A walk in the Austin Chalk

[LSCHNELLE]

42 minutes ago, Ptychodus04 said:

This is 100% true. Several specimens that I’ve found over the years (all housed in the Perot Museum collections) have extended the known geological range of the respective  genus/species/ family. One extended the known range of a particular family of sea turtles buy something like 50 million years! 
 

Our knowledge continues to grow as long as responsible parties are out looking for fossils.

 

The cidarid I found was from the Duck Creek Formation. Useless for this conversation but interesting since I’ve never really looked into the ID for it and can’t find one from the Duck Creek now that this thread has me interested.

If correct, Bill Thompsons Monograph has a citarid from the Georgetown Formation of Central Texas which is nearly equivalent to the Duck Creek Formation.  This is how I use his book - to look for similar finds.  But then, I am no expert on echinoid ID. It is a Temnocidaris hudspethensis.  There is also one pictured from the Duck Creek.  Maybe, that is helpful to you. 

[Jared C]

19 hours ago, LSCHNELLE said:

As an amateur paleontologist, the closest similar find I am aware of is the early Campanian Prionocidaris anacochoensis sp. nov. that Bill Thompson has a picture of in his Monograph

Well, whether the book is correct or not, I'm pleased to know that Prionocidaris at least existed in a similar time frame and so there's a chance of it - Prionocidaris is my favorite extant genus of the cidaroids today, albeit mainly for aesthetic reasons. It's a beautiful animal.

 

Here's Prionocidaris baculosa, from the Philippines. This has been my computer wallpaper for a couple of weeks now.

Edited May 9, 2022 by Jared C
geography blunder

[LSCHNELLE]

4 hours ago, LSCHNELLE said:

If correct, Bill Thompsons Monograph has a citarid from the Georgetown Formation of Central Texas which is nearly equivalent to the Duck Creek Formation.  This is how I use his book - to look for similar finds.  But then, I am no expert on echinoid ID. It is a Temnocidaris hudspethensis.  There is also one pictured from the Duck Creek.  Maybe, that is helpful to you. 

@Ptychodus04

It maybe more correct to call this Stereocidaris rather than Temnocidaris per Charles Finsley's Field Guide to Fossils of Texas. The former looks to be Early Cretaceous while the latter may be Late Cretaceous. 

[LSCHNELLE]

2 hours ago, Jared C said:

Well, whether the book is correct or not, I'm pleased to know that Prionocidaris at least existed in a similar time frame and so there's a chance of it - Prionocidaris is my favorite extant genus of the cidaroids today, albeit mainly for aesthetic reasons. It's a beautiful animal.

 

Here's the indonesian Prionocidaris baculosa, from the Philippines. This has been my computer wallpaper for a couple of weeks now.

Really cool looking and amazing sea creatures! 

[Ptychodus04]

2 hours ago, LSCHNELLE said:

@Ptychodus04

It maybe more correct to call this Stereocidaris rather than Temnocidaris per Charles Finsley's Field Guide to Fossils of Texas. The former looks to be Early Cretaceous while the latter may be Late Cretaceous. 

 

It's been so long since I dug out that book, I forgot that I had it in my library. 

[DPS Ammonite]

Here is a good site from London for echinoid IDs:

 

https://www.nhm.ac.uk/our-science/data/echinoid-directory/index.html

 

If we can’t find a local expert, maybe Dr Andrew B. Smith (manager of above database)  knows one or can help with an ID.

 

Anyone know of a local professional to help with an ID?

[Jared C]

@JohnJ, I recall that you know of two other Austin Chalk cidarids - do you know much more about those specimens? Are they comparable to what you've seen of mine? 

[JohnJ]

1 hour ago, Jared C said:

@JohnJ, I recall that you know of two other Austin Chalk cidarids - do you know much more about those specimens? Are they comparable to what you've seen of mine? 

 

It's been many years since, and I have not had the chance to study or photograph them.  

[Jared C]

Ok, I used @DPS Ammonite's link, which is extremely thorough, in conjunction with William Morgan's "Collectors guide to Texas Creteceous echinoids" and Rosemary & Thomas Aker's "Texas cretaceous echinoids", and I've at least narrowed these specimens down to either Cidarinae or Stereocidarinae.

