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Disclaimer: I'm still not 100% sure if the layer I'm hunting in is the basal Atco, but I am under the impression that it is for now. Hopefully I'll be able to do a hunt at Midlothian with the DPS some time soon to get a reference for what the Atco is really supposed to look like. In the past month, I've taken another visit to my little Atco spot to try and learn the place a bit better. I scouted farther upstream and downstream as well as another creek not so far out. There were some pretty cool finds, but I'll keep the story short since I've already covered this locality in a previous report. After a bit of creek walking, I was relieved to see that the latest storm had washed out some fresh conglomerate for me to start splitting at the main gravel bar. Most of the teeth present in the matrix are extremely weathered from reworking, but now and then, a pristine specimen can be revealed and carefully extracted. The first of these discoveries came from just the second rock I had picked up. Some of you may relate to that moment of disbelief when you open the two slabs and realize you are face to face with a huge tooth in mint condition. I hate having to glue broken teeth together, so I proceeded with extreme caution. Still not totally sure if this is Cretodus houghtonorum or Cretodus crassidens, but for now I am tentatively calling it C. houghtonorum since its cusp is more gracile and seems to lack the ovular shape of C. crassidens. One interesting feature of the tooth is the presence of a an extra little cusplet which can be seen in the labial views between the central cusp and distal cusplet. Whatever species it may be, it is a first in my collection, so I am am pretty content. I traveled a little ways up a feeder creek and came across the root of a decently sized Cretalamna gertericorum. The matrix was hard, so I ended up having to clean it at home. Sadly the central cusp was really banged up. Tough to spot, but the root of C. gertericorum Cretalamna gertericorum. On the left is the new specimen and on the right is one from my first visit to the site after recent repairs. At a later gravel bar, I finally found something sticking out of the matrix that I had been really hoping to find. Some of you may remember that my last trip to this spot had yielded a prearticular tooth to a meter long pycnodont fish called Acrotemnus streckeri. These fish are also documented as having pharyngeal teeth. I managed to finally pocket one at this site and one at the later site I'll soon cover. I can't say for sure these are from A. streckeri, but their large size does make it a candidate. Pycnodont pharyngeal in situ A couple of pharyngeal teeth I will tentatively assign to Acrotemnus streckeri. It's kinda neat these teeth share the bluish grey color of the prearticular tooth. Before I show off the final find from the main Atco site, I'll quickly go over the second location I visited. The plan was to locate the Atco there as well, but with all of the modifications made to the creek, I wasn't able to find the source of the Atco rubble I found scattered along the stream. Nothing remarkable was found, but that isn't too say I didn't come out with at least a dozen small teeth. Here a couple pictures of some interesting geologic formations. Huge ripples were found on a lot of the washed out matrix. Located in the uppermost Arcadia Park was this limy layer that was rich in vertebrate material and gastropods. I came across this giant concretion that really stood out. I wonder if anything's inside it. And here is an overview of the smaller finds from the trips: Top L to R: Squalicorax falcatus, Cretodus houghtonorum, and Cretalamna gertericorum Bot L to R: Xiphactinus sp., Acrotemnus streckeri, and various ptychodus Back to the main site, as I was wrapping up the day, I came across some hardened material on the shale bottom of the creek bed above the conglomerate layer. Usually these sort of things are only broken oyster bits, but the shape and density of this one seemed odd so I went in for a closer look before noticing how dark the object was underneath the algal growths. It soon became clear that this was a string of 5 very large fish vertebrae and I begun working around the fossil to pop it out whole. Thankfully, I was able to do just that and the sight as I flipped it over sent me jumping up and down. I scoured the surrounding area, but did not locate any more of the fish. Makes me imagine one day 90ish million years ago this chunk of fish was all that was left after a shark attack or maybe something of the like. After bringing it home, I was able to scrub off the larger chunks of algae, but a hard "calcareous" layer remained attached directly to the bone. I tried soaking it over multiple nights in a bleach water solution and slowly worked off pieces with a dental pick during the day. The plan was to use the other side as display, so I wasn't too concerned with abusing the algal side, but of course I would have liked to have as little damage done as possible. One of the verts was offset, so it quickly broke off from the stress of picking at it. Later another vert came off, but this wasn't an issue as I could easily glue them back later. The work was tedious and took time. On the display side, I worked off the shale with a needle and frequent brushing. Slowly the form become more and more apparent. Soon enough, I decided it was time to get the paraloid out. On a site with so many professional preppers, I'm sure this doesn't look all that impressive, but I am suuuper happy to have this on display and proud of the work. It's fun to hold and imagine the sheer size of the beast these bones once belonged to. I hope you all enjoy it as well. Thanks for reading

