Mysterious jumble inside Pennsylvanian concretion

[deutscheben]

This concretion came from a Pennsylvanian Shelburn Formation site in Vermilion County, Illinois. The fossils are found scattered throughout concretions in a shale layer and indicate a near-shore marine origin, with the most common fossils being tiny to small bivalves, gastropods, goniatites and inarticulate brachiopods, along with occasional plant material. 
 

This one has me puzzled though. The concretions don’t split neatly like those from Mazon Creek, so unless the specimens were already exposed by weathering in the field I just smash them and hope it exposes a fossil. This is the only one that looks like this, showing a jumble of negative impressions of organic shapes, some of which are reminiscent of ribs and vertebrae. I can’t make out anything definite, though, so it may just be a suggestively preserved plant or crinoid, or who knows. The section with impressions is about 20 mm wide. Thanks!

 

 

 

 

 

 

 

[Fossildude19]

Looks like disarticulated fish remains. 

Whether they are from regurgitant or just a solitary individual is not apparent, to me .

[deutscheben]

1 hour ago, Fossildude19 said:

Looks like disarticulated fish remains. 

Whether they are from regurgitant or just a solitary individual is not apparent, to me .

Thanks! I thought it looked fishy, but I have been wrong about that before.

[Fossildude19]

1 minute ago, deutscheben said:

Thanks! I thought it looked fishy, but I have been wrong about that before.

Could also be some other vertebrate, but there isn't much to go on, here. 

Fish is likely, but tetrapod is a possibility. 

[jdp]

I think this is a lysorophian, a kind of recumbirostran 'microsaur.' This is actually of serious interest scientifically. 

[Titan]

@deutschebenThat is super cool! Awesome find.

[deutscheben]

9 hours ago, jdp said:

I think this is a lysorophian, a kind of recumbirostran 'microsaur.' This is actually of serious interest scientifically. 

My goodness, that is unexpected and exciting! Thank you for the ID. If you don’t mind me asking, what features led you to think that? And do you have any suggestions for a professional to contact? 

[jdp]

2 minutes ago, deutscheben said:

My goodness, that is unexpected and exciting! Thank you for the ID. If you don’t mind me asking, what features led you to think that? And do you have any suggestions for a professional to contact? 

So firstly, the presence of elongate ribs and ossified centra means this is 100% a tetrapod. The anatomy that I'm picking up on is the apparent presence of a midline suture in the neural arches, which is typically a go-to diagnostic charateristic for lysorophians. I'm not 100% confident of the ID (there are some other recumbirostrans which might be overall similar in shape) but I'd be pretty confident of that ID for now. Lysorophians are a weird group of elongate-bodied tetrapods (possibly early reptiles) which seem to have been pretty common in terrestrial ecosystems. This specimen is particularly interesting because it comes from the same formation and area as Lysorophus, which is itself known only from an isolated vertebra, and will help with some of the taxonomic issues in the group. I'm pretty confident that impressions of more of the skeleton are probably embedded in the concretion, and that we can reveal fine details of that using imaging tools like micro-CT.

 

In terms of who you'd want to get in touch with about this, there are a few people who have really focused on this group, the Recumbirostra, in the past few years, and in terms of current workers looking at lysorophians, that really comes down to two people: Arjan Mann (currently at Carleton University in Ottawa) and myself. Let's talk a bit more in a private message and we can discuss how you want to go forward with this specimen!

[bigred97]

Very cool find! I have to say that I was thinking it was more along the lines of some type of flora, like a cone or some type of root. But there is interesting structure there for sure and I certainly can see why it would be identified as a tetrapod. How awesome is that! Please keep us up to date about where this leads. I would love to learn more about it.

[RuMert]

Turned out a great find then