 

Now, the most obvious difference between sterocidarinae and other cidarids are one or more fully developed interambulacral plates in each interambulacral zone without a functioning tubercle. It seems to me that that phenomenon preferentially occurs on the aboral side. 

 

Here is the best photo I can manage to show of what I think reveals that. The black arrows point to interambulacral plates that have reduced ( so presumably not functioning) tubercles. The plates that are less obvious due to glare are roughly outlined with black dots. My question is- are those plates I'm referring to fully developed? My inexperienced eyes think "not quite". Please give your thoughts, this might make or break the ID.

 

I would also like to pull out another interesting candidate - "Texas Cretaceous echinoids" refers to a Taylor group Cidarid (the Taylor group is the group above the Austin group. I found my echnoids in the dessau formation which is near the top of the austin group) called "Cidaris dixiensis". The age is a close fit, and this guess also has a few advantages over Stereocidarinae, but also its own potential problems:

Pros for "Ciadris dixiensis"

- While Stereocidarinae are, from what I gather, usually large echinoids, mine are small - and Cidaris dixiensis is also described as small. 

-The age is a decent fit

- The tubercles are perforated and without crenulation (though this trait is also shared with Stereocidarinae)

- The areoles on mine are indeed weakly depressed

 

Doubts about Cidaris dixiensis:

- This point is more confustion than anything - with C. dixiensis, it's described that the interambuculacral plates have many granules which get larger as they near the areoles. My specimens do have seemingly many granules, but I would say it's unfair to say they get larger as they approach areoles because the granules on the scrobicular circle around each areole are anyway larger than the granules surrounding them. This feature is present in other cidarids - just look at a close up of a scrobicular cirlce, and you can see that the granulation leading up becomes "larger". Look at the granules, for example, in the image below for an example of what I mean. 

 

doubt #2 - Cidaris dixiensis is dubious, only described from two plates.

 

 

 

What do you guys think?

Edited May 10, 2022 by Jared C
typos

[pachy-pleuro-whatnot-odon]

1 hour ago, Jared C said:

What do you guys think?

 

Most of this actually goes right over my head (even if certain anatomical terms are surprisingly similar those used in vertebrate palaeontology ).

 

2 hours ago, Jared C said:

doubt #2 - Cidaris dixiensis is dubious, only described from two plates.

 

But my personal stance concerning dubious genera and species is that they're not necessarily invalid, just never had sufficient evidence to support them. New finds, however, may be brought in their support or prove their invalidity. So I wouldn't worry too much about your second doubt, calling this Cidaris dixiensis or, if it makes you feel any better "cf. Cidaris dixiensis". Your finds may, in fact, be what's needed to validate the species. That having been said, though, the more limited and fragmentary the remains, the more problematic the comparison against them, as the character set will simply be less complete. Therefore using "cf." may be warranted until the species is more firmly established. Or you could go the other direction, and change the name of your find only once new evidence has shown the older name to be incorrectly applied to your specimen. If that makes sense...

 

However, the reason I'm mostly writing this post is to tell you your first image, the one of your specimen itself, is broken. Not sure whether this is the case for everyone, but I can imagine this may make it difficult for others to comment

[Ptychodus04]

2 hours ago, pachy-pleuro-whatnot-odon said:

However, the reason I'm mostly writing this post is to tell you your first image, the one of your specimen itself, is broken. Not sure whether this is the case for everyone

Broken for me as well.

[Jared C]

@pachy-pleuro-whatnot-odon @Ptychodus04, the image should be fixed now

[Ptychodus04]

13 minutes ago, Jared C said:

@pachy-pleuro-whatnot-odon @Ptychodus04, the image should be fixed now

 

It is working now. I can't add any info since I'm relatively uneducated in this realm of paleontology.

[pachy-pleuro-whatnot-odon]

2 hours ago, Jared C said:

@pachy-pleuro-whatnot-odon @Ptychodus04, the image should be fixed now

 

2 hours ago, Ptychodus04 said:

It is working now.