The weather's finally warming up here in DFW, and with that, it's time to move on from the comforts of dry land and return to the ways of creek stomping. These past few months, I've been mostly hanging around cuts and construction sites within the Washita Group, and to be honest, I've gotten a little sick of it. During that period, I steadily accrued a sizable list of potential Eagle Ford and Atco locations within the metroplex, and I was itching for the opportunity to finally go and check them out. Yesterday, I circled a few spots on the map and hit the road. Well, the first couple of sites were more or less complete duds. Stop 1 was situated in the Turner Park Member of the Britton. Lots of cool stuff can be found here and it's one of the more prettier formations, but I'm still trying to figure it out. I only spent about 30 minutes there, and nothing really impressed me. Nevertheless, I was at least rewarded with my first ptychodus from DFW (yeah it took awhile). Stop 2 was a famous site within the Camp Wisdom Member of the Britton. There were some interesting cephalopod specimens to be had, but nothing worth taking home. I did not lose hope, though. I knew that my third site was the most promising of the bunch and I accordingly saved most of the day for it. Stop 1 in the Turner Park, and my first ptychodus from DFW (P. anonymous) The Atco lies just above the Arcadia Park Formation of the Eagle Ford Group in DFW. It's famous for being densely packed with a diverse array of vertebrate material dating to the Coniacian, mostly concentrated within a thin layer dubbed the "Fish Bed Conglomerate" just at the contact of the Eagle Ford and Austin groups. The key to finding this layer is to look for matrix that is highly concentrated in phosphatic pebbles and fossils. Down in Austin, I think it gets a bit overshadowed by the Eagle Ford. In DFW, however, I would say the Atco reigns supreme. After a decent drive and trek, I stepped into the creek and began my descent through the Austin Chalk in search of this coveted conglomerate. It was difficult to tell where exactly I was stratigraphically since the Arcadia Park seems to be a bit calcareous whereas the Austin Chalk can be a bit marly. Where the calcareous marl ends and marly chalk begins is tougher to differentiate in practice, especially for someone less experienced like me. I eventually reached a large gravel bar and decided to pause the walking and have a look for any clues. I didn't find anything out of the ordinary in my initial scan, and almost picked up my backpack to move on. However, I took a moment to take a closer look at what I had first subconsciously written off as concrete. In this chunk of rock, I saw hundreds of tiny rounded phosphatic pebbles. Once my eyes reached the edge of the block, I spotted the unmistakable serrated blade of a Squalicorax falcatus tooth. There was no doubt, this was Atco matrix! The material was noticeably greyer than I had expected. Down in Central TX, the Atco is about as white as the rest of the overlying chalk. With all of the odd bits and bobs intermingling with the grey rock, it really does look like something manmade. I pulled out the rock hammer and began searching the bar for more chunks of fish bed conglomerate. It's amazing the things your eyes can miss when you unknowingly tune things out. There were very obvious shark teeth encased in many of the rocks I had walked by earlier. I collected several larger pieces and sat down to begin extracting teeth. Found my nicest shark vert yet. Unfortunately, it was super fragile and lots of it broke apart in cleaning. My first oddball tooth from the Atco. It has the shape of Cretalamna appendiculata (in the strict sense), but the presence of labial striations pushes me towards a posterior tooth of Cretodus crassidens. It also notably has doubled cusplets on one side. That same tooth post extraction. It broke in half by the time it got home, so I'll be doing a bit of consolidating. Funky little guy. There were some very large slabs of Atco conglomerate washed out atop the gravel bar. I did some hammering to break them into more manageable chunks so I could rinse them in the flowing creek. As I split one of the large slabs in half, I let out an annoyed sigh as I saw a decent Cretalamna appendiculata tooth crumble from the point my hammer had hit the stone. I tried to push that misfortune out of my mind as I perused across the newly exposed surface for any other teeth. I quickly spotted some fine serrations poking out of a chip of matrix that had just come loose. It was a Squalicorax falcatus doing its best chameleon impression. Please don't break please don't break Voila! By far the largest Squalicorax in my ever-growing collection! Florida megs better watch out... My constant hunt for micros at home adequately prepared me to keep an eye out in the field. I was able to spot a couple of Ptychotrygon triangularis oral teeth throughout the day. I also managed to find a mediocre Scapanorhynchus raphiodon and my first decent Ptychodus whipplei! Managed not to lose it in the