of my finds, so I had to store a couple of them in the two backpacks I carried onto the plane. TSA pulled one bag aside but not the other, and when the agent came to look at the bag closer, she asked me, "are these rocks?" My guess is that TSA agents see a lot of things come through security, but "rocks" was a first for her. 

Edited May 6, 2022 by historianmichael

[Tidgy's Dad]

How absolutely splendid! 

Some of those finds are spectacular, I love the huge ammonites and the decapod. 

Thank you so much for sharing. 

[Ludwigia]

Thanks for the report. Looks like you had a very special time with a very special host

[Tidgy's Dad]

3 minutes ago, Ludwigia said:

Thanks for the report. Looks like you had a very special time with a very special host

Yes, someone I would love to go collecting brachiopods with, for sure. 

[RandyB333]

Wonderful finds Mike! Looks like the trip was well worth it. Makes me want to get back out there!

[FossilDAWG]

You sure had a great trip!  I collected once with Mike and he was an excellent host.  I think I found examples of all those species except Placenticeras syrtale (yours are very nice) and the decapod.  I'm going to take a WAG that the decapod will turn out to be a Cenomanocarcinus based on the line of nodes across the carapace, but that is a very tentative suggestion.

 

Don

[historianmichael]

24 minutes ago, FossilDAWG said:

I'm going to take a WAG that the decapod will turn out to be a Cenomanocarcinus based on the line of nodes across the carapace, but that is a very tentative suggestion.

Necrocarcinus (Cenomanocarcinus) vanstraeleni is reported from the Carlile Shale of New Mexico, and that is what Mike found a few years ago, but I don't see the resemblance. Maybe I just can't see it.

[Jeffrey P]

Mike you're definitely taking advantage of your time in southwest. A day collecting with Mike is always splendid. Hope to do that again someday. Congratulations on your prolific finds, especially the Placenticeras syrtale and the lovely Cameleolopha. Thanks for sharing your adventures.

[FossilDAWG]

It's always hard to get a clear view of decapods when they are flattened or the photos don't covey any sense of their 3-dimensionality.  There seems to be a line of irregularly shaped nodes running across the carapace, but I haven't any sense of how "node-like" they actually are or if they are just discoloration.  Unfortunately the carapace seems to be pretty crushed, and I can't make out if the margins and especially the frontal region is present, so any stab at an ID would be very very tentative (hence the WAG comment).

 

When I was flying out of Albuquerque with my luggage full of goodies I was about 5 pounds over the weight limit and so they were going to charge me an extra $100 baggage fee.  Fortunately I was at the airport early enough that I had time to walk to the post office just off the airport and fill up and ship a large flat rate box.  That cost a lot less than $100 and it got the weight of my luggage below the cut-off.  Since then I often just plan ahead to stop at a post office and mail things back home once in a while, so I don't have to worry about trying to get it on the plane.

 

Don

[historianmichael]

46 minutes ago, FossilDAWG said:

It's always hard to get a clear view of decapods when they are flattened or the photos don't covey any sense of their 3-dimensionality.  There seems to be a line of irregularly shaped nodes running across the carapace, but I haven't any sense of how "node-like" they actually are or if they are just discoloration.  Unfortunately the carapace seems to be pretty crushed, and I can't make out if the margins and especially the frontal region is present, so any stab at an ID would be very very tentative (hence the WAG comment).

 

Well we should hopefully know soon enough. I too had issues making out the margins and it is unfortunately only a partial carapace. From what I saw though, there is a short line of nodes and two isolated nodes.

 

 

[PFOOLEY]

On 5/6/2022 at 1:28 PM, historianmichael said:

Necrocarcinus (Cenomanocarcinus) vanstraeleni is reported from the Carlile Shale of New Mexico, and that is what Mike found a few years ago, but I don't see the resemblance. Maybe I just can't see it.

 

This is the specimen I mentioned...

 

 

 

 

...from this post.

 

 

LINK:

 

[PFOOLEY]

Dang, Michael...great report here! 

 

I must say that I really enjoyed your visit...I am always down for Upper Cretaceous conversation. I am happy you found some great pieces and that they made it home with you.

 

Let us know how it goes with the crab. I posted the one I found above...it wasnt too far from where we were in the very same horizon.

[historianmichael]

I heard back today from Rodney Feldmann at Kent State. He stated that the specimen is a rather incomplete example of Cenomanocarcinus enodis. I believe the idea is that the right half of the carapace and some walking legs are preserved in the nodule. As it turned out, I had the specimen upside down.