Chronicles in the Maastrichtian: Part II

[Andúril Flame of the West]

With the surprisingly warm weather early last week, I could not resist heading out for what is likely to be the last hunt of the season. Although I did not have the greatest luck on my last trip, I decided to hit the new Severn spot once again - and I couldn't be happier that I did!

 

Upon arriving I was greeted by the open expanse of weathered marl, reminiscent of the western badlands despite the bustling city only a few miles away. Chunks of orange ironstone stood out against the dark Severn matrix and abundant Exogyra costata oysters littered the ground. The Exogyra often occur in small clusters, presumably what would have been oyster beds at the bottom of the shallow Cretaceous sea. 

 

 

 

A couple of poorly preserved Exogyra weathering out of the marl. 

 

Although I had collected a nice handful of Exogyra on my adventure at the site, I could not resist slipping another into the rucksack .

 

 

 

 

The single Exogyra costata specimen collected on this trip. Although it is only a partial specimen, the bottom valve had a particularly interesting appearance. 

 

I wandered across the weathered slopes, keeping my eye out for my vertebrate quarry. Due to the poorly preserved nature of the fossils found at this site, I had an exceptionally difficult time differentiating fossils from suggestively shaped rocks. After the first hour, I had only collected about one piece that I felt was a fossil. Although the vertebrate remains remained elusive, I chanced upon an unexpected fossil - a nice chunk of lignite. The marl was rather rich in lignite, with carbonized remains of ancient plants appearing rather frequently. However, these tended to be highly fragmentary and would disintegrate at the slightest disturbance. 

 

 

 

 

A nice chunk of lignite that popped right out of the matrix. The lignite, indicative of a nearshore environment, hints at the exciting possibility of finding the remains of certain terrestrial Mesozoic reptiles in the Severn marls...

 

After finding the chunk of lignite, the finds slowed once again. The misshapen ironstone concretions were certainly making their best bone impressions! . 

 

While investigating a cluster of Exogyra, I happened upon my first vertebrate fossil of the trip. 

 

 

A nice-sized shark tooth of a similar size to that recovered on my last trip. Based on responses to my last post, I am unsure if it would be appropriate to label this tooth as Scapanorhynchus sp. Any insight would be appreciated .

 

Following the discovery of the first shark tooth, my eyes quickly began gravitating to the suddenly abundant fossils that littered the ground. It was not long before I had gathered a small sampling of surface-collected Severn shark teeth. 

 

 

A few more shark teeth found shortly after I happened upon the first. Unfortunately, the teeth are very poorly preserved and some smaller, brittle teeth disintegrated under the slightest pressure. 

 

 

A few of the smaller shark teeth. The poor preservation combined with the weathered condition of these teeth renders them almost unrecognizable. 

 

 

The shark tooth haul of the day. 

 

Along with the shark teeth, numerous white bone fragments littered the matrix. Although these initial seemed quite similar to the concretions and pebbles that lay alongside them, I gradually began to develop an eye for bone. Like the shark teeth, the bones were coated in a white, crusty covering and many were extremely fragile from constant weathering. 

 

 

 

A handful of fish vertebrae and some miscellaneous bone fragments. 

 

 

Some chunkosaurus, possibly from marine turtles or mosasaurs. 

 

 

 

The largest bone fragment of the day. This is likely too fragmentary to be identified, though I would be curious to see if any members have suggestions. 

 

A view from the end of the bone. 

 

 

 

What I have tentatively identified as a fish jaw section, possibly from a fish similar to Enchodus. 

 

 

Another intriguing bone fragment.

 

After having spent several hours at the site, I was far more successful than I had been on the last trip. With my eyes attuned to the preservation of the fossils, I decided to give the place I had started at another try. I happened upon several bone fragments before my eyes landed on the last thing I expected to see weathering out of the steep slope...

 

 

...a large mosasaur vertebra! The processes were missing and it was badly weathered, but it was a season-maker. In my excitement, I forgot to take in-situ pictures, though it seemed to be little more than another concretion before I picked it up. 