gravel. Ptychotrygon triangularis Lots of beat up Scapanorhynchus raphiodon that day Ptychodus whipplei. The bits and pieces I have from Austin look like they were crapped off a cliff by a coyote as some Texas fossilers like to say. After getting a nice sunburn, I decided to get up and explore more of the area to perhaps find a source for this matrix. I spotted a little tributary that seemed promising and had a gander. Some outcrops have a beauty that only fossil hunters can truly appreciate... You who are reading this, I know your mouth is watering A little ways farther, the source is found. As I walked up the small feeder creek, I periodically inspected the pieces of fish bed conglomerate that were scattered in the way of the flowing water. One ball of matrix had an unsuspecting appearance, but something about it wouldn't let me leave it alone. There was what initially seemed to be some part of a bivalve erupting from it, but the color and texture gave off enamel vibes. After hammering off some chalk, I still couldn't figure it out. I eventually extracted the entire thing. It was extremely smooth and came to an edge at the top. The surface was mostly bluish gray and semi translucent. It took a second for the cogs in my brain to start working and realize I'd seen something very similar before. @Jared C and I have been recently discussing Hadrodus, and, of course, one of his best discoveries is a large fragment of Hadrodus hewletti of which shares many visual characteristics with the object in my hand. I was excited to realize I was holding the tooth to a gargantuan pycnodont fish. Just after extraction Occlusal view and side pics For scale. Stay tuned for the identity of this monster After this discovery, my stomach growled, signaling it was about time to head back. This was only my first excursion in the Atco of North Texas, and it had already proven to be one to remember. For sure, this will be a site to return to. As I walked along the banks towards my exit, my eyes were still honed in on the ground as is the curse set upon every fossil hunter. I usually don't find anything on my return walks, but I was delighted to see the sheen of black enamel poking out of some Atco chalk just several feet above the fish bed conglomerate. I popped it out and quickly identified it as Ptychodus, though the species I was unsure of. At the moment, I think it is P. atcoensis as it seems to be a good match with a specimen in Hamm's paper on the Atco. It's got radiating ridges and a marginal area similar to some P. anonymous. That paper mentions Meyer (1974) suggested that the taxon could be transitional between P. mortoni and P. anonymous and I certainly understand that reasoning. It's a little beat up, but that's a rare species and a special one. In situ Radiating ridges and concentric ridges in the marginal area as expected for P. atcoensis Once I got home, I began researching more on my fish tooth to try and pin an ID. My initial idea was that it could be a Hadrodus incisor like what Jared had in his collection based on size and coloration alone. Jared was quick to point out that the morphology differed greatly between my tooth and most incisors. This was a valid hole in the argument and I went back to the drawing board. The tooth was most certainly pycnodont in origin, but the world of pycnodonts is much deeper than most people realize. When examining the edge of the tooth I noticed a characteristic I couldn't come up with a name for until I saw it in one of the papers on Hadrodus Jared had shared. "Papilla-like tubercles" were the things lining the edge, and thankfully the author of the paper offhandedly brought up another genus of pycnodont that shared this trait: Acrotemnus. After some searching, I found a recently published paper by Shimada on a newly discovered specimen of Acrotemnus streckeri from Big Bend in the Ernst Member of the Boquillas Formation. And wouldn't ya know it, Hamm stated that the Ernst Member can be correlated with the Atco Formation (though I should mention a discrepancy in that Shimada places the Ernst Member in the Turonian and not the Coniacian which Hamm asserts the Atco + Ernst to be). The Acrotemnus paper had some high quality images of the dentition of the specimen, and I found the most similarity in size and morphology with the prearticular teeth of their fish. The Shimada paper mentioned that most pycnodonts are small, only reaching about 25 cm in size. To people who are unfamiliar with pycnodonts, these teeth may not look all that crazy, being measured only as 1-2 centimeters . However, scaling the body with the size of the dentition shows that Acrotemnus streckeri reached lengths of at least 1 - 1.3 meters, making it some of the largest pycnodonts to exist at the time! This definitely shattered my preconceived notions about pycnodont fish. Already, the Atco has proven to be one of the most interesting formations in North Texas. This site is a bit of a laborious drive for me, but I'm certain many future adventures will be had and many more fascinating discoveries with it. Thanks for reading!