 

Yup, for me too... And, unfortunately, can't really help either, as I don't know anything about urchins 

[LSCHNELLE]

On 5/9/2022 at 10:32 AM, Jared C said:

Well, whether the book is correct or not, I'm pleased to know that Prionocidaris at least existed in a similar time frame and so there's a chance of it - Prionocidaris is my favorite extant genus of the cidaroids today, albeit mainly for aesthetic reasons. It's a beautiful animal.

 

Here's Prionocidaris baculosa, from the Philippines. This has been my computer wallpaper for a couple of weeks now.

Attached is Plate 183 A & B from Bill Thompson's Echinoids of Texas Monograph - reported specimen from the Anacocho for your comparison with your specimen.  Stephen Crane is the collector (very reputable) and it is from the U.T Paleo Lab.  So, the ID of stratigraphic formation is not likely to be in error.  So, apparemtly, very close in age to yours - but more than just an echinoid plate.  Still, the genus and new species could be incorrect.  I'm not sure if anyone in the scientific community has reviewed it.  But, it certainly could be used to check things out. Bill gave me permission to use the image from his book.  Thanks Bill.  PS:  There is a typo.  It should say Upper Cretaceous - Gulfian Series. 

Edited May 11, 2022 by LSCHNELLE
correction of plate title for Anacocho age

[Jared C]

Wow, what a find that is.  At first inspection it does look strikingly similar. I wonder if we're moving into the green zone here

[erose]

There is a species known as "Cidaris" texanus Clark, 1891.  It was thought to be from the Washita in Bexar County.  But apparently there are also Austin Chalk and Anacacho Limestone specimens.  It may be a closer match. The HGMS book includes it and Bill T. has a photo of the holotype from the Smithsonian. Neither Bill nor HGMS have an image for "Cidaris" dixiensis Cragin, 1893 so that one is completely up in the air as well.

 

As far as new species, I would take those erected by Bill T. with a grain of salt. Some of his IDs are probably fine but often he based them on a few or even a single specimen. There are numerous mistakes/typos and the list of errata is long. And his work has not been peer reviewed in any real sense.  I'll give him credit for attempting to include everything he could. But he would also fall into the category of being a "splitter" and there will have to be a great deal of sorting out by the experts before we can confidently use all his new species.

[LSCHNELLE]

As I already clearly stated, disclaimers are in there. Of course how many people have actually reviewed Bill's work. I wonder how many would have when most people writing those books (like Charles Finsley's) were in fact amateurs.  Stephen Crane and his family are mentioned multiple times in Charles book and this is one of his finds.  I found no reason to not rely on the Anacacho specimen regardless of its current genera or species accuracy.

 

Certainly you could have an echinoid expert review Jared C's finds and make a more solid  determination.  That would be a really good thing! But, in the absence of anything else but a few tiny plates from a Citarid sp. that is clearly much less useful to anyone, I would compare it to the best available.  The same argument could be made against C. species as has been made against some of Bill's books finds - not enough fossils or fossil parts for a true determination. 

Edited May 11, 2022 by LSCHNELLE
Errata

[erose]

My apologies for derailing the real subject: Jared’s specimens. They just need to be compared to the handful of known possibilities to see if there is a clear match. 

[Jared C]

Resurrecting this thread a year and half later with what I think is the closest we'll get to an ID, which many folks, especially @DPS Ammonite, were interested in.

 

My misinterpretation of what constitutes a fully developed interambulacral plate had me running into dead ends for a while. @JohnJ gave me tips and steered me in the right direction, suggesting that the Stereocidarinae were still in the running. John's excellent pictures of the specimen and comparison with some other genera got me to the right place.

 

The specimens compare best with Stereocidaris sceptrifera, from the campanian of Europe. But, the geographic separation (since, for new readers, these specimens are from Texas) and absence of literature on this form in the new-world means that this species may be undescribed. Not totally surprising, since american late cretaceous echinoids are poorly described, but still an exciting possibility   

 

John's new images of the critters, below:

 

 

 

 

...and, a reference to the European Stereocidaris sceptrifera, from one of our forum members @JamieLynn