 

 

 

 

The vertebra is quite busted up from being exposed to the elements, though some consolidation should help preserve it. Owing to its poor preservation, I do not know if an identification would be possible. In case there is a chance of ID, my understanding is that the three main species of mosasaur recognized from the Severn are Halisaurus platyspondylus, Mosasaurus condon, and Mosasaurus maximus. The vertebra seems to bear a resemblance to that of M. maximus, though the condition makes it very difficult to tell.

 

Overcoming the initial excitement of the discovery, I had to wonder how many times I had walked over the vertebra... and what else I may have overlooked. 

 

Thanks for stopping by and happy hunting! 

 

 

 

Edited November 13, 2023 by Andúril Flame of the West

[Al Dente]

Interesting site. I’m fairly sure the one on the right that I circled is Serratolamna serrata and the circled one on the left is probably the same.

 

 

[Tidgy's Dad]

Nice finds.

[Fossildude19]

Great report!

Hard to hunt a site like this until your vision gets dialed in to what the fossils look like.
All of those concretions don't help matters any.

Glad you had a good day - thanks for showing us!

 

[Jeffrey P]

Interesting finds from a formation that now has very limited exposure. Vertebrate finds aren't especially noteworthy in the Severn compared to the plentiful and well-preserved mollusk fauna. The amount of bone material you've uncovered does appear noteworthy, though I expect most of it will be unidentifiable reptile remains.  Good report and thanks for sharing.

[patelinho7]

A diagnostic piece of bone! Congratulations. That's is a noteworthy find. I'm envious of your vertebra! Keep it up, hopefully you find more.

[patelinho7]

Out of curiosity, does it look like any of the vertebrate remains could be prepped into something that looks more recognizable, like finds from Big Brook? Or are they all too far gone to be brought back?

[Andúril Flame of the West]

5 hours ago, Jeffrey P said:

Interesting finds from a formation that now has very limited exposure. Vertebrate finds aren't especially noteworthy in the Severn compared to the plentiful and well-preserved mollusk fauna. The amount of bone material you've uncovered does appear noteworthy, though I expect most of it will be unidentifiable reptile remains.  Good report and thanks for sharing.

 

Yes, I've heard that Severn vertebrates are not particularly useful for research, especially with the poor preservation of the specimens from this locale. In learning about the Severn both here on the forum and through literature, I've come across many references to the original-shell mollusks preserved in the upper layers of the formation. I also came across your collection of Severn invertebrates which is quite impressive! In my last trip report I briefly mentioned a short trip that I made to a site that did expose the shell-laden Severn layer. I didn't have the opportunity to find much, though I did collect relatively complete specimens of two of the most common bivalves. 

 

 

 

With the generous guidance of @historianmichael, I was able to prep the shells and keep them relatively intact. 

 

 

 

 

 

Although I will continue to visit the site that is the subject of this post, it is also on my bucket list to scout for new exposures of the Severn shell layer when the spring hunting season starts up. 

 

4 hours ago, patelinho7 said:

Out of curiosity, does it look like any of the vertebrate remains could be prepped into something that looks more recognizable, like finds from Big Brook? Or are they all too far gone to be brought back?

 

Funny that you mention this; as I was writing the trip report I was going to say that these fossils lacked the comparably immaculate preservation of those from Big Brook! I have only made two trips out to this site, so I am not incredibly versed in the variety of preservation that can be seen here, but I am inclined to say no. When surface collecting, I came across several fish vertebra that simply disintegrated when I attempted to gently free them from the matrix. Many of the other fossils were also very brittle, and I would imagine that an attempt to prep them would likely result in a disintegrated/shattered fossil. Even the mosasaur vertebra, which had been exposed to the elements on the weathered marl slope, was quite friable and I had to quickly consolidate it to prevent more material from coming off. That being said, I was limited to surface collecting. Perhaps some fossils that are still buried in the matrix and protected from the elements are in better condition than those that I managed to find. Even so, I do not believe that the preservation at this particular site is capable of producing finds that match those of Big Brook. 

 

From the digging that I have done in the literature, some of the old sites that exposed the shelly layer did come across some vertebrate remains. The photographs taken indicated that these were well preserved, so there may be hope of finding well preserved vertebrate remains somewhere in the Severn.