Hopefully, this will be the last time I post on this fauna until I announce the finished publication! I had originally identified this as a cretodus, but after reviewing Everhart and Welton, I am having very serious doubts as to the validity of this ID. The teeth are both labially and lingually striated. The lingual striations look totally different than the pattern found on the scapanorhynchids. The teeth have accessory cusplets, sometimes two on a side. The base of the teeth are more robust than that of scapanorhynchids, too. As you can tell by the photos, even the worn teeth have pronounced striations. Any help at to identifying these teeth to genus (maybe even species?) level would be wonderful! Thanks!

This has me stumped! An orectolobid, but what? I am assuming it is a cantioscyllium, but it doesn't have the cusps that most fish of this genus have. Unlike C. decipiens, there are no strong striations. Instead, there are some small ones on the labial edge, and the lingual edge has a kind of rim. Also, there is one small transverse striae found on either side of the mesial ridge. Any ideas? There are four teeth discovered in this fauna, so they can't be pathological. Thanks!

I'm coming to the experts once again! This is a very strange ptychotrygon tooth. It appears to be P. triangularis, but it is so elliptical. The low crown is similar to some of Bourdon's P. eutawensis, but according to Woodward's original description, there is a bit of ornamentation on the labial apron, which this doesn't have. Could this simply be a pathological tooth? Thanks!

A couple of questions concerning these fish. Are all nursallia teeth characterized by the eight or so bumps on one side of the tooth? Did pycnodonts regularly shed their teeth? Most of the teeth I have found are hollowed out basally, which makes me think that they were shed, I have a few that look like they have remnants of jaw fragments attached, which makes me think that these teeth belonged in the mouth of a fish that had died. How do you tell the difference between pycnodontid and lepidotid teeth? Thanks!

Hey all! I have this tooth that appears to be a cretodus. It has plications on both the labial and lingual faces, with the lingual plications being smaller than the labial. Cretodus so far. Iy measures 3.88 mm in height and 3.42 mm mesio-distally, The problem arises with the accessory cusps. Welton and Farish state that Cretodus semiplicatus only has one accessory cusp on each side of the main cusp. Although one side of the cusps is missing, the other side obviously has two cusps. Was Welton and Farish mistaken, or is this tooth not even cretodus? Thanks! Randy

Going through some scapanorhynchus teeth to photograph for a museum bulletin I'm working on, I came across this tooth. It is different in that there seems to be at least one striation on the labial face. The striations on the lingual face are pretty distinct, but seem to be worn (depositional wear?). Could the labial striation also be depositional wear? But the really odd thing is the pair of cusplets. Scapanorhynchus raphiodon and Scapanorhynchus puercoensis are both found within 25 miles of this site, but the cusplets on these species are smaller in relation to the main cusp, and are more pointed. In Bourdon's NMMNHS Bulletin 52, there is a photo of S. sp. cf. tenuis (Figure 15, image I bottom left) that shows a tooth with two accessory cusplets on either side of the main cusp. However there is not a noticeable gap between the two cusplets found on either side of the main cusp. Could this tooth simply be pathological, or might I have missed the species entirely? Thanks for your help!

Hey all, I am having a heck of a time trying to identify this tooth. Both Shimada and Kirkland suggest that it is a schlerorhynchid, but I have not found anything in the literature that resembles this morphology. The shoulders of the tooth are slightly oriented labially, the apical cusp is rounded (due to deposition or weathering? If so, why is the keel still so pronounced?), there are no transverse ridges, there is a fairly large lingual uvula, and there is a single arched lingual ridge on each shoulder. This one has me stumped! Any and all help will be greatly appreciated! Randy

Hey all, does anyone know of a good source of information for the identification of orectolobiformes? Or someone I could contact concerning these sharks? I have five teeth that most likely belong to different species, but have been having a hard time with their IDs. I am going through Cappetta's 2012 handbook, have gone through Welton and Farish, and looked up orectolobiformes on the Fossil Forum, to no avail. I will most likely be posting pictures later today or tomorrow. Thanks!

These tiny teeth (?) have me stumped, as did a bit of the Cabezon fauna I am working on. This site has been very helpful in identifying some of the rarer fossils, and I am asking for your help once again. At first glance, I thought these four dots were fungal or some other type of current plant material, but examining them under a microscope I am pretty convinced these have enameloid structures. Any idea of what they could be from? I am assuming some form of teleost at this time. Thanks for all of the help, past, present, and future!

Hey all! This small jaw fragment was in the thousands of fossils pulled out of anthills. I am assuming it is a teleost. Other than several species of sharks, rays, and sawfish, there are pycnodonts, enchodus, and Protosphyraena. This looks like nothing I've found yet. Any ideas?

Hello all! I have around a dozen of these teeth. (Found in New Mexico. Coniacian.) The very prominent lingual protuberance should be diagnostic, but I can't find a match. Eostriatolamia tenuiplicatus looks good, but the crown has striations, and these don't. Archaeolamna kopingensis also looked good, but the secondary cusps of this species are oriented away from the main cusp. Leptostyrax macrorhiza also has labial striations. The narrowness of the cusps and crown also has me baffled. Any ideas?

Found close to Paderborn, Germany (Erwitte-Formation) alongside with some echinoids (most likely Micraster cortestudinarium),an ammonite and countless Inoceramidae clams. Marly Limestone Formation of the lower Coniacium or upper Turonium. I was wondering if it could be some kind of petrified drift wood, palm or root?

Good day, all! Can anyone tell me the differences between Myledaphus and Pseudohypolophus? All responses will be greatly appreciated!

Here is another Cabezon taxa that I am having a hard time identifying. Is it Pseudohypolophus? Rhombodus? Myladephus? Something else? Any help will be greatly appreciated! Randy

This is a well worn tooth from the Cabezon fauna. With the lingual and labial plications, I am assuming this is a Cretodus. The narrow cusp leads me towards C. semiplicatus. However, the accessory cusp is not as triangular as I would expect to see from this species. Am I right in my assumption concerning the species, or am I off base? Thanks!